Determination of diltiazem hydrochloride enantiomers in dog plasma using chiral stationary-phase liquid chromatography.
ABSTRACT The separation and determination of d- and l-diltiazem hydrochloride in dog plasma by a two-column high-performance liquid chromatographic technique are described. Diltiazem hydrochloride and its metabolites were extracted from dog plasma and analyzed on a conventional column (Nucleosil 5C18) with a volatile buffer system. The column effluent of diltiazem hydrochloride was collected and evaporated. The enantiomeric ratio of the collected diltiazem was determined using a chiral column (Chiralcel OC). The method was accurate and sensitive.
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ABSTRACT: The simultaneous stereospecific assay of four stereoisomers of diltiazem hydrochloride in bulk drug and aqueous solution was developed using HPLC on a Chiralcel OF column. The four isomers were quantitated with good precision by the internal standard method. The chiral inversion of (+)-cis-diltiazem hydrochloride in vitro, stability of its (2S, 3S) configuration in the solid and aqueous states was examined by HPLC. Chiral inversion of (+)-cis-diltiazem hydrochloride was not observed in the solid state, and its (2S, 3S) configuration was stable to heat, humidity and light. Chiral inversion of (+)-cis-diltiazem hydrochloride (2S, 3S) was observed in aqueous solution under UV, but not in aqueous solution stored at 80°C for 5h nor under visible light for 10 h. The (+)-cis-diltiazem hydrochloride (2S, 3S) epimerized to (+)-trans-diltiazem hydrochloride (2R, 3S) with a half-life of 5h in aqueous solution under UV but the reverse chiral inversion of (+)-trans-diltiazem hydrochloride (2R, 3S) to (+)-cis-diltiazem hydrochloride (2S, 3S) was not observed.Chromatographia 09/1995; 41(7):450-454. · 1.44 Impact Factor