Identification—
B:
Place in a small separator a volume of Injection, equivalent to about 30 mg of edrophonium chloride, add 15 mL of pH 9.6 alkaline borate buffer (see
Buffer Solutions in the section
Reagents, Indicators, and Solutions) and 5 mL of a 1 in 1000 solution of thymol blue in pH 9.6 alkaline borate buffer, and mix. Add 10 mL of chloroform, shake thoroughly, and allow to settle: a yellow color is produced in the chloroform layer.
C:
It responds to the tests for
Chloride 
191
.
Assay—
Pipet a volume of Injection, equivalent to about 50 mg of edrophonium chloride, into a glass-stoppered, 50-mL centrifuge tube. Add 5 mL of pH 8.0 phosphate buffer (see
Buffer Solutions in the section
Reagents, Indicators, and Solutions) and 5 g of sodium chloride. Wash the solution with four 20-mL portions of a mixture of equal volumes of solvent hexane and ether. Transfer the aqueous phase to a 100-mL volumetric flask, add 0.1 N hydrochloric acid to volume, and mix. Transfer a 5-mL aliquot of this solution to a 50-mL volumetric flask, add 0.1 N hydrochloric acid to volume, and mix test solution. Dissolve an accurately weighed quantity of
USP Edrophonium Chloride RS in 0.1 N hydrochloric acid, and dilute quantitatively and stepwise with the acid to obtain a Standard solution having a known concentration of about 50 µg per mL. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 273 nm, with a suitable spectrophotometer, using 0.1 N hydrochloric acid as the blank. Calculate the quantity, in mg, of C
10H
16ClNO in each mL of the Injection taken by the formula:
(C / V)(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Edrophonium Chloride RS in the Standard solution;
V is the volume, in mL, of Injection taken; and
AU and
AS are the absorbances of the test solution and the Standard solution, respectively.
