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  • 1990-1994  (7,646)
  • 1980-1984  (4,446)
  • Analytical Chemistry and Spectroscopy  (11,781)
  • Gas chromatography
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Amino acids 6 (1994), S. 205-211 
    ISSN: 1438-2199
    Keywords: Amino acids ; Amino acid enantiomers ; Chiral analysis ; Chirasil-L-Val ; Gas chromatography ; Mass spectrometry ; Selected ion monitoring ; D-Serine ; D-Alanine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The relative amounts of free D-amino acids (D-AA) in the urine of seven healthy volunteers (age 27 to 49 years) were determined using chiral phase (Chirasil-L-Val) capillary gas chromatography in conjunction with selected ion monitoring mass spectrometry. The absolute amounts of free D-AA were determined by pre-column derivatization of the amino acids witho-phthaldialdehyde andN-isobutyryl-L-cysteine followed by high-performance liquid chromatographic separation and fluorescence detection of the isoindol derivatives formed. The following most abundant D-AA were found (highest and lowest absolute and relative amounts): D-Ser (379.8 — 30.1µMol/L; 56.5 — 19.0%), D-Ala (53.8 — 7.6µMol/L; 19.6 — 5.7%), D-Thr (5.8 — 0.25µMol/L; 3.4 — 1.0%), D-Val (3.7 — 0µMol/L; 4.2 — 0%), and D-Phe (3.5 — 0.35µMol/L; 4.8 — 1.4%).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 38 (1994), S. 22-28 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chiral separation ; Capillary column ; 2,6-Di-O-pentyl-3-O-propionyl-γ-cyclodextrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary 2,6-Di-O-pentyl-3-O-propionyl-γ-cyclodextrin has been synthesized and used for enantiomer separation in capillary gas chromatography. Experimental results showed that the stationary phase has good enantiomer selectivity toward amino acids, amines, alcohols, diols, epoxides, and lactones,etc. 2,6-Di-O-pentyl-3-O-propionyl-γ-cyclodextrin has good thermal stability: the highest recommended temperature isca 170°C.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Pentachlorophenol residues ; Off-flavours ; Wines and corks ; Electrolytic conductivity detector/mass spectrometry ; detectors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic methodology with selective detection is presented for the analysis in wines and corks of pentachlorophenol residues, which are suspected to be the most likely precursors of some off-flavours described in several wine samples. After derivatisation, pentachlorophenol acetate residues were monitored by electrolytic conductivity detection and/or mass spectrometric detection in the selective ion mode at m/z 264 and 266. Recoveries varied from 80 to 96% for wine samples fortified with 5 to 100 μg l−1 and from 83 to 91% for corks (fortified at 25 to 100 μg kg−1). The proposed methodology allowed for a determination limit of μg l−1 for wine and 10 μg kg−1 for corks.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 38 (1994), S. 475-478 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Phenolic acids ; Olive and elm tree tissues ; Soil phenolics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method for the separation of phenolic acids along with shikimic and quinic acids by means of capillary gas chromatography is described and discussed. The method involves the previous derivatization of the acids to trimethylsilyl derivatives and it has been applied to the separation of acids extracted from olive leaves and roots, elm leaves and a soil A horizon. Quite good results were achieved both from qualitative and quantitative points of view. Qualitative differences have been pointed out in the phenolic acid composition of two olive cultivars and between leaves and roots of the same cultivar; also two elm species can be discriminated on the basis of the phenolic acid content.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Porous polymer stationary phase ; Selectivity studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The behaviour of GC columns packed with the copolymer of methacrylic ester of p,p'-dihydroxydiphenylpropane diglicydyl ether and divinylbenzene was studied. Selectivity studies were made for three polymer samples of different molar ratio of monomers. To determine the selectivities of these copolymers retention indices for seven test compounds in comparison to those obtained on Porapak Q are calculated. Additionally, the efficiency of porous polymer purification was studied by a SFE-GC-MS technique.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 38 (1994), S. 595-598 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chiral / enantiomeric separation ; Amphetamine ; Methamphetamine ; Cyclodextrin-derivatized phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Enantiomeric separation of amphetamine and methamphetamine as achiral derivatives on 2,6-di-O-pentyl-3-O-trifluoroacetyl-β-cyclodextrin, 2,6-di-O-pentyl-3-O-trifluoroacetyl-γ-cyclodextrin and 2,6-di-O-pentyl-3-O-propionyl-γ-cyclodextrin stationary phase in capillary gas chromatography is described. Trifluoroacetic anhydride and acetic anhydride were used as derivatizing reagents. Excellent precision was obtained for concentrations down to 0.1% / e.e. On 2,6-di-O-pentyl-3-O-propionyl-γ-cyclodextrin the elution order of R,S-amphetamine was reversed when the derivatizing reagent was changed but could not be reversed on any of the other phase types.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Nitrogen phosphorus detection ; Atrazine and simazine ; Freeze-dried water analysis ; ELISA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The determination of atrazine in freeze-dried water samples containing simazine, 0.6% glycine as stabilizer and other pesticides has been compared using three different techniques: (i) direct rapid-magnetic particlebased ELISA, (ii) dichloromethane liquid-liquid extraction (LLE) and Florisil column clean-up prior to ELISA determination and (iii) LLE, Florisil column clean-up and gas chroamtography with nitrogen phosphorus detection (GC-NPD). The methodology developed in this paper has shown the advantages of the introduction of a clean-up step prior to ELISA determination and its correlation with GC-NPD determinations. Atrazine could be determined at levels between 0.1 to 5 μg l−1 in water smaples using the different methods described in this paper. The crossreactivity problems found in the ELISA test associated with the presence of simazine are also discussed.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 39 (1994), S. 71-73 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Spectinomycin ; Silylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic assay for spectinomycin hydrochloride is described. The method is based on that prescribed by the United States Pharmacopeia (USP XXII). The method involves silylation of spectinomycin hydrochloride; phenazone is used as an internal standard. Spectinomycin and phenazone have adequate stability under the prescribed conditions. The stationary phase is 3% OV-17 on Gaschrom Q 100–120 mesh. The selectivity of the proposed method is better than that of the GLC method described in the USP XXII.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Enantiomer separation ; Permethylated cyclodextrin stationary phases ; Side-chain fluorinated alkylbenzenes ; Thermodynamic data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of racemic side-chain fluorinated alkylbenzenes and bromofluorinated analogues by capillary gas chromatography using permethylated α, β and γ-cyclodextrins dissolved in polysiloxanes of different polarity as stationary phases is described. The influence of the achiral polysiloxane matrices on the separation of enantiomers is discussed in the light of the results obtained with the different phases. For a part of the tested compounds thermodynamic data are determined which describe the interaction of enantiomers with the stationary phase. The mechanism of separation is discussed on this basis and by comparison with data for structurally similar compounds.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Method validation ; Reggedness test ; Residual solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Ruggedness testing is performed on a gas chromatographic method for the quantitative determination of residual solvents in steroids. Eight experimental variables or factors which were expected to influence the quantitative results were selected. These factors were divided into two independent groups, i.e. four factors related to the injection process and four factors related to separation and detection. In order to determine interaction between factors and quadratic effects, a central composite design was selected for the set-up of the experiments. Because in the method an internal standard is used, relative peak area was used as response. A deviation of up to 2.5% per factor for the quantitative results was regarded as acceptable. Other responses studied are related to the system suitability. Observed main, quadratic and interaction effects were translated into rugged intervals of the experimental variables by graphical presentation. It was found that besides main effects significant interaction effects were present, for example between the temperature of the injector and the split-flow. Interaction effects can easily result in the reduction of the rugged intervals by a factor of 2. The calculated rugged intervals were compared with the precision of the instrument or factor settings in order to estimate the ruggedness of the factors. Eventually, the maximum effect of the variation in the instrument settings on the quantitative results regarding the precision of the factor settings was found to be only 2.2%. Overall, the method proved to be rugged for most factors, except for the split-flow of the injector for which the method was only rugged to a limited extent.
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  • 11
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention/structure and retention/temperature ; relationships ; Experimental design ; Enthalpy-entropy compensation ; para-Hydroxy benzoic esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An experimental design has been used to study the effect of column temperature on the gas chromatographic retention of eightpara-hydroxy benzoic esters. A rapid procedure has been developed to reduce the number of experiments compared with traditional methods. Capacity factors were determined and the enthalpy and entropy of transfer from the mobile phase to the stationary phase, ΔHo and ΔSo, respectively, were calculated using the linear Van't Hoff equation (dependence of ln k′ on 1/T). A retention prediction system (RPS) for these compounds in GC was investigated. The molecular connectivity index was used to describe the quantitative structure relationships. Enthalpy — entropy compensation revealed that the mechanism was similar for all the compounds studied.
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  • 12
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Priority pollutants ; EPA methods ; Unleaded gasoline ; Volatile organochlorine compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The complete separation of the sixty volatile organochlorine (VOC) priority pollutants has been achieved by coupling two different liquid-modified adsorption chromatography columns. Two temperature programs were used to obtain the complete separation in a relatively short analysis time. Detection was by FID alone
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 38 (1994), S. 93-97 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention index ; Adsorption effects ; Terpene alcohols ; Fused-silica capillary columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention indices of 6 selected hydroxy compounds (aliphatic and bicyclic alcohols, phenols) were determined on 2 HP-5 fused-silica, capillary columns with different film thicknesses (0.11 μm and 0.33 μm) at 8 different oven temperatures between 80 and 150°C. For some substances the I-T plot was found to show a minimum which cannot be explained by the common retention-index temperature-dependence in gas-liquid chromatography. This result is discussed in terms of adsorption at the liquid-solid interface of the capillary column.
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  • 14
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary Phase and solute polarity ; Molecular structural coefficients ; Retention index ; Takács equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Molecular structural coefficients, Sc, for one hundred solutes have been calculated by means of the Takács equation using retention data obtained with over fifty stationary phases, SP. Employing data of seven SP's (characterized in our laboratories) it was found that the variation of Sc with column temperature was linear for most solutes. With data of n-decane and the ten McReynolds probes on up to fifty SP's of polarity less than RP=72, at 120°C, it was found that the Sc of n-decane and cis-hydrindane decreased slightly with increasing SP polarity, while the Sc of non-alkanes remained constant or increased very little as the SP polarity increased. The points for n-decane fit well to a second order polynomial. Again using a temperature of 120°C, the increments of Sc for solutes belonging to an homologous series were correlated with the polarity of SP's. Reasonably straight lines were obtained for all the chemical functions studied, Sc increasing with increasing SP polarity.
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  • 15
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary phase characterization ; Principal component analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In this study, several new stationary phases were characterized by principal component analysis. Fourteen new stationary phases, including substituted phenyl and oligoethyleneoxide functionalities on polysiloxane polymers, were tested and compared to three well known stationary phases. The main features of these phases were studied using a series of test solutes of varying chemical characteristics representing the data set for principal component analysis. Two principal compounds were found to account for 99.20% of the variance (the first accounted for 94.96% and the second for 4.24%). The data were represented as a two-dimensional map for visual representation of the characteristics of these stationary phases. The first principal component represented a selectivity based on polarity (r2=0.998), while the second showed Lewis acid-base characteristics of the phases. Polarizable and amphoteric characteristics of these phases also became evident using this evaluation method.
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  • 16
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid-liquid extraction ; Supercritical fluid extraction ; Pesticides ; Freeze-dried water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The stability of freeze-dried water samples spiked with eight agrochemicals (atrazine, simazine, linuron, carbaryl, propanil, fenitrothion, parathion and fenamiphos) were examined to evaluate their suitability as candidate reference materials for their determination in water samples. In addition, two different extraction procedures, liquid-liquid and supercritical fluid extraction, were compared for the isolation and trace enrichment of target analytes from freeze-dried water samples. Final analytical determinations were by gas chromatography-nitrogen phosphorus detection and electronic impact mass spectrometry, and by liquid chromatography-diode array detection. The whole methodology developed in this paper permitted the determination of pesticides spiked in water at levels varying from 0.03 to 6.9 μg L−1.
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 38 (1994), S. 624-628 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Ion-trap detection ; Nitriles ; Cerelas ; Perfluoroacylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Bromoxynil and ioxynil have been determined inplants and soil by gas chromatography. These herbicides are extracted from soil samples with methylene chloride at acidic pH. Plant samples are extracted with a basic acqueous solution and extracts purified by solvent partitioning. Herbicide residues are submitted to perfluoroacylation prior to GC separation. These compoiunds are determined by ion-trap detection with single ion monitoring; N-(3-chloro-4 methyl-phenyl_ perfluoropropyl amide is used as internal standard. The detection limit of the method is near 0.001 μg g−1 for the samples studied. The proposed methods are sensitive and reproducible enough to allow determination of these herbicides at residue levels in plants and soil.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 39 (1994), S. 11-14 
    ISSN: 1612-1112
    Keywords: Supercritical fluid extraction (SFE) ; Gas chromatography ; Pesticide residues ; Oxadixyl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This work describes the study of a degradation curve of Oxadixyl in field-treated potato and tomato samples. The residues were extracted using classical and supercritical fluid (SFE) extraction methods and analyzed by HRGC/ECD. The extraction techniques were compared and the results indicate the advantages of using SFE as an alternative method for pesticide analyses in these samples.
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 39 (1994), S. 706-712 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Short chain fatty acids ; Intestinal fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The quantification of short chain fatty acids in their free form, by gas chromatography, is the method of choice provided that the underivatized acids elute with good peak shape and reproducibility. In biological samples not only the highly polar acids themselves but also deposits of nonvolatile sample components may interact with the column or the packing material. As a result, the peak symmetry of the fatty acids and their reproducibility can become increasingly poor. Reduction of the nonvolatile matrix components by filtration of the sample has been examined in order to achieve direct analysis of the short chain fatty acids in intestinal samples by packed column GC. Membrane filter units (0.8 μm) allow a quick and simple filtration of the samples. This pretreatment reduces the peak tailing and the broadening of the peaks. The method, when applied to different intestinal samples, allowed the quantification of short chain fatty acids in hundreds of samples without derivatization. Good results are obtained at sample concentrations higher than 0.2 mmol l−1 for each acid.
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 39 (1994), S. 224-227 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; C1−C4 alkyl tert-butyl ethers ; Retention index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of C1−C4 alkyl tert-butyl ethers with the general formula (CH3)3C−O−R (R-alkyl substituent) on fused-silica capillary columns coated with dimethylsilicone and cyanopropylmethylsilicone stationary phases was investigated. Retention indices were determined at two temperatures in order to understand their chromatographic behaviour. The respective standard deviations were 0.3 and 0.5 i.u.
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  • 21
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Organonitrogen pesticides ; Organophosphorus pesticides ; Apples ; Solvent extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic method employing a capillary column and a selective nitrogen/phosphorus detector (NPD) has been developed for the determination of organophosphorus (OP) and organonitrogen (NP) pesticides in horticultural samples (apples). The separation of sixteen pesticides and the internal standard was performed in thirteen minutes. The analytical characteristics of the method, including linear response ranges, detection limits, and reproducibility, have been studied using a 1∶1 mixture of ethyl acetate and xylene as extraction solvent. The possibility of mutual interference between pesticides has also been studied. A procedure for the quantitative extraction of the sixteen pesticides from apple samples has also been developed; for fifteen of the pesticides recoveries 〉85% were obtained after 90 minutes extraction. The effect of different solvents both on recovery and on the sensitivity of the subsequent chromatography were also investigated. It was found that the sensitivity required must be considered when the solvent for sample treatment is selected.
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  • 22
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 39 (1994), S. 419-426 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Chirasil-Val ; Amino acid enantiomers ; N-Isobutyryl-cysteine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Free D-amino acids (D-AA) were detected as native constituents in juices of vegetables (cultivars of cabbage, tomato, carrot, garlic) and fruits (organes, clementine, grapefruit, lemon, apples, pear, grapes) using gas chromatography (GC) or high-performance liquid chromatography (LC). For investigation by GC, AA enantiomers were converted into theirN(O)-pentafluoropropionyl 2-propyl esters and resolved on a Chirasil-L-Val capillary column. For determination by LC, precolumn derivatization of AA enantiomers usingo-phthaldialdehyde together with the chiral thiolsN-isobutyryl-L-cysteine orN-isobutyryl-D-cysteine and fluorescence detection of the diastereomeric isoindole derivatives, resolvable on an octadecylsilyl stationary phase, were used. D-Ala (0.6–3.8%) was detected in all freshly pressed plant juices usually in the highest relative amounts. Other D-AA detected were D-Asx (0.1–1.9%), D-Glx (0–1.3%), D-Ser (0–1.7%), D-Arg (0.4–1.2%, in grapes, orange, grapefruit, and clementine) and D-Leu and D-Val (1% in cabbage). Absolute amounts of native D-AA were totally 28–57 μmol L−1 in fruit juices, 14.5 μmol L−1 in a tomato juice and 8.5 μmol L−1 in a carrot juice.
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  • 23
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 8 (1994), S. 52-52 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 24
    ISSN: 0269-3879
    Keywords: Rat plasma norepinephrine ; HPLC ; ethylenediamine condensation ; peroxyoxalate chemiluminescence ; blood pressure reduction ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A calcium antagonist, diltiazem, was infused continuously into Sprague-Dawley rats through the left femoral vein at four different flow rates. The mean arterial blood pressure and concentrations of plasma norepinephrine (NE) were measured in each single rat (n = 5) and the correlations between them were studied. Blood (150 μL) was collected 13 times during the infusion. Plasma NE was determined by HPLC-ethylenediamine condensation reaction-peroxyoxalate chemiluminescence detection system (HPLC-ED-PO-CL).In four cases from 5 rats, the blood pressure reduction caused by diltiazem was inversely correlated to logarithm of plasma NE concentration. The relation was expressed as Y = -α logX + m. The coefficients of correlation were -0.9506, -0.9293, -0.9341 and -0.8675, respectively. The correlation for the last rat was worse (r = -0.0799). The good correlation would imply that the sympathetic nervous system released NE to maintain blood pressure up to the normal level, responding to the blood pressure reduction caused by diltiazem.The present experiment proved the feasibility of the determination method of NE utilizing HPLC-ED-PO-CL detection in applying to the individual rats.
    Additional Material: 3 Ill.
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  • 25
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 8 (1994), S. 32-36 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Experimentally defined relationships have been found to describe adequately the retention and separation of bovine and porcine insulins as well as their desamido products on reversed phases C4 30 nm and C18 10 nm pore diameter. The equations are valid for a region of initial acetonitrile concentrations from 16 to 31% and gradient rates from 0.04 to 0.60%/min. The peak heights showed an exact non-linear relationship with the time interval between the first and last peak of interest, independent of their retention time.The number of experiments required for obtaining the parametric estimates of the models depends on the particular task, but in all cases is less than eight.The relationships found permit the correct choice to be made in advance both for analysis conditions for a particular column and for different requirements of insulin analysis.
    Additional Material: 2 Ill.
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  • 26
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 8 (1994) 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 27
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A high-performance liquid chromatographic method for the determination of aspartic acid, glutamic acid, glutamine, glycine, taurine, and γ-aminobutyric acid in brain tissue is described. Amino acids were derivatized with o-phthalaldehyde/N-acetyl-L-cysteine, a fluorescent labelling mixture, in the presence of 0.1 M borate buffer pH 9.5. The derivatization reaction was sensitive to the pH and concentration of borate buffer. A drift in the fluorescent response less than 4% was obtained with the reported conditions after 4 h of reaction. The resolution of the amino acid derivatives was accomplished in a reversed-phase column with a methanol gradient in 50 mM acetate buffer pH 5.5. These conditions also allowed the separation of the major tissue free physiological amino acids. L-Norvaline was used as an internal standard for both peak identification and quantification. Within-day and between-day precision were less than 6.2%, and the accuracy ranged from 99.1 to 104%. The applicability of the method was demonstrated in a study in rats in which the levels of the assayed amino acids in discrete areas of brain were examined.
    Additional Material: 4 Ill.
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  • 28
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An HPLC method using a glassy carbon working detector for measuring cysteine and reduced glutathione (GSH) in biological samples was developed. Oxidized glutathione (GSSG) was also measured after reduction with glutathione reductase. This study was conducted in human plasma. Cysteine and GSH standard curves were linear in the physiological range, presenting detection limits of 22.0 pmol and 6.0 pmol respectively. Plasmatic results found were 43.92 ± 4.15, 4.50 ± 0.65, and 0.19 ± 0.12 mM (means ± SE), for cysteine, GSH and GSSG, respectively. Peak specificity for cysteine and reduced glutathione was certified by their disappearance after treatment with N-ethylmaleimide.
    Additional Material: 2 Ill.
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  • 29
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 8 (1994) 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 30
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 8 (1994), S. 158-164 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An analytical procedure suitable for routine use has been developed and validated for the simultaneous separation and quantification of most of the antidepressant drugs (bicyclic, tricyclic and tetracyclic) and their metabolites in human serum by reversed-phase high performance liquid chromatography with ultraviolet detection. The method has good sensitivity and specificity, without the need for long and complex extraction procedures. The results obtained with three different analytical columns were compared and an improvement in specificity by selection of column and detection wavelength used was achieved.
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  • 31
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A highly sensitive gas chromatographic-mass spectrometric method for the determination of etodolic acid, as methyl ester, in plasma was developed. The feasibility and specificity of the method was ascertained monitoring the concentration levels in plasma samples collected from 12 male healthy volunteers given epicutaneously 5 g of 10% etodolac gel formulation.
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  • 32
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: One of the most important problems for the use of liposomes as a drug delivery system is the modification of the vesicle induced by the liquid medium in which they are introduced (blood plasma for in vivo studies and the saline buffer solution for in vitro studies).Using thin-layer chromatography (TLC) we compared the behaviour of phosphatidylcholine (used for liposomes preparation) to that of the following unfilled liposomes: multilamellar liposomes (MLV); small unilamellar vesicles (SUV); and reverse phase evaporation vesicles (REV), before and after storage for 15 min in Krebs-Henseleit solution (37°C, pH 7.4, aereated continuously with 95% O2 + 5% CO2). All variants contained the same amount of phosphatidylcholine.Thin-layer chromatography was performed on silica gel 60 as adsorbant. Two types of solvents were tested: one based on chloroform/alcohol (n-butanol or n-propanol or methanol)/water mixture (in different ratios) and another based on alcohol/alcohol/water mixture (n-butanol/n-propanol/water in 4/3/3 volume ratio). In all variants of chloroform containing solvents no differences were found between phosphatidylcholine and all types of liposomes.When using as solvent n-butanol/n-propanol/water significant differences were found between all types of liposomes before and after storage in Krebs-Henseleit solution. Their presence, after TLC treatment, was shown in electron microscopy studies.
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  • 33
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    Biomedical Chromatography 8 (1994), S. 202-204 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Capillary electophoresis can be applied to the rapid characterization of tryptic digests of proteins. The addition of phytic acid to the separation buffer was found to improve resolution considerably when the technique was applied to differentiate between tryptic digests derived from variant haemoglobins. Moreover, analysis time was of the order of 15 min, which is considerably shorter than that obtained using gradient reversed-phase high-performance liquid chromatography or two-dimensional paper chromatography-electrophoresis.
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  • 34
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A high-performance liquid chromatographic (HPLC) assay method has been developed for the quantitative determination of iothalamate and p-aminohippuric acid (PAH) concentrations in serum and urine samples in the male rat. Glomerular filtration rate (GFR) was measured as clearance of iothalamate, while effective renal blood flow (ERBF) was measured as clearance of PAH. The method is simple, rapid and sensitive and detects iothalamate and PAH in rat serum and urine following administration of bolus doses and continuous infusions of iothalamate and PAH. Samples of serum and urine were deproteinized with two volumes of acetonitrile containing the internal standard, and an aliquot chromatographed on a C18 reversed-phase column. The mobile phase was comprised of 0.1 M sodium phosphate with 1.2 mM tetrabutylammonium phosphate: methanol, 85:15 (v/v), at a flow rate of 1.0 mL/min. The analytical column eluate was monitored with a UV detector at 254 nm with quantitation achieved using peak-height ratios. The precision of the method was 6.6 and 3.6% for iothalamate in serum and urine, and 5.6 and 4.9% for PAH in serum and urine, respectively. The lower limit of quantitation was 0.63 μg/mL for iothalamate and 1.25 μg/mL for PAH in serum, and 3.1 μg/mL for iothalamate and 1.5 μg/mL for PAH in urine. Recovery of iothalamate from serum and urine was 99.9 and 93.5%, respectively. Recovery of PAH from serum and urine was 99.8 and 92.6%, respectively.The present study demonstrated that non-radioactive iothalamate and PAH can be measured simultaneously using a HPLC assay to measure GFR and ERBF in the male rat.
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  • 35
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    Biomedical Chromatography 8 (1994), S. 175-179 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: This paper describes the use of high-performance capillary electrophoresis (HPCE) for screening of thalassaemias. Preparation of globin was performed by adding 1mL of haemolysate to 20 volumes of cold acidified acetone. Separation of globins was accomplished in a 25 mM disodium phosphate buffer at pH 11.8 using an uncoated capillary column of 50 cm × 75 μm (i.d.). Distinct peaks of alpha, beta and gamma were resolved within 6min. The coefficient of variations for within-day and between-day runs were 4.7% and 6.37% respectively. Using this simple and rapid procedure up to 30 specimens could be analysed in a single day. This method appears to be reliable and can be used for mass screening of various haemoglobinopathies.
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  • 36
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An analytical method has been developed with which to measure the microsomal enzyme activities responsible for oxidative theophylline metabolism. Three metabolites: 3-Methylxanthine (3-MX); 1-methylxanthine (1-MX); 1,3-dimethyluric acid (1,3-DMU), with acetaminophen as an internal standard (IS), were separated by solid phase extraction using a Sep-Pak C18 cartridge, followed by high performance liquid chromatography on a reversed-phase column with isocratic elution using 25 mM acetate buffer containing 4% acetonitrile and 2.5 mM tetra-n-butylammonium hydrogen sulphate (pH 5.25) as the mobile phase. The analytes were clearly resolved and no interference with foreign peaks was observed. A linear relationship was obtained for the metabolites over the concentration range of 0.5-5.0 μg/mL, and their analytical recovery was almost 100%. This method can be used to assess drug interactions involving alterations in the biotransformation of theophylline.
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  • 37
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    Biomedical Chromatography 8 (1994), S. 205-205 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 38
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Fluorescence and chemiluminescence detection were compared for HPLC analysis of the fluorescamine derivative of histamine. The kinetic behaviour of the chemiluminescent response for the derivative was characterized in a static system. An HPLC method was optimized for the derivative using fluorescence detection. Fluorescence detection was linear over the range of 166-1666 pg on column for the fluorescamine-histamine derivative with a limit of detection of 13 pg on column. Using a detector designed for optimal use with chemiluminescence, the chemiluminescence response of the fluorescamine derivative was linear over a range of 1.66-16.6 ng on column with a limit of detection of 1.0 ng on column. These results exemplify a case in which superior detectibility is provided by fluorescence over chemiluminescence, and contradicts many reports comparing fluorescence to chemiluminescence. The authors conclude that chemiluminescence should be considered when indicated by conditions established for separation that are favourable for the observation of chemiluminescence. These conditions include sufficiently low excitation energies corresponding to an excitation maximum greater than 400 nm, favourable dipole character of analytes, mobile phases of high organic content, and an appropriate pH of the mobile phase.
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  • 39
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    Biomedical Chromatography 8 (1994), S. 255-257 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A stereospecific HPLC method was developed for the analysis of (-) and (+) pentazocine in human serum. Each enantiomer and the internal standard nalophine were isolated from serum using a liquid-liquid extraction procedure. Recoveries of 99.05 ± 5.37 and 97.42 ± 2.78% were obtained for (-) and (+) pentazocine, respectively. Resolution of the enantiomers was obtained by using an ovomucoid chiral stationary phase with a mobile phase of methanol: acetonitrile: 10 mM phosphate buffer, pH 5.8 (20:5.3:74.7 v/v/v). A resolution (Rs) value of 1.80 was obtained for the pentazocine enantiomers. Linear calibration curves were obtained in the 10-100 ng/mL range for each enantiomer in serum. The detection limit based on a signal-to-noise ratio of 3 was 5 ng/mL for each enantiomer in serum using fluorescence detection with excitation at 275 nm and emission set at 335 nm. The lowest quantifiable level was found to be 10 ng for each enantiomer. Precision and accuracy of the method were in the 3.8-4.8% and 1.3-4.2% ranges, respectively.
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  • 40
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    Biomedical Chromatography 8 (1994), S. 278-282 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Fluvoxamine, a serotonin re-uptake inhibitor, was quantified in plasma by modifying a previously published procedure for monitoring plasma concentrations of tricyclic antidepressants. Alkalinized plasma samples were extracted with n-hexane/isoamyl alcohol, followed by back-extraction with diluted phosphoric acid, The extracts were analysed by reversed-phase liquid chromatography using a C-18 column, with phosphate/acetonitrile as the mobile phase. The assay was linear from 10 to 800 μg/L. Precision studies showed within-run and day-to-day coefficients of variation to be 4.5 and 6.8%, respectively. Desipramine interfered with the detection of fluvoxamine. The assay was used to measure a total of 8 plasma samples from 4 alcohol-dependent patients medicated with fluvoxamine as an adjunct to relapse prevention psychotherapy. In these patients, the plasma concentrations ranged from 54 to 241 μg/L. Dosage of fluvoxamine, duration of treatment, interval between last dosage and blood collection were associated with effects on plasma concentrations that were consistent with the pharmacokinetic profile of fluvoxamine.
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  • 41
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    Biomedical Chromatography 8 (1994), S. 294-296 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We developed a new HPLC method for the determination of p-aminobenzoic acid (PABA) and its metabolites (p-aminohippuric acid, N-acetyl-p-aminohippuric acid, N-acetyl-p-aminobenzoic acid) in urine. As the internal standard m-hydroxybenzoic acid was used. In the isocratic elution the mobile phase consisted of methanol and 0.02 M. ammonium acetate (20:80 v/v, pH 4.0). The separation was carried out on the C18, reversed-phase column, particle size 5 μm. The separated components were detected at 280 nm. The method can be used in the assessment of the response of pancrease (secretion of digestive enzymes) to soya feeding as well as in the diagnosis of the exocrine pancreatic diseases of animals.
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  • 42
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An isocratic reversed-phase high performance liquid chromatographic method has been developed for the determination of dobutamine in the plasma of dialysed patients. A solid phase extraction method with a Sep-Pak C18 cartridge was used to isolate the drug and isoxsuprine (internal standard) from plasma. The separation was carried out on an ODS-Hypersil column with 0.1 M phosphate buffer: acetonitrile: methanol (72 : 20 : 8 v/v/v) as the mobile phase. The recovery of dobutamine added to plasma by the extraction procedure was 87 ± 2.3% (mean ± SD). The accuracy and reproducibility of the method were within acceptable limits over the concentration range 0-1000 ng/ mL. Quantification was by fluorescence detection at 275 nm excitation and 310 nm emission wavelengths with a detection limit of 5 ng/ mL for dobutamine. This procedure was applied to ascertain the pharamacokinetics of dobutamine infusion in nine patients with cardiogenic shock and end-stage renal disease undergoing haemodialysis.
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  • 43
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    Biomedical Chromatography 8 (1994), S. 313-314 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A high performance liquid chromatographic method for the determination of endogenous formaldehyde in dimedone adduct form in biological samples is described. The simple procedure involves extraction of the formaldehyde of different binding force in biological samples with methanol containing dimedone as the capture molecule and separation on a C18 reversed phase column with methanol as eluent.
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  • 44
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    Biomedical Chromatography 8 (1994), S. 63-68 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An enzyme linked immunosorbent assay (ELISA) was developed to detect the anabolic steroid boldenone in equine blood and urine. The polyclonal antiserum was raised in rabbits, employing boldenone-17-hemisuccinate-bovine serum albumin as antigen. Boldenone-17-hemisuccinate-horseradish peroxidase served as enzyme conjugate. Sensitivity of the assay was 26.0 ± 3.0 pg/well. Among the endogenous steroids tested only progesterone and testosterone exhibited moderate cross-reactivities, 3.4 and 2.5%, respectively. These crossreactivities are of no importance for the boldenone assay. For the reduction of background levels, srceening for boldenone of equine serum was performed after extraction. Urine samples were determined directly after dilution, omitting hydrolysis of boldenone conjugates. Positive screening results were confirmed by means of two independent HPLC systems combined with off-line detection, employing the boldenone ELISA. Methandienone served as internal standard to ascertain retention factors. In horses treated with boldenone-17-undecylenate the presence of boldenone in serum was confirmed up to 28 days and in unhydrolysed urine up to 56 days post applicationem.
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  • 45
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An automated system is described for the simultaneous extraction and derivatization of nucleophilic compounds from various biological media. The method includes the use of a solid-phase reagent containing a 9-fluorenylacetate activated ester. The reagent is based on a controlled pore, polystyrene divinylbenzene support prepared through a silica template procedure. An X-Y-Z robotic arm equipped with a needle is used in conjunction with a syringe pump for aspirating and dispensing samples and standards into the HPLC system. A precolumn cartridge containing the solid-phase reagent is put on-line in place of the fixed-volume injection loop. Injections of biological fluids such as urine or plasma with minimal sample treatment and handling are made directly into this reactor. The analytes are dervatized as they are extracted, allowing virtually unlimited sample volumes to be injected. The polymeric cartridge can be used for up to 100 injections without accruing unacceptable reductions in sensitivity. A detection limit of 500 p.p.t. (parts per trillion) of amphetamine in urine was achieved with this system.
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  • 46
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    Biomedical Chromatography 8 (1994), S. 95-98 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Simple isocratic HPLC separation of a series of thiazolyl steroids with the 17β-2′ linkage is described. The chromatographic and spectral characterization utilizes both on-the-fly UV spectral maxima and absorbances changes.
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  • 47
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    Biomedical Chromatography 8 (1994), S. 105-105 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 48
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A novel electrophilic reagent for alcohols, phenols, amines and thiols, 4-(N-chloroformylmethyl-N-methyl)amino-7-N,N-dimethylaminosulphonyl-2, 1, 3-benzoxadiazole (DBD-COCI) was synthesized. The reactivity of the reagent to these nucleophiles was studied using high-performance liquid chromatography (HPLC) with precolumn derivatization techniques.DBD-COCI reacted in benzene solution at the room temperature or 60°C with androsterone (a representative of hydroxyls), (-)-mandelic and D,L-lactic acid (hydroxy acid), estrone (phenol), benzylamine (primary amine), phenetidine (aromatic amine) and α-mercapto-N,2-naphthylacetamide (thiol) to give fluorescent products bearing fluorescence wavelengths at between 543 nm and 555 nm (excitation at between 437 nm and 445 nm). The base catalyst, quinuclidine was required to complete the reaction with the nucleophiles except aromatic amines. The reaction solution was subjected to a reversed phase HPLC and the detection limits of the derivatives were at the femto mol range on column.
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  • 49
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    Biomedical Chromatography 8 (1994), S. 137-141 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Minute amounts of cerebrospinal fluid samples from alcoholics were subjected to separation by HPLC-molecular sieving, combined with multispectral UV analysis of the acquired data. A significant difference in the protein/polypeptide pattern within the molecular weight range of 7-10 kDa has been observed between samples, taken directly after detoxification and 2 weeks later. Spectral analysis of the results suggests that the components are of peptidergic nature. On the other hand, albumin content did not differ significantly, suggesting that the blood-brain barrier was not affected. An enzyme marker, dynorphin converting enzyme, remained unchanged in both groups.
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  • 50
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    Biomedical Chromatography 8 (1994), S. 151-151 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 51
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    Biomedical Chromatography 8 (1994), S. 196-198 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The separation of Vitamin B complex and folic acid was achieved on silica gel layers impregnated with Mn++, Fe++, Co++, Ni++, Cu++, Cd++, Zn++ or Mg++ (0.1%, 0.2%, 0.3%, 0.4% of each ion). Three new solvent systems n-propanol: n-butanol: water: ammonia (7:5:1:2, by vol), n-propanol: n-butanol: water: ammonia (7:5:1:1.5, by vol), n-propanol: n-butanol: water: ammonia (7:5:0.75:2, by vol) were developed. The spots of vitamins were located by exposing the chromatoplate to iodine vapours.
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  • 52
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    Biomedical Chromatography 8 (1994) 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 53
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    Biomedical Chromatography 8 (1994) 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 54
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    Biomedical Chromatography 8 (1994), S. 267-272 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The interaction between 22 anticancer drugs and carboxymethyl-γ-cyclodextrin (CM-γ-CD) was studied by reversed-phase charge-transfer thin-layer chromatography and the relative strenth of interaction was calculated. CM-γCD formed inclusion complexes with 11 compounds, the complex always being more hydrophilic than the uncomplexed drug. The inclusion forming capacity of drugs differed considerably according to their chemical structure. Both principal component analysis and cluster analysis found a relationship between the inclusion complex forming capacity and hydrophobicity parameters of anticancer drugs. This result suggests that the preponderant role of hydrophobic interactions is in inclusion complex formation.
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  • 55
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    Biomedical Chromatography 8 (1994), S. 259-266 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: With the view of purifying soluble human brain acetylcholinesterse (AChE) into its separate isoforms, various preparative chromatographic procedures were compared. Chromatofocusing of cerebrospinal fluid (CSF) AChE revealed two major activity peaks, whilst that of caudate nucleus AChE showed one major peak, Both CSF and caudate nucleus AChE eluted at isoelectric points (pI) of between 5.5 and 5.2 Chromatofocusing failed to separate AChE into its individual isoforms, based on qualitative isoelectric focusing. Preparative purification by affinity chromatography showed a better AChE yield with the use of procainamide as a ligand, vis-à-vis acridinium. Maximum recovery for CSF and caudate nucleus AChE was 10 and 43% using acridinium and procainamide, respectively. Qualitative analysis by SDS-PAGE of affinity-purified AChE revealed four major bands between 50 and 62kDa, corresponding to the catalytic subunits of AChE as verified by an anti-AChE polyclonal antibody. A size-exclusion column also allowed brain AChE purification, with the latter eluting at a putative molecular mass of 310 kDa. Unfortunately, cation-exchange using the state-of-the-art SMART system failed to separate AChE into its isoforms. AChE aggregation is given as one major obstacle precluding good resolution of isoforms.
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  • 56
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A simple and highly sensitive column-switching high performance liquid chromatographyic method with fluorescence detection for the determination of free phenylacetic acid (PAA) in human plasma and urine is described. The method is based on the direct derivatization of plasma and urine PAA with 6,7-dimethoxy-1-methyl-2(1H)-quinoxalinone-3-propionylcarboxylic acid hydrazide (DMEQ-hydrazide). The derivatization reaction proceeds in aqueous solution in the presence of pyridine and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide at 37°C. The resulting DMEQ derivative of PAA is separated from endogenous interfering substances by a column-switching chromatographic system consisting of a precolumn (YMC-Pack C4) for sample clean-up and an analytical column (L-Column ODS) for the complete separation of the derivative. The derivative is detected fluorimetrically at 445 nm wih excitation at 367 nm. The detection limits (signal to noise ratio = 3) for PAA is 10 fmol in a 10 μL injection volume. The recoveries from plasma and urine are 75 and 96%, respectively. The present method is highly sensitive and simple compared to conventional liquid-liquid extraction procedures. The sensivity allows the direct determination of free PAA in an extremely small amount (5 μL) of plasma and urine.
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  • 57
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: L-thyroxine and D-thyroxine were separated on ligand exchange chiral thin layer chromatographic plates, using a solvent system consisting of acetonitrile:methanol:water 60:15:15 v/v, at a wavelength of 254 nm. The methodology, chiral recognition mechanism (s) involved and its application are discussed.
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  • 58
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    Biomedical Chromatography 8 (1994), S. 236-241 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A multipurpose fluidized-bed receptor-affinity purification system based upon the biological recognition between an immobilized receptor and its soluble protein ligands is described. The fluidized affinity sorbent consists of a soluble form of interleukin-2 receptor chemically bonded to an aldehyde derivative of controlled pore glass beads, which have a pore diameter of 1000 Å and a particle density of 1.2-1.3 g/mL. The fluidized-bed separation device used in this study consists of a specially designed column fitted at the inlet end with a perforated distributor plate covered with a screen and the top outlet with an adjustable piston. The fluidized-bed consisting of a loose gel matrix permits the unimpeded passage of cell debris and particulate matter, while the target protein is captured by the affinity beads. Purification of the humanized-anti-Tac monoclonal antibody is used as a model system to determine the operational parameters. Also, fluidized-bed receptor-affinity chromatography has been successfully employed in the purification of recombinant interleukin-2 and single chain anti-Tac(Fv)-Pseudomonas exotoxin immunotoxin from unclarified inclusion body extracts. Overall, fluidized-bed receptor-affinity chromatography is found to be a productive affinity method suitable for the purification of recombinant human interleukin-2 and related molecules.
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  • 59
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    Biomedical Chromatography 8 (1994), S. 301-305 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: This report describes high performance liquid chromatographic analysis of transplanted pancreatic islets. A reversed phase ODS column made it possible to measure rat insulin I, II, rat C-peptide I, II and glucagon simultaneously in isolated rat islets without using radioisotopes. Freshly isolated islets contained 118.0 ± 9.7 ng (mean ± SE, n = 6) insulin and 3.01 ± 0.60 ng glucagon per islet. The insulin I/II ratio was 1.22 ± 0.03. Isolated islets were then cultured in vitro or transplanted into mice under the renal capsule. Transplantation induced mild hypoglycemia in the recipients. The graft mean survival time was 7.2 ± 0.4 days (n = 5). Both cultured (n = 7) and transplanted (n = 6) islets showed similar alterations of polypepide hormones on day 4. Insulin decreased to one third and glucagon remained unchanged. The insulin I/II ratio increased twofold. In conclusion, it was suggested that the general fate of isolated islets was caused by ischemia and denervation. Relatively, ischemia may not damage α cells but may damage β cells because α cells are peripherally located. Denervation may release β cells from a resting state under neural tonic inhibition. Mild hypoglycemia and an increased insulin I/II ratio were related to the accelerated insulin synthesis in the isolated islets.
    Additional Material: 3 Ill.
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  • 60
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A simple and sensitive assay method for NO synthase activity is described. Using glassy carbon as electrode and 30% methanol solution with 10 mM NH4Cl as mobile phase, NO2- can be measured without disturbing ECD-detectable substance in NO synthase assay mixture. The NO2- production in the assay mixture of rat cerebellum NO synthase increased with protein and in a time-dependent manner. The Km value for the substrate, L-arginine, was 1.25 μM. The enzyme activity was inhibited in a concentration-dependent manner by a NO synthase inhibitor, NNA. The Ki value for NNA was 0.166 ± 0.060 μM. This ECD-HPLC method for determining NO synthase activity has advantages compared with the diazo-coupling method of the Greiss reagent and the isotopic method in which the conversion of the substrate, [14C]L-arginine, to the product, [14C]L-citrulline is measured; it is simple, sensitive and is convenient for studying the NO synthase activity with various compounds as the substrate.
    Additional Material: 5 Ill.
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  • 61
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    Biomedical Chromatography 8 (1994), S. 29-31 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A high performance liquid chromatographic method to measure plasma and urine fenoprofen levels in equine biofluids is described. Liquid-liquid extraction with diethylether was used to isolate the drug from plasma and urine. The accuracy and reproducibility of the method were within acceptable limits over the concentration range 0-10 μg/mL and 0-20 μg/mL respectively from plasma and urine. Detection limits were 0.05 μg/mL (2 mL plasma) and 0.2 μg/mL (0.5 mL urine). This procedure was applied to ascertain the pharmacokinetics of a 3 g dose of fenoprofen calcium in a horse.
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  • 62
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    Biomedical Chromatography 8 (1994) 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 63
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A fully automated in-line extraction reversed-phase high-performance liquid chromatography (HPLC) method with chemiluminescence detection was developed for the analysis of human and rat plasma catecholamines (CAs), norepinephrine (NE), epinephrine (E) and dopamine (DA). N-Methyldopamine (N-MeDA) was used as an internal standard. The method involves collection of plasma samples, which are first diluted with a sample dilution buffer containing N-MeDA, and in-line extraction of CAs using a carboxylic acid small resin precolumn (SERUMOUT-CEX). This pre-extraction process was coupled with an HPLC system including reversed-phase mode separation on an analytical column (TSK gel ODS-80Ts), fluorogenic derivatization with ethylenediamine (ED) and finally postcolumn peroxyoxalate chemiluminescence reaction detection using bis [4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl]oxalate (TDPO) and hydrogen peroxide. The optimized mobile phase compositions, flow rates, operation timing for the adsorption and desorption of CAs in the precolumn, the separation in the analytical column and the optimum fluorogenic and chemiluminogenic reaction conditions were investigated.The detection limit for all the CAs was about 1 fmol (signal-to-noise ratio is 2). Excellent linearity of the calibration curves for CAs was observed in the range from 5 to 500 fmol for each CA using the internal standard. The relative standard deviations of the method for determining NE (183 fmol), E (23.6 fmol) and DA (6.1 fmol) in 50 μL of human plasma (n = 3) were 2.8, 2.7 and 3.1%, respectively, for the within-day assay and 5.0, 3.8 and 4.0%, respectively, for the between-day assay. The method was applicable to the determination of CAs in 25-50 μL of human or rat plasma.
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  • 64
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    Biomedical Chromatography 8 (1994), S. 26-28 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A rapid method for the determination of iopanoic acid (IOP) in dog plasma utilizing a Hisep column was developed. A mobile phase of 12% methanol, 88% 0.05 M phosphate buffer pH 3.4 yielded a k′ of 8.5 with no interference from proteins present in plasma. Recoveries of IOP from spiked plasma ranged from 97% to 103% at 270 μmol/L and 1.75 mmol/L respectively. Replication was ±2.8% at 1.75 mmol/L and ±6% at 21 μmol/L. A method utilizing 2,4,6-triiodobenzoic acid as internal standard was also developed for comparison.
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  • 65
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    Biomedical Chromatography 8 (1994), S. ii 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 66
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    Biomedical Chromatography 8 (1994), S. 142-144 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A method for the preparation of a p-aminobenzene sulphonyl ethyl containing crosslinked Sepharose 4B (ABSE-Sepharose 4B-CL) is described. trypsin, bovine serum albumin (BSA) and concanavalin A (Con A) were immobilized onto this matrix by diazotization. Conditions for the coupling reaction were investigated. The activity of immobilized trypsin reached 1.4 × 104U/g, and 25 mg BSA can be coupled onto 1 g ABSE-Sepharose 4B-CL under the optimal conditions. An affinity medium with immobilized Con A as ligand was prepared by this method, and was used in the separation of a human monoclonal antibody.
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  • 67
    ISSN: 0269-3879
    Keywords: Capillary zone electrophoresis ; laser desorption/ionization mass monitoring ; Agkistrodon Acutus snake venom ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Fractions of seven protein principles with fibrinolytic or thrombin-like activities obtained from Agkistrodon acutus snake venom purified by two steps of normal pressure chromatography were separated further by capillary zone electrophoresis (CZE). Mass determination for these fractions were achieved by performing laser desorption/ionization mass monitoring (LDIM). The comparative study between CZE and LDIM on the separation of these fractions was made.
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  • 68
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A highly sensitive and reversed-phase high-performance liquid chromatographic method for the determination of the enantiomeric composition of ibuprofen in rat plasma is described. The method is based on the resolution of the diastereomeric amides formed on reaction of the ibuprofen enantiomers with (-)-2-[4-(1-aminoethyl)phenyl]-6-methoxybenzoxazole ((-)-APMB) in the presence of 2,2′-dipyridyl disulphide (DPDS) and triphenylphosphine (TPP) in dichloromethane. The reaction mixture was allowed to stand at room temperature for 5 min, and the reaction was completed by evaporation with a stream of nitrogen at 40°C. The minimum quantifiable concentrations were 0.2 μg/mL and 0.4 μg/mL for S-ibuprofen and R-ibuprofen, respectively, in a 10 μL injection volume. The method was applied to the determination of enantiomeric ibuprofen in plasma after oral administration to rats.
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  • 69
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    Biomedical Chromatography 8 (1994), S. 153-157 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A simple HPLC procedure has been developed for the simultaneous determination of a mixture of standard carbaryl, carbofuran, carbendazim, dimethoate, malathion and methyl parathion from a spiked agricultural soil sample. The pesticide mixture has been extracted using methanol-water. A concave gradient elution with acetonitrile-phosphate buffer for 15 min followed by linear elution for 5 min, using a wavelength of 224 nm for detection, has been found to resolve the mixture efficiently.
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  • 70
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    Biomedical Chromatography 8 (1994), S. 219-223 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A high-performance liquid chromatographic method for the determination of amiloride in airway surface liquid is described. It involves extraction of the drug with methanol from filter paper on which the sample is absorbed and chromatography on a Zorbax Rx column; the mobile phase is 25% acetonitrile in 0.05 M phosphate buffer; detection by fluorescence at 360/420 nm. Triamterene is used as an internal standard. The range of the assay is 2.0-2033.4 ng/sample, with adequate precision and accuracy. A power curve y = axb best describes the relationship between the peak-height ratio and concentration. Recovery of amiloride is non-linear, probably due to an adsorption process. Accuracy of the assay at lower amounts may be affected by the choice of filter paper a well as by presence of endogenous plasma components. The assay was used to measure amiloride amount in airway surface liquid after administration of 2.5 and 4.5 mg of nebulized amiloride.
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  • 71
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 3 Ill.
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  • 72
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Capillary gas chromatography with electron capture detection is described for the quantification of chloral hydrate (CH) and is metabolites trichloroethanol (TCE) and trichloroacetic acid (TCA) in 0.1-1 mL of plasma samples. The method, with 2,2′-dichloroethanol (DCE) as internal standard, involved extraction of chloral hydrate and trichloroethanol with diethyl ether and methylation of trichloroacetic acid with 3-methyl-1-tolyltriazene (MTT), followed by diethyl ether extraction. The method has a detection limit of 5 ng/mL for CH and TCE and 10 ng/mL for TCA and also allows the determination of TCE-glucuronide in 0.1-1 mL of plasma samples. It exhibits good linearity and precision. The method was applied to samples of plasma from a neonate after a single dose of 40 mg/kg of chloral hydrate and from an adult after a single dose of 6.25 mg/kg.
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  • 73
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: High-resolution separation of a PCR product from a mixture of DNA restriction fragments was achieved using capillary gel electrophoresis. The capillary gel electrophoretic separation gives an excellent resolution of two fragments of the 500-bp PCR product and the 506-bp DNA fragment, which differs by only 6 bp, and the complete separation of a broader chain lenght range of DNA fragments up to 12kbp within 20min. The plate number of gel-filled capillary was achieved to be 2 million plates per meter. Capillary gel electrophoresis is applied to the gene diagnosis for heart disease through apolipoprotein E genotyping. The advantages and limitations of capillary gel electrophoresis in the application to PCR analysis and DNA diagnosis are discussed.
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  • 74
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A Measuring method sensitive to prolyl endopeptidase (EC 3.4.21.26, PEP) activity using native peptides (Arg-Vasopressin or substance P) as substrates was established. The investigation of three different derivatization reagents, Which had been developed for an amino acid analysis, demonstrated that 4-fluoro-7-nitrobenzo-2-oxa-1,3-diazole (NBDF) was the most suitable for the detection of Arg-Gly-NH2, which was released from Arg-vasopressin by PEP. Arg-Gly-NH2 was reacted with NBDF at 65°C for 5 min at pH 7.6 and the reaction mixture was analysed by HPLC on a reverse-phase column by monitoring the gluorescence intensity. The detection limit was 1 picomol per injection and the linear standard calibration curve could be constructed in the range of 1 to 100 picomol per injection with a 3.0% relative standard deviation. This sensitive detection method for peptide was applied to the measurement of PEP activity Using Arg-vasopressin as a substrate and 1 × 10-3 unit of PEP activity was detectable. This method was also applicable to the measurement of PEP activity Using subsytance P as a substrate by detecting the derivative of its fragment peptide (Arg-Pro-Lys-Pro).
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  • 75
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    Biomedical Chromatography 8 (1994), S. 315-316 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Aminoglycoside antibiotics were separated by thin layer chromatography. Separation was achieved on untreated silica gel layers using various combinations of solvent systems, dioxane:ammonia, methanol:ammonia and propanol:ammonia. These antibiotics were visualized with the help of iodine vapours.
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  • 76
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    Biomedical Chromatography 8 (1994), S. 145-147 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Determination of 4(3H)-quinazolinone, a newly found antiviral and immunopatentiating constituent was proposed as a method of evaluating the quality of two antiviral Chinese herbal drugs Daqingye (Folium Strobilanthis) and Banlangen(Radix Strobilanthis) and their preparations (‘Antipyretic and common cold granules’, ‘Banlangen granules’). An HPLC method for determining the content of 4(3H)-quinazolinone was established with satisfactory results. The method showed good linearity (r = 0.9998, n = 5) in the range of 0.25-50 μg/mL of 4(3H)-quinazolinone, the average recovery was above 99% with RSD 〈 0.78% (n = 3).
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  • 77
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    Biomedical Chromatography 8 (1994), S. 165-169 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An epoxy-activated continuous bed can be prepared for immobilization of Proteins in a simple, rapid, and cost-effective way. The concentration of epoxy groups on the continuous bed was as high as 600 μmol/mL compressed bed (compression of the bed decreases the peak broadening). Human transferrin, human serum albumin and particularly urease were employed as model proteins. The immobilization of urease was virtually completed within 1h in 1 M potassium phosphate, pH 7.4. The binding capacity was 97 mg of urease/mL compressed bed. This bed is of clinical interest, since it is inexpensive to prepare and permits reproducible enzymatic determination of urea in serum and urine (the chromatographic step is finished within 1-2 min).
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  • 78
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Carbonic anhydrase (CA)-immobilized aminopropyl silica precolumn was developed for direct injection determination of certain sulphonamide drugs in biological fluids by column-switching (CS) high-performance liquid chromatography. Under the optimized conditions, only the sulphonamide drugs with an unsubstituted sulphonamide group were retained on the CA precolumn and separated on a reversed-phase analytical column. Of these, the retention of hydrochlorothiazide (HCT), chlorothiazide, acetazolamide, furosemide (FS) and chlorthalidone was almost quantitative. The peak area of HCT was proportional to the concentration in the range of 1-100 nmol/mL with relative standard deviations of 3.7% (5 nmol/mL) and 0.7% (100 nmol/mL).This CS system was applied to urine and plasma samples spiked with HCT and FS. Endogenous components of these were effectively removed, and HCT and FS were selectively retained on the CA precolumn. Almost quantitative recoveries and reproducibility were obtained.
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  • 79
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    Biomedical Chromatography 8 (1994), S. 199-201 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The separation of reducing monosaccharides derived from glycosidoproteins and glycolipids by capillary zone electrophoresis (CZE) is dependent on the pH and concentration of the borate buffer. Five saccharides were completely separated in a fused silica capillary tube (50 μm i.d., 65 cm) containing 50 mM borate buffer (pH 10.5) as carrier, with high resolution, at an applied potential of 20 kV after the reducing saccharides were derivatized with 1-naphthylamine. On-column UV (254 nm) monitoring allowed quantitation of these saccharides at least in the concentration range of 10-100 mM in reaction solution. This method was applied to the determination of the monosaccharides composition of various carbohydrate materials to demonstrate its usefulness.
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  • 80
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    Biomedical Chromatography 8 (1994), S. 212-218 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A polymer immobilized o-nitrobenzophenone reagent was prepared for analysis of amine drugs in micellar electrokinetic chromatography (MEKC). A model compound, propylamine, was used to characterize the reagent's performance in MEKC. Derivatizations were performed on the CE instrument with reagent in the sample vial. The yielded derivative was directly sampled from the reaction mixture, and directly injected onto the MEKC system. The derivatization reagent was also applied to the derivatization of n-alkyl amine mixtures and amino acids. The method was validated for adamantanamine in urine and amino acids. The method was validated for adamantanamine in urine and in plasma by single-blind spike analysis. Precisions and accuracies for all samples were less than 6.0% for urine samples and 10% for plasma samples. The procedure was a direct injection technique requiring minimal sample preparation for the analysis of drugs in biofluids.
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  • 81
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    Biomedical Chromatography 8 (1994), S. 230-235 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A sensitive and selective liquid chromatographic procedure to quantitate the deflazacort metabolite 21-hydroxy-deflazacort (DF-21OH) in human plasma was developed and validated. DF-21OH and fludrocortisone acetate (internal standard, IS) were isolated from human plasma (2 mL) by solid-phase extraction onto C-18 cartridges. Potential interferences were selectively removed and analytes were eluted with ethyl acetate. Following evaporation, the residue was reconstituted for HPLC analysis. Separation was achieved by gradient elution using a 5 μm YMC Basic column (2.0 × 100 mm) with mobile phases consisting of 20% methanol and 50% acetonitrile in 50 mM phosphate buffer (pH 3) at a temperature of 50°C. Flow rate was maintained at 0.3 mL/min., and analytes were quantified spectrophotometrically at 246 nm.The assay was validated over the range 1.0 to 500 ng/mL DF-21OH. Calibration curves were prepared using a weighted (1/concentration) nonlinear quadratic regression algorithm. Peak-height ratios were proportional to the amount of DF-21OH added to plasma. Assay precision (%RSD) ranged from 4.2 to 11%, with a corresponding assay accuracy (% relative error) of ±2.8%. Absolute recovery of DF-21OH from plasma was 78-86% over the concentration range. The minimum quantitation limit was 1.0 ng/mL.
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  • 82
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    Biomedical Chromatography 8 (1994), S. 242-246 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An immunoaffinity capillary electrophoresis technique has been developed for the analysis of cyclosporin A in human tear fluid following topical application of the drug. The technique combines the selectivity of immunoaffinity separation with the high-resolution of capillary electrophoresis by immobilizing monoclonal antibody fragments directly onto the internal surface of the capillary. This technique was used to measure cyclosporin levels in tears obtained from corneal transplant patients during normal and drug toxicity episodes in the course of their treatment. Comparison of this technique with HPLC detection of cyclosporin in tears showed a good correlation, with the immunoaffinity CE technique having the advantage of being able to simultaneously detect toxic metabolites of cyclosporin in the same sample.
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  • 83
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    Journal of Chemometrics 8 (1994), S. 21-36 
    ISSN: 0886-9383
    Keywords: GRAM ; Tucker ; Unfold ; NBRA ; Second-order ; Three-way ; PARAFAC ; Trilinear ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: If an analytical instrument or instrumental method gives a response matrix when analyzing a pure analyte, the instrument or instrumental method is called a second-order method. Second-order methods that generate a response matrix for a pure analyte of rank one are called rank-one second-order methods. If the response matrix of a pure analyte is not rank one, essentially two cases exist: medium rank (between two and five) and high rank (greater than five). Subsequently, medium- and high-rank second-order calibration tries to use medium- and high-rank second-order methods to analyze for analytes of interest in a mixture. A particular advantage of second-order methods is the ability to analyze for analytes of interest in a mixture which contains unknown interferences. Keeping this advantage is the challenge on moving away from rank-one second-order calibration methods. In this paper a medium-rank second-order calibration method is proposed based on least-squares restricted Tucker models. With this method the second-order advantage is retained.
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  • 84
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    Journal of Chemometrics 8 (1994), S. 101-101 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 85
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    Journal of Chemometrics 8 (1994), S. 103-110 
    ISSN: 0886-9383
    Keywords: Taguchi ; Robust design ; Design of experiments ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper is intended to convey the essence of Taguchi's design approach to chemists and others with an interest in chemometrics. Although most Taguchi-style applications worldwide have been in electronics and in elaborately transformed manufactures, examples are increasingly found in chemical processes and in the food industry.Foremost among Taguchi's contributions is the concept of designing processes and products to be robust to the uncontrollable environmental influences which they experience during their operation or lifetime. This concept is explained with a worked example.
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  • 86
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    Journal of Chemometrics 8 (1994), S. 127-145 
    ISSN: 0886-9383
    Keywords: Compression ; Multivariate analysis ; B-splines ; FT-IR spectra ; Second-order ; Two-dimensional ; Hyphenated methods ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to improve the storage and CPU time in the numerical analysis of large two-dimensional (hyphenated, second-order) infrared spectra, a data-preprocessing technique (compression) is presented which is based on B-splines. B-splines have been chosen as the compression method since they are wellsuited to model smooth curves. There are two primary goals of compression: a reduction of file size and a reduction of computation when analyzing the compressed representation. The compressed representation of the spectra is used as a substitute for the original representation. For the particular example used here, approximately 0.16 bit per data element was required for the compressed representation in contrast with 16 bits per data element in the uncompressed representation. The compressed representation was further analysed using principal component analysis and compared with a similar analysis on the original data set. The results shows that the principal compotent model of the compressed representation is directly comparable with the principal component model of the original data.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 87
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 88
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. i 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 89
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 181-203 
    ISSN: 0886-9383
    Keywords: RAFA ; GRAM ; Eigenvalues ; Bias ; Variance ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rank annihilation factor analysis (RAFA) is a method for multicomponent calibration using two data matrices simultaneously, one for the unknown and one for the calibration sample. In its most general form, the generalized rank annihilation method (GRAM), an eigenvalue problem has to be solved. In this second paper expressions are derived for predicting the bias and variance in the eigenvalues of GRAM. These expressions are built on the analogies between a reformulation of the eigenvalue problem and the prediction equations of univariate and multivariate calibration. The error analysis will also be performed for Lorber's formulation of RAFA. It will be demonstrated that, depending on the size of the eigenvalue, large differences in performance must be expected. A bias correction technique is proposed that effectively eliminates the bias if the error in the bias estimate is not too large. The derived expressions are evaluated by Monte Carlo simulations. It is shown that the predictions are satisfactory up to the limit of detection. The results are not sensitive to an incorrect choice of the dimension of the factor space.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 90
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 243-243 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 91
    ISSN: 0886-9383
    Keywords: Fitting ; Non-linear ; Least squares ; Refinement ; Constraints ; MSE ; Confidence ; C ls ; XPS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A non-linear least squares iterative refinement has been implemented which shows high performance on a multiple-peak spectrum including baseline or background. Constraints as well as links within a range are introduced to drive the mathematical optimization: each peak parameter (i.e. height, position, Gaussian/Lorentzian mixing ratio and HWHM on both left and right sides) has assigned to it an allowed range of variation and can be strained to be correlated with other parameters belonging either to the same peak (symmetrical peaks) or to other peaks (doublets, triplets, etc.). Peak shapes typical of XP spectra are used and applications in the field of XPS are discussed. Through emulated curves with Poisson distributed noise, the accuracy and precision of back-calculated (refined) parameters have been estimated. Moreover, a confidence level calculated from X2 and degrees of freedom has been suggested to check the overall fitting of experimental curves where the signal-to-noise ratio is a priori unknown. An application to real C ls XP spectra is described as an example and a list of suggestions is given to match operator requirements. Finally, features of NLLSRC are discussed with respect to other approaches.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 92
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 263-272 
    ISSN: 0886-9383
    Keywords: Molecular descriptors ; Principal component analysis ; Chemometrics ; Pattern recognition ; Total surface area ; PCDD PCDF ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New theoretical molecular indices are defined. They contain information about the whole molecular structure in terms of size, shape, symmetry and atom distribution. These indices are calcualted from the (x, y, z) co-ordinates of a molecule within different weighting schemes in a straightforward manner and represent a very general approach to describe molecules, molecular fragments, macromolecules and molecular conformations in a unitary conceptual framework. Their interpretability is quite evident and is defined by the same mathematical properties as the algorithm used for their calculation. Examples on the total surface area, toxicity of PCDD and PCDF and reaction rate of catalysed reactions show a high modelling power of these indices.
    Additional Material: 4 Tab.
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  • 93
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 301-302 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 94
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 333-347 
    ISSN: 0886-9383
    Keywords: PLS ; ATR ; Paper ; Resolution ; Infrared ; FTIR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attenuated total reflectance Fourier transform infrared spectrometry (ATR-FTIR) has been used to determine the amount of styrene-butadiene latex on the surface of coated papers and to predict the composition of the polymer. Spectrum recording was performed on the sample in its usual form without any modification.For quantitative analysis, partial least squares (PLS) regression, principal component regression (PCR) and multi-linear regression (MLR) were used to calculate models for prediction. The best result is obtained with PLS.We analysed two series of paper samples. The first analysis concerns the measurement of the quantity of latex of a constant quality on the coating surface. For 15 samples the concentration varied between 5 and 25 parts (grams per 100g of mineral pigments). We compared the predictive results at various resolutions. We obtained a relative error of 0.15 parts in latex at 4 cm-1 resolution. The second analysis concerns the measurement of the styrene/butadiene ratio in various types of latex. We obtained a relative error of 0.156 parts for styrene determination and 0.161 parts for butadiene determination.
    Additional Material: 7 Ill.
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  • 95
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 375-376 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 96
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 391-407 
    ISSN: 0886-9383
    Keywords: Neural networks ; Non-linear multivariate regression ; Pattern classification ; Kalman filter ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Finding methods for the optimization of weights in feedforward neural networks has become an ongoing developmental process in connectionist research. The current focus on finding new methods for the optimization of weights is mostly the result of the slow and unreliable convergence properties of the gradient descent optimization used in the original back-propagation algorithm. More accurate and computationally expensive second-order gradient methods have displaced earlier first-order gradient optimization of the network connection weights. The global, extended Kalman filter is among the most accurate and computationally expensive of these second-order weight optimization methods. The iterative, second-order nature of the filter results in a large number of calculations for each sweep of the training set. This can increase the training time dramatically when training is conducted with data sets that contain large numbers of training patterns. In this paper an adaptive variant of the global, extended Kalman filter that exhibits substantially improved convergence properties is presented and discussed. The adaptive mechanism permits more rapid convergence of network training by identifying data that contain redundant information and avoiding calculations based on this redundant information.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 97
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 439-443 
    ISSN: 0886-9383
    Keywords: Pattern recognition ; Principal component analysis ; Inverse mapping ; Optimization ; Material design ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An inverse mapping method called PCB (principal component backing), in which the point representing an unknown sample from a low-dimensional principal component subspace is back-projected to the high-dimensional original feature space, is proposed. Two sorts of boundary conditions, non-linear inverse mapping and linear inverse mapping, are used to obtain an accurate solution in the PCB method. The method is applied to the material design of high-Tc superconductors, predicting the composition and process conditions for the synthesis of F-doped Bi-based materials. Samples in the ‘optimal’ region with the highest Tc of the Bi-based ceramics have been predicted.
    Additional Material: 1 Ill.
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  • 98
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994) 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 37-44 
    ISSN: 0886-9383
    Keywords: Bootstrap ; Confidence interval ; Non-linear regression ; Monte Carlo methods ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Non-linear regression models describing the toxicity of a mixture of rotenone and pyrethrins as an insecticide, the catalytic dehydration of n-hexyl alcohol and the Michaelis-Menten model for characterizing reaction rates in enzyme systems will be used to illustrate the accuracy of bootstrap methods in non-linear regression. Classical and bootstrap confidence intervals for the parameter estimates will be presented.
    Additional Material: 5 Tab.
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  • 100
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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