Identification—
Transfer an amount of finely ground Tablets, equivalent to 100 mg of Astemizole, to a 100-mL volumetric flask, add methanol to volume, mix, and filter. Prepare a Standard solution of
USP Astemizole RS in methanol having a concentration of 1 mg per mL. Separately apply 10 µL of each solution to a thin-layer chromatographic plate (see
Chromatography 
621
) coated with a 0.25-mm layer of chromatographic silica gel mixture. Develop the chromatogram in a solvent system consisting of a mixture of toluene, dioxane, methanol, and ammonium hydroxide (60:30:10:1) 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, and examine 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:
simulated gastric fluid TS (without the enzyme); 800 mL.
Apparatus 2:
100 rpm.
Time:
45 minutes.
Procedure—
Determine the amount of astemizole (C
28H
31FN
4O) dissolved from UV absorbances at the wavelength of maximum absorbance at about 285 nm of filtered portions of the solution under test, suitably diluted with
Medium, in comparison with a Standard solution having a known concentration of
USP Astemizole RS in the same
Medium.
Tolerances—
Not less than 80% (Q) of the labeled amount of astemizole (C28H31FN4O) is dissolved in 45 minutes.
Chromatographic purity—
Mobile phase, Standard preparation, and Chromatographic system—
Proceed as directed in the
Assay under
Astemizole.
Test solution—
Use the Assay preparation.
Procedure—
Inject a volume (about 10 µL) of the
Test solution into the chromatograph, record the chromatogram, and measure the peak responses. Calculate the percentage of each impurity in the portion of Tablets taken by the formula:
100(ri / rs),
in which
ri is the peak response for each impurity; and
rs is the sum of the responses of all of the peaks: not more than 0.25% of any individual impurity is found; and the sum of all impurities is not more than 1.0%.
Assay—
Mobile phase, Standard preparation, and Chromatographic system—
Proceed as directed in the
Assay under
Astemizole.
Assay preparation—
Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed quantity of the powder, equivalent to about 50 mg of astemizole, to a 50-mL volumetric flask. Add 25 mL of Mobile phase, mix for 30 minutes, dilute with Mobile phase to volume, and centrifuge. Use the supernatant as the Assay preparation.
Procedure—
Separately inject equal volumes (about 10 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 astemizole (C
28H
31FN
4O) in the portion of Tablets taken by the formula:
50C(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Astemizole RS in the
Standard preparation; and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
