83A] Determination of aspartic acid and asparagine

Abstract

Aspartic acid, asparagine, glutamic acid, and glutamine can be determined in the same specimen by making use of two principles. The dicarboxylic amino acids are adsorbed on acid-treated alumina and can be eluted separately, glutamic acid by acid elution, and aspartic acid by alkaline elution. Neither glutamine nor asparagine is adsorbed on the alumina. The solution from which the dicarboxylic acids have been removed is then subjected to acid hydrolysis to convert glutamine and asparagine to the corresponding acids and rechromatographed on alumina. Glutamic acid is determined by oxidation (ninhydrin) to succinic semialdehyde, which is converted to the dinitrophenylhydrazone, extracted selectively for an acid hydrazone, and estimated colorimetrically in alkaline solution. The aspartic acid eluate is estimated by using the ninhydrin color directly. Neither cystine, 13-alanine, nor ∼-aminobutyric acid interferes with the aspartic determination, but glutathione does (approximately 15% of the aspartic acid color).