Positive- and negative-ion mass spectrometry and rapid clean-up of some carbamate pesticides

Abstract

Positive-ion electron impact (PIEI), positive-ion chemical ionization (PICI) and negative-ion chemical ionization (NICI) mass spectra of 9 carbamate pesticides are presented. In the PIEI mode, the spectra showed small molecular peaks, intense or base peaks due to M − CH 3NHCO + H and peaks at m z 58 due to CH 3NHCO. In the PICI mode, peaks due to M + H, M + C 2H 5, M − CH 3NHCO + 2H, CH 3NHCO( m z 58) and M-28 appeared. The cations at m z 58 found in both PIEI and PICI modes seem very useful for screening of a carbamate. In the NICI mode, the spectra showed peaks due to M − CH 3NHCO and characteristic anions appearing at mass numbers higher than molecular ones, which were probably due to dimerization of [M − CH 3NHCO] − followed by hydrogen attachment. Carbamates, which had been added to urine, plasma, whole blood, the liver, kidney and brain, could be rapidly isolated by use of Sep-Pak C 18 cartridges with chloroform as an elution solvent. They could be detected by wide-bore capillary gas chromatography with a SPB-5 column, with satisfactory separation from impurities in their underivatized forms.