Mephobarbital

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

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

DOWNLOAD PDF HERE

1 DEFINITION

Mephobarbital contains NLT 98.0% and NMT 100.5% of mephobarbital (C₁₃H₁₄N₂O₃), calculated on the dried basis.

2 IDENTIFICATION

Change to read:

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197M (CN 1-May-2020)

B.

Sample: 200 mg of Mephobarbital

Analysis: Boil the Sample with 10 mL of 1 N sodium hydroxide.

Acceptance criteria: Ammonia is evolved.

C.

Diluent: Sodium hydroxide solution (1 in 500)

Sample solution: 12 mg/mL of Mephobarbital prepared as follows. Shake about 60 mg of Mephobarbital with 5 mL of Diluent, and filter. Use the filtrate.

Analysis 1: Add 3 drops of mercuric nitrate TS to 1 mL of the Sample solution.

Acceptance criteria 1: A white precipitate is formed, and it is soluble in 6 N ammonium hydroxide.

Analysis 2: Add silver nitrate TS to 1 mL of the Sample solution.

Acceptance criteria 2: A white precipitate is formed, and it dissolves readily in 6 N ammonium hydroxide.

3 ASSAY

Procedure

Sample solution: 10 mg/mL of Mephobarbital in dimethylformamide

Analysis: Transfer 50 mL of Sample solution to a 200-mL flask. Add 4 drops of thymolphthalein TS. Titrate with 0.1 N lithium methoxide in toluene VS using a magnetic stirrer and a cover for the flask to protect against atmospheric carbon dioxide. Perform a blank determination.

Each mL of 0.1 N lithium methoxide is equivalent to 24.63 mg of mephobarbital (C H N O ).

Acceptance criteria: 98.0%–100.5% on the dried basis

4 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.1%

5 SPECIFIC TESTS

Loss on Drying 〈731〉

Analysis: Dry a sample at 105° for 4 h.

Acceptance criteria: NMT 1.0%

Melting Range or Temperature, Class I〈741〉: 176°–181°

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

USP Reference Standards 〈11〉

USP Mephobarbital RS