» Mephobarbital Tablets contain not less than 95.0 percent and not more than 110.0 percent of the labeled amount of mephobarbital (C13H14N2O3).
Packaging and storage Preserve in well-closed containers.
Identification The mephobarbital obtained in the Assay melts between 174 and 181 (see Melting Range or Temperature 741) and meets the requirements for Identification test A under Mephobarbital.
Medium: a 1% solution of 3-(dodecyldimethylammonio) propanesulfonate in pH 8.0 phosphate buffer (prepared by dissolving 10.0 g of 3-(dodecyldimethylammonio) propanesulfonate in 400 mL of warm water, and adding 250 mL of 0.2 M monobasic potassium phosphate and about 220 mL of 0.2 M sodium hydroxide; the solution is then cooled to room temperature, and adjusted with 0.2 M sodium hydroxide to a pH of 8.0, followed by diluting with water to 1000 mL, mixing, and degassing); 900 mL.
Apparatus 2: 75 rpm.
Time: 75 minutes.
Procedure Determine the amount of C13H14N2O3 dissolved by employing UV absorption at the wavelength of maximum absorbance at about 244 nm on portions of the solution under test passed through 0.45-µm nylon filters, suitably diluted with Medium, if necessary, in comparison with a Standard solution having a known concentration of USP Mephobarbital RS in the same Medium.
Tolerances Not less than 70% (Q) of the labeled amount of C13H14N2O3 is dissolved in 75 minutes.
Uniformity of dosage units 905: meet the requirements.
procedure for content uniformity
Alkaline borate solution Dissolve 6.2 g of boric acid and 7.45 g of potassium chloride in 500 mL of water, add 210 mL of sodium hydroxide solution (1 in 25), and mix. Add water to make 2000 mL of solution, and mix.
Standard solution [notePrepare the Standard solution and the Test solution concomitantly.] Dissolve an accurately weighed quantity of USP Mephobarbital RS in Alkaline borate solution to obtain a solution having a concentration of about 10 mg per mL, and quantitatively dilute with water to obtain a solution having a known concentration of about 1.5 mg per mL.
Test solution Transfer 1 Tablet to a glass-stoppered centrifuge tube, crush the tablet, and add 25.0 mL of Alkaline borate solution. Insert the stopper, shake for 10 minutes, and centrifuge until clear, filtering the supernatant, if necessary. Dilute a portion of the subsequent liquid quantitatively, and stepwise if necessary, with water to obtain a solution having a concentration of about 1.5 mg of mephobarbital per mL.
Procedure Transfer 3.0 mL each of the Standard solution and the Test solution to separate 200-mL volumetric flasks, dilute each with a 1 in 3 solution of Alkaline borate solution in water to volume, and mix. Concomitantly determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 245 nm, with a suitable spectrophotometer, using a 1 in 3 solution of Alkaline borate solution in water as the blank. Calculate the quantity, in mg, of C13H14N2O3 in the Tablet taken by the formula:
(TC/D)(AU / AS)in which T is the labeled quantity, in mg, of mephobarbital in the Tablet; C is the concentration, in mg per mL, of USP Mephobarbital RS in the Standard solution; D is the concentration, in mg per mL, of mephobarbital in the Test solution, based upon the labeled quantity per Tablet and the extent of dilution; and AU and AS are the absorbances of the solutions from the Test solution and the Standard solution, respectively.
Assay Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 300 mg of mephobarbital, to an extraction thimble. Extract with 15 mL of solvent hexane, allow the thimble to drain, transfer to a continuous-extraction apparatus provided with a tared flask, and extract the mephobarbital with chloroform for 2 hours. Evaporate the chloroform on a steam bath with the aid of a current of air, cool, dissolve the residue in about 10 mL of alcohol, evaporate, dry the residue at 105 for 1 hour, cool, and weigh. The weight of the residue represents the weight of mephobarbital (C13H14N2O3) in the portion of Tablets taken.
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USP32NF27 Page 2884Pharmacopeial Forum: Volume No. 30(2) Page 514