Carboxymethylcellulose Sodium Paste

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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1 DEFINITION

Carboxymethylcellulose Sodium Paste contains NLT 16.0% and NMT 17.0% of carboxymethylcellulose sodium.

2 IDENTIFICATION

A.

Sample solution: Digest a quantity of Paste, equivalent to 1 g of carboxymethylcellulose sodium, with 50 mL of water until the solution is virtually complete. Filter.

Analysis: To 30 mL of the Sample solution add 3 mL of hydrochloric acid. Filter the solution, and save the filtrate for Identification test C.

Acceptance criteria: A white precipitate is formed.

B.

Sample solution: The remainder of the Sample solution prepared in Identification test A

Analysis: To the Sample solution add an equal volume of barium chloride TS.

Acceptance criteria: A fine, white precipitate is formed.

C. IDENTIFICATION TESTS-GENERAL, Sodium (191): The filtrate from Identification test A meets the requirements of the tests.

3 ASSAY

PROCEDURE

Sample: 2 g

Titrimetric system (See Titrimetry (541).)

Mode: Direct titration

Titrant: 0.1 N perchloric acid in dioxane VS

Endpoint detection: Potentiometric

Analysis: Transfer the Sample to a glass-stoppered, 250-mL conical flask. Add 75 mL of glacial acetic acid, attach a condenser, and reflux for 2 h. Cool, transfer the mixture to a 250-ml beaker with the aid of small volumes of glacial acetic acid. Titrate with Titrant. Each mL of 0.1 N perchloric acid is equivalent to 29.67 mg of carboxymethylcellulose sodium.

Acceptance criteria: 16.0%-17.0%

4 SPECIFIC TESTS

MICROBIAL ENUMERATION TESTS (61) and TESTS FOR SPECIFIED MICROORGANISMS (62): The total bacterial count does not exceed 103 cfu/g, and the tests for Salmonella species and Escherichia coli are negative.

CONSISTENCY

Apparatus: A penetrometer fitted with a polished cone-shaped metal plunger weighing 150 g, having a detachable steel tip of the following

dimensions: the tip of the cone has an angle of 30°; the point of the tip is truncated to a diameter of 0.381 ± 0.025 mm; the base of the tip is 8.38 ± 0.05 mm in diameter, and the length of the tip is 14.94 ± 0.05 mm.

The remaining portion of the cone has an angle of 90°, is 28 mm in height, and has a maximum diameter at the base of 65 mm. The containers for the test are flat-bottom metal cylinders that are 100 ± 6 mm in diameter and NLT 65 mm in height. They are constructed of at least 1.6-mm (16-gauge) metal, and are provided with well-fitting, water-tight covers.

Sample: Paste

Analysis: Place the required number of containers in an oven, bring them and a quantity of the Sample to a temperature of 82 ± 2.5°, and pour the Sample into one or more of the containers, filling to within 6 mm of the rim. Cool to 25 ± 2.5" over a period of NLT 16 h, protected from drafts. Two h before the test, place the containers in a water bath at 25 ± 0.5°. If the room temperature is below 23.5° or above 26.5", adjust the temperature of the cone to 25 ± 0.5° by placing it in the water bath.

Without disturbing the surface of the substance under test, place the container on the penetrometer table, and lower the cone until the tip just touches the top surface of the test substance at a spot 25-38 mm from the edge of the container. Adjust the zero setting and quickly release the plunger, then hold it free for 5 s. Secure the plunger, and read the total penetration from the scale. Make three or more trials, each so spaced that there is no overlapping of the areas of penetration. Where the penetration exceeds 20 mm, use a separate container of the test substance for each trial. Read the penetration to the nearest 0.1 mm.

Calculate the average of the three or more readings, and conduct further trials to a total of 10 if the individual results differ from the average by more than ±3%.

Acceptance criteria: The final average of the trials is 30.0–36.0 mm, indicating a consistency value of between 300 and 360.

Loss on Drying 〈731〉

Analysis: Dry at 105° for 3 h.

Acceptance criteria: NMT 2.0%

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers, and avoid prolonged exposure to temperatures exceeding 30°.