Aspirin
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
C9H8O4 180.16
Benzoic acid, 2-(acetyloxy)-.
Salicylic acid acetate CAS RN: 50-78-2; UNII: R16CO5Y76E.
Aspirin contains not less than 99.5 percent and not more than 100.5 percent of C9H8O4 calculated on the dried basis.
Packaging and storage-Preserve in tight containers.
USP REFERENCE STANDARDS (11)
USP Aspirin RS
1 Identification
A: Heat it with water for several minutes, cool, and add 1 or 2 drops of ferric chloride TS: a violet-red color is produced.
B: Spectroscopic Identification Tests (197), Infrared Spectroscopy: 197K.
LOSS ON DRYING (731)-Dry it over silica gel for 5 hours: it loses not more than 0.5% of its weight.
READILY CARBONIZABLE SUBSTANCES (271)-Dissolve 500 mg in 5 mL of sulfuric acid the solution has no more color than Matching Fluid Q.
RESIDUE ON IGNITION (281); not more than 0.05%.
2 Substances insoluble in sodium carbonate TS
A solution of 500 mg in 10 mL of warm sodium carbonate TS is clear.
CHLORIDE (221)-Boil 1.5 g with 75 mL of water for 5 minutes, cool, add sufficient water to restore the original volume, and filter. A 25-ml portion of the filtrate shows no more chloride than corresponds to 0.10 mL of 0.020 N hydrochloric acid (0.014%).
SULFATE-Dissolve 6.0 g in 37 mL of acetone, and add 3 mL of water. Titrate potentiometrically with 0.02 M lead perchlorate, prepared by dissolving 9.20 g of lead perchlorate in water to make 1000 mL of solution, using a pH meter capable of a minimum reproducibility of ±0.1 mV (see pH (791)) and equipped with an electrode system consisting of a lead-specific electrode and a silver-silver chloride reference glass-sleeved electrode containing a solution of tetraethylammonium perchlorate in glacial acetic acid (1 in 44) (see Titrimetry (541)): not more than 1.25 mL of 0.02 M lead perchlorate is consumed (0.04%). [NOTE-After use, rinse the lead-specific electrode with water, drain the reference electrode, flush with water, rinse with methanol, and allow to dry.]
3 Limit of free salicylic acid
Dissolve 2.5 g in sufficient alcohol to make 25.0 mL. To each of two matched color-comparison tubes add 48 mL of water and 1 mL of a freshly prepared, diluted ferric ammonium sulfate solution (prepared by adding 1 mL of 1 N hydrochloric acid to 2 mL of ferric ammonium sulfate TS and diluting with water to 100 mL). Into one tube pipet 1 mL of a standard solution of salicylic acid in water, containing 0.10 mg of salicylic acid per mL.. Into the second tube pipet 1 mL of the 1 in 10 solution of Aspirin. Mix the contents of each tube: after 30 seconds, the color in the second tube is not more intense than that in the tube containing the salicylic acid (0.1%).
Change to read:
Assay-Place about 1.5 g of Aspirin, accurately weighed, in a flask, add 50.0 mL of 0.5 N sodium hydroxide VS, and boil the mixture gently for 10 minutes. Add phenolphthalein TS, and titrate the excess sodium hydroxide with 0.5 N sulfuric acid VS. Perform a blank determination (see
Titrimetry (541) (CN 1-Aug-2024)). Each mL of 0.5 N sodium hydroxide is equivalent to 45.04 mg of C9H8O4
