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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 698-702 
    ISSN: 0935-6304
    Keywords: Capillary column gas chromatography ; Microwave-induced plasma emission spectrophotometric detector ; Photodiode array spectrophotometer ; Element-specific detector ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A microwave-induced plasma emission spectrophotometric detector (MIPD) was used as an element-specific detector for capillary column gas chromatography. The atmospheric pressure microwave helium plasma generated with an original device called a SURFATRON was used as an atomization and excitation source. Combining a photodiode array spectrophotometer with the above system made the emission spectrophotometric detector very powerful. A wide range of spectra could be instantly monitored without any mechanical device.However, the spectrum of atmospheric helium emission plasma was complicated by the presence of air around the plasma discharge. An on-line background correction scheme was developed to handle such complicated spectra.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 4 (1981), S. 500-507 
    ISSN: 0935-6304
    Keywords: Liquid chromatography ; Weak anion exchanger ; Octadecyl bonded packing ; Urine analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The analysis of ultraviolet-absorbing constituents in urine was undertaken by anion-exchange and reversed-phase liquid chromatography. A newly developed anion exchanger (TSK-IEX540 DEAE) was used for ion-exchange mode liquid chromatography and its high polarity and physical strength greatly reduced the analysis time. Up to 80 peaks were resolved within 30 min. Hydrophobicity values were used to predict the retention times of acids in reversed-phase mode liquid chromatography.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 6 (1983), S. 20-26 
    ISSN: 0935-6304
    Keywords: Reversed-phase mode liquid chromatography ; Rekker's hydrophobic fragmental constant ; Calculation of concentration of organic modifier ; Prediction of retention time of phenols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chromatographic behavior of phenols in reversed-phase mode liquid chromatography differs from that of non-ionic compounds such as alkyl alcohols, alkylbenzenes, halogenated benzenes, polyaromatic hydrocarbons, and aromatic acids. Therefore, the retention times of 61 phenols were measured in a system of an octadecyl bonded silica gel and acetonitrile/water mixtures. The logarithm of the capacity ratio (log k') was found to be a linear function of the hydrophobicity (log P) in acidic acetonitrile/water mixtures. This result was applied to a different octadecyl bonded silica gel. Eight phenols were selected as standard compounds, and their log k' values were measured in 0.05 M phosphoric acid in 10 to 90% acetonitrile/water mixtures. An empirical polynomial relation was obtained between the concentration of acetonitrile and the slope of the log k' vs log P curve. Finally the capacity ratio of all phenols were calculated in given eluents by the equations derived from the measurements of standard compounds and the calculated log P values. The difference between predicted capacity ratios and measured ones was within 10%.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0935-6304
    Keywords: Liquid chromatography, HPLC ; Reversed phase mode ; Prediction of retention time ; Prediction of pKa ; Hydrophobic fragmental constant ; Aromatic acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For optimization of liquid chromatography separations, several approaches have been reported, among them the use of the hydrophobic fragmental constant, as proposed by Rekker [1]. The fragmental constant is derived from the partition coefficients of various solutes between octanol and water and represents a summation of solubility parameters: van der Waals volume, π - π interactions, hydrogen bonding, etc. With these constants the optimization of reversed phase mode liquid chromatography using octadecyl bonded silica gels as packing was feasible, although large error was found for the eluent with a high concentration of organic modifier or water. This is probably due to the heterogeneous solvation of the surface of the packings and to various solvent effects. In addition, when the acid dissociation constant was known, the retention times of aromatic acids in the ionic form were also predicted using the hydrophobic fragmental constant and the dissociation constant. By comparison of the previous data and a method proposed by Perrin et al. [2] it was possible to predict the dissociation constant of aromatic acids and optimize separation in reversed phase mode liquid chromatography using octadecyl bonded silica gels as packing. Furthermore, an equation for calculating the capacity ratios in a given pH eluent was proposed and the predicted and observed capacity ratios of aromatic acids in several eluents were examined in order to improve the above system.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 13 (1990), S. 573-574 
    ISSN: 0935-6304
    Keywords: Electrochromatography ; Multi-channel column ; Sample loading capacity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 4 (1981), S. 454-460 
    ISSN: 0935-6304
    Keywords: Reversed-phase mode liquid chromatography ; Rekker's hydrophobic fragmental constant ; Calculation of concentration of organic modifier ; Prediction of retention time ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The utility of Rekker's hydrophobic fragmental constant has been examined for optimization of reversed-phase mode liquid chromatographic separations. The chromatographic behavior of about 60 non-ionic compounds was measured in different acetonitrile/water mixtures and the logarithm of their capacity factors (log k) was correlated with their calculated hydrophobicities (log P). Linear relations were found in each case between log k and log P. The slope of the various lines was related to the percentage concentration of acetonitrile in the mobile phase. It was shown that, by using nine stand ard compounds and measuring their capacity factors in five eluents with different acetonitrile concentrations, the retention time could be predicted for 60 compounds. Calculation of the concentration of the organic modifier was also possible in a system of well coated octadecyl bonded packings with acetonitrile/water mixtures as eluent. Prediction of the capacity factor was accomplished to within 5% error.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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