A comparison of three mass spectrometric methods for the determination of dioxins/furans (vol 194, pg 235, 2000)

A comparison is presented of the performances of three mass spectrometers o f high specificity in the determination of dioxin/furan congeners. The thre e instruments used in this study were a triple-sector EBE mass spectrometer operated at high mass resolution (HRMS), a quadrupole ion trap (QIT) mass spectrometer, and a triple-stage quadrupole (TSQ) mass spectrometer. The QI T and TSQ instruments were operated in tandem mass spectrometric mode. A mi xture of tetra- to octa-chlorodibenzo-p-dioxins (T-4-O8CDD) containing in a ll seven dioxin congeners was used for much of this study. The factors cons idered in this comparison were the tuning of each instrument, the preparati on and comparison of calibration curves, the 2,3,7,8-T4CDD detection limit for each instrument, ion signals due to H(6)CDDs obtained with each instrum ent from two real samples (air and pyrolysed polychlorinated phenols), aver age relative response factors, and ionization cross sections. For each diox in congener, the response factor is expressed relative to that for the O8CD D congener, whereas the electron impact ionization cross section is express ed relative to that for the T4CDD congener. The relative ionization cross s ections for T-4-O8CDD from HRMS and QIT, and for T-4-P5CDD from TSQ are in good agreement, and show an overall decrease of some 10-20% with increasing degree of chlorine substitution; the variation among three H6CDD congeners is identical in each case. With TSQ, lower relative ionization cross secti ons for H-6-O8CDD are ascribed to mass-dependent fragment ion scattering in the RF-only collision cell. (C) 2000 Elsevier Science B.V.