Sequencher provides N-terminal protein and peptide sequencing by using Amino Acid Analyzer. In the first step the free N-terminal amino acid is converted by phenylisothiocyanate to its phenylthiocarbamoyl derivative under mild alkaline conditions. Then this derivative of the N-terminal amino acid is cleaved as a thiazolinone derivative under acidic conditions. After extraction this thiazolinone amino acid it is converted to the more stable phenylthiohydantoin amino acid derivative that can be identified by using chromatography. This procedure is repeated for identification of the next amino acid.