Guanabenz Acetate Tablets
» Guanabenz Acetate Tablets contain not less than 90.0 percent and not more than 110.0 percent of the labeled amount of guanabenz (C8H8N4Cl2).
Packaging and storage Preserve in tight, light-resistant containers.
USP Reference standards 11
Identification Transfer an amount of powdered Tablets, equivalent to about 8 mg of guanabenz, to a 60-mL separator. Add 10 mL of 0.1 N hydrochloric acid, and shake to disperse the powder. Shake the mixture with three 10-mL portions of chloroform, discarding the chloroform phase each time. Add 5 mL of 1 N sodium hydroxide, and extract with two 25-mL portions of ether, filtering the ether extracts. Evaporate the combined extracts with the aid of a current of air to dryness: the IR absorption spectrum of a potassium bromide dispersion of the residue so obtained exhibits maxima at the same wavelengths as that of a similar preparation of USP Guanabenz Acetate RS.
Medium: water; 1000 mL.
Apparatus 2: 50 rpm.
Time: 60 minutes.
Procedure Determine the amount of C8H8N4Cl2 dissolved from UV absorbances at the wavelength of maximum absorbance at about 272 nm of filtered portions of the solution under test, suitably diluted with Medium, in comparison with a Standard solution having a known concentration of USP Guanabenz Acetate RS in the same medium.
Tolerances Not less than 75% (Q) of the labeled amount of C8H8N4Cl2 is dissolved in 60 minutes.
Uniformity of dosage units 905: meet the requirements.
Extracting solvent, Mobile phase, Standard preparation I, System suitability solution, Chromatographic system, and Assay preparation Proceed as directed in the Assay.
Standard preparation II Pipet 2 mL of Standard preparation I into a 100-mL volumetric flask, dilute with Extracting solvent to volume, and mix.
Procedure Proceed as directed for Procedure in the Assay, except to substitute Standard preparation II for Standard preparation I. Calculate the quantity of any impurity observed having a relative retention time corresponding to the component eluting before guanabenz obtained from the System suitability solution. The amount of any such impurity observed is not more than 2%.
Extracting solvent Dissolve 8.2 g of sodium acetate in 20 mL of water, add 5.7 mL of glacial acetic acid, dilute to 1 L with methanol, and mix.
Mobile phase Prepare a filtered and degassed mixture of water, methanol, and phosphoric acid (57:43:0.3), making adjustments if necessary (see System Suitability under Chromatography 621).
Standard preparation I Transfer about 25 mg of USP Guanabenz Acetate RS, accurately weighed, to a 250-mL volumetric flask. Add 25 mL of water, shake to dissolve the solids, dilute with Extracting solvent to volume, and mix.
Assay preparation Transfer 10 Tablets to a 500-mL volumetric flask. Add 50 mL of water, stir by mechanical means until the solids are well dispersed, add 400 mL of Extracting solvent, and stir for 45 minutes. Dilute with Extracting solvent to volume, mix, and centrifuge a portion of the mixture until a clear supernatant is obtained. If necessary, dilute a portion of the supernatant quantitatively with a mixture of Extracting solvent and water (9:1) to obtain a solution containing about 0.08 mg of guanabenz per mL.
System suitability solution Transfer about 30 mg of guanabenz acetate to a 100-mL stoppered flask. Add about 50 mL of 0.1 N hydrochloric acid, heat on a steam bath for 60 minutes, and allow the solution to cool.
Chromatographic system (see Chromatography 621)The liquid chromatograph is equipped with a 245-nm detector and a 4-mm × 30-cm column that contains packing L1. The flow rate is about 2 mL per minute. Chromatograph replicate injections of Standard preparation I and record the peak responses as directed for Procedure: the relative standard deviation is not more than 2.0%. Inject a volume (about 20 µL) of the System suitability solution into the chromatograph and record the chromatogram: the resolution between guanabenz and the peak eluting before it is not less than 1.6.
Procedure Separately inject equal volumes (about 20 µL) of Standard preparation I and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C8H8N4Cl2 in the portion of Tablets taken by the formula:
(231.08 / 291.13)(CD)(rU / rS)in which 231.08 and 291.13 are the molecular weights of guanabenz and guanabenz acetate, respectively; C is the concentration, in mg per mL, of USP Guanabenz Acetate RS in Standard preparation I; D is the Assay preparation dilution factor, in mL per Tablet; and rU and rS are the peak responses of the Assay preparation and Standard preparation I, respectively.
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USP35NF30 Page 3387