Amino acids are compounds that occur widely in living organisms and in nature. Amino acids include the enantiomers L-amino acid and D-amino acid, most of which exist as L-amino acids. In recent years, it has been revealed that D-amino acids, which exist in trace amounts, have functionalities such as involvement in memory and learning ability1), and it has become increasingly important to analyze them separately from L-amino acids. (R)-BiAC is a derivatization reagent for LC/MS analysis of D/L-amino acids (chiral amino acids) using a pre-column derivatization method. By using (R)-BiAC and the Derivatization Reagents Set, chiral amino acid analysis can be performed with high resolution and in a short time (19 min.), without the use of specialized equipment.