Dantrolene sodium (Chart 1) is the hemihepta hydrate of sodium salt of 1-[5-(4-nitrophenyl)furfulidene amino]imidazolidene-2,4-dione. It is a muscle relaxant reported to act by blocking muscle concentration beyond the neuromuscular junction.1) It is described for the symptomatic relief of muscular spasm due to condition such as stroke, multiple sclerosis, spinal cord injury and cerebral palsy. Dantrolene sodium is used also intravenously in the treatment of malignant hyperthermia.
1)Only few liquid chromatographic methods 2-8) were described for assay of dantrolene sodium in dosage form and biological fluids. The chromatographic methods usually necessitate sample pretreatment and time-consuming extraction steps prior to analysis of the drug. Moreover, these methods required expensive equipment and considerable skills are necessary to operate them successfully. Although no official analytical method for determination of dantrolene sodium is reported in British or the United States pharmacopoeia an official electrometric titration method for determination of the drug is available in the Japanese pharmacopoeia. Besides, no any information is available in the literature to date concerning the electroreduction of dantrolene sodium or its electroanalytical determination. Therefore, the present work aimed to study the electroreduction pathway of dantrolene sodium at the mercury electrode and to describe simple and precise electroanalytical procedures for its determination in bulk form and pharmaceutical formulation.
ExperimentalInstrumentation A Sargent-Welech Polarograph Model 4001 (Fisher, U.S.A.) was used for the present polarographic measurements. The electrolysis cell was as that previously described by Meites. 9) Characteristics of the capillary of the dropping mercury electrode (DME) were: mϭ1.13 mg/s and tϭ3.36 s in a solution of 0.1 M KCl at open circuit conditions for a mercury height of 60 cm. A saturated calomel electrode was used as a reference electrode.Computer-controlled Electrochemical Analyzers Models 273A and 363A-PAR (Princeton Applied Research, Oak Ridge, TN, U.S.A.) controlled via 270/250-PAR software were used for the voltammetric measurements. An electrode assembly (303A-PAR) incorporated with a three-electrode configuration system comprising of a hanging mercury drop electrode (HMDE) or a dropping mercury electrode (DME) as a working electrode (surface areaϭ0.026 cm 2 ), an Ag/AgCl/KCl s reference electrode and a platinum wire auxiliary electrode, was used. A magnetic stirrer (305-PAR) and a stirring bar were used to provide the convective transport during the accumulation step.A potentiostat/galvanostat (Model 173-PAR) incorporated with a digital coulometer Model 179-PAR was used for controlled-potential electrolysis of dantrolene sodium solutions. The coulometric cell used was designed by Princeton Applied Research (PAR) Corporation to have a large electrode surface area to solution volume ratio as possible. A mercury pool as a working electrode, a saturated calomel electrode as a reference a...