Multiresidue method for determination of 20 organochlorine pesticide residues in fruits and vegetables using modified QuEChERS and GC-ECD/GC-MSD

A rapid multiresidue method has been developed for the analysis of 20 organochlorine pesticides (OCs) in fruits and vegetables. The method is based on a modified QuEChERS procedure employing acetonitrile for extraction and partition. Dispersive solid-phase extraction (dSPE), containing primary and secondary amine (PSA) and graphitized carbon black (GCB), was used for cleans-up. Analytical determinations of the 20 OCs were carried out by gas chromatography, using electron capture detector (GC-ECD) and confirmed by mass spectrometry detector (GCMSD). Recovery studies were performed at 0.05, 0.15 and 1.5 mg kg−1 fortification levels, and the results of validation parameters were acceptable (accuracy ranged from 61.2% to 117.6%, precision expressed as %RSD were less than 20 and measurement uncertainty was lower than 50%). The correlation coefficients (r2) obtained for linearity of working range test were higher than 0.995, showing that the method is applicable to routine sample. The limit of detection (LOD) and the limit of quantitation (LOQ) for the OCs tested in apple and lettuce were 0.02 and 0.05 mg kg−1 respectively. The developed method was applied to determine OCs in imported fruits and local vegetables. No residual OCs was detected in any vegetable sample. However, detectable pesticides residues were found in 0.4% (3 apple samples) of the fruit samples. All of the positive samples were contaminated with endosulfan sulfate, which is endosulfan metabolite. None of the samples had contamination higher than the maximum residue limit (MRL) set by Codex.