Butanedioic acid, sulfo-, 1,4-bis(2-ethylhexyl) ester, sodium salt.
Sodium 1,4-bis(2-ethylhexyl) sulfosuccinate
[
577-11-7].
Packaging and storage—
Preserve in well-closed containers.
Clarity of solution—
Dissolve 25 g in 100 mL of alcohol: the solution does not develop a haze within 24 hours.
Identification—
Place a small piece of it 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: the IR absorption spectrum of the film so obtained exhibits maxima only at the same wavelengths as that of a similar preparation of
USP Docusate Sodium RS.
Heavy metals 
231
—
Transfer 2.0 g to a platinum crucible, and ignite until free from carbon. Cool, moisten the residue with 1 mL of hydrochloric acid, and evaporate on a steam bath to dryness. Add 2 mL of 6 N acetic acid, digest on a steam bath for 5 minutes, filter into one of a pair of matched 50-mL color-comparison tubes, and wash the residue with sufficient water to make 25 mL: the limit is 0.001%.
Limit of bis(2-ethylhexyl)maleate—
Place 12.5 g of Docusate Sodium, previously dried at 105
for 2 hours and accurately weighed, in a 100-mL volumetric flask. Pipet 20 mL of pH 10 alkaline borate buffer (see under
Solutions in the section
Reagents, Indicators, and Solutions) into the flask, and add about 70 mL of alcohol. Swirl the flask and contents, with gentle warming, until the solid dissolves. Cool, and add alcohol to volume. Transfer a portion of this test solution to a polarographic cell that is immersed in a water bath regulated at 25 ± 0.5
, and deaerate by bubbling through the solution, for 10 minutes, purified nitrogen that previously has been passed through a solution prepared by mixing 4 volumes of alcohol and 1 volume of water. Insert the dropping mercury electrode of a suitable polarograph, and record the polarogram from
0.5 volt to
1.6 volts, using a saturated calomel electrode as the reference electrode (see
Polarography 801). Determine the height of the diffusion current at the current plateau at about
1.45 volts. To a separate 50-mL portion of the solution add 25 mg of USP Bis(2-ethylhexyl)maleate RS, accurately weighed, and when solution is complete, deaerate a portion of the resulting solution, and record the polarogram, as directed in the foregoing. The diffusion current for the test solution of Docusate Sodium is not greater than one-half the diffusion current of the solution containing the added USP Bis(2-ethylhexyl)maleate RS [not more than 0.4% of bis(2-ethylhexyl) maleate].
Assay—
Tetra-n-butylammonium iodide solution—
Transfer 1.250 g of tetra-n-butylammonium iodide to a 500-mL volumetric flask, dilute with water to volume, and mix.
Salt solution—
Transfer 100 g of anhydrous sodium sulfate and 10 g of sodium carbonate to a 400-mL beaker, and add water to dissolve the two salts. Transfer the solution to a 1000-mL volumetric flask, dilute with water to volume, and mix.
Procedure—
Dissolve about 50 mg of Docusate Sodium, accurately weighed, in 50 mL of chloroform in a glass-stoppered, 250-mL conical flask. Add 50 mL of
Salt solution and 0.5 mL of
bromophenol blue TS, and mix. Titrate with
Tetra-n-butylammonium iodide solution until about 1 mL from the endpoint, and shake the stoppered flask vigorously for about 2 minutes. Continue the titration in 2-drop increments, shaking vigorously for about 10 seconds after each addition, and then allow the flask to stand about 10 seconds. Continue the titration until the chloroform layer just assumes a blue color. Each mL of
Tetra-n-butylammonium iodide solution is equivalent to 3.009 mg of C
20H
37NaO
7S.
Auxiliary Information—
Staff Liaison :
Elena Gonikberg, Ph.D., Scientist
Expert Committee : (MDGRE05) Monograph Development-Gastrointestinal Renal and Endocrine
USP29–NF24 Page 749
Pharmacopeial Forum : Volume No. 31(3) Page 753
Phone Number : 1-301-816-8251
