A: Infrared Absorption 197M.

B: It responds to the tests for Chloride 191.

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

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

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

Procedure— Apply 20-µL portions of the Test solution and USP Methylphenidate Hydrochloride Erythro Isomer Solution RS to a suitable thin-layer chromatographic plate (see Chromatography 621) 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 1 N sulfuric acid. Any spot in the lane from the methylphenidate hydrochloride at the same RF as 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 1 in 2500 solution of sodium hydroxide in methanol.

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

Spray reagent 2— Use hydrogen peroxide solution.

Standard solution— Dissolve a suitable quantity of USP -Phenyl-2-piperidineacetic Acid Hydrochloride RS in Sodium hydroxide–methanol to obtain a solution having a known concentration of about 240 µg per mL.

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

Procedure— Apply 10-µL portions of the Test solution and the Standard solution to a suitable thin-layer chromatographic plate (see Chromatography 621) 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 30 minutes. Spray the plate with Spray reagent 1 followed 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 solution having the same RF value as the principal spot from the Standard solution is not larger or more intense than that produced by the Standard solution (0.6%).