The use of omicron-phthalaldehyde for fluorescence detection in conventional amino acid analyzers. Sub-nanomole sensitivity in the analysis of phenylthiohydantoin-amino acids.

A conventional amino acid analyzer has been modified for fluorescence detection using omicron-phthalaldehyde. The original ninhydrin system is retained, and the amino acid analyzer can be used with either of the detection systems. The fluorescence detection is used for identification of PTH-amino acids after back hydrolysis, when nanomole amounts of proteins are sequenced. Impurities in the water and the chemicals used for buffer preparations are limiting factors for the sensitivity of the fluorescence detection system. A 100-fold increase in sensitivity above the original ninhydrin system is obtained.