Cleanup of biologigal samples for determining p,p'-DDT and its metabolites.

A method is described for extracting tissue samples with hexane-acetone and hydrolyzing the fat and protein with aqueous sodium hydroxide. p,p'-DDT and its metabolites are measured on a gas chromatograph with an electron capture detector after cleanup on an alumina column. The new cleanup procedure gives 98% recoveries for p,p'-DDT and its metabolites added to fat in vitro, compared with 84% recovery by a modified commonly used method. Comparison by Student's t-test of the new method with the modified method on 32 cattle biopsy, 46 birds, and 20 fish samples for in vivo incurred p,pi-DDT residues showed that the results by the new method were significantly higher at the 95% confidence level. Alkali-hydrolyzed extract did not contaminate the detector. The new procedure avoids the use of dimethylformamide and shortens the time of analyses. A correlation (r=0.68) was observed between the fat-soluble protein concentration of the n-hexane extract and the p,p'-DDT residues.