Aspirin Boluses

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

Aspirin Boluses contain NLT 90.0% and NMT 110.0% of the labeled amount of aspirin (C₉H₈O₄).

2 IDENTIFICATION

A. PROCEDURE

Analysis: Crush 1 Bolus. Boil a portion of the powder, equivalent to 300 mg of aspirin, with 50 ml of water. Cool and add a drop of ferric chloride TS.

Acceptance criteria: A violet-red color is produced.

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

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: 0.4 mg/mL of USP Aspirin RS and 0.01 mg/mL of USP Salicylic Acid RS in Diluent

Sample stock solution: Nominally 4 mg/mL of aspirin prepared as follows. Finely powder NLT 10 Boluses. Transfer a portion of the powder to an appropriate volumetric flask and dilute with Diluent to volume. Stir the solution by mechanical means for 15 min.

Sample solution: Nominally 0.4 mg/mL of aspirin from Sample stock solution in Diluent. Pass a portion of this solution through a filter of 0.5-µm or finer pore size. Use the filtrate.

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 254 nm

Column: 4.6-mm x 25-cm; 5-µm packing 11

Flow rate: 1 mL/min

Injection volume: 20 µL

System suitability

Sample: Standard solution

[NOTE-The relative retention times for salicylic acid and aspirin are 0.6 and 1.0, respectively.]

Suitability requirements

Resolution: NLT 2.0 between salicylic acid and aspirin

Relative standard deviation: NMT 2.0% for aspirin

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of aspirin (C₉H₈O₄) in the portion of Boluses 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%

3 PERFORMANCE TESTS

DISSOLUTION (711)

Medium: 0.5 M phosphate buffer (see Reagents. Indicators, and Solutions-Buffer Solutions), pH 7.4; 900 mL

Apparatus 2: 75 rpm

Time: 45 min

Diluent: Acetonitrile and formic acid (99:1)

Standard solution: USP Aspirin RS in Diluent at a suitable concentration. [NOTE-Prepare the solution at the time of use.]

Sample solution: Pass a portion of the solution under test through a suitable filter. Dilute with Diluent, if necessary.

Instrumental conditions

Mode: UV-Vis

Analytical wavelength: The isosbestic point of aspirin and salicylic acid at 265 ± 2 nm

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of aspirin (C₉H₈O₄) dissolved:

Result = (A_u /A_s ) × C_s × V × D × (1/L) × 100

A_u = absorbance of the Sample solution

A_s = absorbance of the Standard solution

C_s = concentration of the Standard solution (mg/mL)

V = volume of Medium, 900 mL

D = dilution factor of the Sample solution, if necessary

L = label claim (mg/Bolus)

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

UNIFORMITY OF DOSAGE UNITS (905): Meet the requirements

4 IMPURITIES

LIMIT OF SALICYLIC ACID

Mobile phase, Diluent, Sample solution, Chromatographic system, and System suitability: Proceed as directed in the Assay.

Salicylic acid standard solution: 0.01 mg/mL of USP Salicylic Acid RS in Diluent

Analysis

Samples: Sample solution and Salicylic acid standard solution

Calculate the actual concentration (C), in mg/mL, of aspirin (C₉H₈O₄) in the Sample solution taken:

Result = C_u × (F/100)

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

F = percentage of the labeled amount of aspirin (C H O ) in the portion of Boluses taken, as determined in the Assay

Calculate the percentage of salicylic acid (C₇H₆O₃) in the portion of Boluses 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 Salicylic acid standard solution

C_s = concentration of USP Salicylic Acid RS in the Salicylic acid standard solution (mg/mL)

C_u = actual concentration of aspirin in the Sample solution

Acceptance criteria: NMT 0.3%

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.

Labeling: Label Boluses to indicate that they are for veterinary use only.

USP Reference Standards 〈11〉

USP Aspirin RS

USP Salicylic Acid RS