Clotrimazole Lotion

Clotrimazole Lotion contains not less than 90.0 per cent and not more than 110.0 per cent of the stated amount of clotrimazole, C22H17ClN2.

Usual strength.1.0 per cent w/v.

Identification

In the Assay, the principal peak in the chromatogram obtained with the test solution corresponds to the peak in the chromatogram obtained with the reference solution(c).

Tests

pH (2.4.24). 5.0 to 7.0.

Microbial contamination (2.2.9).1.0 g is free from Staphylococcus aureus and Pseudomonas aeruginosa.

Clotrimazole related compound A. Not more than 5.0 per cent.

 Determine by liquid chromatography (2.4.14).

Calculate the percentage of clotrimazole related compound A using the chromatograms of reference solution (c) and the test solution as obtained underAssay.

Other tests. Comply with the tests stated under Lotion.

Assay. Determine by liquid chromatography (2.4.14).

Test solution. Transfer the equivalent of 10 mg of Clotrimazole from freshly mixed lotion to a screw-capped, 50-ml centrifuge tube. Add 10.0 ml of internal standard solution, place the cap on the tube, and heat at 50° in a water bath for 5 minutes, with occasional shaking. Remove the tube from the bath, and shake vigorously for 5 minutes. Cool in a methanol–ice bath for 15 minutes, and promptly centrifuge. Transfer the supernatant liquid to a test tube. Add 10.0 ml of dehydrated alcohol to the residue in the centrifuge tube, and repeat the extraction as directed above, beginning with “place the cap on the tube”. Transfer the supernatant liquid to the test tube containing the supernatant liquid from the first extraction.

Internal standard solution. A 0.007  per cent w/v solution of testosterone propionate RS in dehydrated alcohol.

Reference solution (a). A 0.2  per cent w/v solution of clotrimazole RS in dehydrated alcohol.

Reference solution (b). A 0.01 per cent w/v solution of clotrimazole related compound A RS [(o-Chlorophenyl)diphenylmethanol RS] in dehydrated alcohol.

Reference solution (c). Mix reference solution (a), reference solution (b) and the internal standard solution in the ratio (5:5:10). 

Chromatographic system

     –   a stainless steel column 30 cm x 3.9 mm, packed with octadecylsilane bonded to porous silica (10 µm) and a guard column 6 cm ´ 2.1 mm, packed with the same column material (10 µm),

     –   mobile phase: a mixture of 1 volume of abuffer solution prepared by dissolving 4.35 g of dibasic potassium  phosphate in 1000 ml of water and 3 volumes of methanol,

     –   flow rate: 1 ml per minute,

     –   spectrophotometer set at 254 nm,

     –   injection volume: 20 µl.

The relative retention time with respect to clotrimazole for clotrimazole related compound A and testosterone propionate is about 0.9 and 1.5, respectively.

Inject the reference solution (c). The test is not valid unless the resolution between the peaks due to clotrimazole related compound A and clotrimazole is not less than 1.2 and the resolution between the peaks due to clotrimazole and testosterone propionate is not less than 1.9. The relative standard deviation for replicate injections is not more than 2.0 per cent.

Inject the reference solution (c) and the test solution.

Calculate the content of C22H17ClN2 in the lotion.

Storage. Store in tight containers, and at a temperature between 2° to 30°.