Mass Fragmentographic Method for the Determination of Trace Amounts of Putative Amino Acid Neurotransmitters and Related Compounds from Brain Perfusates Collected In Vivo

Abstract

A mass fragmentographic method for the determination of trace amounts of amino acid neurotransmitter candidates from brain perfusates is described. The analytical procedure includes the measurements of glycine, β-alanine, γ-aminobutyric acid, proline, aspartic acid, and glutamic acid; αalanine, leucine, and sarcosine, undergoing gas chromatographic coelution, are detected simultaneously. Amino acids extracted from dried perfusate residues are converted to the corresponding N-pentafluoropropionyl hexafluoroisopropyl esters by a single-step procedure. Gas chromatographic separation of the amino acid derivatives is achieved on a packed glass column filled with trifluoropropylsilicone as stationary phase. The limit of detection for the different derivatives (signal-to-noise, 3:1) ranges from 50 femtomol to 1 picomol. Deuterium-labeled amino acid analogues are used as internal standards for quantitative measurements. The mass spectral characteristics of the derivatives are compared and discussed. The technique has been applied to the assay of amino acids released in vivo within the pigeon optic tectum, demonstrating the capabilities of the present analytical approach.