Indirect resolution of enantiomers of penicillamine by TLC and HPLC using Marfey's reagent and its variants

TLC and HPLC methods were developed for indirect chiral separation of penicillamine (3,3-dimethylcysteine) enantiomers after derivatization with Marfey's reagent (FDNP-Ala-NH(2)) and two of its structural variants, FDNP-Phe-NH(2) and FDNP-Val-NH(2). The binary mobile phase of phenol-water (3:1 v/v) and solvent combinations of acetonitrile and triethylamine phosphate buffer were found to give the best separation in normal and reversed-phase TLC, respectively. The diastereomers were also resolved on a reversed-phase C18 HPLC column with gradient elution of acetonitrile and 0.01 m trifluoroacetic acid. The results due to these three reagents were compared. The method was successful for checking the enantiomeric impurity of l-penicillamine in d-penicillamine and to check the enantiomeric purity of pharmaceutical formulations of d-penicillamine. The method was validated for linearity, repeatability, limit of detection and limit of quantification.