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» Phenylbutazone contains not less than 98.0 percent and not more than 102.0 percent of C19H20N2O2, calculated on the dried basis.
Packaging and storage Preserve in tight containers.
USP Reference standards 11
B: Ultraviolet Absorption 197U
Solution: 10 µg per mL.
Medium: sodium hydroxide solution (1 in 2500).
Absorptivities at 264 nm, calculated on the dried basis, do not differ by more than 2.0%.
Melting range 741: between 104 and 107.
Loss on drying 731 Dry it in vacuum at a pressure of 30 ± 10 mm of mercury at 80 for 4 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.1%, 2.0 g being used for the test.
Chloride 221 Boil 2.0 g with 60 mL of water for 5 minutes, cool, and filter. To a 30-mL portion of the filtrate add 1 mL of 2 N nitric acid and 1 mL of silver nitrate TS: the filtrate shows no more chloride than corresponds to 0.10 mL of 0.020 N hydrochloric acid (0.007%).
Sulfate 221 To a 30-mL portion of the filtrate obtained in the test for Chloride add 2 mL of barium chloride TS: the mixture shows no more sulfate than corresponds to 0.10 mL of 0.020 N sulfuric acid (0.01%).
Heavy metals, Method II 231: 0.001%.
Acetate buffer Transfer 2.72 g of sodium acetate to a 1000-mL beaker, and dissolve in about 700 mL of water. Adjust with glacial acetic acid to a pH of 4.1. Filter through a 0.5-µm filter, dilute with filtered water to 1000 mL, and mix.
Mobile phase Prepare a filtered and degassed mixture of acetonitrile with 560 mL of Acetate buffer (440:560). Make adjustments if necessary (see System Suitability under Chromatography 621).
Internal standard solution Dissolve 300 mg of desoxycorticosterone acetate in 200 mL of acetonitrile, and mix.
Standard preparation Dissolve an accurately weighed quantity of USP Phenylbutazone RS in acetonitrile, with the aid of sonication, and dilute quantitatively with acetonitrile to obtain a solution having a concentration of about 1.4 mg per mL. Pipet 10 mL of this solution into a 50-mL volumetric flask, add 10.0 mL of Internal standard solution, dilute with acetonitrile to volume, and mix. [NoteUse this solution within 8 hours of its preparation. ]
Assay preparation Transfer about 140 mg of Phenylbutazone, accurately weighed, to a 100-mL volumetric flask, add 75 mL of acetonitrile, and sonicate to dissolve. Dilute with acetonitrile to volume, and mix. Pipet 10 mL of this solution into a 50-mL volumetric flask, add 10.0 mL of Internal standard solution, dilute with acetonitrile to volume, and mix. [noteUse this solution within 8 hours of its preparation. ]
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm column that contains packing L7, preceded by a pre-column that contains packing L2. The flow rate is about 2.4 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the resolution, R, of phenylbutazone and the internal standard is not less than 3.5, and the relative standard deviation of the ratio of their peak responses in replicate injections is not more than 2.0%.
Procedure Separately inject equal volumes (about 25 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. The relative retention times are about 1.0 for the internal standard and 0.7 for phenylbutazone. Calculate the quantity, in mg, of C19H20N2O2 in the portion of Phenylbutazone taken by the formula:
500C(RU / RS)in which C is the concentration, in mg per mL, of USP Phenylbutazone RS in the Standard preparation; and RU and RS are the ratios of the peak response of the phenylbutazone to that of the internal standard for the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 4296Pharmacopeial Forum: Volume No. 28(5) Page 1440