A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

Standard preparations— Dissolve USP Loxapine Succinate RS in methanol and mix to obtain Standard preparation A having a known concentration of 0.5 mg per mL. Dilute portions of Standard preparation A quantitatively with methanol to obtain Standard preparation B and Standard preparation C having known concentrations of 0.25 mg per mL and 0.1 mg per mL, respectively.

Test preparation— Dissolve an accurately weighed quantity of Loxapine Succinate in methanol to obtain a solution containing 50 mg per mL.

Procedure— Separately apply 5 µL of the Test preparation and each of the three Standard preparations to a suitable high performance thin-layer chromatographic plate (see Chromatography 621) coated with a 0.10-mm layer of chromatographic silica gel mixture. Allow the spots to dry, and develop the chromatogram in a solvent system consisting of a mixture of ethyl acetate, methanol, and ammonium hydroxide (9:1:0.1) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, air-dry, examine the plate under short-wavelength UV light, and compare the intensities of any secondary spots observed in the chromatogram of the Test preparation with those of the principal spots in the chromatograms of the Standard preparations: no secondary spot from the chromatogram of the Test preparation is larger or more intense than the principal spot obtained from Standard preparation A (1.0%), and the sum of the intensities of the secondary spots obtained from the Test preparation corresponds to not more than 2.0%.

Solvent— Use dimethyl sulfoxide.

(Official January 1, 2007)