Abstract
A gas chromatographic method was developed for the determination of dinoseb, dinoterb and 4, 6-dinitro-o-cresol (DNOC) in citrus fruits by methylation using trimethylsilyldiazomethane (TMSD).These dinitrophenol pesticides were extracted by homogenizing the sample with acetone. After evaporation of the acetone, the pesticides were extracted with dichloromethane. After evaporation, the residue was dissolved in ethyl acetate and the pesticides were methylated with TMSD in the presence of methanol at room temperature for 30min and then cleaned up with a Sep-Pak® Florisil cartridge using diethyl ether-hexane (1:1). The eluate was concentrated and analyzed on a gas chromatograph equipped with an electron capture detector using a SUPELCO SPB-5 capillary column.The calibration curves were linear in the range of 0.01-0.2μg/mL. The detection limits of the respective pesticides in citrus fruits were 0.005μg/g. The recoveries of the pesticides added to citrus fruits at 0.05ppm ranged from 73 to 85%.
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