Gas chromatography-time-of-flight mass spectrometry for sensitive determination of organic microcontaminants

Abstract

In this study the spectrum storage rate, linearity of response, and detection limits of time-of-flight mass spectrometry in combination with capillary gas chromatography (GC–TOF-MS) were evaluated. TOF-MS was found to be a very powerful technique with limits of detection in the low pg range for organophosphorus pesticides (OPPs, 1–6 pg), triazine herbicides (4–60 pg) and polycyclic aromatic hydrocarbons (0.3–6 pg). Spectral information of good quality was obtained at spectrum storage rates of up to 500 Hz. For all analyte classes response concentration plots were linear in the range 2 pg–1 ng, which is very important in TOF-MS. GC–TOF-MS was applied to the determination of the above compound classes in various extracts, which were obtained by means of miniaturized extraction procedures. The analytes were extracted from aqueous samples (surface water, tea) and sediment into an organic solvent and 1 μL of the extract was injected into the GC system using a split injector. One software tool, automated spectral peak deconvolution, turned out to be very valuable. It enabled calculation of spectra from overlapping peaks even if their retention times differed only three scans. Peaks were reported with their deconvoluted spectrum, the so-called peak true spectrum. In actual practice this means that peaks had to be separated for 0.3 or 0.15 s at a spectrum storage rate of 10 and 20 Hz, respectively. Three extraction procedures combined with GC–TOF-MS allowed the analysis of the microcontaminants at 0.1 μg/L in surface water, at 2 μg/L in tea, and at 0.01 mg/kg in sediment with a signal-to-noise ratio (S/N) of 10. In other words, relevant real-life detection limits can be obtained even under split injection conditions. ©1999 John Wiley & Sons, Inc. J Micro Sep 11: 663–675, 1999