Standard solution— Transfer 20 mg each of choline chloride and USP Succinylmonocholine Chloride RS, accurately weighed, to a 50-mL volumetric flask, dissolve in 40 mL of methanol, dilute with methanol to volume, and mix.

Test solution— Prepare, immediately prior to use, a solution of Succinylcholine Chloride in methanol having a concentration of about 50 mg per mL.

Procedure— Separately apply 2 µL of the Test solution and 5 µL of the Standard solution to a suitable high-performance 10- × 10-cm thin-layer chromatographic plate (see Chromatography 621) coated with a 0.10-mm layer of chromatographic cellulose. Allow the spots to dry, and immediately place the plate, its coated surface toward the nearer wall, in the dry trough of a twin-trough chromatographic chamber whose other trough contains a solvent system consisting of the upper layer of a mixture of butyl alcohol, water, and 96% formic acid (65:35:15) that has been shaken and allowed to stand for 24 hours until the phases have separated. Equilibrate the chromatographic chamber for 30 minutes, and tilt the chamber to introduce the developing solvent into the trough containing the plate. Develop the chromatogram until the solvent front has moved about three-fourths of the length of the plate, remove the plate from the developing chamber, quickly and thoroughly evaporate the solvent with the aid of a current of air, and dry at 105 for 15 minutes. [note—During the drying, support the plate in such a manner that only the upper and lower edges of the plate, outside the chromatographic zone, are in direct contact with any heated surface.] Spray the plate with potassium iodoplatinate TS, dry at 105 for about 2 minutes, and allow to cool to room temperature: any spots from the Test solution are not greater in size or intensity than the spots, occurring at the respective RF values (approximately 0.6 for succinylmonocholine chloride, and 0.5 for choline chloride), produced by 5 µL of the Standard solution, corresponding to 0.8% of each compound. Estimate the size and intensities of any other spots detected by comparison with the spot produced by succinylmonocholine chloride in the Standard solution. The total of any such spots detected is not more than 2.0%.