Hydrolysis of Samples for Amino Acid Analysis

There is no single hydrolysis method that will effectively cleave all proteins to single amino acids completely and quantitatively. This is owing to the varying stability of the peptide bonds between the different amino acids and the amino acid side chains, which are themselves susceptible to the reagents and conditions used to cleave the peptide bonds (Table 1). The classical hydrolysis conditions, to which all other methods are compared, is liquid phase hydrolysis in which the protein or peptide sample is heated in 6M hydrochloric acid under vacuum at 110°C for 18–24 h (1). The various methods of hydrolysis described here are summarized in Table 2.