Reversed-phase high-performance liquid chromatographic analysis of cinchona alkaloids in pharmaceuticals

An high-performance liquid chromatographic assay for quinidine and dihydroquinidine sulphates in pharmaceutical dosage forms has been developed. The method makes use of a reversed-phase system with a C18 bonded column and theophylline as an internal standard. Recovery of both compounds is quantitative and the method compares favourably with that of the United States Pharmacopoeia with regard to speed and precision. The method should also be suitable for the control of quinine salts in pharmaceuticals.