The application of gas-liquid chromatography and mass spectrometry of amino acids to the diagnosis and study of metabolic disorders

The present study was aimed at the development of a method suitable for the gas-liquid chromatographic analysis of amino acids and for the diagnosis and study of aminoacidurias• The derivatives of choice were found to be the N-neopentylidene amino acid ethyl esters which could be separated by gas chromatography and readily identified by mass spectrometry. The method was adaptable to the analysis of physiological fluids and i t was applied to the detection of some 15 of the known disorders of amino acid metabolism. The characteristic mass spectra of these volatile derivatives makes them useful for the structural elucidation of ninhydrin positive metabolites. To make the procedure more amenable to routine clinical investigations, a rapid \u27on-column\u27 methylation technique was developed which eliminated the time consuming acid-catalysed esterification step. This simplified derivatisation offers advantages in speed and convenience over previously pxablished methods. It was applied to the analysis of seriam amino acids and was shown to be useful for metabolic pathway studies employing deuteriiam labelled amino acids such as tyrosine. A closer examination of the new pyrolysis technique led to the identification of some by-products of the decomposition of the trimethylanilinium hydroxide reagent. Finally, the pyrolysis procedure was developed further to give a synthetic route to the benzyl esters of fatty acids and amino acids. Preliminary findings have indicated that the benzyl esters and the l-naphthylmethyl esters may be suitable derivatives for the high pressure liquid chromatography of carboxylie acids using ultra-violet and fluorescent detectors