Determination of pesticides in soil samples by supercritical fluid chromatography-atmospheric pressure chemical ionisation mass spectrometric detection

This paper presents an analytical technique for the determination of pestic ides in soil by packed-column supercritical fluid chromatography interfaced with atmospheric pressure chemical ionisation mass spectrometry (pSFC-APCI -MS). The technique provides a versatile method for the detection and quant ification of pesticides belonging to three different commonly used classes, triazines (ametryne, atrazine), carbamates (carbofuran) and sulfonylureas (chlorsulfuron, metsulfuron methyl and benzsulfuron methyl). The APCI mass spectra for all the pesticides studied consisted of protonated molecule ion s as the most abundant ion at low cone voltages, except for metsulfuron met hyl and benzsulfuron methyl, which gave a fragment ion as the most abundant ion with the protonated molecule ion at low intensity. Increasing the cone voltage provided informative fragmentation patterns for all species. The t echnique shows good linearity over the concentration range of 0.1-50 mu g m l(-1), with r(2) values as follows: atrazine 0.997, ametryne 0.995, carbofu ran 0.999, benzsulfuron methyl 0.999, chlorsulfuron 0.995 and metsulfuron m ethyl 0.997. The detection limits in the selected ion mode were atrazine 20 1, ametryne 144 and carbofuran 385 pg, which were calculated by using the s tandard solution, and benzsulfuron methyl 2.045, chlorsulfuron 1.435 and me tsulfuron methyl 2.414 ng, which were determined by using spiked soil sampl es. The pSFC-MS system was shown to have a high degree of reproducibility. The technique was then applied to the determination of the above pesticides in soil samples. The results obtained show that there is no matrix effect from the soil and that the detection limits for all pesticides in soil were similar to those found for the standard solutions.