Analytical and preparative enantioseparation of dl-penicillamine and dl-cysteine by high-performance liquid chromatography on α-acid glycoprotein and β-cyclodextrin columns using ninhydrin as a reversible tagging reagent

Two sulfur-containing amino acids, dl-cysteine (Cys) and dl-penicillamine (PenA), were condensed with ninhydrin to form their spirothiazolidine derivatives. These were separated by HPLC using α-acid glycoprotein (AGP) and β-cyclodextrin (β-CD) columns. The resolution conditions were optimized and the results were compared. Since the method provided resolution greater than 2 it was also applied to preparative separation. After separation, each of them was detagged using Zn dust and 10% aqueous trifluoroacetic acid. For analytical purposes dinitrophenyl (DNP) derivatives of dl-Cys and dl-PenA were also prepared and were resolved on both the columns. The detection was carried out using photodiode array detection system at 231 nm. The limits of detection were found to be 0.01% and 0.004% for spirothiazolidine carboxylic acid and DNP derivatives, respectively.