Assay—
[NOTE—Use low-actinic flasks in preparing the solutions, and otherwise protect the solutions from unnecessary exposure to bright light. Complete the assay without prolonged interruption.
] Dissolve about 250 mg of Pyrvinium Pamoate, accurately weighed, in 125 mL of glacial acetic acid in a 250-mL volumetric flask, dilute with methanol to volume, and mix. Transfer 5 mL of this solution to a 500-mL volumetric flask, dilute with methanol to volume, and mix. Similarly dissolve an accurately weighed quantity of
USP Pyrvinium Pamoate RS in glacial acetic acid, using 1 mL for each 2 mg taken, and dilute quantitatively and stepwise with methanol to obtain a Standard solution having a known concentration of about 10 µg per mL. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 505 nm, with a suitable spectrophotometer, using methanol as the blank. Calculate the quantity, in mg, of C
75H
70N
6O
6 in the portion of Pyrvinium Pamoate taken by the formula:
25C(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Pyrvinium Pamoate RS in the Standard solution, calculated on the anhydrous basis, and
AU and
AS are the absorbances of the solution of Pyrvinium Pamoate and the Standard solution, respectively.
;)
921
:
not more than 6.0%, a 200-mg specimen being used for the test, and a mixture of 10 mL of methanol and 10 mL of chloroform being used as the solvent.