ADDUCT ION FORMATION IN THE METHANE-ENHANCED NEGATIVE CHEMICAL IONIZATION MASS-SPECTROMETRY OF 2-(ALKYLTHIO)-S-TRIAZINES AND 2-ALKOXY-S-TRIAZINES

Adduct Ions corresponding to [M + 11]−, [M + 13]−, and [M + 25]− are observed at significant abundance in the high-pressure, methane-enhanced, negative chemical ionization (NCI) mass spectra of seven 2-(aikylthk>)-S-trlazlnes. Under the same experimental conditions an adduct ion at [M + 12]−Is noted In the mass spectra of six 2-alkoxy-s-trlazlnes. These adduct ions are Interferences In the mass spectral analysis of these compounds. Detailed studies using methane-d4, 1802/CH4, and Ar as alternate NCI enhancement gases reveal that the species responsible for adduct ion formation originate from the methane gas. This was confirmed by high-resolution accurate mass measurements of the adduct ions. Colllslonally activated decomposition tandem mass spectrometry experiments were performed In an attempt to elucidate the structure of the adducts. The variation of the adduct Ion abundance as a function of sample pressure, emission current, repeller voltage, and Ion source temperature is also reported and possible mechanisms for the formation of the adduct Ions are examined. © 1990, American Chemical Society. All rights reserved.