Determination of oxybutinin chloride in pharmaceuticals by reversed-phase ion-pair liquid chromatography with two counter-ions in the eluent.

A reliable stability-indicating method using reversed-phase ion-pair high-performance liquid chromatography for the determination of the anticholinergic drug oxybutinin chloride in pharmaceuticals is reported. Sample extraction is easy and fairly rapid and recovery and precision of the method are excellent. Due to the simultaneous use of an organic amine and of an alkanesulphonate in the mobile phase, good selectivity towards related (quaternary ammonium) anticholinergic drugs was obtained.