Buffered Aspirin Tablets

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

Buffered Aspirin Tablets contain Aspirin and suitable buffering agents. Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of aspirin (C₉H₈O₄).

2 IDENTIFICATION

A. The retention time of the aspirin peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

B. ▲Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K▲ (CN 1-May-2020)

Sample: Shake a quantity of finely powdered Tablets, equivalent to about 500 mg of aspirin, with 10 mL of chloroform for several min. Centrifuge the mixture. Pour off the clear supernatant, and evaporate it to dryness.

Acceptance criteria: Meet the requirements

3 ASSAY

Procedure

Mobile phase: 2 g/L of sodium 1-heptanesulfonate in a mixture of acetonitrile and water (15:85). Adjust with glacial acetic acid to a pH of 3.4.

Diluent: Acetonitrile and formic acid (99:1)

Standard solution: 0.5 mg/mL of USP Aspirin RS in Diluent

Sample stock solution: Nominally 5 mg/mL of aspirin prepared as follows. Transfer a quantity, equivalent to about 100 mg of aspirin from NLT 20 finely powdered Tablets, to a suitable container. Add 20.0 mL of Diluent and 10 glass beads. Shake vigorously for 10 min, and centrifuge.

Sample solution: Nominally 0.5 mg/mL of aspirin in Diluent from Sample stock solution

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 280 nm

Column: 4.0-mm × 30-cm; packing L1

Flow rate: 2 mL/min

Injection volume: 10 µL

System suitability

Sample: Standard solution

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of aspirin (C₉H₈O₄) in the portion of Tablets taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U= peak response of aspirin from the Sample solution

r_S= peak response of aspirin from the Standard solution

C_S= concentration of USP Aspirin RS in the Standard solution (mg/mL)

C_U= nominal concentration of aspirin in the Sample solution (mg/mL)

Acceptance criteria: 90.0%–110.0%

4 PERFORMANCE TESTS

Dissolution 〈711〉

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 a total of 1000 mL of solution with a pH of 4.50 ± 0.05; 500 mL

Apparatus 2: 75 rpm. [Note—Where the Tablet is composed of multiple layers, a stainless steel wire helix may be used, if needed, to hold the Tablet in proper orientation in the apparatus.]

Time: 30 min

Standard solution: A known concentration of USP Aspirin RS in Medium. Prepare the Standard solution at the time of use. [Note—A quantity of methanol not to exceed 1% of the total volume of the Standard solution may be used to dissolve the Reference Standard prior to dilution with Medium.]

Sample solution: Pass a portion of the solution under test through a suitable filter, and dilute with Medium, if necessary.

Instrumental conditions

Mode: UV

Analytical wavelength: 265 nm

Analysis

Samples: Standard solution and Sample solution

Determine the percentage of the labeled amount of aspirin (C₉H₈O₄) dissolved from UV absorbances at the isosbestic point of aspirin and salicylic acid at about 265 nm.

Tolerances: NLT 80% (Q) of the labeled amount of aspirin (C₉H₈O₄) is dissolved.

Uniformity of Dosage Units 〈905〉: Meet the requirements

5 IMPURITIES

Limit of Free Salicylic Acid

Mobile phase, Diluent, and Chromatographic system: Proceed as directed in the Assay.

System suitability solution: 0.015 mg/mL of USP Salicylic Acid RS and 0.5 mg/mL of USP Aspirin RS in Diluent

Standard solution: 0.015 mg/mL of USP Salicylic Acid RS in Diluent

Sample solution: Use the Sample stock solution prepared as directed in the Assay.

System suitability

Samples: System suitability solution and Standard solution

[Note—The relative retention times for salicylic acid and aspirin are about 0.7 and 1.0, respectively.]

Resolution: NLT 2.0 between salicylic acid and aspirin, System suitability solution

Relative standard deviation: NMT 4.0%, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of salicylic acid (C₇H₆O₃) in the portion of Tablets taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U= peak response of salicylic acid from the Sample solution

r_S= peak response of salicylic acid from the Standard solution

C_S= concentration of USP Salicylic Acid RS in the Standard solution (mg/mL)

C_U= nominal concentration of aspirin in the Sample solution (mg/mL)

Acceptance criteria: NMT 3.0%

6 SPECIFIC TESTS

Acid-Neutralizing Capacity 〈301〉: NLT 1.9 mEq of acid is consumed for each 325 mg of aspirin in the Tablets.

7 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.

USP Reference Standards 〈11〉

USP Aspirin RS

USP Salicylic Acid RS