Improved procedure for single DB-XLB column GC-MS-SIM quantitation of PCB congener distributions and characterization of two different preparations sold as "Aroclor 1254"

Complete PCB congener distributions in a panel of Aroclor mixtures were pre viously obtained by combining data from several HRGC systems. In that study quantitation of minor components may have been unreliable due to single le vel calibration against high levels of individual congener standards. Two l ots of Aroclor 1254 had markedly different congener distributions. In this study, the design and performance of a congener-specific PCB analysis metho d employing GCMS-SIM detection of congeners separated on a DB-XLB capillary column are discussed. Quantitation is carried out against a 6-level inclus ive standard curve of a mixture of 144 congeners found in Aroclors. A separ ate procedure to measure trace levels of PCB 126 in Aroclors using the same system, combined with levels initially acquired for other congeners, facil itates estimation of TEQ values (Toxic Equivalencies of the PCB mixtures to 2,3,7,8-TCDD). PCB congener profiles of 15 Aroclor 1254 mixtures are prese nted. These profiles show that the less common, high TEQ variety of Aroclor 1254 was manufactured by an atypical, two-stage chlorination process that was apparently used during the final 1% of Aroclor 1254 production (ca. 197 4-1976).