USP Reference standards 
11
—
USP Promazine Hydrochloride RS.
NOTE—Throughout the following procedures, protect test or assay specimens, the Reference Standard, and solutions containing them, by conducting the procedures without delay, under subdued light, or using low-actinic glassware.
Assay—
[NOTE—Use low-actinic glassware.
] Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 50 mg of promazine hydrochloride, to a 100-mL volumetric flask. Add 50 mL of 0.1 N hydrochloric acid, and shake by mechanical means for about 1 hour. Dilute with 0.1 N hydrochloric acid to volume, mix, and centrifuge a portion of the mixture. Transfer 10.0 mL of the clear, supernatant to a 250-mL separator, and proceed as directed in the
Assay under
Promazine Hydrochloride Injection, beginning with “add 20 mL of water.” Calculate the quantity, in mg, of C
17H
20N
2S·HCl in the portion of Tablets taken by the formula:
C(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Promazine Hydrochloride RS in the Standard solution, and
AU and
AS are the absorbances of the solution from the Tablets and the Standard solution, respectively.
