Effectiveness of Three Solid Phase Extraction Adsorbents for Sample Clean-Up Prior To Gas Chromatography Analysis of Organochlorine and Pyrethroid Pesticides in Fruits and Vegetables

Three solid phase extraction (SPE) cartridges, based on anion exchanger and non-polar interactions, have been evaluated as clean-up columns prior to organochlorine and pyrethroid pesticides analysis in fruits and vegetables samples. Without a clean-up method the interferences in the fruits and vegetables affected the quantitation of organochlorine and pyrethroid pesticides in fruits and vegetables samples. The objective of this study is to compare the effectiveness between SAX/PSA, Florisil and C18 SPE clean-up columns to eliminate matrix interferences from grape, orange, tomato, carrot and green mustard in the determination of organochlorine (gamma-HCH, heptachlor, aldrin, dieldrin, endrin, captafol) and pyrethroid (permethrin, cypermethrin, fenvalerate) pesticides using gas chromatography with electron capture detection (GC-ECD). The results showed that SAX/PSA was the most effective clean-up column as compared to Florisil and C18. The mean recoveries were between 70-120% for all samples at fortification levels of 0.01, 0.02 and 0.1 mg/kg, except for captafol that was below 70%. Although Florisil was not effective in removing interferences as significantly as SAX/PSA, the analytical recoveries were between 70 and 120% for all samples at fortification levels of 0.01, 0.02 and 0.1 mg/kg, except for captafol, which was more than 120%. In contrast, the C18 column showed that the mean recovery for captafol was within 70-120% for grape at fortification levels of 0.01, 0.02 and 0.1 mg/kg, and for orange and tomato only at 0.1 mg/kg. In addition, the C18 column resulted in unacceptable range of mean recoveries for heptachlor, aldrin and permethrin from grape at all fortification levels and permethrin from orange at 0.01 and 0.02 mg/kg fortification levels. The SPE extracts produce cleaner chromatograms allowing quantitation of pesticides by GC-ECD after ethyl acetate extraction with a limit of detection (LOD) between 0.003 and 0.015 mg/kg in grape samples using SAX/PSA clean-up column. The method was confirmed by gas chromatography-mass spectrometry (GC-MS) which able to detect cypermethrin in tomato, chinese parsley, chinese celery, chilli, brinjal, french beans, green mustard and capsicum from the determination of a total of 508 samples obtained from Malaysian markets. Only the mean value of cypermethrin in brinjal was found to exceed the permissible level according to the Malaysia Food Regulations 1985.

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