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  • 1995-1999  (164)
  • 1998  (164)
  • Analytical Chemistry and Spectroscopy  (163)
  • Nuclear reactions
  • 1
    Electronic Resource
    Electronic Resource
    Mixing in Stars and the Evolution of the 3He Abundance (1998)
    Springer
    Space science reviews 84 (1998), S. 199-206 
    Details
    ISSN: 1572-9672
    Keywords: Nuclear reactions ; Nucleosynthesis ; Abundances ; Stars:Evolution ; Interior ; Rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We first recall the observational and theoretical facts that constitute the so-called 3He problem. We then review the chemical anomalies that could be related to the destruction of 3He in red giants stars. We show how a simple consistent mechanism can lead to the destruction of 3He in low mass stars and simultaneously account for the low 12C/13C ratios and low lithium abundances observed in giant stars of different populations. This process should both naturally account for the recent measurements of 3He/H in galactic HII regions and allow for high values of 3He observed in some planetary nebulae. We propose a simple statistical estimation of the fraction of stars that may be affected by this process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005027519798
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  • 2
    Electronic Resource
    Electronic Resource
    Raman scattering tensors of tyrosine (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 4 (1998), S. 61-71 
    Details
    ISSN: 1075-4261
    Keywords: L-tyrosine ; polarized Raman spectra ; Raman tensor ; ab initio MO calculation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Polarized Raman scattering measurements have been made of a single crystal of L-tyrosine by the use of a Raman microscope with the 488.0-nm exciting beam from an argon ion laser. The L-tyrosine crystal belongs to the space group P212121 (orthorhombic), and Raman scattering intensities corresponding to the aa, bb, cc, ab and ac components of the crystal Raman tensor have been determined for each prominent Raman band. A similar set of measurements has been made of L-tyrosine-d4, in which four hydrogen atoms on the benzene ring are replaced by deuterium atoms. The effects of NH3 → ND3 and OH → OD on the Raman spectrum have also been examined. In addition, depolarization ratios of some bands of L-tyrosine in aqueous solutions of pH 13 and pH 1 were examined. For comparison with these experimental results, on the other hand, ab initio molecular orbital calculations have been made of the normal modes of vibration and their associated polarizability oscillations of the L-tyrosine molecule. On the basis of these experimental data and by referring to the results of the calculations, discussions have been presented on the Raman tensors associated to some Raman bands, including those at 829 cm-1 (benzene ring breathing), 642 cm-1 (benzene ring deformation), and 432 cm-1 (Cα-Cβ-Cγ bending). © 1998 John Wiley & Sons, Inc. Biospectroscopy 4: 61-71, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Evidence for global mobility in the premelting of a polynucleotide from temperature-dependent Raman optical activity (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 4 (1998), S. 107-111 
    Details
    ISSN: 1075-4261
    Keywords: conformational mobility ; nucleic acid dynamics ; Raman optical activity ; RNA ; temperature dependence ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The backscattered Raman and Raman optical activity (ROA) spectra of poly(rA)-poly(rU) at 20°C and 45°C in buffered aqueous solution between 650 and 1750 cm-1 are reported. Although the intensity of the majority of the Raman bands increase by varying amounts as the temperature is raised in accordance with the well-known hypochromic effect, the reverse effect is found for the ROA signals which we attribute to thermal accessibility of a greater number of distinct conformations leading to cancellation of ROA signals. The difference ROA spectrum obtained by subtracting the spectrum recorded at 45°C from that recorded at 20°C displays a very similar sign pattern to those at both 20°C and 45°C throughout the spectral region examined. This indicates that the same average structure is maintained in this temperature range and that the thermal fluctuations are correlated through the bases, the glycosidic link, the sugar ring, and the phosphate backbone of both strands. These results indicate that ROA may be a useful new probe of the dynamics of nucleic acid in solution. © 1998 John Wiley & Sons, Inc. Biospectroscopy 4: 107-111, 1998
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    FTIR microspectroscopic study of cell types and potential confounding variables in screening for cervical malignancies (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 4 (1998), S. 75-91 
    Details
    ISSN: 1075-4261
    Keywords: FTIR microspectroscopy ; cervical cancer ; leukocytes ; lymphocytes ; erythrocytes ; semen ; mucins ; fibroblasts ; thrombocytes ; bacteria ; nylon ; Candida albicans ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: FTIR microscopy was applied to the analysis of cell types and other variables present in Pap smears to ascertain the limitations of infrared spectroscopy in the diagnosis of cervical cancer and dysplasia. It was found that leukocytes, and in particular lymphocytes, have spectral features in the phophodiester region (1300-900 cm-1) suggestive of what has previously been described as changes indicative of malignancy. Endocervical cells and fibroblasts have similar spectral features to HeLa cells and consequently could also confound diagnosis. The use of ethanol as a fixative and dehydrating agent results in retention of glycogen in cervical cell types and thus minimizes spectral changes in the glycogen region due to sampling technique. Spectra of seminal fluids exhibit strong bands in the phosphodiester/carbohydrate region; however, sperm contamination should be easily detectable by the presence of a distinctive doublet at 981/968 cm-1. Erythrocyte spectra exhibit a reduction in glycogen band intensity, but can be discerned by a relatively low-intensity νs $PO^{-}_{2}$ band. Endocervical mucin spectra exhibit a reduction in glycogen bands and a very pronounced νs $PO^{-}_{2}$ band, which is similar in intensity to the corresponding band in HeLa cells. Thrombocytes have strong bands in the phosphodiester region, but thrombocytes can be discerned from other cell types by the presence of two small broad bands at 980 and 935 cm-1. Candida albicans is characterized by strong bands in the polysaccharide region which could potentially obscure diagnostic bands if C. albicans is present in large numbers. Spectra of bacteria common to the female genital tract, in general, also have strong absorptions in the polysaccharide region; however, bacterial contamination is usually minimal and would not be expected to obscure cervical cell spectra. Nylon threads and bristles from cervical sampling implements produce characteristic IR profiles which allow for easy identification. Given the number of potential confounding variables associated with cervical cytology, a multivariate statistical or neural network analysis would appear to be necessary before the implementation of FTIR technology in clinical laboratories. © 1998 John Wiley & Sons, Inc. Biospectroscopy 4: 75-91, 1998
    Additional Material: 10 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Pressure-induced structural rearrangements of bovine pancreatic trypsin inhibitor studied by FTIR spectroscopy (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 4 (1998), S. 209-216 
    Details
    ISSN: 1075-4261
    Keywords: high pressure ; FTIR spectroscopy ; bovine pancreatic trypsin inhibitor ; hydrogen-deuterium exchange ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Fourier transform infrared (FTIR) spectroscopy combined with resolution enhancement techniques, second-derivative and difference spectroscopies, have been used to characterize pressure-induced changes in the structural rearrangements of bovine pancreatic trypsin inhibitor (BPTI) in D2O solution at 25.0°C. According to the observed changes in the amide I′ band up to 550 MPa, the secondary structure elements of BPTI, such as the α-helix, 310-helix, β-sheet, and β-turn, are scarcely rearranged except for the loop structure of residues of 9-17 and 36-43. The polypeptide backbone is not extensively unfolded up to 550 MPa. The minor pressure-induced structural rearrangements are completely reversible. A further increase in pressure above 1000 MPa associated with the precipitation of BPTI in D2O buffer solution induces the partial structural rearrangements of the α-helix, β-turn and/or 310-helix, and β-sheet. The polypeptide backbone of BPTI is not fully unfolded even above 1000 MPa. Most of the protected backbone amide protons involved in the β-sheet remain intact in the pressure range where BPTI is not precipitated, while those involved in the α-helix and β-turn and/or 310-helix are exchanged with solvent deuterons. The protected backbone amide protons located near the surface regions are more easily exchanged with solvent deuterons by application of high pressure than those involved in the core. © 1998 John Wiley & Sons, Inc. Biospectroscopy 4: 209-216, 1998
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    The binding of biotin analogues by streptavidin: A Raman spectroscopic study (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 4 (1998), S. 197-208 
    Details
    ISSN: 1075-4261
    Keywords: Raman spectroscopy ; protein-ligand interactions ; streptavidin complexes ; biotin analogues ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Raman spectra of anhydrous complexes of streptavidin (Strep) with biotin (Bio) and some Bio analogues [Biotin methyl ester (MEBio), desthiobiotin (DEBio), 2′-iminobiotin (IMBio), and diaminobiotin (DABio)] were recorded. The vibrational results indicate that the interaction with some of these ligands is able to modify the overall structure of the protein and this binding results in a decrease in the βsheet content and an increase in the α-helix content. To further confirm the conformational changes of the protein structure due to Bio analogue binding, the curve-fitting analysis of the amide I Raman band of neat Strep and of the complexes were performed. The intensity ratio of the components due to the β-sheet and α-helix conformations decreased in the Strep-MEBio, Strep-IMBio (pH 11), and Strep-Bio systems, whereas in all the other systems the changes were not significant. This behavior differs from that of Avi bound to the same ligands and suggests that Strep and Avi differ in their binding selectivity. A good correlation was found between the secondary structure percentages of the Avi and of the Strep complexes and ΔG°. On the basis of this linear relationship, the vibrational results allow for an acceptable evaluation of the dissociation constants of the Strep complexes, not previously reported in the literature. The present results indicate a correlation between the type of interaction and the effects of the protein-substrate bonding on the overall structure of the proteins. The amino acid residues in the binding site appear to be positioned in a such a way as to provide a precise fit of Bio. Even slight change in the substrate structure causes a weakness in the strength of the binding. The vibrational results confirm that both the imidazolidinone and the thiophan rings are important in the Strep-Bio interactions, but the former is more responsible for the high affinity of the binding. One of the Tyr residues is hydrogen bound with the ureido ring and another Tyr could be involved in the binding pocket. Trp residues do not directly bind the ligand and probably stabilize other binding site residues which in turn interact directly with Bio. © 1998 John Wiley & Sons, Inc. Biospectroscopy 4: 197-208, 1998
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Vibrational study of phosphate modes in GDP and GTP and their interaction with magnesium in aqueous solution (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 4 (1998), S. 219-227 
    Details
    ISSN: 1075-4261
    Keywords: guanosine 5′-diphosphate ; guanosine 5′-triphosphate ; magnesium ; vibrational spectroscopy ; Raman spectroscopy ; FTIR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Raman and infrared spectra were examined for guanosine 5′-diphosphate (GDP) and guanosine 5′-triphosphate (GTP) in aqueous solution. The vibrational modes were assigned on the basis of isotopic frequency shifts and relative intensities in the Raman and infrared spectra. The observed frequency shifts on 18O isotope labeling made it possible to identify the bands from each phosphate group (α, β, γ). Frequency shifts were observed as Mg2+ complexes with GDP and GTP. The results suggested that Mg2+ binds to GDP in a bidentate manner to the α, β P · · O bonds and in a tridentate manner to the α, β and γ P · · O bonds of Mg·GTP. The results indicate that structure of Mg2+ coordinated to GTP in aqueous solution differs somewhat to that found for Mg·ATP. © 1998 John Wiley & Sons, Inc. Biospectroscopy 4: 219-227, 1998
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Surface structure of human mucin using X-ray photoelectron spectroscopy (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 4 (1998), S. 257-266 
    Details
    ISSN: 1075-4261
    Keywords: X-ray photoelectron spectroscopy ; surface analysis ; MUC1 mucin ; structure ; glycosylation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: X-ray photoelectron spectroscopy (XPS) is a surface sensitive analytical technique that measures the binding energy of electrons in atoms and molecules on the surface of a material. XPS was used to determine the distribution of the oligosaccharide side chains in the glycoprotein, MUC1 mucin. Low-resolution XPS spectra provided elemental composition of MUC1 mucin (fully glycosylated), mucin polypeptide (nonglycosylated), and carbohydrates found in mucin. The nitrogen content of MUC1 mucin was determined to be intermediate between the mucin polypeptide and the carbohydrates. Assuming a uniform distribution of carbohydrate on MUC1 mucin, the average thickness of the carbohydrate layer was calculated to be 4.9 nm using the low-resolution N 1s signals. High-resolution XPS spectra give detailed information about the chemical bonding of the surface molecules. Calculations based on the high-resolution O 1s spectra showed a carbohydrate thickness of 6.6 nm. These experimentally determined values agree reasonably well with an estimated 5 nm of carbohydrate thickness from a simple model which assume that the core protein is a rodlike molecule approximately 5 nm in diameter. Although the carbohydrate coating on the MUC1 mucin appears to be thick enough to cover the core protein entirely, fully glycosylated breast milk MUC1 mucin is susceptible to proteolytic digestion without removal of any oligosaccharide side chain, suggesting areas of exposed core protein. A possible explanation is that the oligosaccharide side chains may form patches of carbohydrate along the core protein with regions of exposed core protein. © 1998 John Wiley & Sons, Inc. Biospectroscopy 4: 257-266, 1998
    Additional Material: 7 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    On the use of ultraviolet resonance Raman intensities to elaborate molecular force fields: Application to nucleic acid bases and aromatic amino acid residues models (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 4 (1998), S. 379-393 
    Details
    ISSN: 1075-4261
    Keywords: molecular force field ; resonance Raman intensities ; aromatic amino acids ; nucleic acid bases ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Normal modes analyses for different molecules with biological interest have been performed and checked via the calculation of resonance Raman intensities. For this purpose, molecular orbital calculations were used to determine bond order changes in the lowest-lying electronic transitions. These bond order changes were used to calculate resonance Raman intensities in order to obtain correct vibrational assignments and reliable force fields. © 1998 John Wiley & Sons, Inc. Biospectroscopy 4: 379-393, 1998
    Additional Material: 1 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Resonance Raman spectroscopic study of the caa3 oxidase from Thermus thermophilus (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 4 (1998), S. 365-377 
    Details
    ISSN: 1075-4261
    Keywords: resonance Raman ; Thermus thermophilus ; oxidase ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The terminal caa3 oxidase of Thermus thermophilus has been studied by resonance Raman spectroscopy. Using different excitation wavelengths in the Soret band region, it was possible to disentangle the resonance Raman spectra of the fully oxidized and fully reduced state in terms of the component spectra of the individual hemes a, a3, and c. For the heme a and a3 groups, the spectra reveal only minor differences compared to those of beef heart cytochrome c oxidase attributable to subtle modifications of the heme environment. These differences are not more pronounced than those between the oxidases from beef heart and Paracoccus denitrificans confirming the view that this oxidase of Th. thermophilus is a typical member of the aa3 oxidase superfamily. The heme c component spectra display far-reaching similarities with those of c-type cytochromes which serve as mobile electron carriers in the respiratory chain. These results imply that caa3 oxidase represents an integrated version of the noncovalent redox complex between cytochrome c and cytochrome c oxidase in higher organisms. On the other hand, the structural changes of cytochrome c in the noncovalent complex have no counterpart in the heme c component of the caa3 oxidase indicating a specific cytochrome c binding site for the mitochondrial enzyme. © 1998 John Wiley & Sons, Inc. Biospectroscopy 4: 365-377, 1998
    Additional Material: 10 Ill.
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  • 11
    Electronic Resource
    Electronic Resource
    Special issue on “hot topics” from the ECSBM'97 conference (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 4 (1998), S. S1 
    Details
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: No abstract.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Enantiomeric Distribution of 2-Pentanethiol in Guava Fruit (Psidium guajava L.) by Multidimensional Gas Chromatography with Sulfur Chemiluminescence Detection (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 371-372 
    Details
    ISSN: 0935-6304
    Keywords: chemiluminescence detector ; guava ; MDGC ; 2-pentanethiol ; Psidium guajava ; SCD ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 13
    Electronic Resource
    Electronic Resource
    Separation of Triacylglycerols by High Temperature Gas Chromatography on Seven Different Stationary Phases (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 363-367 
    Details
    ISSN: 0935-6304
    Keywords: high temperature gas chromatography ; triacylglycerol ; lipids ; Jatropha multifida ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Identification of Volatile Compounds in Sunflower Oil by Headspace SPME and Ion-Trap GC/MS (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 368-370 
    Details
    ISSN: 0935-6304
    Keywords: Solid-phase microextraction ; headspace analysis ; gas chromatography ; mass spectrometry ; volatile analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Analysis of Wine Bouquet Components Using Headspace Solid-Phase Microextraction-Capillary Gas Chromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 373-377 
    Details
    ISSN: 0935-6304
    Keywords: Headspace solid-phase microextraction (HS/SPME) ; capillary gas chromatography ; volatile wine aroma compounds ; aromatic pattern ; chemometric classification ; HS/SPME standard addition method ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Headspace solid-phase microextraction (HS/SPME) was studied and optimized for the capillary gas chromatographic (CGC) analysis of wine aroma compounds. The results were compared with those obtained using the direct sampling mode (DI/SPME) and using liquid/liquid extraction with Kaltron. The aromatic patterns obtained by HS/SPME-CGC were applied to the chemometric classification of wine varieties. The HS/SPME-CGC standard additional method is an appropriate technique for the quantitative analysis of volatile wine aroma compounds.
    Additional Material: 8 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    Solvent Trapping during Large Volume Injection with an Early Vapor Exit, Part 2: Chromatographic Results and Conclusions (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 378-382 
    Details
    ISSN: 0935-6304
    Keywords: Large volume injection ; on-column injection ; flooded zone ; solvent trapping ; temperature measurement on precolumn wall ; water analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Solvent trapping reconcentrates volatile components after injection or on-line transfer of large volumes. When an early vapor exit is used, typically after a 5-10 m × 0.53 mm i.d. uncoated precolumn, the solvent trapping process differs from that described previously. The visual experiments and the conclusions drawn therefrom, as described in a previous paper, are supplemented with chromatographic results. They show that even hexane can be quantitatively analyzed in 250 μl of a pentane solution. Injection of a volume of 250 μl by vaporizer/precolumn solvent splitting was used in the analysis of gasoline in drinking water. Conditions for the transfer of a 1000 μl volume can easily be adjusted through detection of the front end of the flooded zone by a thermocouple mounted on the outer wall of the precolumn.
    Additional Material: 5 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Comprehensive Two-Dimensional Gas Chromatography (GC×GC) as a Diagnostic Tool (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 63-64 
    Details
    ISSN: 0935-6304
    Keywords: Injection port performance ; comprehensive two-dimensional GC ; GC× ; GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    CE/MALDI-MS of Peptides and Low Molecular Weight Drugs Using Non-Volatile Buffers (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 59-62 
    Details
    ISSN: 0935-6304
    Keywords: capillary electrophoresis ; mass spectrometry ; MALDI ; CE-MALDI ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    Trace Compounds in Urban Rain and Roof Runoff (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 65-68 
    Details
    ISSN: 0935-6304
    Keywords: GC-MS ; rain ; roof runoff ; fatty acids ; phenols ; alkanes ; chlorinated compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 6 Ill.
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  • 20
    Electronic Resource
    Electronic Resource
    An Improved (S)-Leucine-Derived π-Acidic HPLC Chiral Stationary Phase for the Resolution of π-Acidic Racemates (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 69-71 
    Details
    ISSN: 0935-6304
    Keywords: liquid chromatography ; chiral separations ; chiral stationary phase ; separation of enantiomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 21
    Electronic Resource
    Electronic Resource
    Determination of Phenols, Inorganic Anions, and Carboxylic Acids in Kraft Black Liquors by Capillary Electrophoresis (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 3-10 
    Details
    ISSN: 0935-6304
    Keywords: Co-electroosmotic capillary electrophoresis ; high performance liquid chromatography ; phenolic lignin degradation compounds ; inorganic anions ; organic modifiers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Two methods are presented for the quantitative capillary electrophoretic (CE) determination of phenolic lignin degradation compounds as well as of inorganic anions and organic acids in Kraft black liquors. Important phenolic lignin degradation compounds can be rapidly separated by co-electroosmotic CE after acidification of the liquors and subsequent extraction of the compounds with chloroform. A capillary electrophoretic separation of phenolic compounds is performed by using a phosphate/borate electrolyte system and UV detection at 214 nm. In addition, a HPLC method using a gradient with water, methanol, and acetic acid is also developed. Inorganic ions which are of importance to the pulping process can be determined by simply diluting the black liquors after sampling and subsequent analysis with a chromate electrolyte system and indirect UV detection at 185 nm. In addition, the concentration of low molecular aliphatic carboxylic acids can be determined simultaneously within the same run. By method optimization it is possible to separate the anions within one minute and, at the same time, to increase the resolution of the solutes. The electrolyte systems for the CE separations were optimized by varying the pH value and by adding organic solvents. Short separation times are obtained by adding a polycationic EOF modifier (hexadimethrine bromide) to the electrolyte which reverses the electroosmotic flow. A migration of the anionic analytes in the same direction as the electroosmotic flow is thus established.
    Additional Material: 8 Ill.
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  • 22
    Electronic Resource
    Electronic Resource
    A Measurement Technique for Organic Nitrates and Halocarbons in Ambient Air (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 201-208 
    Details
    ISSN: 0935-6304
    Keywords: PAN ; peroxyacetyl nitrate ; alkyl nitrate ; chlorinated hydrocarbons ; halocarbons ; capillary GC-ECD ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A cryogenic preconcentration/high-resolution gas chromatographic technique has been developed for the rapid, simultaneous quantitation of C1-C4 organic nitrates and halocarbons in ambient air. Whole-air samples are collected in TedlarTM bags by an evacuated-chamber method. Samples were stable in 0.010-cm-thick bags for 24 h if they were immediately stored in a freezer at -25°C. Analytes in a 50-cm3 air sample were efficiently preconcentrated on fused-silica beads at -180°C and thermally desorbed at 30°C. High-resolution gas chromatography with a cross-linked polydimethylsiloxane fused-silica capillary column and an electron-capture detector were used for separation and quantitation of the analytes. An analysis time of about 12 min was facilitated by sample cryofocusing at -180°C and oven temperature programming. Recoveries of the analytes by the evacuated-chamber method were better than 95%. The sensitivity of the technique for sample volumes of 50 cm3 is in the sub-parts-per-trillion by volume (ppt[v]) range for many of the analytes, with an average precision of about ±5% for analytes at levels of about 10 ppt(v).
    Additional Material: 4 Ill.
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  • 23
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    Electronic Resource
    Separation of Enantiomers of Drugs by Capillary Electrophoresis, Part 6. Hydroxypropyl-β-cyclodextrin as Chiral Solvating Agent (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 215-224 
    Details
    ISSN: 0935-6304
    Keywords: capillary electrophoresis ; enantiomer separation ; hydroxypropyl-β-cyclodextrin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Following an extended screening project, 86 racemic drugs were investigated by capillary zone electrophoresis in the presence of the chiral solvating agent (CSA) hydroxypropyl-β-cyclodextrin. A total of 42 drugs out of 86 tested was thereby separated into enantiomeric pairs. Statistical analysis of the numerous experiments performed un der identical conditions reveals a loose correlation of the migration separation factor (αm) with the migration retardation factor (Rm). For a subset of 23 drugs, a drop in the concentration of the CSA was also studied, showing the way to further optimization.
    Additional Material: 6 Ill.
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  • 24
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    Electronic Resource
    Development of a Dual Capillary Column GC Method for the Trace Determination of C2-C9 Hydrocarbons in Ambient Air (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 209-214 
    Details
    ISSN: 0935-6304
    Keywords: Dual capillary gas chromatography ; non-methane hydrocarbons (NMHCs) ; refocusing ; PLOT column ; carbon dioxide interference ; ambient air analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analytical method based on a dual capillary gas chromatographic technique combining the advantages of GasPro PLOT and a non polar narrow bore WCOT column was developed for the analysis of air samples containing C2-C9 NMHCs. A refocusing step was not required due to the fast heating rate of the sample preconcentration trap and the resolving power of the PLOT column for C2 and C3 NMHCs. Water had to be removed from the air samples to avoid plugging of the columns if the initial GC oven temperature was below ambient temperature. To dry air samples, a scrubber and a cryogenic technique were employed. The interferences caused by carbon dioxide were reduced by purging the loaded sample preconcentration trap with helium. The dual column system was compared to a method employing a refocusing device and a single narrow bore WCOT column. Both systems provided a high degree of precision. However, the dual column approach was superior to the single column system due to better resolution of low molecular weight components.
    Additional Material: 7 Ill.
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  • 25
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    Electronic Resource
    Evaluation of Enantioselective Interactions in Direct Separation of Enantiomers by Gas Chromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 197-199 
    Details
    ISSN: 0935-6304
    Keywords: Chiral recognition of 2-pentanol enantiomers ; enantioselective interactions ; capillary gas chromatography ; permethylated-β-cyclodextrin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 26
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    A Chiral Recognition Mechanism Proposed for Resolving π-Acidic Racemates on π-Acidic Chiral Stationary Phases Derived from (S)-Leucine (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 464-470 
    Details
    ISSN: 0935-6304
    Keywords: liquid chromatography ; chiral separation ; chiral recognition mechanism ; chiral stationary phase ; separation of enantiomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A chiral recognition mechanism which can rationalize the resolution of N-(3,5-dinitrobenzoyl)-α-amino amides on chiral stationary phases (CSPs) obtained from N-(3,5-dinitrobenzoyl)leucine amide derivatives has been proposed on the basis of the chromatographic resolution behavior of various N-(3,5-dinitrobenzoyl)-α-amino acid derivatives and N-(various benzoyl)leucine N-propyl amides. The proposed chiral recognition mechanism utilizes two hydrogen bonding interactions between the CSP and the analyte and a π-π donor-acceptor interaction between the N-(3,5-dinitrobenzoyl) groups of the CSP and the analyte. From the chiral recognition mechanism proposed, it has been concluded that the resolution of π-acidic N-(3,5-dinitrobenzoyl)-α-amino acid derivatives on π-acidic CSPs derived from N-(3,5-dinitrobenzoyl)leucine amide delivatives is not unusual, but is merely the extension of the resolution of the π-basic racemates on π-acidic CSPs. However, the chromatographic behavior of the resolution of N-(3,5-dinitrobenzoyl)phenylglycine derivatives on CSPs derived from N-(3,5-dinitrobenzoyl)leucine amide derivatives is different from that of the resolution of other N-(3,5-dinitrobenzoyl)-α-amino acid derivatives. To rationalize this exceptional behavior, a second chiral recognition mechanism which utilizes two hydrogen bonding interactions (which are different from those of the first chiral recognition mechanism) between the CSP and the analytes and a π-π donor-acceptor interaction between the N-(3,5-dinitrobenzoyl) group of the CSP and the phenyl group of the analytes has been proposed to compete with the first chiral recognition mechanism. In this instance, it has been proposed that the separation factors and the elution orders of the resolution of N-(3,5-dinitrobenzoyl)phenylglycine derivatives are dependent on the balance of the two competing chiral recognition mechanisms.
    Additional Material: 3 Ill.
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  • 27
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    Electronic Resource
    The Correct Meaning of “Coating Efficiency” vs. the “Utilization of Theoretical Efficiency” (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 121-123 
    Details
    ISSN: 0935-6304
    Keywords: gas chromatography ; capillary columns ; column efficiency ; column comparison ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The correct meaning of the the term “utilization of the theoretical efficiency” vs. the “coating efficiency” is explained.
    Additional Material: 1 Tab.
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  • 28
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    Self-Made Y-Splits for Hyphenated Capillary Gas Chromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 125-127 
    Details
    ISSN: 0935-6304
    Keywords: multidimensional gas chromatography ; self-made connectors ; effluent splitting ; press fit connectors ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 29
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    Electronic Resource
    Determination of Petroselinic Acid in Umbelliferae Seed Oils by Automated Gas Chromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 133-136 
    Details
    ISSN: 0935-6304
    Keywords: GC ; analysis of vegetable oil ; petroselinic acid ; butyl esters ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 30
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    Electronic Resource
    Miniaturized Injection Method Using Silver-Coated Capillaries in DNA Sequencing by Multiplexed Capillary Electrophoresis (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 287-290 
    Details
    ISSN: 0935-6304
    Keywords: DNA ; capillary electrophoresis ; sample injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Silver-coated capillaries were used for direct sample injection in multiplexed capillary electrophoresis. The absence of an additional electrode simplifies mechanical alignment, reduces contamination, and decreases the amount of sample needed. Capillaries were coated by a silver paint which is a suspension of silver particles in an organic solvent. To provide electrical contact, the upper part of the capillary and a platinum wire were wound together by a copper wire. Electrical resistance from the platinum wire to the tip of the capillary was small enough (7 ω to 50 ω) to inject large amounts of DNA samples. Electrokinetic injection from eight separate sample vials to eight capillaries was demonstrated for DNA sequencing by multiplexed capillary electrophoresis. Signal-to-noise ratio and resolution were good enough to call up to 350 base pairs.
    Additional Material: 3 Ill.
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  • 31
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    Electronic Resource
    The Use of Non-Splitting Injection Techniques for Trace Analysis in Narrow-Bore Capillary Gas Chromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 491-497 
    Details
    ISSN: 0935-6304
    Keywords: Fast GC ; narrow-bore columns ; trace analysis ; splitless injection ; on-column injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The use of hot splitless, cold splitless, and on-column injections for trace analysis in narrow-bore capillary GC is evaluated. Despite the low flow rates for the columns used, the required splitless times for splitless injections can be surprisingly short if liners with a small inside diameter are used. On-column injection can be applied by using an appropriate normal-bore precolumn coupled to the narrow-bore analytical column using a specially designed low dead volume column connector. The effects of the experimental conditions such as sample volume, injection temperature, and initial oven temperature on peak focusing and the discrimination and degradation behavior of the analytes are discussed. The possibilities to obtain sensitive and fast separations are illustrated by various applications.
    Additional Material: 7 Ill.
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  • 32
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    Electronic Resource
    Silver (I)-Mediated Separations by Nonaqueous Capillary Electrophoresis: Nonaqueous Argentation Electrophoresis (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 498-504 
    Details
    ISSN: 0935-6304
    Keywords: Nonaqueous solvents ; capillary electrophoresis ; charge transfer complexation ; argentation ; silver ion ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This study represents the first application of Ag(I) charge transfer complexation in nonaqueous capillary electrophoresis. This method applies the principles of argentation chromatography to nonaqueous electrophoretic separations and is termed “nonaqueous argentation electrophoresis”. Since the separations are performed in 100% nonaqueous media, the advantages of nonaqueous solvents, such as enhanced solubility and flexibility in selectivity enhancement, compared to an aqueous or mixed hydroorganic solvent, are realized. A variety of compounds were separated. Qualitatively, the separation of eleven sulfonamides in 100% acetonitrile is shown to improve greatly upon the addition of Ag(I). These results also show that nonaqueous argentation electrophoresis provides fast, well-resolved separations of compounds, such as N-containing heterocyclics, that can selectively complex with Ag(I). Migration data and separation selectivities of these compounds by nonaqueous argentation electrophoresis were compared to previous aqueous argentation electrophoresis results. Selectivities were found to be significantly different for the two separation media. Ag(I) complexation provides an effective means of manipulating selectivity in nonaqueous capillary electrophoresis.
    Additional Material: 9 Ill.
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  • 33
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    Separation of Chlorophenols by Capillary Zone Electrophoresis. The Influence of pH of the Electrophoretic Buffer on Selectivity (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 309-314 
    Details
    ISSN: 0935-6304
    Keywords: Chlorophenols ; separation ; CZE ; pH ; organic modifiers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 34
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    Method for Gradient Elution in Micro-Flow Liquid Chromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 291-297 
    Details
    ISSN: 0935-6304
    Keywords: Gradient ; liquid chromatography ; micro-HPLC ; mixer ; electrospray mass spectrometry ; cytochrome c ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This paper describes a new method for gradient elution at low flow rate. By adjusting the solvent composition flowing into a dynamic mixer, we can program the concentration of solvent, B, inside a dynamic mixer to form a time-resolved solvent gradient delivered to the column. The input gradient is related to the output gradient by the equation, Bin = Bout + τ × dBout/dt, in which τ is the gradient response time constant at specified flow rate, and Bin and Bout are input and output concentration of solvent B, respectively.
    Additional Material: 8 Ill.
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  • 35
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    Detection of Tertiary Amines with Chemiluminescent Reaction Using Tris(2,2′-bipyridine)ruthenium(III) Prepared by On-Line Photochemical Oxidation (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 315-316 
    Details
    ISSN: 0935-6304
    Keywords: Tertiary amine ; ruthenium ; chemiluminescence ; photochemical oxidation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 36
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    Analysis of Rotenoids by High Temperature High Resolution Gas Chromatography-Mass Spectrometry (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 513-518 
    Details
    ISSN: 0935-6304
    Keywords: Cold on-column injector ; high temperature high resolution gas chromatography ; rotenoids ; PS-090 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A short glass capillary column coated with PS-090 (20% phenyl-80% methylpolysiloxane, of 10 m × 0.30 mm i.d.; with 0.1 μm film thickness) was used to analyze samples from Tephrosia candida; eighteen rotenoids were separated and identified without derivatization by HT-HRGC and HT-HRGC-MS. The mass spectra show the typical fragmentation pattern for rotenoids, with the base peaks either at M+, or originating from RDA (Retro Diels-Alder) rearrangements. HT-HRGC and HT-HRGC-MS were shown to be extremely valuable and neglected techniques for structural studies as well as the routine analysis of rotenoids in crude extracts. Possible applications to other classes of aromatic natural products, e.g. flavonoids, are envisaged.
    Additional Material: 1 Ill.
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  • 37
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    Identification and Quantitation of Hydroxytyrosol in Italian Wines (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 549-553 
    Details
    ISSN: 0935-6304
    Keywords: Hydroxytyrosol ; GC-MS ; wine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Hydroxytyrosol (HTy) is a potent natural antioxidant found in olive oil and in mill waste waters. Although wines are rich in polyphenols, hydroxytyrosol has not been identified in wines so far. We have analyzed ten wines from different grape varieties grown in several Italian regions, using a gas-chromatograph coupled to a mass selective detector (GC-MS). Solid-phase extraction of wine samples was performed on a C18 column, with ethyl acetate used as eluting agent. Eluates were derivatized with bis(trimethylsilyl)trifluoroacetamide (BSTFA) and analyzed by GC-MS using one target and two qualifying ions. The detection limit was 15 pg/μL, with 49% average recovery. Under these experimental conditions hydroxytyrosol was detected in all wines analyzed. Its average concentrations in red and white wines were 4.0 mg/L and 1.9 mg/L, respectively.
    Additional Material: 3 Ill.
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  • 38
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    Electronic Resource
    Chiral Capillary Electrochromatography on a Vancomycin Stationary Phase (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 575-576 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography (CEC) ; chiral separations ; Vancomycin stationary phase ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 39
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    Electronic Resource
    Liquid Chromatographic Determination of the Constituents in Shao-yao-tang and Related Chinese Herbal Preparations (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 569-573 
    Details
    ISSN: 0935-6304
    Keywords: Chinese herbal preparation ; Shao-yao-tang ; pharmaceutical analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A high-performance liquid chromatographic method for the separation of twenty one constituents of Shao-yao-tang including six flavonoids, six alkaloids, three anthraquinones, three carboxylic acids, one monoterpene, one saponin, and one aldehyde was developed. Detection at 275 nm with a linear gradient elution system consisting of tetrabutylammonium bromide (TBA) and acetic acid solution was found to be suitable for determination of nineteen marker substances in an unpretreated Shao-yao-tang extract within 75 min. This method can also be used to analyze 11-14 components in a number of Chinese herbal preparations such as San-huang-hsieh-hsin-tang, Ching-chieh-lien-chiao-tang, San-tsung-kuei-chien-tang, Chai-hu-ching-kan-tang, and Ching-yin-li-ke-tang.
    Additional Material: 3 Ill.
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  • 40
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    A GC/MS Method for Determining UV Stabilizers in Polyethyleneterephthalate Bottles (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 317-320 
    Details
    ISSN: 0935-6304
    Keywords: GC/MS analysis ; SIM mode ; UV stabilizers ; PET ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 41
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    Solvent Trapping during Large Volume Injection with an Early Vapor Exit, Part 1: Description of the Flooding Process (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 355-362 
    Details
    ISSN: 0935-6304
    Keywords: Large volume injection ; solvent evaporation ; flooded zone ; solvent trapping ; on-column injection ; water analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Using a specially treated glass capillary, evaporation of the solvent during large volume injection into a precolumn was visually investigated in order to better understand the solvent trapping process. Using an early vapor exit, the process differs from the classical description of solvent trapping. First, there is a substantial pressure drop over the solvent-coated (“flooded”) precolumn, causing evaporation to take place not only at the rear edge, but also within the flooded zone or at its front end (which may result in almost complete loss of volatile solutes). Secondly, the evaporation rate increases as the liquid enters deeper into the precolumn, eventually turning partially concurrent evaporation into a fully concurrent evaporation with massive loss of volatiles. Thirdly, the capacity of the precolumn to retain liquid is substantially higher than observed in systems without early vapor exit
    Additional Material: 10 Ill.
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  • 42
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    Sorption Tubes Packed with Polydimethylsiloxane: A New and Promising Technique for the Preconcentration of Volatiles and Semi-Volatiles from Air and Gaseous Samples (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 332-340 
    Details
    ISSN: 0935-6304
    Keywords: gas chromatography ; sorptive preconcentration ; air sampling ; VOCs ; nitro-PAH's ; PAHs ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This paper is concerned with the determination of volatile and semi-volatile organic components in air and gaseous (headspace) samples, focusing primarily on polar analytes. Samples were analyzed by preconcentration on different (ad)sorbents followed by thermal desorption and analysis by capillary gas chromatography. The performance of a cartridge filled with 100% polydimethylsiloxane (PDMS) particles was compared to that of adsorbents like Tenax TA and Carbotrap 300. Though the PDMS phase is non-polar it showed adequate retention for both polar and non-polar components. The blank runs of the PDMS trap were significantly better than those of most adsorbents and did not deteriorate, as was the case with all the conventional adsorbents investigated. With respect to trapping efficiencies, the PDMS phase performed better for most of the analytes under investigation compared to the adsorbents. For a range of analytes including triethylamine, butanone, diacetyl, nicotine, and acetic acid the PDMS phase performed exceptionally well whereas all adsorbents showed unsatisfactory performance. The packed PDMS traps were employed for the determination of organic acids, PAH's and nitro-PAH's in air and for the analysis of the headspace of cacao and hop.
    Additional Material: 9 Ill.
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  • 43
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    Quantitative Aspects of Comprehensive Two-Dimensional Gas Chromatography (GC×GC) (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 47-54 
    Details
    ISSN: 0935-6304
    Keywords: multidimensional gas chromatography ; comprehensive two-dimensional gas chromatography ; GC×GC ; characterization of petroleum samples ; quantitative analyses ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A software program was developed to enable the quantification of the complex 3D-data sets as produced by GC×GC. Using this software, it was demonstrated that the detectability limit of GC×GC in our study is 18 times better than that of ‘normal’ capillary gas chromatography (CGC). This enhancement is due to the signal increase produced by the thermal modulation effect. The relative standard deviation of 0.9% as measured on a test mixture was excellent. Furthermore, a comparison was made for the group-type separation of heavy gas oils between the hyphenation of LC and GC (LC-GC) and GC×GC. Although these separations are different in nature, the agreement of the results of both methods was very good. The results of GC×GC may even be more accurate, since, different from CGC, even in the most complex chromatograms the baseline in the second dimension chromatograms is always present.
    Additional Material: 5 Ill.
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  • 44
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    Simultaneous Determination of Haloacetic Acids in Environmental Waters using Electrospray Ionization Liquid Chromatography Mass Spectrometry (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 55-58 
    Details
    ISSN: 0935-6304
    Keywords: liquid chromatography-mass spectrometry ; electrospray ionization ; haloacetic acids ; trace analysis of environmental water samples ; waste water samples ; river water samples ; seawater samples ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Negative ionization electrospray liquid chromatography mass spectrometry was developed for the simultaneous determination of all nine haloacetic acids containing bromine and chlorine. Haloacetic acids were separated on a crosslinked polystyrene resin column using 3% acetic acid dissolved in acetonitrile:water (20:80) as mobile phase. The precision of this method varied from ±2.2 to ±7.1% for nine haloacetic acids. In addition, quantitative results obtained with spiked water samples at three different concentrations are described. The limit of detection of the proposed method using 200 mL of water samples was between 0.003 and 0.070 μg/L. This method was successfully applied to the trace determination of haloacetic acids in waste water, river water, and seawater.
    Additional Material: 1 Ill.
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  • 45
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    Determination of Enantiomer Ratios of Bornane Congeners in Biological Samples Using Heart-Cut Multidimensional Gas Chromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 39-46 
    Details
    ISSN: 0935-6304
    Keywords: Bornane congeners ; toxaphene compounds ; heart-cut multidimensional gas chromatography ; enantioselectivity ; chiral GC separation ; biological samples ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The enantiomeric ratios of the chlorinated bornanes, 2-exo, 5,5,9,9,10, 10-heptachlorobornane (B[20030]-(022)), 2-endo,3-exo,5-endo,6-exo,8, 8,10,10-octachlorobornane (B[12012]-(202), Parlar No. 26), 2-exo,3-endo,6-endo,8,9,10,10-heptachlorobornane (B[21001]-(112)), 2,2,5,5,9,9, 10,10-octachlorobornane (B[30030]-(022), Parlar No. 38), 2-endo,3-exo,5-endo6-exo,8,8,9,10,10-nonachlorobornane (B[12012]-(212), Parlar No. 50), and 2,2,5,5,8,9,9,10,10-nonachlorobornane (B[30030]-(122), Parlar No. 62) were determined in a hake liver (Merluccius merluccius) and in two whitebeaked dolphin blubber (Lagenorynchus albirostris) samples. The analysis was performed by heart-cut multidimensional gas chromatography using an electron capture detector (ECD). Ultra 2 (5%-phenyl-95%-methylsilicone) was used as stationary phase in the first column and enantioselectivity was obtained in the second column with a phase consisting of a mixture of OV-1701 and heptakis(2,3,6-O-tert- butyldimethylsilyl)-β-cyclodextrin (10 : 1). All reference standards were also tested on the enantioselective column alone. The comparison of the two systems showed that deviations of ±0.12 from the racemic enantiomer ratio can be observed for the single column due to co-eluting impurities which are present in the reference standards. In most of the heart-cut chromatograms of the biota samples about 15 peaks could be found, showing the importance of a multidimensional separation system for an interference-free quantification by ECD. In all biological samples a significant deviation from the racemic enantiomer ratio was found for B[30030]-(022) (Parlar No. 38) and for B[30030]-(122) (Parlar No. 62). This indicates that an enantioselective disposition of the congeners occurs. In addition, considerations are presented concerning the relationship between congener structure and enantiomeric disposition.
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  • 46
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    Electronic Resource
    Identification and Linkage of Tarballs from the Coasts of Vancouver Island and Northern California Using GC/MS and Isotopic Techniques (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 383-395 
    Details
    ISSN: 0935-6304
    Keywords: Oil ; oil spill ; GC/MS ; GC/FID ; carbon isotope ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---During January and February 1996, a significant number of tarball/patty incidents occurred along the coasts of Vancouver Island, Washington, Oregon, and California. Samples of the tarballs were collected from the affected beaches and analyzed by gas chromatography/mass spectrometry (GC/MS) and gas chromatography/flame ionization detector (GC/FID) using a tiered analytical approach developed for determining the origin of oils. Selected samples were further analyzed using a carbon isotopic technique. Also, the relative abundances of a large number of “source-specific marker” compounds, in particular alkylated series of polycyclic aromatic hydrocarbons within the same alkylation isomeric groups, were compared. Results of the analysis revealed that (1) California/Oregon samples were chemically similar and consistent with the same source. They were identified to be bunker type fuel; (2) The tarball samples collected from British Columbia and Ocean Shores, Washington were chemically similar and consistent with the same source (also bunker type fuel). They were found to be similar to but may have a source different than the California/Oregon samples; (3) The source of the tarball/patty samples was neither Alaska North Slope oil nor California Monterrey Miocene oil; (4) The spilled oil samples have been highly weathered since release, and the California samples were more heavily weathered than the British Columbia samples.
    Additional Material: 7 Ill.
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  • 47
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    Electronic Resource
    Niacin Determination in Legumes by Capillary Electrophoresis (CE). Comparison with High Performance Liquid Chromatography (HPLC) (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 81-86 
    Details
    ISSN: 0935-6304
    Keywords: Available niacin ; capillary electrophoresis ; total niacin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Available and total niacin content in lentils and faba beans have been analyzed by capillary electrophoresis (CE), and the results compared with those obtained by high performance liquid chromatography (HPLC). Acidic and enzymatic hydrolysis have been carried out for available niacin determination, and an alkaline extraction performed for total niacin. The extracts were subsequently purified using a strong anion exchanger resin. Precise conditions for purification had to be worked out for each one of the two analytical methods (HPLC and CE). The HPLC analysis for available and total niacin was carried out in an ion-pair reverse phase column with UV detection at 261 nm. For the CE separation, the following conditions were employed: a 20 mM sodium tetraborate; 15 mM sodium dodecyl sulfate and 20% isopropyl alcohol solution as separation buffer; 30 kV and 25 or 30°C. Separation was carried out in a 70 cm effective length × 75 μm i.d. fused-silica capillary using on-column UV detection at 254 nm. The results obtained by CE for lentils and faba beans were similar to those obtained by HPLC.
    Additional Material: 2 Ill.
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  • 48
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    Electronic Resource
    Chiral Separation of Bencynonate and Econazole by Cyclodextrin-Modified Capillary Zone Electrophoresis (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 421-423 
    Details
    ISSN: 0935-6304
    Keywords: Capillary zone electrophoresis ; chiral separation ; cyclodextrins ; bencynonate ; econazole ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 49
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    Electronic Resource
    The Use of the Helium Ionization Detector for Gas Chromatographic Monitoring of Trace Atmospheric Components (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 75-80 
    Details
    ISSN: 0935-6304
    Keywords: gas chromatography, helium ionization detector (HID) ; formaldehyde ; atmospheric oxygenates ; volatile organic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Two different gas chromatographic detectors, the helium ionization detector (HID) and the more commonly used flame ionization detector (FID), were used in parallel to compare their responses to a number of organic compounds. Atmospherically important oxygenated species were analyzed, as well as hydrocarbons and chlorinated and sulfur containing organics. The HID exhibited the better response to all compounds investigated, most notably to formaldehyde and higher oxygenates. A gas chromatographic system was developed to trap and analyze atmospheric organic compounds with HID detection. This required careful choice of the adsorbent material and removal of inorganic components (namely nitrogen and oxygen) before analysis. Real air samples were then taken and analyzed qualitatively for a range of olefinic and aromatic compounds.
    Additional Material: 6 Ill.
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  • 50
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    Electronic Resource
    Packed Column SFC of Gas Oils. Part II: Experimental Design Optimization of the Group-Type Analysis using CO2-SF6 as the Mobile Phase (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 94-102 
    Details
    ISSN: 0935-6304
    Keywords: supercritical fluid chromatography ; experimental design optimization ; Diesel fuel ; group-type analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---An optimization procedure is presented for group-type analysis of diesel fuel by supercritical fluid chromatography using packed silica column and a mixed mobile phase. A set of five responses, four values of resolution of a performance mixture and analysis time, was modeled using a Doehlert matrix for experimental design. Optimized experimental conditions for the five responses were obtained from a response surfaces optimization, taking into account various constraints on SF6 content in mobile phase and analysis time. The predicted and experimental resolutions were in good agreement for the different optimized conditions and one of them was selected to for application to a given diesel fuel for comparison with the results obtained by SFC using pure CO2 and by HPLC. The conditions found in this study provide an alternative method for the determination of mono-, di-, and polyaromatic compounds in middle distillates.
    Additional Material: 9 Ill.
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  • 51
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    Use of a Drying Cartridge in On-Line Solid-Phase Extraction-Gas Chromatography-Mass Spectrometry (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 450-456 
    Details
    ISSN: 0935-6304
    Keywords: Drying cartridge ; gas chromatography ; solid-phase extraction ; microcontaminants ; water samples ; on-line SPE-GC ; mass spectrometric detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A drying cartridge was used and optimized for the in-line elimination of water from the desorption eluent in on-line solid phase extraction-gas chromatography (SPE-GC). The cartridge is essentially a small stainless-steel precolumn packed with a drying agent which can be regenerated by simultaneous heating and purging with a moisture-free gas. The drying cartridge was mounted on an additional valve instead of between the SPE-GC transfer valve and the on-column injector to enable regeneration of the cartridge during the GC run and, thus, to increase sample throughput. Three drying agents were tested, viz. sodium sulfate, silica, and molecular sieves. Although molecular sieves have the highest capacity, silica was preferred because of practical considerations. Large-volume injections were performed through the in-line drying cartridge using a mixture of 23 microcontaminants ranging widely in polarity and volatility. Four solvents were tested. With pentane and hexane, the more polar analytes were retained by the drying cartridge. Ethyl acetate and methyl acetate gave much better (and closely similar) recoveries for all analytes. Because water elimination on the silica cartridge proved to be less critical than with ethyl acetate, this solvent was finally selected. The entire SPE-drying cartridge-GC set-up was combined with mass spectrometric (MS) detection for the determination of a mixture of micropollutants in real-life water samples. With 10-ml tap water samples spiked at the 0.5 μg/l level, for the majority of the test compounds the analyte recoveries generally were 60-106%, and (full-scan) detection limits typically were 0.01-0.03 μg/l. Some very polar analytes such as, e.g. dimethoate, were (partially) sorbed onto the silica packing of the drying cartridge.
    Additional Material: 4 Ill.
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  • 52
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    Comparison of Supercritical Fluid Extraction with Solvent Sonication for Chemical Warfare Agent Determination in Alkyd Painted Plates (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 457-463 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical Fluid Extraction (SFE) ; ultrasonication extraction ; gas chromatography ; derivatization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Supercritical fluid extraction (SFE) of alkyl alkylphosphonofluoridates and dialkyl alkylphosphonates from painted plates was investigated. It was found that SFE recoveries compared favorably with conventional solvent sonication results. Stability studies of the samples were carried out over a period of two months. This investigation showed that the concentration of phosphonofluoridates decreased over a long period.
    Additional Material: 8 Ill.
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  • 53
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    Enantiomeric Distribution Studies of Linalool and Linalyl Acetate. A Powerful Tool for Authenticity Control of Essential Oils (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 107-112 
    Details
    ISSN: 0935-6304
    Keywords: Linalool; linalyl acetate ; enantioseparation by enantioselective gas chromatography ; enantiomer distributions in natural products obtained by different extraction processes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The enantiomeric distributions of linalool and linalyl acetate in various natural products are measured by enantioselective gas chromatography on alkyl-substituted cyclodextrins. Different plant cultivars were investigated by four extraction processes: steam distillation, solvent extraction, supercritical fluid extraction, and headspace analysis. Careful attention must be paid to linalool which undergoes partial racemization under certain processing conditions. In most cases, enantiomeric distribution is a powerful tool for authenticity testing.
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  • 54
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    Chloro-bis-propyl Ethers in the Elbe River - Isomeric Distribution and Enantioselective Degradation (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 113-120 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective GC of chlorinated bis(propyl) ethers ; environmental analysis ; contamination of the Elbe River ; cyclodextrin derivatives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Cyclodextrin derivatives are evaluated as chiral stationary phases for the enantiomer separation of chlorinated bis(propyl) ethers (BPE). The enantiomeric composition of the 2,3,2′,3′- and 1,3,2′,3′-isomers of tetrachlorobis(propyl) ether in the Elbe River has been quantitatively determined by enantioselective gas chromatography and coupled gas chromatography/mass spectrometry in selected-ion-monitoring mode. Significant enantiomeric discriminations are observed in selected water samples, indicating that enantioselective bio-degradation mechanisms are at least partly responsible for the overall degradation processes.
    Additional Material: 5 Ill.
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  • 55
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    On-site Monitoring System for Hazardous Air Pollutants Using an Adsorption-Thermal Desorption-Capillary GC System Equipped with a Photoionization Detector and an Electrolytic Conductivity Detector (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 471-474 
    Details
    ISSN: 0935-6304
    Keywords: Adsorption/thermal desorption sampling instrument ; capillary gas chromatography ; electrolytic conductivity detector ; photoionization detector ; environmental air monitoring ; hazardous air pollutants ; volatile organic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 56
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    Chromatographic Properties of Miniaturized Silica Rod Columns (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 477-479 
    Details
    ISSN: 0935-6304
    Keywords: Silica rod column ; micro-HPLC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 57
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    High Temperature Gas Chromatography and High Temperature Gas Chromatography - Negative Chemical Ionization Mass Spectrometry of Derivatized Triglycerides Containing Oxygenated Fatty Acid Acyl Groups (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 152-160 
    Details
    ISSN: 0935-6304
    Keywords: Epoxytriacylglycerols ; high temperature gas chromatography ; hydroxytriacylglycerols ; ketotriacylglycerols ; lipids ; negative chemical ionization mass spectrometry ; SOP-50 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Five seed oils consisting of unusual triacylglycerols have been examined by high temperature gas chromatography using glass capillary columns coated with the stationary phase SOP-50 (50%-diphenyl-50%-dimethylpolysiloxane, methoxy-terminated). The investigated hydroxy, epoxy, and ketokonjuene triacylglycerols were first derivatized in order to permit analysis by high temperature gas chromatography. Structural elucidation of the intact triacylglycerols was performed with high temperature gas chromatography/negative chemical ionization-mass spectrometry using NH3 as a reagent gas. Individual derivatized lipid species with a molecular weight up to 1176 g/mol could be identified.
    Additional Material: 10 Ill.
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  • 58
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    Capillary Electrochromatography as a Method Development Tool for the Liquid Chromatographic Separation of DUP 654 and Related Substances (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 161-168 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography ; optimization ; mixture design ; DUP 654 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Capillary Electrochromatography (CEC) offers a rapid, economical, and efficient means for resolving nonionic compounds in the reversed phase mode on octadecylsilane (ODS) columns. A CEC optimization on a Hypersil ODS capillary column was employed to identify a suitable mobile phase for the pressure-driven (reversed phase ODS) separation of the anti-inflammatory 2-phenylmethyl-1-naphthol (DUP 654), and its related substances. The proportions of mobile phase modifiers methanol, acetonitrile, and water as well as pH were employed as variables in a stacked mixture design. Comparable response surface profiles were obtained for the CEC separations at pH 4 and pH 8. However, subtle differences were evident in the quality of separations obtained in the liquid chromatographic (LC) mode when using a specially-prepared column packed with exactly the same stationary phase as used in the CEC experiments. A mapping of the response surface for separations on a commercially available Hypersil ODS LC column revealed obvious differences. The differences indicate that the transfer of ODS based separation methods between CEC and LC involves more than simply transferring the conditions from one mode to the other.
    Additional Material: 7 Ill.
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  • 59
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    Stereoisomeric Flavor Compounds LXXXI: Dill Ether and Its cis-Stereoisomers: Synthesis and Enantioselective Analysis (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 185-188 
    Details
    ISSN: 0935-6304
    Keywords: Dill ether ; stereoselective synthesis ; dill ether stereoisomers ; enantioselective GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 60
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    Liquid Chromatographic Resolution of Pyrethroic Acids and Their Esters on Chiral Stationary Phases (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 189-192 
    Details
    ISSN: 0935-6304
    Keywords: Chiral stationary phases ; pyrethroic acids ; enantiomer separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 6 Ill.
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  • 61
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    Investigation into the Effects of Sample Dissolving Solvents and Sample Matrices on the Separation Obtained in Capillary Electrophoresis. Part 1: FSCE (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 193-196 
    Details
    ISSN: 0935-6304
    Keywords: capillary electrophoresis ; dissolving solvent selection ; optimization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 62
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    Off-Line SFE-MEKC Determination of Diuron in Sugar Cane and Orange Samples (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 519-522 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical Fluid Extraction (SFE) ; Micellar Eletrokinetic Capillary Chromatography (MEKC) ; Diuron ; sugar cane ; orange ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 63
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    HPLC Separation of the Major Constituents of Gardeniae Fructus (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 523-526 
    Details
    ISSN: 0935-6304
    Keywords: High-performance liquid chromatography ; gardenia constituent separation ; genipin gentiobioside ; geniposide ; crocin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 64
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    Effects of Permeation of Helium through the Walls of Fused Silica Capillary GC Columns (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 531-539 
    Details
    ISSN: 0935-6304
    Keywords: gas chromatography ; carrier gas flow ; loss modified Poiseuille flow ; hold-up times ; peak widths ; velocity profiles ; permeability of helium through fused silica ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Hold-up times and peak widths have been measured in long fused silica GC capillary columns at high temperature with helium as the carrier gas. The results lead to the conclusion that the helium permeates through the column walls. The conventional Poiseuille theory of carrier gas flow has been extended to include this phenomenon. The resulting “loss modified Poiseuille” model, which uses literature values for the permeability of fused silica to helium, has been used to simulate the observed behavior. Good agreement between simulation and experiment validates the model. Simulations have been used to explore the effect of column permeability on hold-up times, peak widths, and velocity profiles over a broad range of column geometries.
    Additional Material: 5 Ill.
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  • 65
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    Capillary Electrophoresis Coupled On-Line with Nitrogen-Selective Thermionic Detection Using an Eluent-Jet Interface (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 540-544 
    Details
    ISSN: 0935-6304
    Keywords: capillary electrophoresis ; thermionic detector ; nitrogen-selective detection ; eluent-jet interface ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The on-line coupling of capillary electrophoresis (CE) with a thermionic detector (TID) originally developed for gas chromatography (GC) is reported for the first time. An eluent-jet interface previously used to combine micro-liquid chromatography and mass spectrometry can now be used to couple CE and TID. Preliminary results demonstrate the possibility of performing direct nitrogen-selective detection, even for less volatile compounds. Detection limits of 4-12 pg N/s were obtained for the four tested compounds piperidine, dimethylformamide, tetra-n-butylammonium hydroxide, and nicotinic acid. Optimization of both the TID and the eluent-jet interface can be performed independently; optimum TID parameters agree rather closely with the detector specifications under GC conditions. The nitrogen-selective TID proved to be linear over more than three orders of magnitude with acceptable repeatability. The on-line coupling of CE and TID may well become an interesting approach for the rapid and direct analysis of ionic and high-molecular-mass N-containing compounds.
    Additional Material: 4 Ill.
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  • 66
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    Analysis of the Triglycerides and the Free and Derivatized Fatty Acids in Fish Oil by Capillary Electrochromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 545-548 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography (CEC) ; fish oil ; triglycerides ; free fatty acids (FFAs) ; fatty acid methyl esters (FAMEs) ; fatty acid phenacyl esters (FAPEs) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Capillary ElectroChromatography (CEC) on a fused silica capillary column (40 cm L × 100 μm i.d.) packed with 3 μm octadecylsilica (ODS) was evaluated for the analysis of the triglycerides and their fatty acids in fish oils, and more especially in the oil of Moroccan Sardinia pilchardus. The very high complexity of the lipids in fish oil is well illustrated by CEC with a nonaqueous mobile phase consisting of acetonitrile/isopropanol/n-hexane in the ratio 57/38/5 to which 50 mM ammonium acetate has been added. In order to unravel the complexity, the oil was hydrolyzed and the free fatty acids (FFAs), the methyl esters (FAMEs), and the phenacyl esters (FAPEs) were analyzed by CEC on the same column used for the analysis of the triglycerides. Isocratic elution was achieved with the mobile phase acetonitrile/50 mM MES pH 6 in ratio 9/1. The migration characteristics of FFAs, FAMEs, and FAPEs are compared. The analysis of FAPE derivatives has the advantage that quantification applying UV detection is possible and moreover that the number of double bonds in the fatty acid chains can be elucidated by measuring the UV abundance ratio 240/210 nm.
    Additional Material: 5 Ill.
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  • 67
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    Enantiomeric Separation of Underivatized Aliphatic β-Amino Alcohols by Ligand-exchange Chromatography using N-n-Dodecyl-(1R,2S)-norephedrine as a Coating Reagent for Reversed-phase Column (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 561-564 
    Details
    ISSN: 0935-6304
    Keywords: Ligand-exchange chromatography ; dodecyl-norephedrine ; enantiomeric separation ; amino alcohol ; coating ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Underivatized aliphatic β-amino alcohols with a primary or secondary alcohol moiety were separated into enantiomers by high performance liquid chromatography using octadecylsilanized silica coated with N-n-dodecyl-(1R,2S)-norephedrine as the stationary phase and an aqueous solution containing copper(II) and barbital as the mobile phase.
    Additional Material: 5 Ill.
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    Partially Methylated β-Cyclodextrin Analysis: A Systematic Approach to Appropriate RP Column Selection (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 554-560 
    Details
    ISSN: 0935-6304
    Keywords: LC stationary phases ; octadecyl and octylsilica characterization ; cyclodextrins ; partially methylated cyclodextrins ; heptakis(2,6-di-O-methyl)-β-CD ; evaporative light scattering detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In order to establish guidelines to help the analyst in the choice of the most suitable octadecyl or octyl bonded phase for the LC analysis of a given partially methylated β-CD sample, analyses of four commercially available dimethyl-β-cyclodextrins (DM-β-CDs) have been carried out on nine octyl (C8) or octadecyl (C18) silica bonded or polymeric bonded phases which differ significantly in their hydrophilic and hydrophobic properties. Chromatograms show that the nature of the packing materials has considerable influence on the resolution of complex mixtures composed of closely related compounds such as partially methylated β-CDs. Among various kinds of C8 and C18 bonded phases, silica based and monomeric phases which present both reinforced hydrophobic and polar interactions showed the best performance. Whatever the complexity of the commercial DM-β-CD, the richest chromatographic fingerprints, which best depict the complexity of the mixture, are obtained with Nucleosil 50-5-C8 column. For the simplest mixtures, Nucleosil 50-5-C8 column with acetonitrile-water (34:66) as mobile phase is the most suitable chromatographic system and leads to the best resolution between heptakis (2,6-di-O-methyl)-β-CD and hexakis (2,6-di-O-methyl)-mono(2,3,6-tri-O-methyl)-β-CD (14 OCH3 and 15 OCH3). This chromatographic system might enable an LC-MS coupling for direct identification of the different components in the mixture as well as control of batch to batch variations.
    Additional Material: 5 Ill.
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  • 69
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    HPLC-FID with Superheated Water as the Eluent: Improved Methods and Instrumentation (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 613-616 
    Details
    ISSN: 0935-6304
    Keywords: Micro LC ; FID detection ; superheated water ; alcohols ; aldehydes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In the current study, an HPLC-FID system using superheated water as the eluent is constructed and further improved. Signal stability during temperature programmed operation was improved by using separate thermostatting of the 50 μm capillary restrictor. Operating the restrictor at 75°C prevented the superheated water from sputtering in the restrictor. Conventional octadecyl-modified silica, thermostable polymeric reversed phase and carbon type HPLC columns were used. The feasibility of the system is demonstrated by the analysis of a variety of compounds such as alcohols and aldehydes. It is shown that increased temperatures decrease elution times and, in addition to this, frequently improve peak shapes and column efficiencies. The separation of lower aldehydes is performed at 175°C with a detection limit in the low μg/ml range. The possibility of temperature programming is demonstrated for the separation of a range of alcohols. Furthermore, it is shown that temperature programming can be used for sample enrichment. Large volume injection with low temperature enrichment resulted in good peak shapes and a significant improvement of the detection limit. In this way, detection limits of 0.2 μg/ml (ppm) could be obtained for the aldehydes studied. Finally, the possibilities of using mobile phase additives as, e.g., buffers were briefly examined.
    Additional Material: 5 Ill.
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  • 70
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    Electronic Resource
    Comprehensive Two-Dimensional Gas Chromatography Using a Modulating Cryogenic Trap (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 620-622 
    Details
    ISSN: 0935-6304
    Keywords: Multidimensional gas chromatography ; comprehensive two-dimensional gas chromatography ; kerosene analysis ; cryogenic modulation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 71
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    Evaluation of a Semi-Automated Multidimensional Gas Chromatography-Infrared-Mass Spectrometry System for Irritant Analysis (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 347-354 
    Details
    ISSN: 0935-6304
    Keywords: Fragrances ; chirality evaluation ; semi-automated multidimensional gas chromatography ; infrared spectrometry ; mass spectrometry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The use of a semi-automated, multidimensional gas chromatography (MDGC) Fourier transform infrared (FT-IR) mass spectrometry (MS) system in the determination of components causing contact dermatitis has been investigated. Fragrances are widely used in cosmetic and household products and are the leading cause of contact dermatitis. Such products contain numerous components such as emulsifiers, thickeners, solubilizers, pigments, antioxidants, and many other compounds, which can make it difficult to isolate the compound of interest. MDGC has the capability for component analysis in such complex matrices. A semi-automated MDGC system, which consists of a commercial instrument modified in our laboratory to include two computer controlled valves and a single trap which is manually controlled was evaluated for analysis of irritants in a total of thirteen soaps. Using heartcutting techniques, components causing dermatitis were identified in eight of the thirteen soaps by examining both the infrared and mass spectra obtained and matching them with computer spectral libraries. Results from these analyses show that a baby soap and three other mild soaps were free of irritants. Irritants were identified in the remaining eight soaps. In addition, to demonstrate the versatility of the semi-automated system, the enantiomeric composition of a chiral irritant in two soaps also was determined.
    Additional Material: 8 Ill.
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  • 72
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    Nitrous Oxide as Carrier Gas in Capillary Gas-Liquid Chromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 407-410 
    Details
    ISSN: 0935-6304
    Keywords: Capillary GLC ; nitrous oxide as carrier gas ; carrier gas correlation of retention factors ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---On use of nitrous oxide as carrier gas the retention factors of the chromatographed compounds decrease linearly with increasing average column pressure. Other retention characteristics (relative retention, retention index) change linearly. This effect was demonstrated by using a capillary column coated with nonpolar polydimethylsiloxane phase SE-30. As shown for capillary GLC the linear correlation is valid for the same column:ki(G1,P1) = A ki(G2, P2) + B, where ki(G1, P1) and ki(G2,P2) are the retention factors of compound i at average column pressures P1 and P2 when using carrier gases G1 and G2, respectively; A and B are coefficients.
    Additional Material: 2 Ill.
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  • 73
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    Electronic Resource
    Chiral Resolution of RR, SS-Hydrobenzoin by Liquid Chromatography Using Borate-Cyclodextrin Complexation (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 414-416 
    Details
    ISSN: 0935-6304
    Keywords: chiral separation ; HPLC ; diols ; borate complexation ; cyclodextrin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 74
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    Gas Chromatography of Esters of Dihydrotestosterone and Dihydroepitestosterone (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 417-420 
    Details
    ISSN: 0935-6304
    Keywords: capillary gas chromatography ; dihydrotestosterone esters ; dihydroepitestosterone esters ; Kováts retention indices ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 75
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    Study of the Effect of Mobile Phase Additives on Retention in Reversed Phase HPLC Using Linear Solvation Energy Relationships (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 427-434 
    Details
    ISSN: 0935-6304
    Keywords: Linear solvation energy relationship ; retention ; mobile phase ; stationary phase ; additives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Linear solvation energy relationships (LSERs) were used to delineate which specific intermolecular interactions are responsible for changes in retention for a variety of well characterized analytes when acidic and basic additives were used in reversed phase HPLC. The effects of trifluoroacetic acid, triethylamine and a combination of trifluoroacetic acid and triethylamine on the LSERs were compared to those observed in the absence of additives. These effects were examined using four different mobile phase modifiers and five different stationary phases. Trifluoroacetic acid alone and in combination with triethylamine produced LSER regression coefficients nearly identical to those obtained with no additive present in the mobile phase. Triethylamine alone produced different LSER regression coefficients from the other systems unless the mobile phase contained trifluoroethanol as the mobile phase modifier, or the stationary phase consisted of a polymeric support.
    Additional Material: 3 Ill.
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  • 76
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    2,3-Di-O-pentyl-6-O-tert-butyldimethylsilyl-β-cyclodextrin as a Chiral Stationary Phase in Capillary Gas Chromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 225-233 
    Details
    ISSN: 0935-6304
    Keywords: Chiral GC ; chiral stationary phase ; cyclodextrin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---2,3-Di-O-pentyl-6-O-tert-butyldimethylsilyl-β-cyclodextrin has been evaluated as an enantioselective stationary phase for capillary gas chromatography. Experimental results show a good enantioselectivity towards compounds with different functional groups (haloalkanes, alcohols, esters, terpenoids, amino acid derivatives, and heterocycles). Column stability improves mixing the chiral phase with polysiloxane SE-54 (1 : 1).
    Additional Material: 2 Ill.
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  • 77
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    Electronic Resource
    Roles of Organic Modifiers in Micellar Electrokinetic Capillary Chromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 234-240 
    Details
    ISSN: 0935-6304
    Keywords: Micellar electrokinetic capillary chromatography ; electroosmotic migration ; electrophoretic migration of micelle ; retention mechanism ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In the present work, four organic modifiers, viz. urea, dioxane, methanol, and tetrahydrofuran, were comparatively and systematically studied in terms of their effects on electrokinetic migration behavior and the retention mechanism of homologous solutes in MECC. The results showed that the electroosmotic mobility, μeo, and the electrophoretic mobility of a micelle, μep,mc, decrease linearly with increasing organic modifier concentration. The ability of organic modifiers to lower μeo is greater than their ability to lower μep,mc. The negative values of the slopes of these linear relationships, Deo and Dep,mc, increase along the series the order urea 〈 methanol 〈 dioxane 〈 tetrahydrofuran. The logarithm of the capacity factor (ln k′) of uncharged homologous solute, which is mainly determined by the hydrophobic interaction, decreases linearly with increasing organic modifier concentration, due not only to the decrease in the partition coefficient but also to the decrease in the phase ratio. A linear relationship was observed between the slope of the plot of ln k′ vs. organic modifier concentration and the carbon number of homologous compound. The slope of such a relationship can characterize the hydrophobicity of the organic modifier. The hydrophobicity of such organic modifiers is also found to increase along the series urea 〈 methanol 〈 dioxane 〈 tetrahydrofuran.
    Additional Material: 7 Ill.
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  • 78
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    Comparison of Programmable versus Single Wavelength Fluorescence for the Detection of Three Fluoroquinolone Antibacterials Isolated from Fortified Chicken Liver Using Coupled On Line Microdialysis and HPLC (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 241-244 
    Details
    ISSN: 0935-6304
    Keywords: Fluoroquinolone ; ASTED ; HPLC fluorescence ; sarafloxacin ; flumequine ; oxolinic acid ; chicken liver ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A recently introduced programmable fluorescence detector was compared with a single wavelength fluorescence detector for quantification of fluoroquinolone (FQ) antibacterial agents, which have widely varying spectral characteristics. The two detectors were connected in parallel to an HPLC system to test their performance characteristics. With single wavelength detection, two FQs, flumequine and oxolinic acid could be detected at an emission wavelength of 368 nm in a single chromatogram while a third FQ, sarafloxacin, was not observed at that wavelength. Similarly, when the detector was optimized for sarafloxacin emission at 440 nm, the other two compounds were undetected. In contrast, all three FQs were quantified at their individual maxima in a single run using the programmable fluorescence detection. The applicability of an HPLC - programmable fluorescence detector, in combination with on-line microdialysis, also was evaluated using chicken liver fortified at low ppb levels with the three FQs. After on-line microdialysis sample clean up, the resultant HPLC chromatograms were free of background interference enabling the programmable detector to optimize the quantitation of the three analytes in a single run. The limit of quantification (LOQ) determined for each FQ was 1.0 ppb and the limit of detection (LOD) was 0.2 ppb, an order lower in magnitude than was obtainable with single wavelength detection.
    Additional Material: 3 Ill.
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  • 79
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    Off-Line LC-LC Determination of PAHs in Edible Oils and Lipidic Extracts (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 253-257 
    Details
    ISSN: 0935-6304
    Keywords: Edible oils ; lipids in foods ; HPLC ; Polycyclic Aromatic Hydrocarbons (PAHs) ; off line LC-LC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 80
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    Prevention of Vapor Overflow in Splitless Injection by a Novel Injector Design (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 258-262 
    Details
    ISSN: 0935-6304
    Keywords: capillary gas chromatography ; splitless injection ; large sample volume ; injector design ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 81
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    Statistical Analysis of Liquid Trapping Efficiencies of Fat-Soluble Vitamins Following Supercritical Fluid Extraction (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 245-251 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction (SFE) ; liquid trapping ; fat-soluble vitamins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A series of four complete factorial experiments were performed to determine the major parameters affecting the trapping efficiencies of fat-soluble vitamins after supercritical fluid extraction. The parameters varied were the collection solvent, extraction flow rate, collection temperature, restrictor temperature, and collection pressurization. The identity of the collection solvent was found to have the most profound effect. The viscosity and surface tension of the collection solvent appeared to have great significance.
    Additional Material: 3 Ill.
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  • 82
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    Electronic Resource
    Survey and Trends in the Preparation of Chemically Bonded Silica Phases for Liquid Chromatographic Analysis (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 267-281 
    Details
    ISSN: 0935-6304
    Keywords: Chemically bonded phases, CBPs ; liquid chromatography, HPLC ; preparation; surface characterization ; column evaluation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In order to increase chromatographic selectivity and to extend the analytical capability of reversed phase liquid chromatography (RP HPLC) many investigators have concentrated on the preparation of silica based column packings with chemically bonded phases (CBP). These phases have also been successfully used in sample preparation techniques, mainly in solid phase extraction (SPE). Although alkyl bonded phases (e.g., C2, C8, and C18) are the most widely used packings in RP HPLC and SPE, various specific applications require CBPs with polar functional groups (e.g., -NH2, -NO2, -CN, and/or -OH). The solution of problems with separation of complicated chiral compounds was attempted by applying stationary phases with chiral selectors (e.g., cyclodextrins, Pirkle phases, crown ethers, etc.). On the other hand, packings with pseudo-membrane or liquid crystal properties have been utilized for the separation of various substances of natural origin. Porous silica is commonly used as a support in the preparation of CBPs. Its physico-chemical characteristics, such as: type and structure of siliceous matrix, porosity, type and concentration of silanol groups, as well as surface purity, strongly influence the density and structure of chemically bonded phases. Recognition of these properties is helpful in optimizing separation processes based on RP HPLC elution and/or extraction of substances with polar character.
    Additional Material: 12 Ill.
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  • 83
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    Electronic Resource
    Capillary Gas Chromatography Coupled with Microplasma Mass Spectrometry - Improved Ion Source Design Compatible with Bench-Top Mass Spectrometric Instrumentation (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 282-286 
    Details
    ISSN: 0935-6304
    Keywords: capillary gas chromatography ; microplasma mass spectrometry ; radio frequency plasma ; element-selective detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Capillary gas chromatography was performed with mass spectrometric detection using a novel microplasma ion source for operation in an element-selective mode. The ion source was a 350 kHz radio frequency helium plasma, which was sustained inside the 4 cm end of a 0.32 mm i.d. fused silica capillary column, and located inside the high vacuum chamber of the quadrupole mass spectrometer. Due to the low volume of the ion source, a stable low pressure discharge was produced utilizing only the 2.25 mL min-1 of GC carrier gas (helium) for plasma support. Small amounts of oxygen (0.1-0.2% v/v) were added to the plasma gas in order to prevent carbon deposits and to enhance signal-to-noise ratios. Chlorine and bromine were selectively detected at the 5-20 pg s-1 level (S/N = 2), and both produced a response that was linear within 3 orders of magnitude.
    Additional Material: 3 Ill.
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  • 84
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    Electronic Resource
    Determination of Thermal Decomposition Products from a Phenolic Urethane Resin by Pyrolysis-Gas Chromatography-Mass Spectrometry (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 128-132 
    Details
    ISSN: 0935-6304
    Keywords: Pyrolysis ; GC/MS ; phenolic urethane resin ; thermal decomposition ; metal casting ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 85
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    Multidimensional Gas Chromatography Coupled On-Line with Isotope Ratio Mass Spectrometry (MDGC-IRMS): Progress in the Analytical Authentication of Genuine Flavor Components (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 145-151 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective multidimensional capillary gas chromatography (enantio-MDGC) ; stable isotope ratio mass spectrometry (IRMS) ; multidimensional gas chromatography coupled on-line with isotope ratio mass spectrometry (MDGC-IRMS) ; calibration; isotope discrimination ; authenticity control ; authentication of genuine flavor components ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Multidimensional gas chromatography coupled on-line with isotope ratio mass spectrometry (MDGC-IRMS) is presented as a powerful method for origin-specific analysis. Scope and limitations of this sophisticated coupling technique are discussed with regard to accuracy and precision.
    Additional Material: 6 Ill.
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  • 86
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    Determination of Urinary Pentachlorophenol by SPME and GC/MS (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 137-139 
    Details
    ISSN: 0935-6304
    Keywords: Pentachlorophenol ; urine ; microextraction ; SPME ; GC/MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 87
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    Improvement of Signal-to-Noise Ratio of Electropherograms and Analysis Reproducibility with Digital Signal Processing and Multiple Injections (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 169-174 
    Details
    ISSN: 0935-6304
    Keywords: CZE ; detection limit ; signal-to-noise ratio ; correlation chromatography ; reproducibility ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Poor signal-to-noise ratios and analytical reproducibility in capillary electrophoresis were improved by application of multiple injections of the same sample at (pseudo) randomly chosen time moments. One order of signal-to-noise ratio improvement was achieved in practice using an in-house developed computer-controlled pneumatic sampler. However, it is demonstrated here that better implementation of the capabilities of multiple input requires that the detector signal noise be “pre-whitened”, i.e. spikes, baseline drift, oscillations etc. must be removed from the detector signal before transforming it to the electropherogram in the common form. Such filtering of the detector signal was realized by implementing iterative, menu-driven software written in Matlab, a high-level programming language.
    Additional Material: 5 Ill.
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  • 88
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    Sub-ppt Atmospheric Measurements Using PTV-GC-FID and Real-Time Digital Signal Processing (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 181-184 
    Details
    ISSN: 0935-6304
    Keywords: Trace analysis, atmospheric ; digital signal processing ; signal to noise reduction ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 89
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    Trapping Efficiencies of Various Adsorbents in Supercritical Fluid Extraction with Modified Carbon Dioxide (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 175-180 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical Fluid Extraction (SFE) ; supercritical fluid chromatography ; solid trapping ; solvent trapping ; polymeric phase ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---One way of collecting extracted analytes after a supercritical fluid extraction (SFE) is to pass the depressurized fluid through a trap composed of a solid adsorbent. The influence of the adsorbent nature on the trap efficiency has been studied. First, the retention factors of each compound of a polarity test mix (tetracosane, naphthalene, fluoranthene, acetophenone, N,N-dimethylaniline, 2-naphthol, decanoic acid) have been determined on five high specific area (greater than 800 m2/g) polymeric phases by supercritical fluid chromatography (SFC). The comparison of this values with those obtained on octadecyl silica (ODS) showed that polymeric phases have the greatest retention power. After that, the efficiency of a solid trap filled with the greatest retention power polymeric adsorbent was evaluated by using pure carbon dioxide and 2.5%, 5%, 10%, and 20% methanol-modified carbon dioxide. As expected, this trap permitted a quantitative collection of all the former compounds even when a content as high as 10% of methanol was implemented. A solid trap filled with ODS adsorbent allowed quantitative collection of all the compounds only at a methanol content lower than 2.5%.
    Additional Material: 7 Ill.
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  • 90
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    Studies on the Aroma of Piñuela Fruit Pulp (Bromelia plumieri): Free and Bound Volatile Composition and Characterization of Some Glucoconjugates as Aroma Precursors (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 577-581 
    Details
    ISSN: 0935-6304
    Keywords: Volatiles ; Bromeliaceae ; Bromelia plumieri ; glycosidically bound volatiles ; aroma precursors ; glucoconjugates ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 91
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    Reciprocally Unambiguous Conformity Between GC Retention Indices and Boiling Points within Two- and Multidimensional Taxonomic Groups of Organic Compounds (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 565-568 
    Details
    ISSN: 0935-6304
    Keywords: capillary gas chromatography ; precalculation of retention indices ; boiling points ; two- and multidimensional taxonomic groups of organic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---It was shown that reciprocally unambiguous conformity between GC retention indices (at least for the commonly used standard nonpolar polydimethylsiloxane liquid phases) and boiling points of organic compounds is typical not only within one-dimensional taxonomic groups (homologous series and/or groups of congeners), but also within two- and multidimensional taxonomic groups (with simultaneous variations of some structural fragments). In all cases, this conformity is described by three-parameter non-linear equations log RI = a log Tb + b (n1 + Σ ki ni) + c, where n1 is the serial number of homologue within corresponding series and ni is the number of other structural fragments in the molecules. The coefficients ki in this equation reflect the relative alterations of molecular polarizabilities and may be estimated as ratios of refractions ki = RD(X)/RD(CH2), where X are variable structural fragments within a group of congeners, RD(CH2) = 4.647 cm3mol-1. The approach under discussion permits precalculation of the retention indices of any organic compounds with known boiling points. The precision of proposed method of RI precalculation is comparable with the contemporary level of interlaboratory reproducibility of experimental RI determination with standard nonpolar liquid phases (5-10 i.u.).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 92
    Electronic Resource
    Electronic Resource
    Fast Capillary Gas Chromatography: Comparison of Different Approaches (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 583-586 
    Details
    ISSN: 0935-6304
    Keywords: Fast gas chromatography ; narrow-bore columns ; flash-2D-GC ; dedicated fast GC instrumentation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Savings in analysis time in capillary GC have always been an important issue for chromatographers since the introduction of capillary columns by Golay in 1958. In laboratories where gas chromatographic techniques are routinely applied as an analytical technique, every reduction of analysis time, without significant loss of resolution, can be translated into a higher sample throughput and hence reduce the laboratory operating costs. In this contribution, three different approaches for obtaining fast GC separations are investigated. First, a narrow-bore column is used under conventional GC operating conditions. Secondly, the same narrow-bore column is used under typical fast GC conditions. Here, a high oven temperature programming rate is used. The third approach uses a recent new development in GC instrumentation: Flash-2D-GC. Here the column is placed inside a metal tube, which is resistively heated. With this system, a temperature programming rate of 100°/s is possible. The results obtained with each of these three approaches are compared with results obtained on a column with conventional dimensions. This comparison takes retention times as well as plate numbers and resolution into consideration.
    Additional Material: 4 Ill.
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  • 93
    Electronic Resource
    Electronic Resource
    GC/MS Analysis of Polymethoxyflavones in Citrus Oils (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 587-591 
    Details
    ISSN: 0935-6304
    Keywords: capillary GC ; polymethoxyflavones ; citrus oil ; GC/MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The cold pressed peel oils of three species of citrus fruit, viz. sweet orange, tangerine, and grapefruit, have been examined for polymethoxyflavones by GC and GC-MS. Four GC column stationary phases were compared and separation of the six predominant orange oil polymethoxyflavones was obtained isothermally at 310°C in under ten minutes, including the resolution of the polymethoxyflavones from β-sitosterol. The nature of the stationary phase and the analysis temperature exercise dramatic effects on the resolution and elution order of the components, DB-35ms providing the best overall separation. A temperature programmed separation is also presented and the polymethoxyflavone composition of all three oils, as determined by GC-MS, is described. This is the first reported GC-MS study of the PMFs of these citrus species. While tangerine oil is as rich in polymethoxyflavones as orange oil, they are less abundant and occur at lower concentrations in grapefruit oil. Hydroxy-polymethoxyflavones were identified by GC-MS in tangerine oil. One hydroxy-pentamethoxyflavone, M+ = 388, identified in tangerine was also present at low levels in both orange and grapefruit oils. These results are compared with previous studies utilizing HPLC and GC.
    Additional Material: 6 Ill.
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  • 94
    Electronic Resource
    Electronic Resource
    Determination of Non-Ionic Surfactants of the Alcohol Polyethoxylate Type by Means of High Temperature Gas Chromatography and Atomic Emission Detection (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 597-604 
    Details
    ISSN: 0935-6304
    Keywords: high temperature gas chromatography ; atomic emission detection ; microwave induced plasma ; compound independent calibration ; non-ionic surfactants ; alcohol ethoxylates ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---High temperature gas chromatography (HT-GC) coupled to atomic emission detection (AED) has been applied for the determination of alkyl chain distribution, mole average degree of ethoxylation and weight percent distribution of the corresponding homologues of alcohol ethoxylates without all the actual homologues being available as pure references. Based upon its constant elemental response, the HT-GC-AED system has been evaluated for its applicability to compound independent calibration within the homologous series of the alcohols and alcohol ethoxylates. Discrimination against high molecular weight components by gas chromatography requires conversion to the acetyl or trimethylsilyl derivatives. The latter includes introduction of the hetero atom silicon and thus allows monitoring of the silicon trace. Thus selectivity will be enhanced by excluding detection of compounds which do not react with the derivatization reagent. The method has been validated with the analysis of the technical product Brij 30, consisting of a mixture of alcohol ethoxylates with a vendor-specified mole average degree of ethoxylation of four. The experimental result yields a mole average degree of 4.0 ± 0.1 in the carbon, silicon and oxygen traces.
    Additional Material: 12 Ill.
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  • 95
    Electronic Resource
    Electronic Resource
    Simultaneous Element-Selective Detection of C, F, Cl, Br, and I by Capillary Gas Chromatography Coupled with Microplasma Mass Spectrometry (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 633-639 
    Details
    ISSN: 0935-6304
    Keywords: capillary gas chromatography ; microplasma mass spectrometry ; radio frequency plasma ; element-selective detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Simultaneous element-selective detection of the halogens and carbon was accomplished with capillary gas chromatography coupled with microplasma mass spectrometry. The microplasma ion source was a radio frequency plasma contained inside the last 4-5 cm of the 0.32 mm i.d. fused silica capillary column. The ion source was located inside the high vacuum housing of the MS, and only the GC carrier gas (2.3 mL min-1 of helium) was used for plasma generation. Atomic ions were detected in the positive mode. Detection limits were in the low picogram area, and the selectivity to carbon ranged from 8×102 for fluorine to higher than 104 for the other halogens. By introduction of both hydrogen and oxygen as reagent gases, peak tailing was avoided by suppression of analyte reactions with the silica walls of the ion source. Special attention was given to the fluorine-selective detection due to an interfering background species at m/z 19, assumed to be H3O+ originating from the reagent gases. The background signal was minimized by careful control of the power level.
    Additional Material: 5 Ill.
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  • 96
    Electronic Resource
    Electronic Resource
    Enantiomeric Separations in Capillary Electrophoresis Using 18-Crown-6-tetracarboxylic Acid (18C6H4) as Buffer Additive (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 323-331 
    Details
    ISSN: 0935-6304
    Keywords: Capillary zone electrophoresis ; chiral separations ; chiral crown ethers ; 18-crown-6-tetracarboxylic acid ; synthesis ; applications ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---An overview is presented of the applicability of the crown ether 18-crown-6-tetracarboxylic acid (18C6H4) as buffer additive in capillary electrophoresis (CE) for the separation of enantiomers. The chiral selector 18C6H4 is particularly useful for the separation of racemates having a primary amino function. Unfortunately, the crown ether is no longer commercially available. The synthesis and spectroscopic characterization are therefore described in detail. Moreover, a method is presented for the regeneration of the crown ether after CE application. Some new enantiomeric separations of amino acids i.e. NORLEU, ARG, GLU, m-TYR, and o-TYR are listed and the influence of the pH and temperature of the separation buffer is discussed. An intermediate in the synthetic pathway, namely 18-crown-6-tetracarboxamide, did not exhibit any enantioselectivity in CE.
    Additional Material: 6 Ill.
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  • 97
    Electronic Resource
    Electronic Resource
    On-Line Solid Phase Extraction-Gas Chromatography-Cryotrapping-Infrared Spectrometry for the Trace-Level Determination of Microcontaminants in Aqueous Samples (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 341-346 
    Details
    ISSN: 0935-6304
    Keywords: Large-volume on-column injection ; gas chromatography ; infrared spectrometry ; microcontaminants ; solid-phase extraction ; open-split interface ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A large-volume on-column GC-cryotrapping-IR system was developed for injections of up to 100 μl of organic extracts. Considerable reduction of the solvent-and-water background and enhanced analyte detectability was achieved by using an open-split interface between the GC column and the IR detector and improving the leak-tightness of the system. The system was combined with solid-phase extraction to yield on-line SPE-GC-IR. With this set-up, sample volumes of only 20 ml sufficed to detect, and identify, microcontaminants in tap and surface water at the 0.1-1 μg/L level. Detection limits were on the order of 15 ng/L for tap water when using appropriate functional-group chromatograms. Or, in other words, SPE-GC-IR is a suitable technique for the screening of environmental water samples for functional groups, i.e. classes of compounds, of interest.
    Additional Material: 5 Ill.
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  • 98
    Electronic Resource
    Electronic Resource
    Multiple Peaks in HPLC of Proteins: Bovine Serum Albumin Eluted in a Reversed-Phase System (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 18-24 
    Details
    ISSN: 0935-6304
    Keywords: Reversed-phase HPLC ; capillary electrophoresis ; MALDI-MS ; whey proteins ; multiple peaks ; bovine serum albumin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Elution of a commercial sample of bovine serum albumin (BSA) in a reversed-phase (RP) HPLC system at room temperature gives a distorted peak. If a shallow gradient is used during elution a split peak is observed. The nature of the several parts of this multiple peak is studied using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), size-exclusion chromatography (SEC), amino acid analysis, re-elution in RP-HPLC of collected fractions, capillary electrophoresis (CE), and matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS). This study demonstrates that the split peak of BSA observed in these chromatographic conditions is due to the monomer, dimer and other aggregates existing in the commercial sample of the BSA used. Moreover, it is proved that typical RP-chromatographic conditions do not cause aggregation of BSA.
    Additional Material: 5 Ill.
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  • 99
    Electronic Resource
    Electronic Resource
    Investigation of Structure and Mobility of Silica Bonded Stationary Acridine Phases by Means of Fluorescence and NMR Spectroscopy (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 11-17 
    Details
    ISSN: 0935-6304
    Keywords: Acridine-modified HPLC stationary phases ; ligand mobility ; fluorescence spectroscopy ; time-resolved fluorescence anisotropy ; solid state NMR spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Ligand mobility of silica-based HPLC stationary phases modified by various surface coverages of acridine-9-carboxy(N-aminoethylaminopropyl)amide ligands was investigated by fluorescence spectroscopy, time-resolved fluorescence anisotropy measurements, as well as solid-state 13C-CP/MAS- and 1H-MAS-NMR spectroscopy. Rotational correlation times, τR, of the bound acridine fluorophore obtained from fluorescence anisotropy measurements are significantly longer in the bound phase, than in solution. Also, in time-resolved experiments anisotropies do not decay to zero. These results are interpreted in terms of wobble-in-cone ligand motion. The mobility of the fluorophore in the presence of liquid phase correlates strongly with the solubility of the model compound acridine-9-carboxy-n-butylamide in the same solvent. In the good solvent acetonitrile τR = 3.2 ns is found, whereas in methanol, τR 〉 80 ns is obtained. NMR measurements of the dry phase yield large linewidths, cross polarization constants, TCH, and spin-lattice relaxation times, T1ρH, shifting around the minimum in the correlation time curve. Both fluorescence and NMR data indicate medium to low ligand mobility. No difference in the mobilities of alkyl spacer and aromatic group is observed, probably due to the rigidity of the amide group.
    Additional Material: 6 Ill.
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  • 100
    Electronic Resource
    Electronic Resource
    Enhancement of Signal-to-Noise Ratios in Capillary Gas Chromatography by Using a Longitudinally Modulated Cryogenic System (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 32-38 
    Details
    ISSN: 0935-6304
    Keywords: LMCS ; column bleed ; modulation ; signal enhancement ; capillary GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A Longitudinally Modulated Cryogenic System (LMCS) was evaluated for its use in detection enhancement in capillary gas chromatography. The mechanism for chromatographic re-elution for the LMCS is substantially different to other cryogenic devices. The cooled region of the capillary column in which chromatographic bands may be focused is heated by the surrounding oven temperature either by moving the trap along the column, or by moving the column out of the trap. By continually modulating the LMCS at the detector end of the capillary column, signal-to-noise ratios of routine chromatograms can be readily increased by a factor of ten, thus enhancing chromatographic detection. Base widths of peaks, which are often about 2-3 s or more can be easily reduced to 0.3 s when the LMCS is employed in the detection enhancement mode, thus offering a simple avenue to improved peak height sensitivity in capillary gas chromatography.
    Additional Material: 7 Ill.
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