A novel approach for spectrophotometric determination of succinylcholine in pharmaceutical formulation via host–guest complexation with water-soluble p-sulfonatocalixarene

Abstract

Succinylcholine (SUC) is a quaternary ammonium neuromuscular blocking agent. Direct determination of SUC in bulk drugs and formulations is a challenging analytical task due to the lack of a detectable chromophore and sensitive detection techniques. We have exploited both the strong UV absorbance of p-sulfonatocalix[4]arene (SCX4) and its outstanding complexation properties towards quaternary ammonium compounds to determine SUC. The characteristics of a host–guest complexation between SCX4 and SUC were investigated using UV and ¹H NMR spectroscopy. The Job's plot analysis reveals a 1 : 1 stoichiometry of the host–guest complex with a binding affinity K_a of 7.8 × 10⁴ L mol⁻¹. This novel method is based on spectrophotometric measurement of the formed complex peak after resolving the overlap from the host SCX4 spectrum and was used for the quantitation of SUC. The linear range was found to be from 1.0 × 10⁻⁵ to 18.0 × 10⁻⁵ mol L⁻¹ with a detection limit of 7.3 × 10⁻⁶ mol L⁻¹ (2.88 μg mL⁻¹). This method is straightforward and shows high sensitivity. Moreover, it was successfully employed to determine SUC in pharmaceutical formulation. Subsequent statistical analysis of the obtained results and comparison with the official US pharmacopeial benchmark yielded favorable results.