ENVIRONMENTAL-ANALYSIS BY DIRECT AQUEOUS INJECTION

The precision, sensitivity, and utility of analyzing water-soluble environmental contaminants by direct aqueous injection (DAI) gas chromatography/Fourier transform infrared spectrometry (GC/FT-IR) and gas chromatography/ion trap spectrometry (GC/ITS) has been investigated. Thirteen low molecular weight, highly water-soluble, or poorly-purgeable compounds were studied. DAI results for GC/FT-IR and GC/ITS were collected on a single day at four concentration levels and subjected to regression analysis. Mean regression correlation coefficients for Gram-Schmidt (GS), maximum absorbance (MA), and ion trap full scan quantification approaches were 0.9882, 0.9895, and 0.9670, respectively. Ion trap linear dynamic ranges exceeded four decades. GC/FT-IR identification limits ranged from 5 to 100 ng while the detection limits for the ion trap were 8-400 pg. A 5-day test of DAI ruggedness was carried out using both spectral approaches. Percent relative standard deviation ( % RSD) ranged from 3.5 to 21.1 for GS, from 1.2 to 7.4 for MA, and from 2.3 to 18.7 for GC/ITS. Mean % RSD values for GS, MA, and GC/ITS were 10.5, 2.5, and 8.0, respectively. An environmental sample analyzed by GC/FT-IR detected one analyte while GC/ITS detected a significant number of analytes. The GC/ITS results were compared to those obtained from quadrupole mass spectrometry analysis of methylene chloride extracts derived from the same sample.