(ue ree' a; ure ee' a).
» Urea contains not less than 99.0 percent and not more than 100.5 percent of CH4N2O.
Packaging and storage Preserve in well-closed containers. Store at 25, excursions permitted between 15 and 30.
Labeling Where it is intended for use in preparing injectable dosage forms, the label states that it is sterile or must be subjected to further processing during the preparation of injectable dosage forms.
USP Reference standards 11
USP Endotoxin RS
A: Heat about 500 mg in a test tube: it liquefies, and ammonia is evolved. Continue the heating until the liquid becomes turbid, then cool. Dissolve the fused mass in a mixture of 10 mL of water and 1 mL of sodium hydroxide solution (1 in 10), and add 1 drop of cupric sulfate TS: the solution acquires a reddish-violet color.
B: Dissolve 100 mg in 1 mL of water, and add 1 mL of nitric acid: a white crystalline precipitate of urea nitrate is formed.
Melting range 741: between 132 and 135.
Residue on ignition 281: not more than 0.1%.
Alcohol-insoluble matter Dissolve 5.0 g in 50 mL of warm alcohol, and if any insoluble residue remains, filter the solution on a tared filter, wash the residue and the filter with 20 mL of warm alcohol, and dry at 105 for 1 hour: the weight of the residue does not exceed 2 mg (0.04%).
Chloride 221 A 2.0-g portion shows no more chloride than corresponds to 0.20 mL of 0.020 N hydrochloric acid (0.007%).
Sulfate 221 A 2.0-g portion shows no more sulfate than corresponds to 0.20 mL of 0.020 N sulfuric acid (0.010%).
Heavy metals 231 Dissolve 1.0 g in 20 mL of water, and add 5 mL of 0.1 N hydrochloric acid: the limit is 0.002%.
Other requirements Where the label states that Urea is sterile, it meets the requirements for Sterility Tests 71 and for Bacterial endotoxins under Urea for Injection. Where the label states that Urea must be subjected to further processing during the preparation of injectable dosage forms, it meets the requirements for Bacterial endotoxins under Urea for Injection.
Assay Transfer about 500 mg of Urea, accurately weighed, to a 200-mL volumetric flask, dissolve in and dilute with water to volume, and mix. Pipet 2 mL of this solution into a micro-Kjeldahl digestion flask, and proceed as directed under Nitrogen Determination, Method II 461, beginning with Add 1 g of a powdered mixture. [noteIn this procedure, continue heating the flask until fuming begins, then heat for 1 additional hour. ] Each mL of 0.01 N acid is equivalent to 0.3003 mg of CH4N2O.
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USP35NF30 Page 4979Pharmacopeial Forum: Volume No. 29(5) Page 1589