title: Simultaneous determination of some dihydroxybenzenesulphonic acid derivatives and their degradation product and main impurity (hydroquinone) by ion-pair liquid chromatography.
abstract: A simple and sensitive high-performance liquid chromatography method was developed and validated for the determination of calcium dobesilate (DOB) or ethamsylate (ETM) in the presence of their degradation product, hydroquinone (HQ). The analyses were carried out on Promosil C18 column (4.6 mM × 250 mM, 5 µm particle size) using an ion-pair mobile phase consisting of methanol-1.5 mM tetra-butyl ammonium bromide in 0.06 M phosphate buffer (25 : 75, v/v) at pH 6.0 with fluorescence detection at 286/333 nm. Pindolol was used as an internal standard. The proposed method was found to be rectilinear over the concentration ranges of 0.05-0.5 µg/mL for DOB, 0.1-0.8 µg/mL for ETM and 0.005-0.1 µg/mL for HQ. The method was applied for the determination of the studied drugs in different dosage forms and biological fluids. The results of the proposed method were statistically compared with those obtained by the comparison methods revealing no significance differences in the performance of the methods regarding accuracy and precision. Moreover, applying a time-programmed fluorescence technique was valuable for the detection of trace amounts of HQ as an impurity and allowed purity testing of ETM or DOB within the BP pharmacopeial limit (0.1%).
authors: Department of Analytical Chemistry, Faculty of Pharmacy, University of Mansoura, Mansoura, Egypt.
authors: M M
authors: MM
authors: Tolba
mesh_terms: D002123:Calcium Dobesilate / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D004979:Ethamsylate / Q000032:analysis*; D006873:Hydroquinones / Q000032:analysis*; D015394:Molecular Structure
chemical_list: D006873:Hydroquinones; D004979:Ethamsylate; D002123:Calcium Dobesilate; C031927:hydroquinone
keywords: Calcium dobesilate; Ethamsylate; Fluorescence detection; Human plasma and urine; Stability-indicating assay