Propylene Glycol Alginate

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

Propylene Glycol Alginate is a propylene glycol ester of alginic acid. Each gram yields NLT 0.16 and NMT 0.20 g of carbon dioxide, calculated on the dried basis.

2 IDENTIFICATION

A.

Sample solution: Place 20 mL of the saponified solution obtained in the determination of Esterified Carboxyl Groups in a 250-mL conical flask. Add 50 mL of a solution of periodic acid (1 in 50), swirl, and allow to stand for 30 min. Add 2 g of potassium iodide, titrate with sodium thiosulfate TS to a faint yellow color, dilute the mixture with water to 200 mL, and mix to obtain the Sample solution for Identification test A and Identification test B.

Modified Schiff's reagent: Dissolve 200 mg of rosaniline hydrochloride (C H ClN ) in 120 mL of hot water. Cool, add 2 g of sodium bisulfite (NaHSO ), followed by 2 mL of hydrochloric acid, and dilute with water to 200 mL. [NOTE—Store this solution in a brown bottle at 15° or lower.]

Analysis: To 10 mL of the Sample solution add 5 mL of hydrochloric acid and 10 mL of Modified Schiff's reagent.

Acceptance criteria: A blue to blue-violet color, due to formaldehyde, develops in about 20 min.

B.

Analysis: To 10 mL of the Sample solution prepared in Identification test A add 1 mL of a saturated solution of Piperazine and 0.5 mL of sodium nitroferricyanide TS.

Acceptance criteria: A green color, due to acetaldehyde, develops.

3 ASSAY

CONTENT OF ALGINATE

Analysis: Proceed as directed for Procedure in Alginates Assay 〈311〉, without preliminary drying of the Propylene Glycol Alginate. Acceptance criteria: 0.16–0.20 g of carbon dioxide/g of Propylene Glycol Alginate, calculated on the dried basis

4 OTHER COMPONENTS

4.1 FREE CARBOXYL GROUPS

Sample: 1 g Titrimetric system

Mode: Direct titration

Titrant: 0.1 N sodium hydroxide VS Endpoint detection: Potentiometric

Analysis: Transfer the Sample to a 600-mL beaker. Dissolve in 200 mL of water, stirring by mechanical means for NLT 30 min. Titrate with 0.1 N sodium hydroxide VS to a pH of 7.0.

Calculate the weight, in g, of free carboxyl groups in the Sample taken:

Result = [(V × M_r × N)/W] × F

V    = Titrant volume consumed (mL)

M_r = mEq of CO₂, 44 mg/mEq

N = actual normality of the Titrant (mEq/mL)

W = Sample weight (g)

F = conversion factor, 10−3 g/mg

Acceptance criteria: The weight of free carboxyl groups found, calculated on the dried basis, is NMT 35% of the weight of carbon dioxide yielded by an equal weight of specimen in the Assay.

4.2 ESTERIFIED CARBOXYL GROUPS

Sample solution: The solution obtained in the test for Free Carboxyl Groups

Analysis: Transfer the Sample solution with the aid of water to a 1000-mL conical flask. Add phenolphthalein TS and 50.0 mL of 0.1 N sodium hydroxide VS, insert a stopper in the flask, mix, and allow to stand for 30 min at ambient temperature. Titrate the excess sodium hydroxide with 0.1 N hydrochloric acid VS to a faint pink endpoint. Transfer the solution with the aid of water to a 600-mL beaker, and complete the titration to a pH of 7.0, determining the endpoint potentiometrically.

Calculate the weight, in g, of esterified carboxyl groups in the weight, W, in g, of the specimen taken:

Result = [(V × M_r × N)/W] × F

V = volume of 0.1 N sodium hydroxide consumed (mL)

M_r = mEq of CO₂, 44 mg/mEq

N = actual normality of 0.1 N sodium hydroxide (mEq/mL) W = specimen weight (g)

F = conversion factor, 10−3 g/mg

Acceptance criteria: The weight of esterified carboxyl groups found, calculated on the dried basis, is 40%–85% of the weight of carbon dioxide yielded by an equal weight of specimen in the Assay.

5 IMPURITIES

Change to read:

ARSENIC 〈211〉 , Procedures, Procedure 2 (CN 1-J -2023) : 3 ppm Change to read:

LEAD 〈251〉 , Procedures, Procedure 1 (CN 1-JUN-2023)

Standard solution: 5 mL of Diluted Standard Lead Solution

Test preparation: Add 1.0 g to 20 mL of nitric acid in a 250-mL conical flask, mix, and heat carefully until the specimen is dissolved. Continue the heating until the volume is reduced to 7 mL. Cool rapidly to room temperature, transfer to a 100-mL volumetric flask, dilute with water to volume, and mix. Use a 50-mL portion.

Analysis: Proceed as directed in the chapter, using 15 mL of ammonium citrate solution, 3 mL of potassium cyanide solution, and 0.5 mL of hydroxylamine hydrochloride solution for the test. After the first dithizone extractions, wash the combined chloroform layers with 5 mL of water, discarding the water layer and continuing in the usual manner by extracting with 20 mL of 0.2 N nitric acid.

Acceptance criteria: A 50.0-mL portion of this solution contains NMT 5 µg of lead (corresponding to NMT 10 ppm of Pb).

6 SPECIFIC TESTS

MICROBIAL ENUMERATION TESTS 〈61〉and TESTS FOR SPECIFIED MICROORGANISMS 〈62〉: The total bacterial count does not exceed 200 cfu/g, and the tests for Salmonella species and Escherichia coli are negative.

LOSS ON DRYING 〈731〉: Dry a sample at 105° for 4 h: it loses NMT 20.0% of its weight.

ASH

Sample: 3 g

Analysis: Weigh the Sample in a tared crucible, and incinerate at 650 ± 25° until free from carbon. Cool in a desiccator, weigh, and determine the weight of the ash.

Acceptance criteria: NMT 10.0% on the dried basis

7 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in well-closed containers.