THE CHROMATOGRAPHIC DETERMINATION OF GLUTAMIC, ASPARTIC, AND CYSTEIC ACIDS USING AN ANION EXCHANGE RESIN

Optimum conditions for the separation of the acidic amino acids glutamic, aspartic, and cysteic on an anion exchange resin, Dowex-1 × 8, have been studied. The sample to be analyzed is adjusted to pH 7 and placed on a column of Dowex-1 × 8 previously equilibrated with 0.1 M acetate buffer at pH 4. Glutamic and aspartic acids are separated by elution with 0.1 M acetate buffer at pH 4.0–4.6. Cysteic acid is eluted with 0.2 M acetate buffer at pH 5.5–5.9. With this method quantitative separation of synthetic mixtures of the acidic amino acids has been achieved. This method has also been used to determine the dicarboxylic amino acids in acid hydrolyzates of various proteins, of normal protein-free plasma, and of normal urine.