Gas chromatographic method for determination of p,p'-DDT in DDT technical and formulated products: collaborative study.

A gas chromatographic (GC) method for determination of p,p'-DDT in technical and formulated products was developed and it performed well in an initial small collaborative study among 4 laboratories. Samples are dissolved in chloroform, and p,p'-DDT is separated on an OV-210 column and determined by GC analysis with flame ionization detection. 2,2'-Dinitrobiphenyl is used as an internal standard. The method was subjected to an international collaborative study with 10 participating laboratories. Collaborators received matched pairs of technical DDT products and of water-dispersible powder, emulsifiable concentrate, and dustable powder formulations. Relative standard deviations for reproducibility (RSDR) for the paired samples were 1.16, 1.48, 2.08, and 1.80%, respectively. The method has been approved interim official first action by AOAC as a CIPAC-AOAC method.