Chester R. Lapeza

Gas chromatographic/mass spectrometric analysis of human serum for non-ortho (coplanar) and ortho substituted polychlorinated biphenyls using isotope-dilution mass spectrometry

Abstract We have synthesized in our laboratory all of the totally carbon-13-labeled PCBs normally found in human tissues. The mixture of carbon-13-labeled PCBs consists of more than 50 congeners including the 13 c 12 -labeled, coplanar, non-ortho substituted PCBs. We used this spiking material to prepare analytical standards at various concentration levels, and established standard curves using isotope-dilution mass spectrometry for each congener over a range of concentrations normally found in human samples. The PCBs were analyzed on a Finnigan MAT 4500 in either the electron-impact or negative-ion chemical ionization mode on a DB-5 capillary column.

Use of reference pools to compare the qualitative and quantitative determination of polychlorinated biphenyls by packed and capillary gas chromatography with electron capture detection. Part 1. Serum

Serum for reference pools of in vivo polychlorinated biphenyls (PCBs) was obtained from four goats that had received one dose (100 mg kg-1) of a selected technical Aroclor (AR) (1016, 1242, 1254 or 1260) and were allowed to recover for 30 d. These pools were used to assess the differences in an analytical method that determines and quantifies PCBs using packed-column gas chromatography (PCGC) (quantified on the basis of mean mass percent. data for grouped PCB peaks) and capillary-column gas chromatography (CCGC) (quantified on the basis of percent. composition data for specific congeners). With CCGC, results were statistically significantly different (p less than or equal to 0.0002) from results with PCGC for ARs 1016, 1242 and 1254 but not for AR 1260 (p = 0.23). When comparing these gas chromatographic methods using bovine serum spiked in vitro with the same ARs at 17-25 p.p.b., it was found that the methods were not statistically significantly different for any of the ARs (p = 0.30-0.92). Levels of serum PCB determined by the two methods for 12 persons, divided into two groups according to exposure, were compared using the paired t-test. Group 1 consisted of three persons with dietary and/or environmental exposure; one with dietary and/or environmental exposure in addition to occupational exposure dating back 20 years. Group 2 consisted of eight persons with recent occupational exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis and analytical characterization of all tetra to octachlorodibenzo-p-dioxins

Abstract We describe the synthesis and analytical characterization of the tetrachlorodibenzo-through octachlorodibenzo-p-dioxins. We determined the relative response factors for each chlorinated dioxin by both electron impact (EI) and negative chemical ionization mass spectrometry (NCI). An assumption of a 1:1 response factor for a polychlorinated dibenzo-p-dioxin (PCDD) congener within a group with the same number of chlorines is valid in EI but is not a valid assumption in NCI. We have determined the proton nuclear magnetic resonance chemical shift and coupling constants for each PCDD. All of the tetrachlorinated through heptachlorinated congeners, with two exceptions, gave appropriate first order proton spectra in Benzene-d6. The vapor phase infrared absorption bands are unique for each PCDD congener and allow a second method of structural assignment.