Capillary electrophoresis for the determination of bromide, chloride and sulfate as impurities in calcium acamprosate Original Research Article

A capillary zone electrophoresis method with indirect UV absorbance detection is reported for the determination of bromide, chloride and sulfate as impurities in calcium acamprosate. Separation was carried out on a 60.2 cm (50 cm to the detector) × 75 μm i.d. fused-silica capillary at a potential of −10.6 kV and 25°C. For each electrophoretic run, the capillary was first coated with polybrene to reverse the electrosmotic flow, then separation was carried out using an electrolyte containing 10 mM potassium chromate as visualization agent and 1 mM sodium borate. Standard and test solutions were hydrodynamically injected at a pressure of 0.3 psi for 6 s. The tests performed for validation demonstrated the reliability of the method for the determination of chloride, bromide and sulfate as inorganic impurities in the drug substance, under the conditions used. The limit of quantitation ranged between 8 and 20 mg kg−1 for the different anions.