Complete PCB Congener Distributions for 17 Aroclor Mixtures Determined by 3 HRGC Systems Optimized for Conlprehensive, Quantitative, Congener-Specific Analysis

Three HRGC systems (1: 30m DB-XLB capillary with MS-SIM detection; 2: 60m DB-XLB capillary with full-scan, ion.trap MS detection; and 3: Parallel dual·column DB·17 and series-coupled HP5IHT5 with ECD detection) were used to completely charac· terize multiple lots of 8 different·numbered Aroclor mixtures by quantitative calibration against 9 solutions containing primary standards of all 209 PCB congeners. Despite lower absolute sensi­ tivity and more Aroclor congener coelutions than the dual·column ECD system, the MS systems enabled measurement of more conge­ ners per Aroclor since their greater linear response range did not require dilution of samples and standards. Pairs of different lots of Aroclors 1248 and 1254 displayed markedly different proportions of congeners, and the 1254 pair displayed strong differences in the extent ofortho-chlorine substitution. The tables ofcongener weight percent distributions among Aroclors are more comprehensive and quantitatively precise than those of prior publications. However, the limitations ofsingle.level calibration precluded measurement of all congeners to the ±IO% accuracy desirable for establishing these Aroclors as secondary standards for comprehensive, quantitative congener'specific PCB analysis.