Identification—
Blend a portion of finely powdered Tablets, equivalent to about 25 mg of glycopyrrolate, with 50 mL of water in a high-speed blender, and filter through very retentive filter paper: the UV absorption spectrum of the filtrate exhibits maxima and minima at the same wavelengths as that of a solution of
USP Glycopyrrolate RS (1 in 2000).
Assay—
pH 5.3 Phosphate buffer—
Dissolve 38.0 g of monobasic sodium phosphate and 2.0 g of anhydrous dibasic sodium phosphate in sufficient water to make 1000 mL, and adjust, if necessary, to a pH of 5.3 ± 0.1.
Bromocresol purple solution—
Dissolve 400 mg of bromocresol purple in 30 mL of alcohol, add 6.3 mL of 0.1 N sodium hydroxide, and dilute with water to 500 mL.
Buffer–dye mixture—
On the day of use, mix equal volumes of pH 5.3 Phosphate buffer and of Bromocresol purple solution, and extract with chloroform until the last extract is colorless.
Standard preparation—
Transfer about 100 mg of
USP Glycopyrrolate RS, accurately weighed, to a 100-mL volumetric flask, add water to volume, and mix. Transfer 10.0 mL of this solution to a second 100-mL volumetric flask, dilute with water to volume, and mix to obtain a
Standard preparation having a known concentration of about 100 µg per mL.
Assay preparation—
Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 10 mg of glycopyrrolate, to a 100-mL volumetric flask, add 50 mL of water, and shake by mechanical means for 10 minutes. Dilute with water to volume, mix, and filter, discarding the first 20 mL of the filtrate. Use the subsequent filtrate as directed in the Procedure.
Procedure—
Transfer 10.0 mL each of the
Standard preparation, the
Assay preparation, and water to serve as the blank to individual separators, each containing 10.0 mL of
Buffer–dye mixture. Mix, and extract each solution with four 25-mL portions of chloroform, filtering the extracts from each solution through chloroform-moistened filter paper into separate 100-mL volumetric flasks. Dilute each solution with chloroform to volume, and mix. Concomitantly determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 410 nm, with a suitable spectrophotometer, using the blank to set the instrument. Calculate the quantity, in mg, of glycopyrrolate (C
19H
28BrNO
3) in the portion of Tablets taken by the formula:
0.1C(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Glycopyrrolate RS in the
Standard preparation; and
AU and
AS are the absorbances of the solutions from the
Assay preparation and the
Standard preparation, respectively.
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