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

In this study the spectrum storage rate, linearity of response, and detecti on limits of time-of-night mass spectrometry in combination with capillary gas chromatography (GC-TOF-MS) were evaluated. TOF-MS was found to be a ver y powerful technique with limits of detection in the low pg range for organ ophosphorus pesticides (OPPs, 1-6 pg), triazine herbicides (4-60 pg) and po lycyclic aromatic hydrocarbons (0.3-6 pg). Spectral information of good qua lity was obtained at spectrum storage rates of up to 500 Hz. For all analyt e classes response concentration plots were linear in the range 2 pg-l ng, which is very important in TOF-MS. GC-TOF-MS was applied to the determinati on of the above compound classes in various extracts, which were obtained b y means of miniaturized extraction procedures. The analytes were extracted from aqueous samples (surface water, tea) and sediment into an organic solv ent and 1 mu L 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 overlappin g peaks even if their retention times differed only three scans. Peaks were reported with their deconvoluted spectrum, the so-called peak true spectru m. 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 extr action procedures combined with GC-TOF-MS allowed the analysis of the micro contaminants at 0.1 mu g/L in surface water, at 2 mu g/L in tea, and at 0.0 1 mg/kg in sediment with a signal-to-noise ratio (S/N) of 10. In other word s, relevant real-life detection limits can be obtained even under split inj ection conditions. (C) 1999 John Wiley & Sons, Inc.