Standard preparation—
Weigh accurately about 50 mg of
USP Eucatropine Hydrochloride RS, dissolve in water, and dilute with water in a volumetric flask to 100 mL. Dilute 10.0 mL of this solution with water to 50.0 mL to obtain a solution having a known concentration of about 100 µg per mL. Prepare this solution fresh.
Procedure—
Transfer duplicate 2-mL portions of the
Standard preparation and of the
Assay preparation to separate glass-stoppered, 40-mL centrifuge tubes. To one set of two tubes add 3 mL of water and 1 mL of sodium hydroxide solution (1 in 100). Heat these tubes in a boiling water bath for 10 minutes, and allow to cool to room temperature. To the remaining set of tubes, which provide the blanks for the
Standard preparation and
Assay preparation, respectively, add 4 mL of water. To each tube add 2 mL of approximately 0.2
M ceric sulfate in diluted sulfuric acid (prepared by dissolving 12.6 g of ceric ammonium sulfate in 50 mL of water and 3 mL of sulfuric acid, and diluting with water to 100 mL) and 20.0 mL of isooctane. Shake by mechanical means for 15 minutes, allow the layers to separate, and remove the isooctane from each tube. Concomitantly determine the absorbances of the isooctane solutions from the hydrolyzed aliquots in 1-cm cells at the wavelength of maximum absorbance at about 242 nm, with a suitable spectrophotometer, against the respective blanks. Calculate the quantity, in mg, of C
17H
25NO
3·HCl in the portion of Ophthalmic Solution taken by the formula:
0.5C(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Eucatropine Hydrochloride RS in the
Standard preparation; and
AU and
AS are the absorbances of the solutions from the
Assay preparation and the
Standard preparation, respectively.
181
.