Oxaprozin

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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C₁₈H₁₅NO₃ 293.32

2-Oxazolepropanoic acid, 4,5-diphenyl-;

4,5-Diphenyl-2-oxazolepropionic acid CAS RN^®: 21256-18-8; UNII: MHJ80W9LRB (USP 1-May-2022).

1 DEFINITION

Oxaprozin contains NLT 98.0% and NMT 102.0% of oxaprozin (C₁₈H₁₅NO₃), calculated on the dried basis.

[NOTE-Because of light sensitivity, protect all oxaprozin samples and Standard solutions from light.]

2 IDENTIFICATION

A. SPECTROSCOPIC IDENTIFICATION TESTS (197), Infrared Spectroscopy: 197K or 197A

B. The retention time of the oxaprozin peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

3.1 PROCEDURE

Solution A: 0.1% phosphoric acid, pH 2.0 ± 0.1

Mobile phase: Acetonitrile and Solution A (45:55)

Standard solution: 0.2 mg/mL of USP Oxaprozin RS in acetonitrile

Sample solution: 0.2 mg/mL of Oxaprozin in acetonitrile

3.2 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 285 nm

Column: 4.6-mm × 15-cm; 5-µm packing L7

Column temperature: 25°

Flow rate: 1.0 mL/min

Injection volume: 20 µL

3.3 System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 0.73%

3.4 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of oxaprozin (C₁₈H₁₅NO₃) in the portion of Oxaprozin taken:

Result = (r_U/r_S) x (C_S/C_U) x 100

r_U = peak response of oxaprozin from the Sample solution

r_S = peak response of oxaprozin from the Standard solution

C_S = concentration of USP Oxaprozin RS in the Standard solution (mg/mL)

C_U = concentration of Oxaprozin in the Sample solution (mg/mL)

Acceptance criteria: 98.0%-102.0% on the dried basis

4 IMPURITIES

4.1 RESIDUE ON IGNITION (281)

NMT 0.3%

Delete the following:

4.2 ARSENIC (211), Procedures, Method II

NMT 1 ppm (USP 1-May-2022)

4.3 ORGANIC IMPURITIES

Solution A: 0.1% phosphoric acid, pH 2.0 ± 0.1

Solution B: Acetonitrile

Mobile phase: See Table 1.

Table 1

Diluent A: Acetonitrile, methylene chloride, and water (48:1:1)

Diluent B: Acetonitrile and water (1:1)

Standard stock solution: 200 µg/mL of USP Oxaprozin RS in acetonitrile

Standard solution: 5 µg/mL of USP Oxaprozin RS in Diluent A from the Standard stock solution

Sensitivity solution: 0.3 µg/mL of USP Oxaprozin RS in Diluent A from the Standard solution

System suitability stock solution: 200 µg/mL of benzil in acetonitrile

System suitability solution: 10 µg/mL each of benzil and USP Oxaprozin RS in Diluent A from the System suitability stock solution and Standard stock solution, respectively

Sample solution A: 1 mg/mL of Oxaprozin prepared as follows. Transfer about 100 mg of Oxaprozin to a 100-mL volumetric flask. Add 2 mL of methylene chloride, 2 mL of water, and 75 mL of acetonitrile. Sonicate after each solvent is added. Dilute with acetonitrile to volume. [NOTE-This is used to monitor all known and unknown impurities, except oxaprozin imidazole analog and oxaprozin amide.]

Sample solution B: 1 mg/mL of Oxaprozin in Diluent B. [NOTE-This is used to monitor only oxaprozin imidazole analog and oxaprozin amide.]

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 238 nm

Column: 4.6-mm × 15-cm; 5-µm packing L7

Flow rate: 1.0 mL/min

Injection volume: 20 µL

System suitability

Samples: Standard solution, Sensitivity solution, and System suitability solution

Suitability requirements

Resolution: NLT 3.0 between oxaprozin and benzil, System suitability solution

Tailing factor: NMT 2.0, Standard solution

Relative standard deviation: NMT 5.0%, Standard solution

Signal-to-noise ratio: NLT 10, Sensitivity solution

Analysis

Samples: Sample solution A and Sample solution B

Calculate the percentage of oxaprozin imidazole analog and oxaprozin amide in the portion of Oxaprozin taken:

Result = (r_U/r_T) x (1/F) x 100

r_U = peak area of oxaprozin imidazole analog or oxaprozin amide from Sample solution B

r_T = sum of the peak areas from Sample solution B

F = relative response factor (see Table 2)

Calculate the percentage of any other impurity in the portion of Oxaprozin taken:

Result = (r_U/r_T) x (1/F) x 100

r_U = peak area of each individual impurity from Sample solution A

r_T = sum of the peak areas from Sample solution A

F = relative response factor (see Table 2)

Acceptance criteria: See Table 2. The reporting threshold is 0.03%.

Table 2

^a 3-(4,5-Diphenyl-1H-imidazol-2-yl)propanoic acid.

^b 2-Hydroxy-1,2-diphenylethan-1-one.

^c 3-(4,5-Diphenyloxazol-2-yl)propanamide.

^d 4-Oxo-4-(2-oxo-1,2-diphenylethoxy)butanoic acid.

^e 1,2-Bis(4,5-diphenyloxazol-2-yl)ethane.

^f 2,3,5,6-Tetraphenylpyrazine.

5 SPECIFIC TESTS

LOSS ON DRYING (731)

Analysis: Dry at 105° for 2 h.

Acceptance criteria: NMT 0.3%

6 ADDITIONAL REQUIREMENTS

6.1 PACKAGING AND STORAGE

Preserve in tight, light-resistant containers, and store at controlled room temperature.

6.2 USP REFERENCE STANDARDS (11)

USP Oxaprozin RS