Chlorinated pesticides and polychlorinated biphenyls (PCBs) remain public health concerns because of their unresolved health impact and their persistence in humans. Current epidemiological studies of cancer, non-Hodgkins lymphoma, and endocrine disruption in National Center for Environmental Health (NCEH) laboratories require exposure assessment of many analytes in thousands of people. Previous methods of analyzing pesticides and PCBs in serum have proven inadequate for timely processing of the number of samples required for epidemiological studies. A new method that involves solid-phase extraction (SPE) and cleanup followed by dual-column gas chromatographic separation and electron capture detection has been developed. Nine surrogate compounds were added to the serum prior to sample workup to provide quality assurance for the SPE steps. These surrogates mimic the chemistry of the analytes in the extraction, cleanup, and gas chromatographic analysis steps. To increase selectivity, extracts were injected onto two gas chromatographs with different capillary columns, a DB-1701 and a DB-5. Recoveries of 17 pesticides, 28 PCB congeners, and one polybrominated biphenyl congener ranged from 40 to 80%. Recoveries from this procedure were found to be similar to those from the previously used liquid-liquid extraction method. Correlation of analyte and surrogate recoveries were compared to examine the ruggedness of the technique. The SPE method was found to provide improved sample throughput by a factor of 15.

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A method is presented that can be used to determine the residue level of certain chlorinated pesticides and polychlorinated biphenyls (as Aroclor 1260) in serum. The method involves the following: (1) extraction of denatured serum with organic solvents; (2) elution of the organic extract through micro-Florisil columns to obtain two fractions; (3) acid treatment of the less polar Florisil fraction and its subsequent elution through deactivated silica gel to obtain two fractions; and (4) analysis of all three fractions using gas-liquid chromatography with electron capture detection. The method produced in vitro recoveries for 10 pesticides spiked in the range of 1-10.7 ppb of 50.4% to 121.6%, and in the range of 4.98-21 ppb, recoveries ranged from 47.7 to 112.6. In vivo "recoveries" of Aroclor 1260 averaged 104.8% and 92.3% for concentration levels of approximately 10 and approximately 30 ppb, respectively. The method could not be compared with the more commonly used hexane extraction technique because of the deleterious effect these extracts had on the gas chromatographic system.