Oxaprozin
(ox'' a proe' zin).
Click to View Image
C18H15NO3 293.32

2-Oxazolepropanoic acid, 4,5-diphenyl-.
4,5-Diphenyl-2-oxazolepropionic acid [21256-18-8].
» Oxaprozin contains not less than 98.5 percent and not more than 101.5 percent of C18H15NO3, calculated on the dried basis.
[note—Because of light sensitivity, protect all oxaprozin samples and Standard solutions from light. ]
Packaging and storage— Preserve in tight, light-resistant containers, and store at controlled room temperature.
USP Reference standards 11
USP Oxaprozin RS Click to View Structure
Identification—
A: Infrared Absorption 197K: previously dried at 105 for 2 hours.
B: Ultraviolet Absorption 197U: previously dried at 105 for 2 hours. The absorbance of the sample at 285 nm is between 0.455 and 0.495.
Solution: 10 µg per mL.
Medium: methanol.
Loss on drying 731 Dry it at 105 for 2 hours: it loses not more than 0.3% of its weight.
Residue on ignition 281: not more than 0.3%.
Arsenic, Method II 211: 1 µg per g.
Chromatographic purity—
Solution A: 0.1% phosphoric acid adjusted with phosphoric acid to a pH of 2.00 ± 0.1.
Solution B— Use acetonitrile.
Mobile phase— Use variable mixtures of Solution A and Solution B as directed for Chromatographic system. Make adjustments if necessary (see System Suitability under Chromatography 621).
Diluent A: a mixture of acetonitrile, methylene chloride, and water (48:1:1).
Diluent B: a mixture of acetonitrile and water (1:1).
Standard stock solution— Dissolve an accurately weighed quantity of USP Oxaprozin RS in acetonitrile to obtain a solution having a concentration of about 200 µg per mL.
Standard solution— Transfer 5.0 mL of Standard stock solution to a 200-mL volumetric flask, and dilute with Diluent A to volume.
Benzil solution: 200 µg of benzil per mL in acetonitrile.
Resolution solution— Transfer 5.0 mL of Benzil solution and 5.0 mL of Standard stock solution to a 100-mL volumetric flask, and dilute with Diluent A to volume to obtain a solution having known concentrations of about 10 µg of each per mL.
Test solution A— [note—Test solution A is used to monitor all known and unknown impurities, except imidazolic acid and oximide. ] Transfer about 100 mg of Oxaprozin, accurately weighed, to a 100-mL volumetric flask; add 2 mL of methylene chloride, 2 mL of water, and 75 mL of acetonitrile; and sonicate after each solvent is added. Dilute with acetonitrile to volume.
Test solution B— [note—Test solution B is used to monitor only imidazolic acid and oximide. ] Transfer about 100 mg of Oxaprozin, accurately weighed, to a 100-mL volumetric flask; add 75 mL of Diluent B to dissolve the Oxaprozin; and dilute with Diluent B to volume.
Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 238-nm detector and a 4.6-mm × 15-cm column that contains 5-µm packing L7. The flow rate is 1.0 mL per minute. The chromatograph is programmed as follows.
Time
(minutes)
Solution A
(%)
Solution B
(%)
Elution
0 70 30 equilibration
0–20 70 30 isocratic
21–60 70®0 30®100 linear gradient
60–61 0®70 100®30 linear gradient
61–70 70 30 isocratic
Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the relative retention times are about 1.1 for benzil and 1.0 for oxaprozin; and the resolution, R, between oxaprozin and benzil is not less than 3.0. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the tailing factor is not more than 2.0, and the relative standard deviation for replicate injections is not more than 5.0%.
Procedure— Inject 20 µL of Test solution A and Test solution B into the chromatograph, record the chromatogram, and measure the areas for all the peaks. Calculate the percentage of each impurity in the portion of Oxaprozin taken by the formula:
100(Fri / rs)
in which F is the relative response factor and is equal to 1.15 for the imidazolic acid peak with a relative retention time of 0.14, 1.21 for any peak with a relative retention time of 0.42, 0.91 for the oximide peak with a relative retention time of 0.73, 0.85 for any peak with a relative retention time of 0.84, 1.29 for any peak with a relative retention time of 1.08, 1.46 for any peak with a relative retention time of 1.50, and 2.09 for any peak with a relative retention time of 1.57; ri is the peak response for each impurity; and rs is the sum of the responses of all the peaks: not more than 0.1% of any individual impurity is found, and not more than 0.5% of total impurities is found. [note—The values of F for all known impurities except imidazolic acid and oximide were found using Test solution A, and the values of F for imidazolic acid and oximide were found using Test solution B. ]
Assay— Dissolve about 400 mg of Oxaprozin, previously dried at 105 for 2 hours and accurately weighed, in about 100 mL of alcohol in a narrow-mouth container, and titrate with 0.1 N sodium hydroxide VS, determining the endpoint potentiometrically (see Titrimetry 541). Each mL of 0.1 N sodium hydroxide is equivalent to 29.332 mg of oxaprozin.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Clydewyn M. Anthony, Ph.D.
Senior Scientific Liaison
1-301-816-8139
(SM22010) Monographs - Small Molecules 2
Reference Standards RS Technical Services
1-301-816-8129
rstech@usp.org
USP35–NF30 Page 4154
Pharmacopeial Forum: Volume No. 32(1) Page 130