Classification of polychlorinated biphenyl residues: isomers vs. homologue concentrations in modeling aroclors and polychlorinated biphenyl residues.

Abstract

SIMCA (soft independent modeling by class analogy), a principal components chemometric modeling program, was used to examine complex mixtures of polychlorinated biphenyl residues (PCBs) in fish and turtles. Individual PCB isomers were measured by electron capture capillary gas chromatography. The authors calculated PCB (Cl/sub 1-10/) congener concentrations by summing 105 isomer concentrations into homologue subgroups. Information theory was used to estimate the maximum information content of the two data sets. The authors compared the results from principal components modeling of samples and Aroclors by using both isomer and Cl/sub 1-10/ homologue concentrations. Modeling of normalized data from Aroclors or their mixtures gave similar sample score plots for both data sets. However, modeling environmental sample congener concentrations gave erroneous classification results when compared to results from modeling isomer data. Although the Cl/sub 1-10/ sums accurately reflect the concentration of PCBs in the sample, calculations to determine PCB profiles as Aroclor mixtures should be made by using individual PCB isomers.