Browsing by Author "McKelvie, Kaylan H."

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    MICRO-FLAME PHOTOMETRIC DETECTION IN MINIATURE GAS CHROMATOGRAPHY ON A TITANIUM TILE
    (2019-06-12) McKelvie, Kaylan H.; Thurbide, Kevin B.
    A novel miniaturized gas chromatography - flame photometric detection device built within a titanium platform (Ti µGC-FPD) is presented. The 7.5 cm x 15 cm monolithic Ti device contains both an OV-101 coated separation column (5 m x 100 µm i.d.) and a shielded cavity to house the hydrogen-rich detector flame. The FPD employs a micro counter-current flame (about 250 µm in diameter) that is stabilized by opposing relatively low flows of oxygen and hydrogen (7-10 mL/min O2 and 40 mL/min H2). Under optimal conditions, the minimum detectable limits are about 70 pg S/s for sulfur and 8 pg P/s for phosphorous. The natural (i.e. unfiltered) selectivity for these responses over carbon is near 104.3 for S/C and 105 for P/C. Even greater selectivity over hydrocarbons can further still be obtained by employing conventional interference filters. Overall, good separations with stable and sensitive detector performance are obtained with the device, and its sturdy Ti structure supports robust operation. Results indicate that this Ti µGC-FPD device may be a useful alternative approach for incorporating selective FPD sensing in µGC analyses.
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    A Rapid Analytical Method for the Selective Quenching-Free Determination of Thiols by GC-FPD
    (Springer, 2018-11) McKelvie, Kaylan H.; Thurbide, Kevin B.
    A rapid method is introduced, which facilitates the selective gas chromatography – flame photometric detection (GC-FPD) analysis of thiols. The method uses lead oxide particles or plumbite solution to complex thiols into a solid lead thiolate moiety that can be physically separated from complex sample matrices and then reconstituted as the original thiol in a simple replacement solvent for analysis. While both red or yellow forms of lead oxide are found to remove thiols from sample solutions, the latter does so about 10 times faster than the former. Comparatively, though, plumbite solution is most rapid in this regard and is still 10-fold faster than solid yellow lead oxide. For example, 98± 1% (n = 3) of a 1-butanethiol standard in hexane (600 ng μL-1) was extracted after only 2 min of contact with a 0.06 M plumbite solution. The method allows thiols to be selectively isolated from co-eluting peaks and other sulfur species, which can simplify their determination. It also allows thiols to be removed from complex hydrocarbon matrices for analysis, which can greatly reduce interference from signal quenching when using a conventional FPD. For instance, analysis of a thiol standard in a commercial gasoline by this method showed that the FPD sulfur signal increased from 16 to 97% of its expected value by removing the quenching hydrocarbon interference. Accordingly, results indicate that this method could be a useful alternative approach for the selective analysis of such thiol-containing samples.