Sample preparation techniques for determination of organochlorine pesticides in Curcuma longa

Abstract

The purpose of this research is to develop a suitable sample preparation technique to analyse and determine the organochlorine pesticides in Curcuma longa. that contains colouring compounds and volatile oils which cause errors in the analysis of organochlorine pesticides in Curcuma longa. by using the GC-µECD. A multiresidue method for the determination of the 17 organochlorine pesticides was carried out by solid phase extraction (SPE) after extracting the sample with a mixture of hexane : dicihloromethane (5:2). The extraction solutions were further cleaned up using mixed mode SPE that contained silica gel, florisil and anhydrous sodium sulfate. The method has been validated and achieved quantitative analysis down to their maximun residue limit. The linearlity range from 1 - 500 ng/mL, method detection limit is in the range of 0.5 - 15.4 ng/g and its method quantitation limit is in the range of 1.4 - 51.2 ng/g. Intra -assay precision, intermediate precision and relative standard deviation were less than 5.5% for all compounds at 5, 25 and 125 ng/g. Recoveries obtained were generally in the range of 60.33 to 180.64%. The method was used to test in 3 Thai markets and 3 commercially - packed samples. All of them were contaminated with DDT and metabolite of DDT in low concentrations and not more than MRLs of USP regulations. The approach can be used as a standard method for quantitative analysis of organochlorine presticides in Curcuma longa. Moreover, it can help boost the export of Thai Curcuma longa. to both Asian and European countries.