Chromatography of amino acids on sulfonated polystyrene resins.

The quantitative separation of amino acids by chromatography on columns of starch has sheen described in previous publications (l-3). In extending these investigations, a systematic study has been made of the separations of amino acids by elution analysis on columns of synthetic ion exchange resins. With a sulfonated polystyrene resin, Dowex-50, it has been possible to develop a chromatographic technique applicable to a wider variety of problems of biochemical interest. Starch columns possess the disadvantage that fluids of high salt content, such as blood plasma or urine, require desalting prior to chromatography (4). Moreover, contamination of the effluent by traces of carbohydrate, coupled with the relat,ively low capacity of these columns, tends to interfere with the isolation of pure compounds (5). Methods in which columns of Dowex-50 are employed have been found to be free from these difficulties. Ion exchange resins of various types have been used in the past to separate amino acids into groups, acidic, basic, and neutral, and also to separate some of the individual basic or acidic amino acids (cf. (6)). The data of Englis and Fiess (7) indicated that certain of the monoamino acids are adsorbed to different degrees by sulfonic acid type resins, but little information was available as to whether columns of ion exchange resins could yield a degree of resolving power comparable with that obtainable with starch or paper. Recently Partridge and coworkers (8-11) have employed displacement development on ion exchange columns for the separation of amino acids on a preparative scale. Those primary fractions containing more than one amino acid were rechromatographed. Their experiments, together with our results by elution analysis (4’), have demonstrated that synthetic resins are capable of separating most of the common amino acids from one another. For analytical experiments, and for isolation work on a small scale, elution analysis would appear to possess higher resolving power and, for this reason, has been employed in the present studies. In Fig. 1 is shown the result obtained upon passage of a complex mixture of amino acids through a 0.9 X 100 cm. column of Dowex-50. This particular resin (Bauman and Eichorn (12)) is one which is available com-