Simultaneous determination of diclofenac and its common counter‐ions in less than 1 minute using capillary electrophoresis with contactless conductivity detection

This paper presents a method for fast and simultaneous determination of diclofenac ( DCF ) and its common counter‐ions (potassium, sodium, and diethylammonium) using CE with capacitively coupled contactless conductivity detection ( CE ‐ C 4 D ). On the basis of a single electropherogram (about 50 s), the proposed method allows the determination of the stoichiometry, absolute quantification and evaluation of the degradation degree of the active pharmaceutical ingredient ( DCF ). A linear working range from 100 to 500 μmol/L was obtained for all analytes in an equimolar TRIS / TAPS (10 mmol/L) solution as the background electrolyte as well as adequate LOD (7, 6, 7, and 10 μmol/L for K + , N a + , diethylammonium, and DCF , respectively). The proposed method was applied to the analysis of pharmaceutical formulations (tablets and spray form) with similar results to those achieved by HPLC ( DCF ) or flame photometry ( K and N a) at a 95% confidence level.