The analysis of nanogram levels of free amino acids by reverse-phase high-pressure liquid chromatography

In recent publications we have described the analysis of peptides and proteins by reverse-phase high-pressure liquid chromatography (1–3). These studies demonstrated that the addition of 0.1% phosphoric acid to the mobile phase allowed the rapid and reproducible analysis of peptidic compounds. In addition phosphoric acid allows uv detection to be used at wavelengths down to 190 nm, thus permitting high sensitivity detection of underivatized samples. It is the purpose of the report to show that this chromatographic system allows the facile analysis of a variety of amino acids. The high sensitivity of the method is demonstrated by the analysis of 0.1 ng of tyrosine.