STATISTICAL-METHOD TO EVALUATE CLEANUP PROCEDURES IN POLYCHLORINATED BIPHENYL ANALYSIS

The clean-up procedure involved in the trace analysis of polychlorinat ed biphenyls (PCBs) was evaluated by studying GC-MS chromatograms of P CB mixtures after the subsequent steps of the procedure. The complex c hromatograms obtained were evaluated using two methods: the individual PCB congener method and a chemometric approach based on a study of th e autocovariance function. The results obtained are statistically comp arable, proving that the statistical approach is able to determine the total PCB content in the sample quantitatively. Moreover, since the a utocovariance method is based on statistical evaluation of the whole c omplex chromatogram, it can overcome the problems that usually arise b ecause of peak overlapping in PCB mixture chromatograms. It also provi des accurate results when the chromatogram shows interfering peaks and low resolution. This is the case with Aroclor 1242, where some compou nds released by the cartridges strongly interfere with the analysis, r esulting in errors in the quantification of individual PCBs, Highly ch lorinated PCBs (i.e., Aroclor 1260) can be quantitatively recovered (m ean recovery, 100 +/- 1%), In contrast, lower proportions (less than 7 5%) of the less chlorinated compounds (i.e,, those containing two and three chlorine atoms) are recovered because they are selectively retai ned by silica and alumina columns.