Determination of suxamethonium in a pharmaceutical formulation by capillary electrophoresis with contactless conductivity detection (CE-C4D)

A simple method based on capillary electrophoresis with a capacitively coupled contactless conductivity detector (CE-C4D) was developed for the determination of suxamethonium (SUX) in a pharmaceutical formulation. A hydro-organic mixture, consisting of 100 mM Tris–acetate buffer at pH 4.2 and acetonitrile (90:10, v/v), was selected as background electrolyte (BGE). The applied voltage was 30 kV, and the sample injection was performed in the hydrodynamic mode. All analyses were carried out in a fused silica capillary with an internal diameter of 50 μm and a total length of 64.5 cm. Under these conditions, a complete separation between SUX, sodium ions and the main degradation products (choline) was achieved in less than 4 min. The presence of acetonitrile in the BGE allowed a reduction of SUX adsorption on the capillary wall. The CE-C4D method was validated, and trueness values between 98.8% and 101.1% were obtained with repeatability and intermediate precision values of 0.7–1.3% and 1.2–1.6%, respectively. Therefore, this method was found appropriate for controlling pharmaceutical formulations containing suxamethonium and degradation products.