Aspirin, Alumina, and Magnesia Tablets
» Aspirin, Alumina, and Magnesia Tablets contain not less than 90.0 percent and not more than 110.0 percent of the labeled amount of aspirin (C9H8O4), the equivalent of not less than 90.0 percent and not more than 110.0 percent of the labeled amount of aluminum hydroxide [Al(OH)3], and not less than 90.0 percent and not more than 110.0 percent of the labeled amount of magnesium hydroxide [Mg(OH)2].
Packaging and storage Preserve in tight containers.
A: The chromatogram of the Assay preparation obtained as directed in the Assay for aspirin and limit of free salicylic acid exhibits a major peak for aspirin, the retention time of which corresponds with that exhibited in the chromatogram of the Standard preparation, obtained as directed in the Assay for aspirin and limit of free salicylic acid.
B: To a 0.7-g portion of finely powdered Tablets add 20 mL of 3 N hydrochloric acid and 5 drops of methyl red TS, heat to boiling, and add 6 N ammonium hydroxide until the color of the solution changes to deep yellow. Continue boiling for 2 minutes, and filter: the filtrate so obtained responds to the tests for Magnesium 191.
Medium: 0.05 M acetate buffer, prepared by mixing 2.99 g of sodium acetate (trihydrate) and 1.66 mL of glacial acetic acid with water to obtain 1000 mL of solution having a pH of 4.50 ± 0.05; 900 mL.
Apparatus 2: 75 rpm.
Time: 45 minutes.
Procedure Determine the amount of aspirin (C9H8O4) dissolved from UV absorbances at the wavelength of the isosbestic point of aspirin and salicylic acid at 265 ± 2 nm of filtered portions of the solution under test, suitably diluted with Medium, if necessary, in comparison with a Standard solution having a known concentration of USP Aspirin RS in the same medium. [notePrepare the Standard solution at the time of use. An amount of methanol not to exceed 1% of the total volume of the Standard solution may be used to bring the Reference Standard into solution prior to dilution with Medium.]
Tolerances Not less than 75% (Q) of the labeled amount of C9H8O4 is dissolved in 45 minutes.
Uniformity of dosage units 905: meet the requirements for Weight Variation with respect to aluminum hydroxide and to magnesium hydroxide, and for Content Uniformity with respect to aspirin.
Acid-neutralizing capacity 301: not less than 1.9 mEq of acid is consumed for each 325 mg of aspirin in the Tablets.
Assay for aspirin and limit of free salicylic acid
Mobile phase Dissolve 225 mg of tetramethylammonium hydroxide pentahydrate and 200 mg of sodium 1-octanesulfonate in 700 mL of water. Add 150 mL of methanol, 150 mL of acetonitrile, and 1.0 mL of glacial acetic acid, and stir. [noteThe composition of the Mobile phase may be adjusted if necessary (see System Suitability under Chromatography 621)].
Solvent mixture To 2 g of anhydrous citric acid add 990 mL of acetonitrile, 990 mL of chloroform, and 20 mL of formic acid, and stir for about 30 minutes. Allow to settle, and decant the clear solution into a suitable container. Use the clear solution as the Solvent mixture.
Internal standard solution Dissolve phenacetin in Solvent mixture to obtain a solution having a concentration of about 2 mg per mL.
Salicylic acid stock standard solution Dissolve a suitable quantity of USP Salicylic Acid RS in Solvent mixture to obtain a solution having a known concentration of about 1 mg per mL.
Standard preparation Transfer about 325 mg of USP Aspirin RS, accurately weighed, to a 50-mL volumetric flask. Add 10.0 mL of Salicylic acid stock standard solution and 5.0 mL of Internal standard solution, dilute with Solvent mixture to volume, and mix.
Assay preparation Weigh and finely powder not fewer than 20 Tablets. Immediately transfer an accurately weighed portion of the powder, equivalent to about 325 mg of aspirin, to a screw-capped, 120-mL bottle, add 5.0 mL of Internal standard solution and 45.0 mL of Solvent mixture, cap the bottle, mix, and sonicate for 2 to 5 minutes. Centrifuge, and use a portion of the resultant clear solution as the Assay preparation.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 280-nm detector and a 4-mm × 30-cm column that contains 10-µm packing L1. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative retention times are about 0.3 for salicylic acid, 0.6 for aspirin, and 1.0 for phenacetin. [noteRecord each chromatogram until the chloroform peak appears at a relative retention time of about 1.8.]; the resolution, R, between the salicylic acid, aspirin, and internal standard peaks is not less than 2.0; the tailing factor for any of these peaks is not more than 2.0; and the relative standard deviation for replicate injections is not more than 3.0%.
Procedure Separately inject equal volumes (about 5 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 aspirin (C9H8O4) in the portion of Tablets taken by the formula:
50C(RU / RS)in which C is the concentration, in mg per mL, of USP Aspirin RS in the Standard preparation; and RU and RS are the ratios of the peak responses of aspirin and phenacetin obtained from the Assay preparation and the Standard preparation, respectively. Calculate the percentage of free salicylic acid in the Tablets taken by the formula:
5000(C / a)(RU / RS)in which C is the concentration, in mg per mL, of USP Salicylic Acid RS in the Standard preparation; a is the quantity, in mg, of aspirin in the portion of Tablets taken, based on the labeled amount; and RU and RS are the ratios of the peak responses of salicylic acid and phenacetin obtained from the Assay preparation and the Standard preparation, respectively: not more than 3.0% is found.
Assay for aluminum hydroxide
Assay preparation Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 250 mg of aluminum hydroxide, to a 150-mL beaker, add 20 mL of water, stir, and slowly add 30 mL of 3 N hydrochloric acid. Heat gently, if necessary, to aid solution, cool, and transfer to a 200-mL volumetric flask. Wash the beaker with water, adding the washings to the flask, add water to volume, and mix.
Procedure Pipet 50 mL of Assay preparation into a 250-mL beaker, then add, in the order named and with continuous stirring, 25.0 mL of 0.05 M Edetate disodium titrant and 20 mL of acetic acid-ammonium acetate buffer TS, and heat the solution near the boiling temperature for 5 minutes. Cool, add 50 mL of alcohol and 2 mL of dithizone TS, and mix. Titrate with 0.05 M zinc sulfate VS until the color changes from green-violet to rose-pink. Perform a blank determination, substituting 50 mL of water for the Assay preparation, and make any necessary corrections. Each mL of 0.05 M Edetate disodium titrant consumed is equivalent to 3.900 mg of Al(OH)3.
Assay for magnesium hydroxide
Assay preparation Prepare as directed in the Assay for aluminum hydroxide.
Procedure Pipet a volume of Assay preparation, equivalent to about 80 mg of magnesium hydroxide, into a 400-mL beaker, add 200 mL of water and 20 mL of triethanolamine, and mix. Add 50 mL of ammonia-ammonium chloride buffer TS and 2 drops of eriochrome black indicator solution (prepared by dissolving 200 mg of eriochrome black T in a mixture of 15 mL of triethanolamine and 5 mL of dehydrated alcohol, and mixing). Cool the solution to between 3 and 4 by immersion of the beaker in an ice bath, then remove, and titrate with 0.05 M edetate disodium VS until the color changes to pure blue. Perform a blank determination, substituting for the Assay preparation, a volume of water equal to the volume of Assay preparation used, and make any necessary corrections. Each mL of 0.05 M edetate disodium is equivalent to 2.916 mg of Mg(OH)2.
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USP32NF27 Page 1589
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.