HPLC Enantioselective Separation of Aromatic Amino and Hydrazino Acids on a Teicoplanin Stationary Phase and the Enantiomeric Purity Determination of L-Isomers Used as Drugs

摘要

A glycopeptide antibiotic (teicoplanin) bonded stationary phase was employed for liquid chromatographic enantioseparation of dopa, #alpha#-methyldopa, carbidopa, and several other structurally related compounds. The influence of mobile phase composition in both reversed-phase and polar organic modes was investigated. Using a hydroorganic mobile phase, complete enantioseparations of #alpha#-methylamino acids were not attained. However, this type of separation is suitable for the enantiomers of dopa. In polar organic mode, a simple mobile phase composed of methanol and the polar additives triethylamine and acetic acid at very low concentrations was suggested. With the exceptions of #alpha#-methyltyrosine and #alpha#-methylphenylalanine, baseline enantioseparations of all investigated compounds were achieved. Liquid chromatographic methods based on the described enantioseparations proved to be useful for the enantiomeric purity determination of the single enantiomeric drugs levodopa, methyldopa, and carbidopa.