(Official April 1, 2006)

A: Crush 1 Tablet, boil it with 50 mL of water for 5 minutes, cool, and add 1 or 2 drops of ferric chloride TS: a violet-red color is produced.

B: Infrared Absorption 197K—Prepare the test specimen as follows. Shake a quantity of finely powdered Tablets, equivalent to about 500 mg of aspirin, with 10 mL of alcohol for several minutes. Centrifuge the mixture. Pour off the clear supernatant, and evaporate it to dryness. Dry the residue in vacuum at 60 for 1 hour.

Test 1— If the product complies with this test, the labeling indicates that it meets USP Drug Release Test 1.

Medium: 0.1 N hydrochloric acid; 900 mL.

Apparatus 2: 60 rpm.

Times: 1 hour and 4 hours.

Procedure— Determine the amount of C9H8O4 dissolved from UV absorbances at the isosbestic point at about 280 nm, using filtered portions of the solution under test, suitably diluted with 0.1 N hydrochloric acid, if necessary, in comparison with a Standard solution having a known concentration of USP Aspirin RS in the same Medium.

Tolerances— The percentages of the labeled amount of C9H8O4 dissolved at the times specified conform to Acceptance Table 1.

Test 2— If the product complies with this test, the labeling indicates that it meets USP Drug Release Test 2.

Medium: water; 1000 mL.

Apparatus 2: 30 rpm.

Times: 1, 2, 4, and 8 hours.

Procedure— Determine the amount of C9H8O4 dissolved from UV absorbances at the isosbestic point at about 265 nm, using filtered portions of the solution under test, suitably diluted with water, if necessary, in comparison with a Standard solution having a known concentration of USP Aspirin RS in the same Medium. [NOTE—Prepare the Standard solution at the time of use. An amount of alcohol not to exceed 5% of the total volume of the Standard solution may be used to bring the Reference Standard into solution prior to dilution with Medium.]

Tolerances— The percentages of the labeled amount of C9H8O4 dissolved at the times specified conform to Acceptance Table 1.

Test 1— If the product complies with this test, the labeling indicates that it meets USP Dissolution Test 1.

Medium: 0.1 N hydrochloric acid; 900 mL.

Apparatus 2: 60 rpm.

Times: 1 hour and 4 hours.

Procedure— Determine the amount of C9H8O4 dissolved from UV absorbances at the isosbestic point at about 280 nm, using filtered portions of the solution under test, suitably diluted with 0.1 N hydrochloric acid, if necessary, in comparison with a Standard solution having a known concentration of USP Aspirin RS in the same medium.

Tolerances— The percentages of the labeled amount of C9H8O4 dissolved at the times specified conform to Acceptance Table 2.

Test 2— If the product complies with this test, the labeling indicates that it meets USP Dissolution Test 2.

Medium: water; 1000 mL.

Apparatus 2: 30 rpm.

Times: 1, 2, 4, and 8 hours.

Procedure— Determine the amount of C9H8O4 dissolved from UV absorbances at the isosbestic point at about 265 nm, using filtered portions of the solution under test, suitably diluted with water, if necessary, in comparison with a Standard solution having a known concentration of USP Aspirin RS in the same Medium. [NOTE—Prepare the Standard solution at the time of use. An amount of alcohol not to exceed 5% of the total volume of the Standard solution may be used to bring the USP Reference Standard into solution prior to dilution with Medium.]

Tolerances— The percentages of the labeled amount of C9H8O4 dissolved at the times specified conform to Acceptance Table 2.

(Official April 1, 2006)

Mobile phase and Diluting solution—Prepare as directed in the Assay.

Standard solution— Dissolve an accurately weighed quantity of USP Salicylic Acid RS in the Standard preparation prepared as directed in the Assay, to obtain a solution having a known concentration of about 0.015 mg of salicylic acid per mL.

Test solution— Use the Stock solution, prepared as directed for Assay preparation in the Assay.

Chromatographic system— Use the Chromatographic system described in the Assay. Chromatograph the Standard solution, and record the peak responses as directed for Procedure in the Assay: the resolution, R, between salicylic acid and aspirin is not less than 2.0; and the relative standard deviation of the salicylic acid peak responses is not more than 4.0%.

Procedure— Proceed as directed for Procedure in the Assay. The relative retention times are about 0.7 for salicylic acid and 1.0 for aspirin. Calculate the percentage of salicylic acid (C7H6O3) in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Salicylic Acid RS in the Standard solution; QA is the quantity, in mg, of aspirin (C9H8O4) in the portion of Tablets taken, as determined in the Assay; and rU and rS are the peak responses of the salicylic acid peaks obtained from the Test solution and the Standard solution, respectively: not more than 3.0% is found.

(Official January 1, 2007)

Mobile phase— Dissolve 2 g of sodium 1-heptanesulfonate in a mixture of 850 mL of water and 150 mL of acetonitrile, and adjust with glacial acetic acid to a pH of 3.4.

Diluting solution— Prepare a mixture of acetonitrile and formic acid (99:1).

Standard preparation— Dissolve an accurately weighed quantity of USP Aspirin RS in Diluting solution to obtain a solution having a known concentration of about 0.5 mg per mL.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed quantity of the powder, equivalent to about 100 mg of aspirin, to a suitable container. Add 20.0 mL of Diluting solution and about 10 glass beads. Shake vigorously for about 10 minutes, and centrifuge (Stock solution). Quantitatively dilute an accurately measured volume of the Stock solution with 9 volumes of Diluting solution (Assay preparation). Retain the remaining portion of Stock solution for the test for Limit of free salicylic acid.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 280-nm detector and a 4.0-mm × 30-cm column containing 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 tailing factor is not greater than 2.0; and the relative standard deviation is not more than 2.0%.

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 aspirin (C9H8O4) in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Aspirin RS in the Standard preparation; and rU and rS are the peak responses of the aspirin peaks obtained from the Assay preparation and the Standard preparation, respectively.