NEGATIVE-ION CHEMICAL-IONIZATION MASS-SPECTROMETRY IN THE ANALYSIS OF POLYCHLORINATED BIPHENYL METHYL SULFONES

Mass spectra of 94 PCB methyl sulphones (MeSO2-CBs) and 2 DDE methyl sulphones (MeSO2-DDEs) were recorded after gas chromatography/mass spectrometry (GC/MS) with negative ion chemical ionization (NICI) using methane as the reagent gas. No significant correlation between the fragmentation of the MeSO2-CBs in MS(NICI) and the structure was found. In general, the most abundant fragments were the molecular ions (M-) and (M-19)-, the latter corresponding to (M-Cl + 0)-. The fragment (M-CH3) was observed for about half of the MeSO2-CBs analyzed. NICI of MeSO2-CBs was found to be 500 to 1000 times more sensitive than electron ionization (EI). 2-MeSO2-DDE and 3-MeSO2-DDE were found to have significantly different mass spectra in NICI. 2-MeSO2-DDE gave no molecular ion (M-) while the mass spectrum of 3-MeSO2-DDE was dominated by the molecular ion (M-). GC/MS(NICI) was applied to the analysis of MeSO2-DDEs and MeSO2-CBs in the blubber and liver from a grey seal. The two MeSO2-DDE isomers were found in both tissues and 23 of a total number of 33 MeSO2-CBs detected in the blubber were identified and 10 of 16 in the liver. MeSO2-CBs are retained in the liver with extremely high selectivity. The concentrations on lipid weight basis of MeSO2-CBs in the blubber and liver were 2.7 mg/kg and 21 mg/kg, respectively, and the concentrations of MeSO2-DDEs were 0.1 mg/kg and 0.8 mg/kg, respectively.