Determination ofd-Amino Acids Labeled with Fluorescent Chiral Reagents,R(−)- andS(+)-4-(3-Isothiocyanatopyrrolidin-1-yl)-7- (N,N-dimethylaminosulfonyl)-2,1,3-benzoxadiazoles, in Biological and Food Samples by Liquid Chromatography

✍ Scribed by Dongri Jin; Taketsune Miyahara; Tomoyuki Oe; Toshimasa Toyo'oka

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 122 KB
• Volume: 269
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1006/abio.1998.3090

✦ Synopsis

D-Amino acids in food and biological samples labeled with R(-)- and S(+)-4-(3-isothiocyanatopyrrolidin-1-yl)-7-(N, N-dimethylaminosulfonyl)-2,1,3-benzoxadiazoles (DBD-PyNCS) were separated by reversed-phase chromatography and detected fluorometrically at 550 nm (excitation at 460 nm). DL-Amino acids were efficiently labeled at 55 degrees C for 20 min in basic medium. The resulting thiocarbamoyl-amino acids were resolved by an isocratic elution using water:30% methanol in acetonitrile (72:28) containing 0.1% trifluoracetic acid as mobile phase for hydrophilic amino acids and gradient elutions using sodium acetate buffer (pH 5. 2)/acetonitrile as gradient solvent mixture for hydrophobic amino acids, respectively. The detection limits (S/N = 3) of DL-amino acids tested were in the range of 0.16-0.75 pmol. The proposed method was applied to determine the D-amino acid(s) in milk, cream, fermented dairy products (yogurt and yakult), tomato products (juice, puree, and catchup), fermented beverages (beer and red wine), and human urine. The existence of D-amino acid(s) was demonstrated in all the samples tested. Furthermore, the identification of the D-amino acid(s) was performed using both isomers of DBD-PyNCS and by on-line HPLC-electrospray ionization-MS.