High-performance liquid chromatographic determination of alpha-amino acids in pharmaceutical dosage forms using aqueous mobile phase containing copper (II) ions.

A simple high-performance liquid chromatographic method was developed and validated for the determination of three alpha-amino acids (glycine, lysine, cysteine) and the amino acid derivative (N-acetylhomocysteine thiolactone) using aqueous mobile phase containing copper (II) ions. These amino acids were extracted from tablets, vials, effervescent salts and syrups and quantitatively diluted by the mobile phase. The separation was carried out on zorbax TMS column. The mobile phase was either 1.0 x 10(-3) M CuSO4 or 1.0 x 10(-3) M CuSO4 with 1.0% trimethylamine, pH 4.0. A linear relationship was obtained between detector response at 232 nm and the concentration of the studied amino acids in the range of 1.5-50 ng/microL. The intraday precision for 10-replicate samples varied from 0.59-2.66 while the interday precision ranged from 0.91-3.55 as CV%. A good recovery percentage was obtained in the analysis of many dosage forms ranging from 96.93 to 100.85 with a CV% from 0.33 to 1.74. The presented chromatographic separation method does not depend on any pretreatment or derivatization. The described chromatographic conditions, for both linearity and sensitivity, are sufficient for the selective determination of the cited amino acids. The interference from other combined pharmaceutical ingredients was resolved.