Development and validation of a capillary zone electrophoretic method for the determination of bisphosphonate and phosphonate impurities in clodronate

Capillary zone electrophoresis with direct UV detection at low wavelength and reversed polarity was applied for the separation and quantitation of bisphosphonate and phosphonate impurities in clodronate bulk material. Polyacrylamide-coated capillaries were used to reduce the interactions between the analytes and the electric double layer of the capillary, and to minimize electroosmotic flow. Study was made of the major factors affecting the separation, i.e., pH and ionic strength of the electrolyte solution and various instrumental parameters. The developed method provided reproducible separations of clodronate and related impurities (between-day precision of migration times: RSD<2.3%, 275 runs). Acceptable validation results in the impurity quantitation range of 0.5–7.5 μg ml−1 (corresponding to 0.1–1.5% of clodronate working concentration) were obtained in specificity, within-day and between-day precision, accuracy and linearity.