A: Prepare a solution containing 10mg of sisomicin per mL.Apply 5µLof this solution,5µLof a solution of USP Sisomicin Sulfate RScontaining 10mg of sisomicin per mL,and 5µLof a mixture of the two solutions (1:1)to a suitable thin-layer chromatographic plate (see Chromatography á621ñ)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 3hours.Remove the plate from the developing chamber,allow the solvent to evaporate,and heat the plate at 110for 15minutes.Spray the plate with a 1in 100solution of ninhydrin in butanol to which 1mLof 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 á191ñ.

Test solution: 10mg per mL,in water.