Fast and sensitive determination of pesticide residues in vegetables using low-pressure gas chromatography with a triple quadrupole mass spectrometer.

In this study, the feasibility of low-pressure gas chromatography (LP-GC) in conjunction with a triple quadrupole mass spectrometer, as a route towards fast pesticide residue analysis, was investigated. A Varian GC-MS system equipped with a mass spectrometer model 1200 was used. LP-GC-MS experiments were performed on a HP-5 10 m x 0.32 mm x 0.25 microm analytical column connected to a 2.5 m x 0.15 mm non-coated restriction precolumn at the inlet end. For comparison purposes conventional GC-MS analysis was performed on a RTX-5 30 m x 0.25 mm x 0.5 microm column. Under the optimized conditions the analysis time was reduced to 13.3 min with the LP-GC approach which corresponds to an almost threefold gain in speed versus the conventional GC (37 min). Despite the poorer separation power of the LP-GC column, the experiments conducted with tomato and onion extracts spiked with 78 pesticides proved that LP-GC-MS is of practical value to perform full scan screening analysis. Moreover, the rate of false negative results was higher in the case of conventional GC-MS while the LP-GC-MS enabled correct identification of pesticides at lower levels since the peaks were improved in both size and shape. Validation experiments were performed on a sample of 12 representative pesticides for comparison of performance characteristics of the LP-GC and GC approaches with mass spectrometer operated in scan, SIM and MS/MS mode. The LP-GC column set-up interfaced to the MS detector was found to be superior to the conventional GC with respect to obtained linearity, accuracy and precision parameters. Also, lower limits of detection in real extracts were achieved using the LP-GC approach. Finally, the LP-GC-MS/MS analysis of tomato samples with incurred pesticide residues demonstrated the applicability of the developed method for analysis of real samples.