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.