note—Throughout the following procedures, protect test or assay specimens, the Reference Standard, and solutions containing them, by conducting the procedures without delay, under subdued light, or by using low-actinic glassware.

A: Infrared Absorption 197K.

B: A solution (1 in 100) in a mixture of water and alcohol (1:1) responds to the test for Chloride 191 in amine hydrochlorides.

Diluting solution: a mixture of methanol and ammonium hydroxide (49:1).

Test solution— Transfer 100 mg of Thioridazine Hydrochloride, accurately weighed, to a 5-mL volumetric flask. Dissolve in and dilute with Diluting solution to volume, and mix.

Standard solutions— Dissolve an accurately weighed quantity of USP Thioridazine Hydrochloride RS in Diluting solution, and dilute quantitatively, and stepwise if necessary, with Diluting solution to obtain a solution having a known concentration of 20.0 mg per mL (Standard solution A). Dilute appropriate portions of this solution quantitatively with Diluting solution to obtain five Standard solutions B to F having known concentrations of 0.1, 0.067, 0.025, 0.02 and 0.01 mg per mL, respectively. The final concentrations of Standard solutions B to F represent 0.5%, 0.33%, 0.125%, 0.1% and 0.05% concentration of Standard solution A, respectively.

Application volume: 5 µL.

Developing solvent system: a mixture of chloroform, isopropyl alcohol, and ammonium hydroxide (74:25:1).

Procedure— Apply equal spots of the Test solution and Standard solutions A to F as directed under Ordinary Impurities 466. Examine the plate under short- and long-wavelength UV light, then spray the plate with Dragendorff's TS, dry the plate with a stream of nitrogen, and then spray with hydrogen peroxide TS: any secondary spot in the Test solution is not more than 0.5%, and the sum of all secondary spots is not more than 0.5%.