Docusate Potassium

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 Potassium contains NLT 95.0% and NMT 100.5% of docusate potassium (C₂₀H₃₇KO₇S), calculated on the dried basis.

2 IDENTIFICATION

Change to read:

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

Sample: Place a small piece of Docusate Potassium on a salt plate, add 1 drop of acetone, and promptly cover with another salt plate. Rub the plates together to dissolve the specimen, slide the plates apart, and allow the acetone to evaporate.

Acceptance criteria: Meets the requirements

B. The sample imparts a violet color to a nonluminous flame. Because the presence of small quantities of sodium masks the color, screen out the yellow color produced by sodium by viewing through a blue

filter that blocks emission at 589 nm (sodium) but is transparent to emission at 404 nm (potassium). [Note—Traditionally, cobalt glass has been used, but other suitable filters are commercially available.]

3 ASSAY

Procedure

Solution A: 2.500 g/L of tetra-n-butylammonium iodide in water

Solution B: A solution containing 100 g/L of anhydrous sodium sulfate and 10 g/L of sodium carbonate in water

Sample: 100 mg

Analysis: Dissolve the Sample in 50 mL of chloroform in a glass-stoppered, 250-mL conical flask. Add 50 mL of Solution B and 500 μL of bromophenol blue TS. Titrate with Solution A until 1 mL from the endpoint, and shake the stoppered flask vigorously for 2 min. Continue the titration in 2-drop increments, shaking vigorously for 10 s after each addition, and then allow the flask to stand for 10 s. Continue the titration until the chloroform layer just assumes a blue color. Each mL of Solution A is equivalent to 3.118 mg of docusate potassium (C₂₀H₃₇KO₇S).

Acceptance criteria: 95.0%–100.5% on the dried basis

4 IMPURITIES

Residue on Ignition 〈281〉: 18.0%–20.0% on the dried basis

Limit of Bis(2-ethylhexyl) Maleate

Mobile phase: Alcohol and water (78:22), filtered and degassed

Standard solution: 80 μg/mL of USP Bis(2-ethylhexyl) Maleate RS in alcohol

Sample solution: 20 mg/mL of Docusate Potassium in alcohol. [Note—If necessary, warm the mixture by using the steam bath to achieve a complete dissolution.]

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 210 nm

Column: 4.6-mm × 3-cm; 3.5-μm packing L1

Column temperature: 30°

Flow rate: 1 mL/min

Injection volume: 3 μL

System suitability

Sample: Standard solution

Suitability requirements

Relative standard deviation: NMT 2.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of bis(2-ethylhexyl) maleate in the portion of Docusate Potassium taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of bis(2-ethylhexyl) maleate from the Sample solution

r_S = peak response of bis(2-ethylhexyl) maleate from the Standard solution

C_S = concentration of USP Bis(2-ethylhexyl) Maleate RS in the Standard solution (mg/mL)

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

Acceptance criteria: NMT 0.4%

5 SPECIFIC TESTS

Loss on Drying 〈731〉

Analysis: Dry in a glass container at 105° for 4 h.

Acceptance criteria: NMT 3.0%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

USP Reference Standards 〈11〉

USP Bis(2-ethylhexyl) Maleate RS C H O 340.51

USP Docusate Potassium RS