Determination of mercaptans at microgram-per-cubic-meter levels in air by gas chromatography with photoionization detection

Abstract

A method for the gas chromatographic (GC) determination of ethyl, tert-butyl, propyl, sec-butyl, and n-butyl mercaptans in air using a photoionization detector (PID) was established by using air sampling bags. Up to 5 mL of sample was injected into a Hewlett-Packard Model 588OA GC fitted with a 9 ft glass column packed with 100/120 mesh Chromosorb W AW DMCS and coated with 15% SF-96 and 6% OV-225. The oven was held at 65 /sup 0/C and the nitrogen flow rate was 30 mL/min. The photoionization detector was attached to the GC and held at 200 /sup 0/C. The GC detection limit was determined to be 0.06 ng for n-butyl mercaptan and 0.02 ng for the remaining mercaptans with precisions (n = 8, 1sigma, 4 ng) of +/- 7.3, +/- 8.5, +/- 8.1, and +/- 10% for ethyl, tert-butyl, propyl, sec-butyl, and n-butyl mercaptan, respectively. With a 5-mL injection volume, sensitivity is about 2 ..mu..g/m/sup 3/ which is as sensitive as detection by smell since the oder threshold is about 2-4 ..mu..g/m/sup 3/.