DIRECT DETERMINATION OF NON-UV-ABSORBING COMPOUNDS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A direct liquid chromatographic method with UV detection has been developed for the determination of ethambutol dihydrochloride, a chemotherapeutic drug lacking in chromophoric groups. It allows the simultaneous separation of [S,S(+)]-ethambutol from meso-[S,R(+/-)]-form and its synthetic precursor [S(+)]-2-amino-1-butanol, although it is not stereospecific for the separation of the [R,R(-)]-enantiomer. Important factors affecting the selectivity and efficiency of separation (CuSO4 concentration, temperature and addition of an organic modifier in the mobile phase) have been studied. Moreover the proposed method allows the quantitative determination of ethambutol dihydrochloride in pharmaceutical formulations in order to verify the agreement with the claimed content for the drug.