An ultramicrotechnique for the detection and separation of small molecular weight peptides from amino acids.

An ultramicroprocedure is described for determining picomole concentrations of small peptides and amino acids in microliter quantities of plasma. A micro Cu-Sephadex G-25 column is used to separate the small molecular weight peptides from the amino acids. The procedure is relatively simple, rapid, reliable, accurate, and very sensitive. The limits of sensitivity depend upon the specific activity of the dipeptides or amino acids used; increasing the specific activity gives greater sensitivity.