Docusate Sodium Syrup

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

Docusate sodium Syrup contains NLT 90.0% and NMT 110.0% of the labeled amount of docusate sodium (C₂₀H₃₇NaO₇S).

2 IDENTIFICATION

A. Thin-Layer Chromatography

Standard solution: 2 mg/mL of USP Docusate Sodium RS in isopropyl alcohol

Sample solution: Dilute a volume of Syrup, equivalent to about 10 mg of docusate sodium, with isopropyl alcohol to obtain a preparation containing about 2 mg/mL, and mix. Use the upper layer of this preparation.

Chromatographic system

(See Chromatography 〈621〉, Thin-Layer Chromatography.)

Mode: TLC

Adsorbent: 0.25-mm layer of chromatographic silica gel mixture

Application volume: 50 μL. [Note—Apply with the aid of a stream of nitrogen.]

Developing solvent system: Ethyl acetate, alcohol, water, and ammonium hydroxide (25:10:20:1). [Note—This is a two-phase system.]

Analysis

Samples: Standard solution and Sample solution

Allow the spots to dry, and develop the chromatogram in the Developing solvent system, until the solvent front has moved three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, and allow the solvent to evaporate.

Expose the plate to iodine vapors in a closed chamber for about 30 min, and locate the spots.

Acceptance criteria: The Sample solution produces a spot at the same R value and of approximately the same size as that obtained from the Standard solution.

3 ASSAY

Procedure

Standard stock solution: 1.0 mg/mL of USP Docusate Sodium RS, first dissolved in alcohol using about 2.5% of the final volume, and then diluted with water to volume. This solution contains 1 mg/mL of USP Docusate Sodium RS.

Standard solution: 10 μg/mL in water from the Standard stock solution

Sample solution: Transfer an accurately measured volume of Syrup, equivalent to about 100 mg of docusate sodium, to a 1000-mL volumetric flask, allowing the pipet to drain for 15 min. Dilute with water to volume, and mix. Transfer 10.0 mL of the solution to a 100-mL volumetric flask, dilute with water to volume, and mix.

Instrumental conditions

(See Ultraviolet-Visible Spectroscopy 〈857〉.)

Mode: Vis

Analytical wavelength: 650 nm

Cell: 1 cm

Analysis

Samples: Standard solution and Sample solution

Transfer 20.0 mL each of the Standard solution and the Sample solution to two individual separators. Place 20 mL of water in a third separator (Blank solution). To each separator add 5 drops of hydrochloric acid, mix by swirling, add 1.0 mL of methylene blue solution (1 in 1000), and mix by swirling. To each separator add 20.0 mL of chloroform, and shake vigorously for 5 min. Wash each chloroform solution, in clean separators, with 20 mL of water, shaking vigorously for 60 s. Discard the washings, and filter each chloroform solution through a layer of 3 g of anhydrous granular sodium sulfate, supported on glass wool, into a 100-mL volumetric flask, washing each separator with two 10-mL portions of chloroform, and filtering the washings into each flask. Dilute each flask with chloroform to volume. Concomitantly determine the absorbances of the Standard solution and the Sample solution, using the Blank solution to set the instrument.

Calculate the percentage of the labeled amount of docusate sodium (C₂₀H₃₇NaO₇S) in the portion of Syrup taken:

Result = (A_U/A_S) × (C_S/C_U) × 100

A_U= absorbance of the Sample solution

A_S= absorbance of the Standard solution

C_S= concentration of USP Docusate Sodium RS in the Standard solution (μg/mL)

C_U= nominal concentration of docusate sodium in the Sample solution (μg/mL)

Acceptance criteria: 90.0%–110.0%

4 SPECIFIC TESTS

pH 〈791〉: 5.5–6.5

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight, light-resistant containers.

USP Reference Standards 〈11〉

USP Docusate Sodium RS