A: 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 Potassium RS.

B: It responds to the flame test for Potassium 191.

Mobile phase, Standard solution, and Chromatographic system— Proceed as directed under Docusate Sodium.

Test solution— Transfer about 1.0 g of Docusate Potassium, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with alcohol to volume, and mix. If necessary, warm the mixture using the steam bath to achieve a complete dissolution.

Procedure— Separately inject equal volumes (about 3 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the responses for the bis(2-ethylhexyl) maleate peaks. Calculate the percentage of bis(2-ethylhexyl) maleate in the portion of Docusate Potassium taken by the formula: in which C is the concentration, in µg per mL, of USP Bis(2-ethylhexyl) Maleate RS in the Standard solution; W is the weight, in mg, of Docusate Potassium taken to prepare the Test solution; and rU and rS are the peak responses of bis(2-ethylhexyl) maleate obtained from the Test solution and the Standard solution, respectively: not more than 0.4% is found.

Tetra-n-butylammonium iodide solution, and Salt solution— Prepare as directed in the Assay under Docusate Sodium.

Procedure— Dissolve about 100 mg of Docusate Potassium, accurately weighed, in 50 mL of chloroform in a glass-stoppered, 250-mL conical flask. Proceed as directed in the Assay under Docusate Sodium, beginning with “Add 50 mL of Salt solution.” Each mL of Tetra-n-butylammonium iodide solution is equivalent to 3.118 mg of C20H37KO7S.