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  • 1
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; α1 glycoprotein ; Enantioseparation ; β-blocking agents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The enantioselectivity of the α1 glycoprotein chiral stationary phase, Chiral AGP® has been evaluated for a number of β-blocking agents. A correlation has been found between the retention behaviour on this stationary phase and the hydrophobicity of the compounds. The separation factor α is higher for compounds that are well retained. Retention, and thus α, are also controlled by pH and the percentage of organic modifier in the mobile phase.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Indirect separation ; Chiral derivatization ; Stable CDA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new chiral derivatizing agent (CDA) (1S, 2S) N-[(2-isothiocyanato)-cyclohexyl)-pivalinoyl amide ((S,S)-PDITC) is described. The CDA is available from 1,2-diamino cyclohexane (DACH) via a straightforward synthesis in both the (R,R) and (S,S)-configuration and can serve as a highly selective, stable reagent for the indirect resolution of chiral primary and secondary amines, amino acids and thiol compounds. The resulting diastereomeric thioureas and dithiocarbamates can be separated by simple RP-HPLC as demonstrated with a number of pharmaceutically important examples of amines and amino alcohol-type drugs. The latter diastereomers are compared with the well-established GITC derivatized compounds. The separation factors (α) of the diastereomeric thioureas range between 1.03 and 2.08 and were usually higher than those of the GITC derivatives. The chemical stability of the PDITC derivatives is excellent due to the absence of hydrolyzable ester groups— considered an advantage compared to GITC derivatives.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 20 (1985), S. 213-218 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Nitro-PAHs ; Diesel particulate extract ; Column switching-HPLC ; Pyrene-butyric acid stationary phase ; π-acceptor ligands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the determination of nitrated polynuclear aromatic hydrocarbons (nitro-PAHs), in particular 1-nitropyrene, in diesel particulate extracts. The method employs a multidimensional HPLC (column switching) technique with final on-line peak identification by UV-VIS spectral comparison with standards. To achieve exceptional chromatographic selectivity for nitro-PAHs, a new pyrene butyric acid amide phase has been prepared which is capable of forming donor-acceptor complexes with them. With this technique it is possible to confirm the presence of 1-nitropyrene in the range 3–100 ng/mg on filter-collected diesel soot. Its utility was demonstrated with diesel exhaust extracts spiked with varying levels of 1-nitropyrene and proved to be highly selective.
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  • 4
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Nitro-PAHs ; Diesel particulate extract ; Column switching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A multicolumn (MC) HPLC method for the determination of 1-nitropyrene (1-NP) at trace-levels via on-line reduction to 1-aminopyrene and fluorescence detection is presented. On the first column, packed with a pyrenebutyric acid amide stationary phase, the nitro-derivatives of PAHs are strongly retained and separated from other matrix components. The nitro-PAHs-containing fractions are transferred onto a RP18-column via stepwise gradient elution and finally separated according to their various lipophilicities and sizes. To increase the overall selectivity and sensitivity of the multidimensional method (MD-HPLC system) post-column, on-line reduction of the nitro-PAHs to the respective amino-PAHs via a short catalysis column is performed thus enhancing the sensitivity significantly (to low pg levels). The applicability of this method for the determination of trace amounts of 1-NP in real samples (diesel particulate extracts) is demonstrated.
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  • 5
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Leucovorin, methotrexate ; On-line, post-column UV irradiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An improved, reversed-phase, high-performance liquid chromatography (HPLC) method with dual UV-fluorescence detection for simultaneous determination of the antifolate methotrexate, the folate leucovorin and their two main metabolites 7-hydroxymethotrexate and 5-methyltetrahydrofolate, respectively is presented. The fluorescence intensity of leucovorin could be significantly increased by on-line, post-column irradiation with UV at 254 nm thus lowering the limit of detection for leucovorin to 0.2 ng absolute at a signal-to-noise ratio 3∶1.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral stationary phase ; Optical resolution of drugs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The synthesis of optically pure (S,S)-N-3,5-dinitrobenzoyl-1,2-diphenylethane-1,2-diamine (DNB-DPE-DA) immobilized via an undecenoyl spacer onto silica gel and the resolving power of this new chiral stationary phase (CSP) for normal phase HPLC are described. The phase shows good enantioselectivity for various chiral compounds containing amide (imide) functionality and π-donor type aromatic subsitutents, and also for some alcohols and sulfoxides. The influence of protic and nonprotic mobile phase components on the enantioselectivity has also been examined.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 32 (1991), S. 407-416 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral selectors ; Tartaric acid derivatives ; Amino alcohols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Direct separation of enantiomeric amino-alcohols using tartaric acid derivatives as chiral complexing agents in organic stationary or mobile phases is described. Among the tartaric acid derivatives studied, only tartrates having hydroxyl groups attached to the asymmetric carbon atoms (C2) and (C3) free, gave enantioselective retention for epherrine stereoisomers. (2R,3R)-di-n-butyl tartrate (DBT) dissolved inn-hexane as stationary liquid phase gave higher stereoselectivity than DBT in dichloromethane. Both hydrophilic (Nucleosil CN) and hydrophobic (porous graphitic carbon) solid supports were found to affect the retention and enantioselectivity when using a chiral liquid stationary phase. A retention model is presented and used qualitatively in the study of the effect of DBT concentration, organic solvent, addition of a competing amine and packing material on retention and stereoselectivity.
    Type of Medium: Electronic Resource
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