Assay—
Transfer about 100 mg of Vanillin, accurately weighed, to a 250-mL volumetric flask, add methanol to volume, and mix. Pipet 2 mL of this solution into a 100-mL volumetric flask, add methanol to volume, and mix. Dissolve an accurately weighed quantity of
USP Vanillin RS in methanol, and dilute quantitatively and stepwise with methanol to obtain a Standard solution having a known concentration of about 8 µg per mL. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 308 nm, with a suitable spectrophotometer, using methanol as the blank. Calculate the quantity, in mg, of C
8H
8O
3 in the portion of Vanillin taken by the formula:
12.5C( A U / A S ),
in which
C is the concentration, in µg per mL, of
USP Vanillin RS in the Standard solution; and
A U and
A S are the absorbances of the solution of Vanillin and the Standard solution, respectively.
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731
—
Dry it over silica gel for 4 hours: it loses not more than 1.0% of its weight.
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