Determination of the dissociation constants of ropinirole and some impurities and their quantification using capillary zone electrophoresis

Ropinirole, 4-[2-(dipropylamino)ethyl]-1,3-dihydro-2H-indol-2-one, is a pot ent antiparkinson's disease drug developed by SmithKline Beecham Pharmaceut icals. Capillary zone electrophoresis (CZE) was used for the determination of the dissociation constants of ropinirole and five structurally related i mpurities, potentially formed during its synthesis and for separation and q uantification of these substances. The dissociation constants obtained from the CZE measurements were confirmed by UV spectrophotometry for some of th e test compounds, obtaining a good agreement between the values. Careful op timization of the running buffer composition permitted base-line resolution of the six compounds in a berate buffer containing acetonitrile and magnes ium sulfate (a 100 mM berate buffer containing 30 mM MgSO4 and 20 vol.% of acetonitrile). It was shown that CZE can determine the level of these impur ities, down to a level of 0.05% of the main component within 15 min. (C) 19 98 Elsevier Science B.V. All rights reserved.