(me fen' i toin; me fen' i toe in).
» Mephenytoin contains not less than 98.0 percent and not more than 102.0 percent of C12H14N2O2, calculated on the dried basis.
Packaging and storage Preserve in tight containers, and store at controlled room temperature.
USP Reference standards 11
B: Ultraviolet Absorption 197U
Solution: 1 mg per mL.
Melting range 741: between 136 and 140.
Loss on drying 731 Dry it at 105 for 4 hours: it loses not more than 1.0% of its weight.
Residue on ignition 281: not more than 0.1%.
Heavy metals, Method II 231: 0.002%.
Mobile phase and System suitability solution Proceed as directed in the Assay.
Test preparation Use the Assay preparation.
Chromatographic system Proceed as directed in the Assay except to use a 225-nm detector.
Procedure Inject a volume (about 10 µL) of the Test preparation into the chromatograph, record the chromatogram, and measure the peak responses. Calculate the percentage of each impurity in the portion of Mephenytoin taken by the formula:
100(Fri / rs)in which F is the relative response factor and is equal to 1.16 for any peak with a relative retention time of 0.66, 0.37 for propiophenone, and 1.0 for all other peaks; ri is the peak response for each impurity; and rs is the sum of the responses of all of the peaks, adjusted for the relative response factor: not more than 1.0% of any individual impurity is found, and not more than 1.5% of total impurities is found.
Mobile phase Prepare a filtered and degassed mixture of water, methanol, and acetonitrile (52:38:10). Make adjustments if necessary (see System Suitability under Chromatography 621).
System suitability solution Transfer about 7.5 mg of propiophenone, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix. Transfer 1.0 mL of this solution to a 10-mL volumetric flask, add about 15 mg of Mephenytoin, dissolve in Mobile phase, sonicate, dilute with Mobile phase to volume, and mix.
Standard preparation Dissolve an accurately weighed quantity of USP Mephenytoin RS in Mobile phase, sonicate, and dilute quantitatively, and stepwise if necessary, with Mobile phase to obtain a solution having a known concentration of about 5.0 mg per mL.
Assay preparation Transfer about 125.0 mg of Mephenytoin, accurately weighed, to a 25-mL volumetric flask, dissolve in Mobile phase, sonicate, dilute with Mobile phase to volume, and mix.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 257-nm detector and a 3.9-mm × 15-cm column that contains packing L7. The flow rate is about 1 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times are about 1.0 for mephenytoin and 1.5 for propiophenone; the column efficiency is not less than 4000 theoretical plates for the mephenytoin peak; and the relative standard deviation for replicate injections for the mephenytoin peak is not more than 2.0%.
Procedure Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C12H14N2O2 in the portion of Mephenytoin taken by the formula:
25C(rU / rS)in which C is the concentration, in mg per mL, of USP Mephenytoin RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 3803Pharmacopeial Forum: Volume No. 27(2) Page 2174