Assay—
Transfer an accurately measured volume of Oral Solution, equivalent to about 10 mg of haloperidol, to a separator, and add 20 mL of dilute hydrochloric acid (1 in 20). Extract the solution with four 20-mL portions of ether, and wash the combined ether extracts with four 5-mL portions of dilute hydrochloric acid (1 in 20). Discard the ether, and add the acid washings to the aqueous phase. Filter the aqueous phase through a pledget of cotton into a 50-mL volumetric flask, add dilute hydrochloric acid (1 in 20) to volume, and mix. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, dilute with methanol to volume, and mix. Concomitantly determine the absorbances of this solution and of a solution of
USP Haloperidol RS in the same medium having a known concentration of about 20 µg per mL, in 1-cm cells at the wavelength of maximum absorbance at about 245 nm, with a suitable spectrophotometer, using a 1 in 10 solution of dilute hydrochloric acid (1 in 20) in methanol as the blank. Calculate the quantity, in mg, of haloperidol (C
21H
23ClFNO
2) in each mL of Oral Solution taken by the formula:
0.5(C/V)(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Haloperidol RS in the Standard solution;
V is the volume, in mL, of Oral Solution taken; and
AU and
AS are the absorbances of the solution from the Oral Solution and the Standard solution, respectively.
905
—