Method of determining the amino acid composition of plant samples and separation of proteins into fractions with buffer solutions.

In the proposed method, the determination of the amount and amino acid composition of extractable and inextractable proteins, nonprotein nitrogen, and free amino acids is performed in one analytical sample. The above-mentioned nitrogenous substances are extracted with borate buffer. Shortened and expanded schemes of separation of proteins into fractions using buffer solutions are given. For the shortened schemes of analysis, the proteins are separated into readily soluble, medium soluble, sparingly soluble, and insoluble fractions, and in the expanded scheme into eight fractions: three fractions of readily soluble proteins, two fractions each of medium- and sparingly-soluble proteins, and insoluble proteins.