Comparative study of methodologies for the analysis of organochlorinated compounds in powdered full-fat milk. I. PCBs

The efficiency of various methods of extraction used for the determination of lipids and PCB levels of powdered full-fat milk is compared using identi cal milk samples and the same clean-up and quantification procedures. The solid-liquid procedure provides the best extraction and is the easiest to use and standarize. Silica gel from Bio-Rad and 400 ml of acetone:hexane (1:1, v:v) gives the greatest efficiency for the recovery of the PCBs. The coefficient of variation associated with the determination of PCBs and the lipids extracted from powdered milk using this methodology are below 7.3% and 1.8%, respectively, lower than those found using other extraction metho ds. These results show that it is not necessary to extract total lipids in orde r to determine PCB content. Extraction of apolar lipids alone can yield clo se to 100% of PCB content, and this approach simplifies the following clean -up steps.