It is an automatic machine to determine the amino acid sequence in a polypeptide chain. The individual amino acids obtained by hydrolysis using Edman’s–Sanger’s method can be separated by cation-exchange chromatography. In this method, amino acids are poured to a column that contains a resin to which a negatively charged group is bound. The amino acids are sequentially released from the charged group in the column by eluting with solutions of increasing pH. As the pH increases, the amino acids release hydrogen ion from the α-carboxyl groups and then from the side chains of the α-amino groups.