Analytical method for minute amounts of polychlorinated biphenyl methylsulfones from fatty tissue

Five methylsulfone (MSF) derivatives of polychlorinated biphenyls (PCBs) containing 2 to 6 chlorine atoms were synthesized and fortified in bovine fat. The samples were saponified in sodium hydroxide ethanol solution, extracted with n-hexane after dilution with a double volume of water, and chromatographed on a column of silica gel eluting successively with n-hexane and 5% and 50% diethyl ether in n-hexane. The third eluate was partitioned between n-hexane and concentrated sulfuric acid and back-extracted with n-hexane from 70% sulfuric acid solution. The extract was further partitioned between n-hexane and 90% acetonitrile and back-extracted with n-hexane from 20% acetonitrile solution. The final extract was analyzed by gas chromatography with electron capture detection. Recovery of the MSF-PCBs from the bovine fat by the clean-up procedure was greater than 93% in most cases. The method can determine 5 ng and 100 ng each of the MSF-PCBs in a 5-g fatty sample with ca. 10 and 6% precision, respectively.