| Resumo: | An optimised version of the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method for simultaneous determination of 14 organochlorine pesticides in carrots was developed using gas chromatography coupled with electron-capture detector (GC-ECD) and confirmation by gas chromatography tandem mass spectrometry (GC-MS/MS). A citrate-buffered version of QuEChERS was applied for the extraction of the organochlorine pesticides, and for the extract clean-up, primary secondary amine, octadecyl-bonded silica (C18), magnesium sulphate (MgSO4) and graphitized carbon black were used as sorbents. The GC-ECD determination of the target compounds was achieved in less than 20 min. The limits of detection were below the EU maximum residue limits (MRLs) for carrots, 10-50 mu g kg(-1), while the limit of quantification did exceed 10 mu g kg(-1) for hexachlorobenzene (HCB). The introduction of a sonication step was shown to improve the recoveries. The overall average recoveries in carrots, at the four tested levels (60, 80, 100 and 140 mu g kg(-1)), ranged from 66 to 111 % with relative standard deviations in the range of 2-15 % (n = 3) for all analytes, with the exception of HCB. The method has been applied to the analysis of 21 carrot samples from different Portuguese regions, and beta-HCH was the pesticide most frequently found, with concentrations oscillating between less than the limit of quantification to 14.6 mu g kg(-1). Only one sample had a pesticide residue (beta-HCH) above the MRL, 14.6 mu g kg(-1). This methodology combines the advantages of both QuEChERS and GC-ECD, producing a very rapid, sensitive and reliable procedure which can be applied in routine analytical laboratories.
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