Primary amine derivatives for negative chemical ionization mass spectrometry

Abstract

In order to utilize the selectivity of negative chemical ionization mass spectrometry for amine analysis we have examined a number of biogenic amine derivatives for detection limits, molecularly specific characterization and ease of preparation using negative chemical ionization mass spectrometry with isobutane as the reagent gas. Nitroaromatic derivatives formed from reaction of tyramine with 2,4-dinitrofluorobenzene, p-nitrobenzoyl chloride and 3,5-dinitrobenzoyl chloride had molecular anion detection limits of less than 25 ng. A mixture of derivatives with low volatility were formed with the nitroaromatic derivatives and were used for examination of complex amines like norepinephrine. Dansyl derivatives gave molecular anions of only 2% relative intensity. Derivatives using 2-methoxy-2,4-diphenyl-3(24)-furanone had complex and unsatisfactory fragmentation patterns. Fluorescamine derivatives of polyfunctional primary amines gave intense molecular anions with detection limits of less than 10 ng. These derivatives were easily prepared in aqueous solutions and on balance they appeared to be the most promising candidates for using negative chemical ionization mass spectrometry to screen for the presence of primary amines.