Determination of urinary amino acids by gas chromatography

We have used gas chromatography to measure amino acids in hydrolysates of urine. Pigments were removed by adsorption on activated charcoal-resin which has been treated with salicylic acid. Nor-leucine was added as an internal standard. The amino acids were converted to their n-propyl- N-acetyl esters, which were separated by gas chromatography and quantitated by a flame ionization detector and an electronic integrator. Although overnight hydrolysis of urine and esterification and acetylation of the amino acids were time-consuming, these operations were well suited to batch processing, so that a single technologist could routinely analyze 10 urine samples per day with a single gas Chromatograph. The method quantitated 16 amino acids in a single Chromatographie run. The precision of analysis of specific amino acids was excellent (coefficient of variation