Identification—
A:
Extract 10mLof it with 25mLof chloroform,filter the chloroform extract through dry,folded filter paper,and evaporate the filtrate to dryness:the residue so obtained responds to Identificationtest Aunder Tropicamide.
B:
The UVabsorption spectrum of the solution employed for measurement of absorbance in the
Assayexhibits 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 30mg of tropicamide,to a 100-mLvolumetric flask,add water to volume,and mix.Transfer 10.0mLof this solution to a separator,add 2mLof sodium carbonate solution (1in 10),extract with four 20-mLportions of chloroform,and combine the extracts in a second separator.Wash the combined extracts with a 25-mLportion of pH6.5phosphate buffer (see
Buffer Solutionsin the section
Reagents,Indicators,and Solutions),and transfer to another separator.Wash the aqueous layer with 10mLof chloroform,and add it to the extracts.Extract the chloroform solution with four 20-mLportions of dilute sulfuric acid (1in 6),combine the acid extracts in a 100-mLvolumetric flask,and add the dilute acid to volume.Dissolve an accurately weighed quantity of
USP Tropicamide RSin dilute sulfuric acid (1in 6),and dilute quantitatively and stepwise with the same solvent to obtain a Standard solution having a known concentration of about 30µg per mL.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 253nm,with a suitable spectrophotometer,using dilute sulfuric acid (1in 6)as the blank.Calculate the quantity,in mg,of C
17H
20N
2O
2in each mLof the Ophthalmic Solution taken by the formula:
(C/V)(AU/AS),
in which
Cis the concentration,in µg per mL,of
USP Tropicamide RSin the Standard solution,
Vis the volume,in mL,of Ophthalmic Solution taken,and
AUand
ASare the absorbances of the solution from the Ophthalmic Solution and the Standard solution,respectively.