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  • 1
    Electronic Resource
    Electronic Resource
    Statistical evaluation of the validity of a method for characterizing stationary phases for reversed-phase liquid chromatography based on retention of homologous series (1994)
    Springer
    Chromatographia 38 (1994), S. 137-146 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Characterization of reversed phases ; Column hydrophobicity ; Column hydrophylicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The validity of a method for characterizing stationary phases for reversed-phase, liquid chromatography, based on the use of homologous series, has been evaluated. The method is based on a retention model which describes the dependence of the logarithm of the capacity factor on mobile phase composition and the carbon number of specific homologous series. A first-order as well as a second-order version of this model was investigated. The second-order model proved to be a significant improvement on the first-order model, even for smaller mobile-phase ranges. Nevertheless both models showed a significant lack of fit, reflecting the incompleteness of these models. Therefore, it is very questionable whether this method is suitable to describe HPLC-column characteristics like hydrophobicity and hydrophylicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290326
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  • 2
    Electronic Resource
    Electronic Resource
    The influence of surface treatments on the electroosmotic flow in micellar electrokinetic capillary chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 303-308 
    Details
    ISSN: 1612-1112
    Keywords: Micellar electrochromatography ; Electroosmotic flow ; Column coatings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An investigation was carried out to study the electroosmotic flow (EOF) in micellar electrokinetic capillary chromatography (MECC). Fused silica capillaries were treated with various reagents to investigate the parameters influencing the magnitude and reproducibility of the EOF. The results for untreated and treated columns were collected and compared under the same experimental conditions. Furthermore, experiments with and without sodium dodecylsulfate (SDS) addition to the buffer were carried out to elucidate the influence of this surfactant on the EOF. The mechanisms behind the effects of these modifications on the EOF and the stability of the coatings on the column wall are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275906
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Abstracts of papers Pharmaceutical and biomedical analysis meeting (1989)
    Springer
    Pharmacy world & science 11 (1989), S. N1 
    Details
    ISSN: 1573-739X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02196050
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    A comparative study of large volume injection techniques for microbore columns in HPLC (1987)
    Springer
    Chromatographia 23 (1987), S. 331-336 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Microbore columns ; Injection techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper focuses attention on the potentially larger signal-to-noise ratios produced by microbore columns in comparison with conventional columns. The increased chromatographic signals by the application of microbore columns are due to the lower chromatographic dilution of elution profiles which are proportional to the square of the column inner radius. Generally less than 1μl sample should be injected into microbore systems to obtain the full benefit of the column performance. However, since more sample can be loaded on conventional columns compared to microbore columns the advantage of improved signal-to-noise ratio can only be realised in situations where very little sample is available. To inject more than 1μl sample, at the same time avoiding extra band-broadening effects, suitable injection techniques must be available. In this study three injection methods for microbore systems that meet this condition, are studied and compared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02316178
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  • 5
    Electronic Resource
    Electronic Resource
    Ageing processes of alkyl bonded phases in HPLC; a chromatographic and spectroscopic approach (1985)
    Springer
    Chromatographia 20 (1985), S. 582-586 
    Details
    ISSN: 1612-1112
    Keywords: Reversed-phase HPLC ; Ageing processes ; Solid state NMR ; FTIR ; Chain dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Laboratory use of HPLC columns packed with C8 and C18 bonded phases leads to changes in selectivities and retention volumes. FTIR,1H NMR of hydrolysed bonded phases and solid state13C- and29Si NMR were applied to characterize the materials. The results of the various techniques are in fair agreement except solid state NMR. Loss of silane and hydrolysis of surface siloxane groups have been observed for the C8 bondes phase, while for the C18 material the latter process seems to dominate. The solid state NMR results have been tentatively explained in terms of changing chain arrangements and mobilities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263215
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  • 6
    Electronic Resource
    Electronic Resource
    Flame ionization detection for the determination of the chemical composition distribution of non-UV absorbing copolymers (1991)
    Springer
    Chromatographia 31 (1991), S. 493-499 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flame ionization detection ; Poly(styrene-co-methyl acrylate) ; Poly(methyl acrylate-co-n-butyl acrylate) ; Chemical composition distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This investigation is focused on the development of HPLC with subsequent flame ionization detection as a tool to determine the chemical composition distribution of non-or poorly UV absorbing copolymers. Experiments were carried out with poly(styrene-co-methyl acrylate) and poly(methyl acrylate-co-n-butyl acrylate) copolymers. HPLC combined with FID provided useful qualitative information. Quantitative information could be obtained after calibration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262395
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  • 7
    Electronic Resource
    Electronic Resource
    The separation of herbicides by micellar electrokinetic capillary chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 25-30 
    Details
    ISSN: 1612-1112
    Keywords: Electrokinetic capillary chromatography ; Micellar agents ; Chlorophenoxy acids ; Herbicides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method for the separation of a number of herbicides consisting of chlorophenoxy acids by micellar electrokinetic capillary chromatography (MECC) was developed. Sodium dodecyl sulphate (SDS), Brij 35, cetyltrimethylammonium bromide (CTAB) and methanol were introduced into the buffers to investigate their effects on the separation of the herbicides. SDS combined with Brij 35 as the micellar agent was found to provide the best overall separation of these components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290454
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  • 8
    Electronic Resource
    Electronic Resource
    Normal phase gradient polymer elution chromatography of polyester resins (1998)
    Springer
    Chromatographia 48 (1998), S. 623-630 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal phase gradient elution ; Polyester resins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Polymers can be characterized by gradient elution techniques in order to obtain information on their chemical composition and molar mass. In this paper, features and applications of Normal Phase Gradient Polymer Elution Chromatography (NP-GPEC) for the characterization of (co)polyesters are investigated. Two polyesters were characterized, using various stationary and mobile phases. Separation was shown to be dominated by end groups in most cases, and to a lesser extent by molar mass. A distinct influence of both column type and mobile phase type was observed. A polymer based polyamine (PA) column povided the best results, although no complete separation between the mono- and di-acid fractions could be obtained. In all cases, separation was governed by sorption rather than by precipitation/redissolution. NP-GPEC was shown to be a potentially interesting technique for the characterization of copolyesters according to the chemical composition of the backbone, independent of end groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467591
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  • 9
    Electronic Resource
    Electronic Resource
    Estimation of the band broadening contribution of HPLC equipment to column elution profiles (1987)
    Springer
    Chromatographia 23 (1987), S. 189-194 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Instrument bandbroadening by extrapolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Methods to determine the contribution of the chromatographic equipment to the total band broadening which involve replacing the column by a union or a capillary tube are not suitable as they involve a fundamental change in the chromatographic system. The linear extrapolation method, based on the estimation of the relative influence of the instrument variance on solutes with different capacity factors, is a more attractive alternative method since the column remains in the chromatographic system. This method is only valid when a number of conditions are satisfied. By meeting these conditions the error in the instrument variance by using the linear extrapolation method was determined. At the same time, ways to minimise these errors were studied. Use of the linear extrapolation method in combination with conventional columns of 4.6 mm i.d. appears to yield inaccurate results. In combination with microbore columns the method can be used, provided the columns have a maximum length of 5cm and contain a packing material with a particle size of 2 or 3μm. The error in the determined instrument variance is then of the order of 2μl2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02311478
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  • 10
    Electronic Resource
    Electronic Resource
    Comparison of extraction methods for the determination of polycyclic aromatic hydrocarbons in soot samples (1991)
    Springer
    Chromatographia 31 (1991), S. 569-574 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Polycyclic aromatic hydrocarbons ; Soot and air samples ; Liquid CO2 extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The results of the analysis of polycyclic aromatic hydrocarbons (PAH) in soot and similar types of sample are often dependent on the extraction method applied, owing to carbonaceous substances present in these samples. The recoveries of three extraction methods, and ultrasonic ether, a Soxhlet toluene and a Soxhlet extraction with liquid CO2 were compared for a typical soot sample. Additionally the CO2 extraction was optimized with respect to the necessary number of transfers during the extraction and the proper method to remove the CO2 after extraction. Finally, the liquid chromatographic pretreatment of the extract, prior to gas chromatographic analyses of the PAH, was improved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02279477
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