» 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.
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.
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 TS: the solution has no more color than Matching Fluid Q.
Residue on ignition 281: not more than 0.05%.
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 silversilver 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%). [noteAfter use, rinse the lead-specific electrode with water, drain the reference electrode, flush with water, rinse with methanol, and allow to dry.]
Heavy metals Dissolve 2 g in 25 mL of acetone, and add 1 mL of water. Add 1.2 mL of thioacetamideglycerin base TS and 2 mL of pH 3.5 Acetate Buffer (see Heavy Metals 231), and allow to stand for 5 minutes: any color produced is not darker than that of a control made with 25 mL of acetone and 2 mL of Standard Lead Solution (see Heavy Metals 231), treated in the same manner. The limit is 10 µg per g.
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%).
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 Residual Titrations under Titrimetry 541). Each mL of 0.5 N sodium hydroxide is equivalent to 45.04 mg of C9H8O4.
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USP32NF27 Page 1582Pharmacopeial Forum: Volume No. 34(5) Page 1143
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.