An Automated Procedure for the Determination of Total Amino Acids and its Application to the Analysis of Tobacco

An automated procedure for the determination of total alpha-amino acids in aqueous solution has been developed which utilizes the Technicon Auto Analyser I. The procedure is based in part on a manual method proposed by Van Slyke wherein the CO₂ produced in the reaction of amino acids with ninhydrin serves as a measure of the alpha-amino acid concentration. Evaluation of the procedure for the determination of alpha-amino nitrogen in extracts of flue-cured and Burley tobaccos indicates that adequately precise results are obtained which show a fairly high correlation (r = 0.8 to 0.9) with results by the classical Van Slyke nitrous acid procedure. The relation of the amino acid content of a variety of tobacco types, as determined by ion-exchange chromatography, to alpha-amino nitrogen results by the automated and nitrous acid procedures has been investigated. While the results indicate that neither procedure provides consistently accurate values for total amino acids in tobacco, it was found that the results by the automated procedure show a somewhat higher degree of correlation with total alpha-amino acids. It is therefore concluded that the automated procedure may be potentially useful in the evaluation of tobacco