Identification—
Transfer a quantity of finely powdered Tablets, equivalent to about 50 mg of ketoconazole, to a suitable flask, add 50 mL of chloroform, shake for about 2 minutes, and filter. Apply separate 10-µL portions of this solution and of a Standard solution of
USP Ketoconazole RS in chloroform containing 1 mg per mL to the starting line of a thin-layer chromatographic plate (see
Chromatography 
621
) coated with a 0.25-mm layer of chromatographic silica gel mixture. Allow the spots to dry, and develop the chromatogram in an unsaturated chamber with a solvent system consisting of a mixture of
n-hexane, ethyl acetate, methanol, water, and glacial acetic acid (42:40:15:2:1) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber, air-dry, and view under short-wavelength UV light: the
RF value of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.
Dissolution 711—
Medium:
0.1 N hydrochloric acid; 900 mL.
Apparatus 2:
50 rpm.
Time:
30 minutes.
Procedure—
Determine the amount of C
26H
28Cl
2N
4O
4 dissolved by employing UV absorption at the wavelength of maximum absorbance at about 270 nm on portions of the solution under test passed through a 0.45-µm filter and suitably diluted with
Medium, if necessary, in comparison with a Standard solution having a known concentration of
USP Ketoconazole RS in the same
Medium.
Tolerances—
Not less than 80% (Q) of the labeled amount of C26H28Cl2N4O4 is dissolved in 30 minutes.
Assay—
Methanol–methylene chloride—
Mix equal volumes of methanol and methylene chloride.
Mobile phase—
Prepare a suitable (7:3) mixture of a solution of diisopropylamine in methanol (1 in 500) and ammonium acetate solution (1 in 200).
Internal standard solution—
Dissolve
USP Terconazole RS in
Methanol–methylene chloride to obtain a solution containing about 5 mg per mL.
Standard preparation—
Transfer about 20 mg of
USP Ketoconazole RS, accurately weighed, to a 50-mL volumetric flask, add 5.0 mL of
Internal standard solution, dilute with
Methanol–methylene chloride to volume, and mix.
Assay preparation—
Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 200 mg of ketoconazole, to a suitable screw-capped bottle, add 50.0 mL of Methanol–methylene chloride, shake by mechanical means for 30 minutes, and centrifuge. Transfer 5.0 mL of the clear supernatant so obtained to a 50-mL volumetric flask, add 5.0 mL of Internal standard solution, dilute with Methanol–methylene chloride to volume, and mix.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 225-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 3 mL per minute. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the relative retention times are about 0.6 for ketoconazole and 1.0 for terconazole; the resolution,
R, between ketoconazole and terconazole is not less than 2.0; and the relative standard deviation is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 20 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of ketoconazole (C
26H
28Cl
2N
4O
4) in the portion of Tablets taken by the formula:
10WS (RU / RS),
in which
WS is the weight, in mg, of
USP Ketoconazole RS taken; and
RU and
RS are the ratios of the peak responses of ketoconazole to those of terconazole from the
Assay preparation and the
Standard preparation, respectively.
