Gas chromatographic-tandem mass spectrometric analysis of pesticides residues in produce using concurrent solvent recondensation-large volume injection

In the present work, the feasibility of the combined use of concurrent solvent recondensation-large volume injection (CSR-LVI) and interspersed calibration for pesticide residue analysis was investigated. Splitless injections of 5-20 mu L extracts containing 0.25-1 g sample per mL(-1) were made into a Carbofrit packed liner and a 0.53 mm I.D., uncoated and deactivated retention gap. The determination was achieved by gas chromatography-tandem quadrupole mass spectrometry (GC-QqQ-MS/MS). The evaluation of the proposed approach was based on analysis of real samples representing a diverse range of commodities such as apples, barley malt, blackcurrants, carrots, clemetines, grapes, leek, plums, rapeseed (green plants) rucola, strawberries and tomatoes. The samples contained a total of 36 different incurred pesticides at different concentration levels. Also, analyses were carried out of artificial samples representing six differing matrices (apples, blackcurrants, carrots, huckleberry, strawberry and tomatoes) which were spiked with pesticides at known concentrations before proceeding with the extraction. When using 15 and 20 mu L CSR-LVI injection, a decrease of about 30% in peak heights compared with injection of 5 mu L was observed. In the case of 5 and 10 mu L injections, no significant difference was observed when employing to the quantification of the incurred and spiked pesticide residues. In the evaluated experimental variants, overall recoveries of the pesticides were 92 +/- 5% with relative standard deviations of 12 +/- 4% on average. All individual recoveries were in the range between 72 and 103 with RSD between 4 and 21%. About 15% of the instrument run time was saved by the application of interspersed calibration with standards injected between sample extracts. (C) 2011 Elsevier B.V. All rights reserved.