Multiresidue determination of 375 organic contaminants including pesticides, polychlorinated biphenyls and polyaromatic hydrocarbons in fruits and vegetables by gas chromatography-triple quadrupole mass spectrometry with introduction of semi-quantification approach

A residue analysis method for the simultaneous estimation of 349 pesticides, 11 PCBs and 15 PAHs extracted from grape, pomegranate, okra, tomato and onion matrices, was established by using a gas chromatograph coupled to an electron impact ionization triple quadrupole mass spectrometer (GC-EI-MS/MS). The samples were extracted by ethyl acetate and cleaned by dispersive solid phase extraction with PSA and/or GCB/C-18 by the methods reported earlier. The GC-EI-MS/MS parameters were optimized for analysis of all the 375 compounds within a 40 min run time with limit of quantification for most of the compounds at <10 mu g/L, which is well below their respective European Union-Maximum Residue Levels. The coefficient of determination (r(2)) was >0.99 within the calibration linearity range of <5-250 ng/mL for compounds with LOQs < 5 ng/mL While for the compounds with LOQs within 5-10 mu g/kg, the lowest calibration level was 5 and 10 mu g/kg as applicable. The recoveries at 10, 25 and 50 ng/mL were within 70-110% (n = 6) with associated RSDs < 20% indicating satisfactory precision. The information generated from the single laboratory validation was further utilized for building a semi-quantitative approach. The accuracies in quantification obtained via individual calibration standards vis-a-vis semi-quantification approach were comparable. For incurred samples, the concentrations estimated by the semi-quantification approach were within +/- 10% of the values obtained by direct quantification. This approach complements the existing GC-EI-MS/MS methods by offering targeted screening and quantification capabilities. (C) 2012 Elsevier B.V. All rights reserved.