Derivatizations for Improved Detection of Alcohols by Gas Chrohatography and Photoionization Detection (GC-PID)

Abstract

Abstract Pentafluorophenyldimethylsilyl chloride (flophemesyl chloride, F1) is a well known derivatization reagent for improved electron capture detection (ECD) in gas chromatography (GC)(GC-ECD), but it has never been utilized for improved detectability and sensitivity in GC-photoionization detection (GC-PID). We have now utilized a wide variety of flophemesyl alcohol derivatives in order to show a new approach for realizing greatly reduced minimum detection limits (MDL) of virtually all alcohol derivatives in GC-PID analysis. This particular derivatization approach is inexpensive and easy to apply, leading to quantitative or near 100% conversion of the starting alcohols to the expected flophemesyl ethers (silyl ethers). Detection limits can be lowered by 2–3 orders of magnitude for such derivatives when compared with the starting alcohols, along with calibration plots that are linear over 5–7 orders of magnitude. Specific GC conditions have been developed for many flophemesyl derivatives, in all cases using packed columns. Both ECD and PID relative response factors (RRFs) and normalized RRFs have been determined, and such ratios can now be used for improved analyte identification from complex sample matrices, where appropriate. We have attempted to describe in this preliminary report some interesting results and approaches for improved GC-PID detection of a large number of alcohols and alcohol analogs. The method of derivatization is extremely simple to perform, and appears to lead to a single, well-defined product of known structure in 100% yield or thereabouts. Chromatography for typical flophemesylalcohol analytes can be excellent, as in Figure 1, with symmetrical peak shape, little or no tailing, and overall excellent MDLs. With GC-detector-computer interfacing, we are able to obtain both chromatograms and preliminary as well as calculated data within a single 5–10 minute time span27 The total amount of time per analysis will obviously depend on the particular analyte derivative and the chromatography obtained. RRFs and normalized RRFs are quite easy to determine, they are fully reproducible, and can serve as good markers for a particular alcohol and its flophemesyl derivative. In view of the calibration plots possible and MDLs, these overall analytical methods for GC-ECD-PID using flophemesyl derivatization should, we hope, find widespread and ready acceptance and utility by the analytical community.