A sweep co-distillation procedure, a published steam distillation procedure, and an adaptation of an established acid reflux procedure for isolating fumigant residues were compared. Residues were detectable by electron capture gas chromatography at levels approaching or surpassing 0.1 ppm. Fumigants used were carbon tetrachloride, carbon disulfide, ethylene dichloride, ethylene dibromide, methyl bromide, and chloroform. Comparison of the three methods, using the same detection for all, showed that acid reflux was the most promising procedure for recovering added fumigants from grain and extracting fumigation residues. This procedure should be further refined.

A collaborative study was made of the sweep co-distillation cleanup method for multiple residues of chlorinated pesticides in edible fats and oils with determination by electron capture GLC using a column of 15% QF-1/10% DC-200 on 80–100 Gas Chrom Q. Heptachlor epoxide, p,p’-DDE, dieldrin, p,p’-TDE, and p,p’-DDT were added at two levels to butterfat and soybean oil. Mean recoveries of pesticides ranged from 86.0 to 102.1% in soybean oil and 86.4 to 98.8% in butter.

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A method is described for determination of residues of the fumigants methyl bromide, carbon disulfide, chloroform, ethylene dichloride, carbon tetrachloride, and ethylene dibromide in cereal grains. Whole or ground grain is boiled in an acid medium, and the volatile fumigants are dried and collected in cold solvent. Residues are determined by analyzing aliquots of the collected solution by electron capture GLC. Recoveries range from 59 to 105%. Extraction appears to be complete in the 2 hr boiling period specified. An unexplained conversion of carbon tetrachloride to chloroform is described.

Nineteen samples of Florisil, calcined at times ranging from 2 to 16 hours and temperatures ranging from 1000 to 1400°F, were evaluated by checking the elution of certain chlorinated pesticides and the retention of butterfat extractives by the column. Results indicated the choice of 1250°F/ three-hour calcination as the desired “activation.” Subsequent evaluations of 22 lots calcined at these conditions over a 5-month period showed consistency in the product as obtained from the manufacturer. This material, designated 60/100 PR (Pesticide Residue) Grade, is suggested for use in certain pesticide residue methodology.