A:Infrared Absorption á197Mñ.

B: It responds to the tests for Chloride á191ñ.

Mobile solvent— Prepare a solution consisting of a mixture of chloroform,methanol,and ammonium hydroxide (190:10:1).

Detecting reagent— Dissolve 0.7g of bismuth subnitrate in 40mLof a mixture of water and glacial acetic acid (4:1).Add 40mLof potassium iodide solution (2in 5),then add 120mLof glacial acetic acid and 250mLof water.

Test solution— Prepare a solution in methanol containing 50mg of Methylphenidate Hydrochloride per mL.

Procedure— Apply 20-µLportions of the Test solution and USP Methylphenidate Hydrochloride Erythro Isomer Solution RSto a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel.Allow the spots to dry,and develop the chromatogram,using the Mobile solvent,in a suitable chamber,lined with absorbent paper and previously equilibrated with the Mobile solvent,until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,and allow the solvent to evaporate.Locate the spots on the plate by spraying first with the Detecting reagent and then with 1Nsulfuric acid.Any spot in the lane from the methylphenidate hydrochloride at the same RFas the erythro isomer is not larger or more intense than that produced by USP Methylphenidate Hydrochloride Erythro Isomer Solution RS,when viewed under ordinary lighting (1%).

Mobile solvent— Prepare a solution consisting of a mixture of chloroform,methanol,and acetic acid (65:25:5).

Sodium hydroxide–methanol— Prepare a 1in 2500solution of sodium hydroxide in methanol.

Spray reagent 1— Mix 850mg of bismuth subnitrate with 40mLof water and 10mLof glacial acetic acid (Solution A).Dissolve 8g of potassium iodide in 20mLof water (Solution B).Mix Solutions Aand Btogether to obtain the Stock solution.[NOTE—This Stock solution may be stored for several months in a dark bottle.]Mix 10mLof the Stock solution with 20mLof glacial acetic acid,and dilute with water to make 100mLto obtain the Spray reagent.

Spray reagent 2— Use hydrogen peroxide solution.

Standard solution— Dissolve a suitable quantity of USPa-Phenyl-2-piperidineacetic Acid Hydrochloride RSin Sodium hydroxide–methanolto obtain a solution having a known concentration of about 240µg per mL.

Test solution— Dissolve 400mg of Methylphenidate Hydrochloride,accurately weighed,in Sodium hydroxide–methanolto make 10.0mL.Use immediately after preparation.

Procedure— Apply 10-µLportions of the Test solutionand the Standard solutionto a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel.Allow the spots to dry,and develop the chromatogram,using the Mobile solvent,in a suitable chamber,lined with absorbent paper and previously equilibrated with Mobile solvent,until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,and allow the plate to dry for 30minutes.Spray the plate with Spray reagent 1followed by Spray reagent 2.[NOTE—After spraying with the Spray reagents,cover the plate with a second plate to prevent fading of the spots.]Examine the plate:any spot in the lane from the Test solutionhaving the same RFvalue as the principal spot from the Standard solutionis not larger or more intense than that produced by the Standard solution(0.6%).