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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 25 (1988), S. 25-30 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Polycyclic aromatic compounds ; Alkylated PAC ; Retention characteristics ; Normal phase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Retention characteristics of series of polymethyl and mono-n-alkyl derivatives of benzene and pyrene, and also of parent polycyclic aromatic hydrocarbons (PAH), were studied using silica and aminopropyl- and cyanopropyl-modified silica. Differences in the selectivities for the studied compound groups were found between the three phases. Deviations from linear behaviour in plots of log (k′)vs. carbon number were observed for the methyl series. These are explained in terms of differences in π-electron delocalisation within the aromatic ring systems. Further, the effect of methyl substitution on selectivity decreased with an increasing number of aromatic rings. Results were obtained which indicated that the primary adsorption site in a cyano column used in normal phase mode, at least for PAH molecules, is the cyano group.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 32 (1991), S. 334-340 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Normal phase separations ; Cyanopropyldimethyl silica ; Chloro-added polycyclic aromatic hydrocarbons ; Environmental samples
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Retention characteristics in normal phase HPLC of highly biologically active chloro-added polycyclic aromatic hydrocarbons (PAHs) were studied. Silica, cyanopropyldimethylsilyl- and aminopropylsilyl- modified stationary phases were investigated. Retention properties of chloroadded PAHs on these phases were shown to be strongly influenced by the number of chloro-additions. This is due to the strong polarity of the methylene carbon at the chloro-addition site. Active silica had a strongly degrading effect on the unstable chloro-added PAHs during separation. Aminopropylsilica did not exhibit sufficient selectivity towards chloro-added PAHs when compared to chlorosubstituted PAHs. Cyanopropyldimethylsilica was shown to be applicable to a group separation of chloro-added and chloro-substituted PAHs. A fast clean-up procedure for chloro-added PAHs in complex samplesis outlined. It involves an initial elimination of more polar substances on a short open column with strongly deactivated silica and a subsequent separation on a cyanopropyldimethylsilyl HPLC column in normal phase mode.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Normal phase separations ; Chloro-substituted polycyclic aromatic hydrocarbons ; Coupled column system ; Environmental samples
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The retention behaviour of chloro-substituted PAHs on several commercial normal bonded phase HPLC columns has been investigated. Chloro-substitution was shown to generally decrease the retention on stationary phases like amino-, diol- and nitrophenylpropyl-modified silica. Dimethylaminosilica exhibited more complex retention characteristics towards chloro-substituted PAHs. On this stationary phase, the position of the chlorine substituents on the aromatic solute seemed to be of greater importance for retention than on the amino-, nitro- and diolsilica. For some chloro-PAHs, the retention was shown to increase with the number of chloro-substitutions, probably due to the large affinity of the electron-rich nitrogen in the stationary phase for the electron deficient π-system of the chloro-PAHs. Chloro-substituted PAHs were strongly retarded on the electron donating 2-(1-pyrenyl)-ethylsilica (PYE) stationary phase. However, the molecular shape of the chloro-derivatives had a large influence on retention, which was considerably decreased for some nonplanar chloro-derivatives of chrysene and benz(a)anthracene. A two-dimensional back-flush HPLC method, consisting of a combination of a nitrophenylsilica column and a PYE column of matched lengths, was shown to be useful for clean-up of chloro-substituted PAHs in environmental samples.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1612-1112
    Schlagwort(e): Reversed-phase ; Polyaromatic hydrocarbons ; HPLC
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Differences in retention time and relative elution order were observed when a standard mixture of 11 PAH was injected on three C-18 columns from different manufacturers under equivalent conditions.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 21 (1986), S. 392-396 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Bonded phases ; Specific selectivity ; Polynuclear aromatic hydrocarbons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method for preparing selective phases for reversed phase chromatography is described. Five different polymeric modified silica gel phases were prepared by simultaneously bonding with silanes, the first phase one line is missing according to the manuscript should read: the first phase being modified with ODS. Modification of the other four phases was achieved by treatment with ODS and cyanopropyl- or cyanodecyl-trichlorosilane, thus yielding reversed phase materials of different properties. The chromatographic selectivity of each phase was demonstrated by elution of a number of standard mixtures containing polyaromatic compounds. The selectivity is described with respect to carbon load and the ODS/CN-ratio of the stationary phase for these compounds. Different PAHs are influenced to a greater or lesser degree. Through introduction of various functional groups in the network of C18 chains of a polymeric modified silica gel, it is possible to design columns with specific selectivities.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 23 (1987), S. 257-260 
    ISSN: 1612-1112
    Schlagwort(e): Chromatography ; Micro-computer ; Integration routines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A routine for the integration of chromatograms, applied to an IBM-PC compatible micro-computer with Hercules graphics, is described. The techique is based on interplay between the chromatographer and the computer, made possible by fast calculation and graphical routines achieved using TURBO-Pascal.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 23 (1987), S. 903-908 
    ISSN: 1612-1112
    Schlagwort(e): Polycyclic aromatic compounds ; Alkylated PAC ; Extraction methods ; Backflush HPLC ; Evaluation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Semipreparative HPLC utilizing a polar bonded phase was applied to the isolation of polycyclic aromatic compounds (PAC) from complex samples using a backflush technique. Aminopropyl- and cyanopropyl-modified silica was tested. Aminopropyl-modified silica was found to be superior in achieving rapid, selective and non discriminating isolation of PAC. This was compared with the most commonly used isolation methods, dimethylsulfoxide (DMSO), dimethylformamide (DMF) and nitromethane liquid-liquid extractions, and silica and SephadexLH-20 open column chromatography. Strong discrimination of alkylated PAC and polycyclic aromatic nitrogen heterocyclics (PANH) was found for the liquid-liquid extractions and the LH-20 column chromatography. These comparisions were made using both standard compounds and a sample of used crankcase oil, indicating the necessity of using a real sample for evaluation of extraction methods. Recoveries of 42 PACs are reported.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 21 (1986), S. 451-453 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Reversed phase separations ; Thiophene silane ; Polynuclear aromatic hydrocarbons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Modification of silica gel with thiophene-propyl-trichlorosilane is described as well as the synthesis of the silane. The chromatographic performance and selectivity are demonstrated with various polyaromatic compounds. Thiophene-modified silica gel was found to exhibit a selectivity comparable with both ODS-and amino-phases.
    Materialart: Digitale Medien
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