Magnesium Salicylate Tablets
»Magnesium Salicylate Tablets contain an amount of magnesium salicylate (C14H10MgO6·4H2O)equivalent to not less than 95.0percent and not more than 105.0percent of the labeled amount of C14H10MgO6.
Packaging and storage— Preserve in tight containers.
Identification—
A: The IRabsorption spectrum of a potassium bromide dispersion of a quantity of finely powdered Tablets exhibits maxima at the same wavelengths as that of a similar preparation of USP Magnesium Salicylate RS.
B: Afiltered solution of Tablets,equivalent to magnesium salicylate solution (1:20),responds to the test for Magnesium á191ñ.
Dissolution á711ñ—
Medium: water;900mL.
Apparatus 2: 50rpm.
Time: 120minutes.
Procedure— Determine the amount of C14H10MgO6dissolved from UVabsorbances at the wavelength of maximum absorbance at about 296nm of filtered portions of the solution under test,suitably diluted with water,in comparison with a Standard solution having a known concentration of USP Salicylic Acid RSin the same medium,using water as the blank.Calculate the quantity of magnesium salicylate (C14H10MgO6),dissolved by the formula:
(298.54/276.24)(900C)(AS/AS),
in which the terms are as defined in the Assay.
Tolerances— Not less than 80%(Q)of the labeled amount of C14H10MgO6is dissolved in 120minutes.
Uniformity of dosage units á905ñ: meet the requirements.
Assay— Weigh and finely powder not fewer than 20Tablets.Weigh accurately a portion of the powder,equivalent to about 500mg of magnesium salicylate,and transfer to a 250-mLvolumetric flask.Dilute with water to volume,mix,and filter,discarding the first 20mLof the filtrate.Dilute an accurately measured portion of the filtrate quantitatively and stepwise,if necessary,to obtain a final concentration of about 20µg per mL.Dissolve an accurately weighed quantity of USP Salicylic Acid RSin water,and dilute quantitatively and stepwise,if necessary,with water to obtain a Standard solution having a known concentration of about 18µg per mL.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 296nm,with a suitable spectrophotometer,using water as the blank.Calculate the quantity,in mg,of C14H10MgO6in the portion of Tablets taken by the formula:
(298.54/276.24)(L/D)(C)(AU/AS),
in which 298.54is the molecular weight of anhydrous magnesium salicylate;276.24is twice the molecular weight of salicylic acid;Lis the labeled quantity,in mg,of magnesium salicylate in each Tablet;Dis the concentration,in mg per mL,of magnesium salicylate in the solution from the Tablets,based on the labeled quantity per Tablet and the extent of dilution;Cis the concentration,in mg per mL,of USP Salicylic Acid RSin the Standard solution;and AUand ASare the absorbances of the solution from the Tablets and the Standard solution,respectively.
Auxiliary Information— Staff Liaison:Daniel K.Bempong,Ph.D.,Scientist
Expert Committee:(PA2)Pharmaceutical Analysis 2
USP28–NF23Page 1174
Phone Number:1-301-816-8143
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