Solution: 50 µg per mL.

Medium: acidified methanol (prepared by adding 9 mL of hydrochloric acid to 100 mL of methanol).

Triethylamine solution, Solvent mixture, Mobile phase, Standard preparation, and Chromatographic system— Prepare as directed in the Assay under Ethacrynic Acid Tablets.

Assay preparation— Select a number of containers of Ethacrynate Sodium for Injection, the combined contents of which, on the basis of the labeled amount, are equivalent to about 500 mg of ethacrynic acid. Add about 5 mL of Solvent mixture to each container, mix to dissolve the contents, and combine the resulting solutions in a 200-mL volumetric flask. Rinse each container with two additional 5-mL portions of Solvent mixture, add the rinsings to the solution in the volumetric flask, dilute with Solvent mixture to volume, and mix. Transfer 20.0 mL of this solution to a 100-mL volumetric flask, dilute with Solvent mixture to volume, and mix.

Procedure— Proceed as directed for Procedure in the Assay under Ethacrynic Acid Tablets. Calculate the quantity, in mg, of C13H12Cl2O4 in each container of Ethacrynate Sodium for Injection taken by the formula: in which N is the number of containers selected for the Assay preparation.