Automated Amino Acid Analysis

Knowledge of the existence of amino acids dates back over a century in many cases, as does knowledge of their existence in proteins (see Vickery and Schmidt, 1931 ). When amino acids were discovered, their identity was established by isolating and purifying the individual compounds and obtaining elemental analyses After the advent of paper chromatography, this technique was used with a variety of different solvents to identify elution characteristics and demonstrate the purity of isolated compounds. Amino acids were located by the use of a reagent that produced a color with the compound. The most common reagent used for locating amino acids is ninhydrin, which produces a purple color with amino acids, a pink or yellor color with amino acids, and various intermediate colors with compounds containing an amino group and a sulfonic acid, and so on. It also reacts with small peptides such as glutathione. The techniques of paper chromatography were applied to the separation of mixtures of amino acids, such as the components of a protein after hydrolysis, and then to the separation of free amino acids in physiologic fluids and tissues. It was extended by the use of two-dimensional chromatography, in which a different solvent was used in each direction Later, electrophoresis was employed as one of the separating techniques