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Abstract
A new method combining QuEChERS (quick, easy, cheap, effective, rugged and safe) and DLLME (dispersive liquid–liquid microextraction) followed by gas chromatography-mass spectrometry with selected ion monitoring (SIM) was developed for the simultaneous determination of 19 pesticides from nine chemical groups exhibiting or suspected to exhibit endocrine-disrupting properties in orange samples. Acetonitrile extract obtained from QuEChERS extraction was used for DLLME as dispersive solvent and carbon tetrachloride as extractive solvent to increase the enrichment factor of the extraction procedure. The effect of several extraction parameters, such as volume extract achieved by the QuEChERS method and subsequently used for DLLME, selection of extractive solvent and its volume, was tested. Under optimum conditions, good linearity, satisfactory recoveries and repeatability were obtained. Limits of quantification (LOQs) achieved (ranging from 0.02 to 47 ng/g) were below the maximum residue limits established by the European Union. The proposed method was applied to the monitoring of pesticide residue levels in oranges commercialised in Portugal.
Acknowledgements
This research was supported by a grant from the FCT project “PTDC/AGR-ALI/101583/2008,” COMPETE FSE/FEDER/OE, “PEst-C/EQB/LA0006/2011,” by the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Academy of Sciences (VEGA, project No. 1/0647/11) and by the Slovak Research and Development Agency under contract No. APVV-0797-11. S.C.C. is grateful to “POPH-QREN-Tipologia 4.2, Fundo Social Europeu e Fundo Nacional MCTES.”