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  • 1
    Electronic Resource
    Electronic Resource
    Capillary supercritical fluid chromatography with nitro- and nitroso-specific chemiluminescence detection (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 6 (1994), S. 395-401 
    Details
    ISSN: 1040-7685
    Keywords: supercritical fluid chromatography ; thermal energy analyzer ; explosives ; tabacco specific nitrosamines ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal energy analyzer (TEA), a gas-phase chemiluminescence detector which is specific for nitro and nitroso compounds, was evaluated as a detector for use with capillary supercritical fluid chromatography. The potential use of the TEA for thermally labile compounds and environmental samples was demonstrated. The TEA showed good sensitivity and broad linear dynamic range; minimum detectable quantities (MDQ) were below 20 pg for pentaerythritol tetranitrate (PETN) with a dynamic range of over 4 orders of magnitude. The analysis of cyclotetramethylene tetranitramine (HMX) was accomplished by using modified (CO2) with a corresponding MDQ of 67 pg. The selectivity of the TEA for nitro and nitroso compounds can be adjusted by changing the pyrolysis temperature. The SFC/TEA system was applied to a variety of nitro and nitroso compounds, and evaluated more extensively for routine analysis of propellant and explosive residues.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220060408
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  • 2
    Electronic Resource
    Electronic Resource
    Supercritical fluid extraction/gas chromatography with thermal desorption modulator interface and nitro-specific detection for the analysis of explosives (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 7 (1995), S. 23-28 
    Details
    ISSN: 1040-7685
    Keywords: supercritical fluid extraction ; gas chromatography ; thermal desorption modulation ; explosives ; chemiluminescence detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Supercritical fluid extraction (SFE) can greatly reduce the sample preparation time of analytes in solid matrices. The on-line coupling of SFE with high-speed gas chromatography (GC) can further reduce the total analysis time. SFE has been coupled to GC with a thermal desorption modulator (TDM) interface. A thermal energy analyzer (TEA), a chemiluminescence detector which is specific for nitro and nitroso compounds, has been coupled to the system to analyze explosives in soil samples.The use of organic modifiers to increase the solvation power of carbon dioxide was necessary for the extraction of various explosives, and did not adversely affect the performance of the system. Thermally labile compounds, however, such as the nitrate esters, were shown to decompose in the modulator before the chromatographic separation.This method allows for the rapid analysis of relatively volatile and thermally stable nitro compounds from solid matrices. The system can be used for screening small samples in short periods of time. Total analysis can be completed in less than 10 minutes and requires only 200 mg of soil. The minimum detectable quantity for the analysis of 2,4-DNT was found to be 2.6 ppb in an actual soil sample.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220070104
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  • 3
    Electronic Resource
    Electronic Resource
    Modifier addition in microcolumn supercritical fluid chromatography with a high pressure pulsed valve (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 6 (1994), S. 449-457 
    Details
    ISSN: 1040-7685
    Keywords: supercritical fluid chromatography ; mixed mobile phases ; methanol modified carbon dioxide ; pulsed valve ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The need for mixed mobile phases at low flow rates suitable for capillary and packed capillary supercritical fluid chromatography (SFC) has led to the use of an air actuated high pressure prime/purge valve for on-line modifier introduction. This valve can consistently deliver small amounts of modifier into the mobile phase, and allows rapid changes of modifier concentrations. Methanol modified carbon dioxide (CO2), from 0.5 to 15 mole percent, has been generated using this valve at a flow rate compatible with a packed capillary column without the need for flow splitting. Two instrumental configurations were used to evaluate the valve. One configuration used separate pumps for the mobile phase and the modifier. The other configuration used only one pump with a pneumatic amplifier as the modifier reservoir. The valve provides reproducible modifier concentrations, percent relative standard deviation (%RSD) for retention times less than 2%, and dependable use, leak free after 〉 250,000 pulses. The use of this valve, with both the 2-pump and 1-pump/pneumatic amplifier configuration is demonstrated. The effects of modifier addition on the retention times of components in several samples are shown.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220060504
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  • 4
    Electronic Resource
    Electronic Resource
    Supercritical fluid chromatography coupled with the Salmonella microsuspension mutagenicity assay (1992)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 344 (1992), S. 442-446 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary On-line bioassay-directed fractionation of environmental samples is important because of the need to assign toxicological activity to certain classes of chemicals. Supercritical fluid chromatography (SFC) was used to fractionate a coal tar standard (SRM 1597) and these fractions were successfully directed into the Salmonella microsuspension mutagenicity assay. The reverse-mutation assay used in these experiments measures mutagenicity in Salmonella typhimurium TA 98 and was performed in a total volume of approximately 200 μl. Coupling of SFC with the microsuspension assay yielded quantitative recovery of the coal tar mutagenic activity, and the SFC chromatogram was compared to the mutagenicity profile to determine the activity of each fraction. This method of coupling SFC with bioassays may have broad applicability for fractionating various environmental samples and for identifying a wide range of biological activities in such samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323740
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  • 5
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    Supercritical fluid chromatography coupled with the Salmonella microsuspension mutagenicity assay (1992)
    Springer
    Details
    Publication Date: 1992-01-01
    Print ISSN: 0937-0633
    Electronic ISSN: 1432-1130
    Topics: Chemistry and Pharmacology
    Published by Springer
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