Micro-analysis of amino acids.

An automated amino acid analyzer has been developed for the analysis of amino acids with the sensitivity at the 10-100 pmol level except for proline which requires greater than 50 pmol. omicron-Phthalaldehyde, in the presence of 2-mercaptoethanol, is used for the fluorometric detection of amino groups (Roth, M. (1971) Anal. Chem. 43, 880-882). A post-column reaction of the amino acid with sodium hypochlorite (Bohlen, P. and Mellet, M. (1979) Anal. Biochem. 94, 313-321) gives oxidation products amenable to detection with omicron-phthalaldehyde. The instrument uses high-performance liquid chromatographic pumps capable of micro-flow rates with a minimum pulsation. The method is suitable for routine analyses of amino acids at picomole levels with reproducibility and accuracy comparable to the ninhydrin-based amino acid analysis.