Determination of choline in pharmaceutical formulations by reversed-phase high-performance liquid chromatography and postcolumn suppression conductivity detection.

Choline is a primary degradation product of succinylcholine chloride. Determination of low concentration choline in succinylcholine chloride bulk drug and formulation is a challenge, due to the lack of sensitive detection methods. A reversed-phase separation method with postcolumn suppression conductivity detection is described for the determination of choline. Hexanesulfonic acid is employed as an ion-pair reagent in the mobile phase, which allows the accomplishment of both reversed-phase separation and a sensitive conductivity detection. Detection sensitivity is significantly enhanced by passing the mobile phase through a postcolumn cation suppressor, where hexanesulfonic acid is removed and the background conductance is reduced. This method is simple and sensitive. No sample derivatization procedure is required. The detection limit for choline is about 10 pmol.