Amino acid composition of human nail, as measured by gas-liquid chromatography

We describe a quantitative method for determination of histidine and 16 other amino acids in a nail hydrolysate. This is based on the formation of trifluoroacetyl amino acid methyl esters and gas-liquid chromatographic analysis with use of two columns of mixed stationary phases. Histidine is determined as a triple derivative Nalpha-trifluroacetyl-Nim-carbethoxy methyl histidinate. The specificity and reproducibility of the method are illustrated. As little as 1 mg of amino acid per gram of nail can be determined, and 15 hydrolysates can be completely analyzed in 10 working days. Data obtained from multiple analyses of 10 nail hydrolysates by the method described closely parallel those obtained in another laboratory, in which an amino acid analyzer was used.