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Received: 15 September 2016
Received in revised form: 7November 2016
Accepted: 9 October 2016
Keywords
Organochlorine pesticides
Fruits
Vegetables
QuEChERS
GC-ECD
Abstract
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.
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Introduction
Pesticides are applied worldwide in agriculture to ensure high crop yields and improve the food production (Rashi etal, 2012). Their applications are especially recommended during production and postharvest treatment of agricultural commodities (Levitt et al., 2001), and also in the public health sector for disease vector control (Crentsil et al., 2011). In Thailand, farmers use insecticides widely in fruit and vegetable production, probably due to their perception that no better alternatives are available, and the investment on pesticides application is good enough for higher income (Hardy, 1995). However, the pesticide residues persist in fruits and vegetables and result in environmental contamination. Furthermore, because fruits and vegetables are mainly...