Electron Capture/Negative Ionization Mass Spectrometric Characteristics of Bioaccumulating Methyl Sulfone-Substituted Polychlorinated Biphenyls

Abstract

Gas chromatography/electron‐capture negative ionization mass spectrometry (GC/ECNI‐MS) was used to separate and detect a mixture of 24, 3‐and 4‐methyl sulfone‐substituted polychlorinated biphenyls (MeSO2‐PCBs). The dominant fragment ions were [M‐CH3]‐ and [M‐Cl+H]‐, and to a lesser extent [M‐2Cl]‐, [M‐2Cl+2H]‐, [M‐CH3‐Cl+H]‐ and [M‐SO2CH3+H]‐). The structures of the 3‐and 4‐MeSO2‐PCBs varied in the degree (i.e. tetrachloro‐to heptachloro‐) and position of chlorine substitution. With the assistance of multivariate statistical analysis, the abundance of several isotopic clusters of fragment ions relative to that of the molecular ion (M‐) was found to vary as a function of MeSO2‐PCB structure. Compared with other congeners, the relative abundance of [M‐CH3]‐ was significantly lower for MeSO2‐PCBs containing the 4‐MeSO2‐2,5‐dichloro moiety, and the hexachloro‐and heptachloro‐MeSO2‐PCBs had higher relative abundances of [M‐Cl+H]‐. Subtle ECNI mass spectral fragmentation rules therefore exist for 3‐and 4‐MeSO2‐PCBs with respect to congener structure; however, both ion source temperature and pressure must be controlled. Increasing the ion source temperature from 100 to 260°C resulted in an large increase in the abundance of [M‐CH3]‐ relative to M‐ from <20% to >100%, for all the MeSO2‐PCBs studied. For the set of ten 3‐/4‐MeSO2‐PCB pairs, the [M‐CH3]‐ relative abundance ratio was independent of ion source temperature, and was ∽4.5 and ∽1.5 for congeners possessing 2,5‐dichloro and 2,5,6‐trichloro substitution on the MeSO2‐containing phenyl ring, respectively. The effect of an increase in ion source temperature, over the same temperature range, on the relative abundance of hydrogen inclusion‐type fragment ions was much less dramatic. [M‐CH3‐Cl+H]‐ and [M‐Cl+H]‐ abundance often increased, but never exceeded ∽40%. Decreasing the methane reagent gas pressure from 0.5 to 0.05 mbar did not significantly alter the ion source temperature effect on the relative abundance of the fragment ions. However, the ECNI response sensitivity decreased by an order of magnitude. © 1997 by John Wiley & Sons, Ltd.

Methyl Sulfonyl Polychlorinated Biphenyls and 2,2-Bis(4-Chlorophenyl)-1,1-Dichlorethene in Gray Seal Tissues Determined by Gas Chromatography With Electron Capture Detection and Atomic Emission Detection

“…The connection between the GC and the cavity of the AED was via a silylated fused silica capillary transfer line (0.7 m ϫ 0.32-mm i.d.) with a partially sealed exit to obtain a decreased outlet diameter [19]. The transfer line was connected with a silica glass tubing delivering an additional makeup gas flow [20] by a Y-shaped glass press-fit connector.…”

“…From a methodological point of view aryl methyl sulfones have been analyzed mainly by means of gas chromatography (GC) with electron capture detection (ECD) or mass spectrometry (MS) detection [13,18,19]. Both detection techniques exhibit high sensitivity, but laborious clean-up steps prior to GC analysis are necessary to separate aryl methyl sulfones from extracted lipids and parent compounds [1,5,6] or other electron-capturing substances.…”

“…Both detection techniques exhibit high sensitivity, but laborious clean-up steps prior to GC analysis are necessary to separate aryl methyl sulfones from extracted lipids and parent compounds [1,5,6] or other electron-capturing substances. In addition, determination of the methyl sulfone derivatives can be difficult due to restrictions that regard the selectivity of the ECD response or the dependence of the MS response on compound structure or instrumental parameters [13,19].…”

Methylsulfone polycglorinated biphenyl and 2,2‐bis(chlorophenyl)‐1,1‐dichloroethylene metabolites in beluga whale (Delphinapterus leucas) from the St. Lawrence river estuary and western Hudson bay, Canada

“…The MeSO 2 ‐PCBs and ‐DDEs in the isolated aryl sulfone fraction were identified and quantified by a MeSO 2 ‐IS method using gas chromatography coupled with electron capture, negative ionization mass spectrometry (GC/ECNI‐MS). The MeSO 2 ‐PCB congener identity was confirmed by ECNI‐MS fragmentation patterns, as was the isomer group of unknown MeSO 2 ‐DDEs for which an authentic standard was not available [24]. The aryl sulfone fractions from STL ( n = 3) and WHB ( n = 3) males with the highest sulfone levels were pooled and concentrated threefold to obtain full, or total ion current GC/ECNI‐MS spectra ( m/z 50–550) of the MeSO 2 ‐DDEs.…”

Methylsulfone Polychlorinated Biphenyl and 2,2-Bis(chlorophenyl)-1,1-Dichloroethylene Metabolites in Beluga Whale (Delphinapterus Leucas) From the St. Lawrence River Estuary and Western Hudson Bay, Canada

“…The MeSO 2 -PCBs and -DDEs in the isolated aryl sulfone fraction were identified and quantified by a MeSO 2 -IS method using gas chromatography coupled with electron capture, negative ionization mass spectrometry (GC/ ECNI-MS). The MeSO 2 -PCB congener identity was confirmed by ECNI-MS fragmentation patterns, as was the isomer group of unknown MeSO 2 -DDEs for which an authentic standard was not available [24]. The aryl sulfone fractions from STL (n ϭ 3) and WHB (n ϭ 3) males with the highest sulfone levels were pooled and concentrated threefold to obtain full, or total ion current GC/ECNI-MS spectra (m/z 50-550) of the The concentrations are arithmetic means with the ranges in parentheses.…”