LIPID METHODOLOGY AND POLLUTANT NORMALIZATION RELATIONSHIPS FOR NEUTRAL NONPOLAR ORGANIC POLLUTANTS

Abstract

This work compares the ability of hexane and chloroform with methanol (C/M) to extract lipid, polychlorinated biphenyls (PCBs), and p,p′-DDE from white croaker (Geneonus lineatus) muscle tissue. Hexane extracted on average 25% of the lipid and 73% of the PCB congeners that were extracted by C/M. Both solvents extracted similar quantities of p,p′-DDE. Consequently, PCB and p,p′-DDE lipid-normalized concentrations using hexane values were 2.9 and 3.9 times greater than with C/M values, and greater than fivefold differences are possible using hexane lipid values with C/M pollutant values. Because the solvents primarily extract different lipid pools, the results conceivably approximate the largest lipid-normalized pollutant concentration differences obtainable using common solvents. The differences suggest that lipid-normalized pollutant concentrations in fish muscle tissue will vary among studies without a standardized total lipid method, but more research is required to better identify complex neutral pollutant and lipid relationships before a final standard methodology can be selected. In the interim, we recommend that the Bligh-Dyer method with C/M be used to obtain total lipid for lipid-normalizing pollutant concentrations. If another solvent or system is used, the C/M extraction should be conducted on representative samples to allow for interconversion of lipid results.