Use of a retention gap for the trace analysis of volatile polar organics at the ppb level by direct aqueous injection

Abstract

Short Communications t 066811 0669respond very strongly to methanol (Figure 1 b). The only solvent interference observed was a slight negative response. The first peakwas due to MEK, and this was followed by the elution of THF, acetone, benzene, TCE, and MIBK. Only the THF peak was affected by this negative perturbation. With a thick-film Carbowax column the methanol coeluted with both MEK and THF and obscured both peaks.All components of the test mixture with the exception of acetone could be determined atthe 1 -ppm level using on-column injection of methanol solutions and a PID. Acetone could be determined in methanol at the 10-ppm level. Figure 1 Chromatograms for methanol solutions of volatile polar organics obtainedusinganFlD(a)anda PID(b).Thesamplecontained 1 ppmeach of acetone, MEK, THF, benzene, TCE, and MIBK. One-microliter aliquots were injected into a 50 m X 0.32 mm 0.2 pm Carbowax bonded-phase fused silica capillary column. Results and DiscussionSince the FID responds to methanol, a broad tailing solvent peak was obtained using that detector (Figure la). In contrast, good chromatograms were obtained using the PID because it does not