APPLICATION OF FACTORIAL DESIGN TO THE STUDY OF PARAMETERS IN THE DETERMINATION OF PESTICIDE RESIDUES IN APPLE BY HEADSPACE SOLID PHASE MICROEXTRACTION COUPLED TO GAS CHROMATOGRAPHY-MASS SPECTROMETRY
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Date
2012
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PACCON International Conference
Abstract
Solid-phase microextraction (SPME) is a solvent-less sample preparation method which combines sample preparation, isolation, concentration and enrichment into one step. SPME process involves two basic steps which are the partitioning of analytes between the polymeric fiber coating and the sample matrix, and desorption of the concentrated extracts into the analytical instrument, without any clean-up step. In this study, factors affecting the solid phase microextraction of pesticide residues (fenobucarb, diazinon, chlorothalonil and chlorpyrifos) were studied using a factorial design. The interactions and effects of temperature, time and salt addition on the efficiency of the extraction of the pesticides were evaluated using 23 factorial designs. A 10 g sample was weighed into 20 mL amber glass vial, fortified with the standard mixture at three concentration levels (10, 50 and 100 µg.L–1) and allowed to rest for 2 hrs. Optimum dilution was made with 10 mL of distilled water containing 10% NaCl and the mixture was shaken ultrasonically for 3 min. The analytes were then extracted with 100 µm PDMS fibers according to the factorial design matrix and desorbed into gas chromatography–mass spectrometry detector. The developed method was applied for the analysis of apple samples and the limit of detections was between 0.01 and 0.2 µg.L–1, which were lower than the MRLs for apples. The relative standard deviations were between 0.1 and 13.37% with average recovery of 80 to 105%. The linearity ranges from 0.5 – 50 µg.L–1 with RSD greater than 0.99