Identification—
A:
Extract 10 mL of it with 25 mL of chloroform, filter the chloroform extract through dry, folded filter paper, and evaporate the filtrate to dryness: the residue so obtained responds to Identification test A under Tropicamide.
B:
The UV absorption spectrum of the solution employed for measurement of absorbance in the
Assay exhibits maxima and minima at the same wavelengths as that of a similar solution of
USP Tropicamide RS, concomitantly measured.
Assay—
Transfer an accurately measured volume of Ophthalmic Solution, equivalent to about 30 mg of tropicamide, to a 100-mL volumetric flask, add water to volume, and mix. Transfer 10.0 mL of this solution to a separator, add 2 mL of sodium carbonate solution (1 in 10), extract with four 20-mL portions of chloroform, and combine the extracts in a second separator. Wash the combined extracts with a 25-mL portion of pH 6.5 phosphate buffer (see
Buffer Solutions in the section
Reagents, Indicators, and Solutions), and transfer to another separator. Wash the aqueous layer with 10 mL of chloroform, and add it to the extracts. Extract the chloroform solution with four 20-mL portions of dilute sulfuric acid (1 in 6), combine the acid extracts in a 100-mL volumetric flask, and add the dilute acid to volume. Dissolve an accurately weighed quantity of
USP Tropicamide RS in dilute sulfuric acid (1 in 6), and dilute quantitatively and stepwise with the same solvent to obtain a Standard solution having a known concentration of about 30 µg per mL. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 253 nm, with a suitable spectrophotometer, using dilute sulfuric acid (1 in 6) as the blank. Calculate the quantity, in mg, of C
17H
20N
2O
2 in each mL of the Ophthalmic Solution taken by the formula:
(C / V)(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Tropicamide RS in the Standard solution,
V is the volume, in mL, of Ophthalmic Solution taken, and
AU and
AS are the absorbances of the solution from the Ophthalmic Solution and the Standard solution, respectively.
71
:
meets the requirements.