Evaluation of extraction and cleanup methods for analysis of DDT and DDE in green alfalfa.

CONCLUSIONS: 1. Hexane:ethanol (2∶1) at a ratio of 6 ml per gram of green alfalfa is the superior solvent mixture for extracting DDT and related materials. 2. Allowing the plant material to stand in the solvent 16 hours after mincing is the most thorough extraction method. 3. Eluting the Florisil column with 20% methylene chloride in petroleum ether increases total residue recovery by 18%. 4. Exhaustive Soxhleting with methanol:chloroform of the plant material after the initial extraction yields only an additional 4.6% residue and probably is of no practical value to commercial residue laboratories.