Application of the Freezing Treatment Method to Determination of Ethiofencarb, Dieldrin and Captan in Onion

A simple and rapid method for gas chromatographic determination of ethiofencarb, dieldrin and captan in onion was developed. The objective of this report was to demonstrate the applicability of the freezing treatment method which was proposed in the previous paper to FPD (S)-GC and ECD-GC.First of all, the sample to be analyzed was frozen to inactivate enzymes. The sample was cut into pieces, placed in a mixer cup containing dilute phosphoric acid and then homogenized. Pesticides in the homogenized sample were extracted with aqueous acetone. The extract was concentrated in vacuo, diluted with NaCl solution and reextracted with hexane. Ethiofencarb in the hexane extract was determined by FPD (S)-GC using a capillary column of ULBON HR-1. For dieldrin and captan analysis, a part of the hexane extract was further cleaned up by Florisil column chromatography and the pesticides were determined by ECD-GC using the same column described above.No interfering peak was found on the gas chromatograms of onion extracts. The recoveries of the pesticides from onion were more than 84%.