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Comparison of Extraction Methods for Analysis of DDT, DDE, and DDD in Alfalfa Hay^1,2,

Department of Dairy Science

G. W. Ware

Department of Entomology, The University of Arizona, Tucson

ABSTRACT

Various extraction methods and solvent systems were compared for analysis of DDT and its analogs in alfalfa hay containing a comparatively low level of these materials. The procedures evaluated were a) high-speed mixing for 10 minutes, b) Soxhlet extraction for 16 hours, c) mechanical shaking for 16 hours, d) refluxing for 1 hour and a combination of a) and b). The solvent mixtures used were acetonitrile: water (1.85:1), hexane:ethanol (2:1), hexane:methanol (2:1), chloroform:ethanol (1:1), chloroform:methanol (1:1), and acetonitrile (100%). Analysis of material from a single extraction using gas chromatography with electron capture detection showed that extraction with chloroform:methanol (1:1) in the high-speed mixer for ten minutes gave the most exhaustive treatment. Mechanical shaking for 16 hours with this solvent mixture was 90% as effective. The least extensive removal was by Soxhleting alone or in conjunction with high-speed mixing. Refluxing for 1 hour or the use of a high-speed mixer gave intermediate results between mechanical shaking and Soxhleting. Solvent costs, ease of handling, convenience of equipment cleaning, and total elapsed time for analysis are other possible considerations in the selection or use of a given method.

¹ Arizona. Agricultural Experiment Station Technical Paper no. 1311.

² This work was supported in part by Grant no. EF-00627-2 from the USPHS and a grant from the United Dairymen of Arizona.