Femtomole level of analysis of biogenic amines and amino acids using functional group mass spectrometry

A general method for the determination of compounds possessing either the primary amine structure, R-CH₂-NH₂ (I), or the α-amino acid structure, RCHNH₂COOH (II), has been devised using gas chromatography and mass spectrometry. Trimethylsilyl derivatives of the biogenic amines (phenylethylamines, indoleethylamines, or Ω-amino acids) produce an intense ion at $\text{m}\text{e}$ 174 upon fragmentation; TMS derivatives of α-amino acids produce an ion at $\text{m}\text{e}$ 218. For maximum sensitivity, chromatograms were obtained with the mass spectrometer tuned to detect a single ion fragment characteristic of a group of structurally related compounds (i.e., functional group GC-MS). At $\text{m}\text{e}$ 174 up to 14 compounds of Type I, including glycine, γ-aminobutyric acid, dopamine, and 5-hydroxytryptamine, could be determined in a single analysis. Detection limits range from 10–100 femtomoles (10^?15 moles). At $\text{m}\text{e}$ 218, eight compounds of Type II, including isoleucine, phenylalanine, tyrosine, and DOPA could be determined. This technique has been applied to the assay of these compounds in extracts containing 0.1 mg mouse brain or abdominal ganglia of the marine molluse, Aplysia californica.