A: Ultraviolet Absorption á197Uñ—

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

Medium: water;900mL,1800mLfor 400-mg Tablets.

Apparatus 1: 100rpm.

Times: 3,6,12,and 24hours.

Procedure— Determine the amount of C15H12N2Odissolved by employing UVabsorption at the wavelength of maximum absorbance at about 284nm on filtered portions of the solution under test,suitably diluted with Dissolution Medium,if necessary,in comparison with a Standard solution having a known concentration of USP Carbamazepine RSin the same Medium.

Tolerances— The percentages (Q)of the labeled amount of C15H12N2Odissolved at the times specified conform to Acceptance Table 1.

PROCEDUREFOR CONTENT UNIFORMITY—

Standard solution— Dissolve accurately measured quantities of methanol and methylene chloride in dimethylformamide to obtain a solution having known concentrations of about 5µg of each per mL.

Test solution— Finely powder 10Tablets,and quantitatively transfer the powder to a 50-mLvolumetric flask.Add about 30mLof dimethylformamide,shake by mechanical means for 60minutes,and sonicate for 2minutes.Dilute with dimethylformamide to volume,and mix.Centrifuge a portion of the solution at about 2500rpm for 20minutes,and use the clear supernatant.

Chromatographic system(seeChromatography á621ñ)— The gas chromatograph is equipped with a flame-ionization detector and a 2-mm ×3-m glass column containing 0.2%phase G39on support S7.The injection port and detector temperatures are maintained at about 170and 300,respectively.The column temperature is programmed as follows.Initially it is maintained at 75for 10minutes,then increased at a rate of 20per minute to 155,and maintained at 155for 30minutes.The carrier gas is helium,flowing at a rate of about 10mLper minute.

Procedure— Separately inject equal volumes (about 2µL)of the Test solutionand the Standard solutioninto the chromatograph,record the chromatograms,and measure the peak responses.Calculate the amount,in µg,of methylene chloride and methanol in each Tablet taken by the formula: in which Cis the concentration,in µg per mL,of methylene chloride or methanol in the Standard solution;and rUand rSare the responses of the corresponding analyte obtained from the Test solutionand the Standard solution,respectively:not more than 23µg of methylene chloride per Tablet is found;and not more than 100µg of methanol per Tablet is found.

TEST1—

TEST2—

Mobile phase— Prepare a filtered and degassed mixture of water,methanol,and methylene chloride (600:450:45).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Internal standard solution— Prepare a solution of phenytoin in methanol containing about 600µg per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Carbamazepine RSin methanol,and dilute quantitatively,and stepwise if necessary,with methanol to obtain a solution having a known concentration of about 200µg per mL.Pipet 10.0mLof this solution into a conical flask,add 10.0mLof Internal standard solution,mix,and filter.This solution contains about 100µg of USP Carbamazepine RSper mL.

System suitability solution— Pipet equal volumes of Internal standard solutionand Standard preparationinto a suitable flask,and mix.

Assay stock preparation— Finely powder 10Tablets,and quantitatively transfer the powder,with the aid of alcohol,to a volumetric flask of such volume that when the solution is diluted to volume a final concentration estimated to be about 4mg of carbamazepine per mLis obtained.Shake by mechanical means for 60minutes.Sonicate for 15minutes,and dilute with methanol to volume.Allow to stand for 10to 15minutes,then filter a portion of the supernatant,and use the clear filtrate.

Assay preparation— Transfer 5.0mLof the Assay stock preparationto a 100-mLvolumetric flask,dilute with methanol to volume,and mix.Pipet 10.0mLof this solution into a conical flask,add 10.0mLof Internal standard solution,mix,and filter.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 230-nm detector,a 4.6-mm ×30-mm guard column that contains 7-µm packing L7,and a 3.9-mm ×30-cm column that contains packing L1.[NOTE—Wash the column with 50to 100mLof methanol before and after use.]The flow rate is about 2mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the relative retention times are about 0.8for phenytoin,and 1.0for carbamazepine;the resolution,R,between phenytoin and carbamazepine is not less than 2.8;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the peak responses.Calculate the quantity,in mg,of carbamazepine (C15H12N2O)in each Tablet taken by the formula: in which Cis the concentration,in µg per mL,of USP Carbamazepine RSin the Standard preparation;Vis the volume,in mL,of the volumetric flask used to prepare the Assay stock preparation;and RUand RSare the peak response ratios of carbamazepine to the internal standard obtained from the Assay preparationand the Standard preparation,respectively.