Docusate Sodium Syrup
» Docusate Sodium Syrup contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of C20H37NaO7S.
Packaging and storage— Preserve in tight, light-resistant containers.
Identification— Dilute a volume of Syrup, equivalent to about 10 mg of docusate sodium, with isopropyl alcohol to obtain a preparation containing about 2 mg per mL, and mix. Apply, with the aid of a stream of nitrogen, 50 µL of the upper layer of this preparation and 50 µL of an isopropyl alcohol solution of USP Docusate Sodium RS containing about 2 mg per mL to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Allow the spots to dry, and develop the chromatogram in a two-phase solvent system consisting of ethyl acetate, water, alcohol, and ammonium hydroxide (25:20:10:1) until the solvent front has moved about 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 minutes, and locate the spots: the test preparation produces a spot at the same RF value and of approximately the same size as that obtained from the Standard solution.
pH 791: between 5.5 and 6.5.
Assay—
Standard preparation— Transfer about 100 mg of USP Docusate Sodium RS, accurately weighed, to a 100-mL volumetric flask, dissolve in 2.5 mL of alcohol, dilute with water to volume, and mix. Transfer 10.0 mL of this solution to a 1000-mL volumetric flask, dilute with water to volume, and mix. The concentration of USP Docusate Sodium RS in the Standard preparation is about 10 µg per mL.
Assay preparation— 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 minutes. 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.
Procedure— Transfer 20.0 mL each of the Standard preparation and of the Assay preparation to individual separators, and place 20 mL of water in a third separator to provide the blank. 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 minutes. Wash each chloroform solution, in clean separators, with 20 mL of water, shaking vigorously for 60 seconds. 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, and mix. Concomitantly determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 650 nm, with a suitable spectrophotometer, using the blank to set the instrument. Calculate the quantity, in mg, of C20H37NaO7S in each mL of Syrup taken by the formula:
(10C / V)(AU / AS)
in which C is the concentration, in µg per mL, calculated on the anhydrous basis, of USP Docusate Sodium RS in the Standard preparation; V is the volume, in mL, of Syrup taken; and AU and AS are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Elena Gonikberg, Ph.D.
Senior Scientist
1-301-816-8251
(MDGRE05) Monograph Development-Gastrointestinal Renal and Endocrine
Reference Standards Lili Wang, Technical Services Scientist
1-301-816-8129
RSTech@usp.org
USP32–NF27 Page 2196