Procedure for content uniformity—
Place 1 Tablet in a 100-mL volumetric flask, add 10.0 mL of water, and shake by mechanical means for 15 minutes. Dilute with methanol to volume, and filter, discarding the first 20 mL of the filtrate. Dilute a portion of the subsequent filtrate quantitatively and stepwise, if necessary, with a mixture of methanol and water (9:1) to obtain a solution containing about 40 µg of carbinoxamine maleate per mL. Concomitantly determine the absorbances of this solution and of a Standard solution of
USP Carbinoxamine Maleate RS, in the same medium having a known concentration of about 40 µg per mL, in 1-cm cells, at the wavelength of maximum absorbance at about 260 nm, with a suitable spectrophotometer, using a mixture of methanol and water (9:1) as the blank. Calculate the quantity, in mg, of C
16H
19ClN
2O·C
4H
4O
4 in the Tablet taken by the formula:
(TC / D)(AU / AS),
in which
T is the labeled quantity, in mg, of carbinoxamine maleate in the Tablet;
C is the concentration, in µg per mL, of
USP Carbinoxamine Maleate RS in the Standard solution;
D is the concentration, in µg per mL, of carbinoxamine maleate in the solution from the Tablet, based upon the labeled quantity per Tablet and the extent of dilution; and
AU and
AS are the absorbances of the solution from the Tablet and the Standard solution, respectively.
501
exhibits an absorbance maximum at 263 ± 2 nm. The absorptivity at 263 nm is within 7.0% of that of a 1 in 50,000 solution of USP Carbinoxamine Maleate RS in dilute sulfuric acid (1 in 70), similarly measured.