Automated amino acid analysis with sensitive fluorescence detection.

The fluorigenic o-phthalaldehyde-mercaptoethanol reagent gives good reproducibility with a very stable baseline when applied to the automated analysis of amino acids at the nanomole level. Determination of even smaller quantities is possible; basic amino acids are then preferably eluted separately at constant pH (for example pH 6.0); this eliminates the baseline irregularities that occur with single column systems at high sensitivity settings. The reagent gives excellent results in the assay of small quantities of biological fluids such as blood plasma.