ANALYSIS OF POLYCHLORINATED-BIPHENYLS BY QUADRUPOLE ION-TRAP MASS-SPECTROMETRY .1. CHEMICAL-IONIZATION STUDIES OF CO-ELUTING CONGENER-77 AND CONGENER-110

A quadrupole ion trap mass spectrometer coupled with a gas chromatogra ph was used to study the reactions of two co-eluting polychlorinated b iphenyl (PCB) compounds, congener 77 (3,3',4,4'-tetrachlorobiphenyl) a nd congener 110 (2,3,3',4',6-pentachlorobiphenyl), with a variety of r eagent cations, Analysis of these co-eluting PCB congeners illustrates the analytical challenges of determining concentrations of a toxic '' co-planar'' congener (77) in the presence of a co-eluting congener (11 0), which is less toxic than 77 but present in environmental samples a t greater concentrations, The principal reactions observed with the qu adrupole ion trap instrument operated in chemical ionization mode were protonation, charge exchange, fragmentation and adduct formation. The composite mass spectra obtained from the reaction of mass-selected re agent ions with the co-eluting PCBs were examined for possible analyti cal strategies, and the most promising method for determination of the se congeners, and perhaps PCBs in general, appears to be chemical ioni zation with mass-selected C2H5+ ions from methane.