Identification test of Phenothiazines

Determine protected from light by thin-layer chromatography, coating the plate with kieselguhr G. Place the dry plate in a tank containing a shallow layer of a mixture of 85 volumes of acetone, 10 volumes of 2-phenoxyethanol and 5 volumes of polyethylene glycol 300 so that the plate dips about 5 mm beneath the surface of the liquid. Allow the solvent to rise 18 cm above the line of application. Remove the plate from the tank and use it immediately.

Mobile phase

Shake a mixture of 100 volumes of light petroleum (40° to 60°) and 2 volumes of diethylamine with 6 to 8 volumes of 2-phenoxyethanol until a persistent cloudiness is obtained, decant and use the supernatant layer.

Test solution

A 0.2 percent w/v solution of the substance under examination in chloroform.

Reference solution

A 0.2 percent w/v solution of the corresponding Reference Substance. Apply to the plate 2 µl of each solution. Allow the mobile phase to rise 12 cm. Dry the plate in air, and examine in ultraviolet light at 365 nm and observe the fluorescence produced after a few minutes. Spray the plate with ethanolic sulphuric acid (10 percent v/v) and observe the color produced. The principal spot in the chromatogram obtained with the test solution corresponds in position, fluorescence and color to that in the chromatogram obtained with the reference solution and has a similar stability for at least 20 minutes after spraying.

Ignore any spot remaining on the line of application. Unless otherwise specified, any secondary spot in the chromatogram obtained with the test solution is not more intense than the spot in the chromatogram obtained with the reference solution.

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