Residue Analysis of Endosulfan in Pigeon Peas

Abstract

Samples of pigeon peas treated with two applications, 8 days apart, with 0.56 or 1.12 kg/ha of active Endosulfan were analyzed by gas chromatography for residues of the two isomers of Endosulfan and a metabolite, Endosulfan sulfate. The 0.56 kg treatment had total residues among six machineshelled samples picked 6 h after last application that varied from 0.61 to 1.10 p/m, all of which are below the 2.0 p/m tolerance assigned to Endosulfan in peas by the Food and Drug Administration. Analysis of six machine-shelled samples harvested 6 h after the last application of 1.12 kg revealed total residues from 1.4 to 2.3 p/m. Five days after the last application, six handshelled samples from the 0.56 kg treatment had 0.07 to 0.11 p/m total residues, while the 1.12 kg treatment had 0.13 to 0.33 p/m. The disappearance of the two isomers of Endosulfan and the appearance of Endosulfan sulfate between the two harvest dates agree fairly well with previous reports on other crops. Preparation of samples for analysis followed the standard chlorinated hydrocarbon residue methodology, except for a slight change in the partition step, and elimination of the column cleanup. Recoveries varied from 71-117% in samples fortified from 0.1 to 3.0 p/m levels, and little interference from co-extractives was found at even the lowest level.