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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In support of a study to relate developmental and cognitive effects with prenatal exposure to selected environmental toxicants, we developed and applied an analytical method to determine the concentration of two persistent pesticides, hexachlorobenzene ( HCB ) and p,p H -dichlorodiphenyldichloroethylene ( DDE ) , and 32 specific polychlorinated biphenyl ( PCB ) congeners in 316 umbilical cords taken in 1986 ± 1987 from women of the Faroe Islands. The analytical method consisted of homogenization of the cords, partitioning, microsilica gel column chromatography for clean -up, and dual -column capillary gas chromatography ( DB -5 and DB -1701 ) with electron capture detection. Several quality control parameters were followed to monitor the performance of the method. Important criteria used before reporting unknown data were the recovery of in vitro -spiked analytes from a bovine umbilical cord ( BUC ) and the percentage lipid obtained for a Certified Reference Material ( CRM ) -350 of mackerel oil ( MO ) . Recoveries of analytes that had been spiked at two concentration ranges ( 0.26 ± 0.95 ng / g whole weight; 0.35 ± 2.42 ng / g whole weight ) into bovine cords ranged from 38.5% to 158% and from 50.4% to 145%, respectively, with a median recovery of 77.7%. Measurement of the percentage lipid for CRM -350 ranged from 73.8% to 107% with a median lipid value of 96.0%. The most prevalent analytes detected ( % ) in unknown umbilical cords were HCB ( 100 ) , DDE ( 100 ) , Ballschmiter / Zell PCBs 153 ( 100 ) , 138 ( 98 ) , 180 ( 98 ) , 170 ( 93 ) , 118 ( 88 ) , 187 ( 86 ) , and 146 ( 83 ) , with corresponding median concentrations ( ng / g whole weight ) of 0.17, 1.19, 0.38, 0.30, 0.17, 0.11, 0.12, 0.09, and 0.07, respectively. Total PCB Ð sum of all measurable PCB congeners Ð had a median concentration of 1.37 ng / g whole weight. The analytes, which were very low in lipid content were also quantified on a lipid -adjusted basis, which provided an analytical challenge in these umbilical cord samples. The gravimetrically measured lipids in the human specimens ranged from 0.01% to 1.43% ( median of 0.18% ) . In the pooled BUCs, our lipid measurements varied from 0.05% to 0.33% with a median value of 0.13%. The utility of using the umbilical cord as a matrix to assess in utero exposure to persistent environmental pollutants, compared with the use of umbilical cord blood or mother's blood, is worthy of debate. Journal of Exposure Analysis and Environmental Epidemiology ( 2000 ) 10, 776 ± 788.

An analytical method is presented for precise identification and quantitation of 29 specific polychlorinated biphenyl (PCB) congeners and 15 chlorinated pesticides in human serum. Analyte surrogates PCB 30, PCB 204, 2,2′,4,4′,5,5′-hexa-bromo-biphenyl, perthane, α-hexachiorocyclohexane, and dichlorobenzophenone were added to each sample. The serum was extracted with an organic solvent and separated by adsorption chromatography into 3 elution fractions for high-resolution gas chromatographic analysis. Each fraction was analyzed by dual-column capillary chromatography followed by electron capture detection. Two capillary columns, DB-5 and DB-1701, with different polarities were used to increase selectivity for each analyte. Quantitation was performed by selecting 2 sets of calibration standard mixtures and 1,2-di-chloronaphthalene as an internal standard. Mean recoveries ranged from 39 to 126% for selected analytes and from 31 to 88% for surrogates. Detection limits for specific congeners and pesticides are reported. Typical chromatographic profiles of calibration standard mixtures, as well as a human sample, are illustrated. Verification of each analyte is assessed, and results of analyses of selected human samples and quality control criteria used to ensure data validity also are presented.