VOLATILE ORGANIC-ANALYSIS BY DIRECT AQUEOUS INJECTION

Gas chromatographic environmental analysis by direct aqueous injection (DAI) was studied for 24 volatile organic analytes (VOAs). Internal s tandardization was used to determine the precision of analyzing these compounds by DAI. Aqueous samples were directly introduced to a gas ch romatograph using fused-silica, mega-bore capillary column separation with subsequent full-scan ion trap mass spectral detection. Triplicate injections at seven levels of VOA standard solutions over a 10(3) con centration range were performed using an autosampler set up for on-col umn injection of 0.2 mu l. Comparison of single-ion response curves to triple-ion response curves showed that triple-ion quantitation was mo re sensitive and precise than single-ion quantitation. Of the 24 VOAs determined at the 20 parts per billion (ppb) level, 19 and 20 were det ected by the single-ion calibration and triple-ion calibration, respec tively. The weighted and non-weighted regression correlation coefficie nts, r(2), for the 24 responses curves by the two methods, ranged from 0.910 to 0.998, with 76 of 96 being greater than 0.990. Precision, as measured by per cent relative standard deviation, was shown to be bes t for later eluting compounds and for higher concentrations. Analysis of an environmental sample by DAI was accomplished in 12 min and indic ated the presence of benzene at 80 ppb and chlorobenzene at 2 ppm. Thi s demonstrated the feasibility of applying this technique for screenin g. Several chlorinated benzenes were also detected, establishing the p otential for expanding the method to include higher boiling compounds.