A: Prepare a solution containing 10 mg of sisomicin per mL. Apply 5 µL of this solution, 5 µL of a solution of USP Sisomicin Sulfate RS containing 10 mg of sisomicin per mL, and 5 µL of a mixture of the two solutions (1:1) to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Allow the spots to dry, place the plate in a developing chamber fitted for continuous-flow thin-layer chromatography, and develop the chromatogram in a solvent system consisting of a mixture of methanol, ammonium hydroxide, and chloroform (60:30:25) for 3 hours. Remove the plate from the developing chamber, allow the solvent to evaporate, and heat the plate at 110 for 15 minutes. Spray the plate with a 1 in 100 solution of ninhydrin in butanol to which 1 mL of pyridine has been added: sisomicin appears as a brown spot, and the spots obtained from the test solution and from the mixture of test solution and Standard solution, respectively, correspond in distance from the origin to that of the spot from the Standard solution.

B: It responds to the tests for Sulfate 191.

Test solution: 10 mg per mL, in water.