A: To a portion of finely powdered Tablets,equivalent to about 800mg of meprobamate,add 5mLof dehydrated alcohol,and heat just below the boiling temperature for about 5minutes,with occasional swirling.Cool,filter into 15mLof solvent hexane,and mix.With the aid of suction,filter the crystals that form,and dry at 60:the crystals of meprobamate so obtained melt between 103and 107,but the range between beginning and end of melting does not exceed 2.

B: Aportion of the crystals obtained in Identificationtest Aresponds to Identificationtest Aunder Meprobamate.

Medium: deaerated water;900mL.

Apparatus 1: 100rpm.

Time: 30minutes.

Procedure— Determine the amount of C9H18N2O4dissolved using the method set forth for the Assay,making any necessary volumetric adjustments.

Tolerances— Not less than 75%(Q)of the labeled amount of C9H18N2O4is dissolved in 30minutes.

Mobile phase— Prepare a filtered and degassed mixture of water and acetonitrile (7:3),making adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Phenacetin stock solution— Dissolve phenacetin in acetonitrile to obtain a solution having a concentration of about 125µg per mL.Pipet 20mLof this solution into a 100-mLvolumetric flask,add 30mLof acetonitrile,dilute with water to volume,and mix.

Standard preparation— Transfer about 50mg of USP Meprobamate RS,accurately weighed,to a 10-mLvolumetric flask,add 3mLof acetonitrile,and shake to dissolve.Dilute with water to volume,and mix to obtain a solution having a known concentration of about 5mg of USP Meprobamate RSper mL.

Resolution solution— Transfer 25mg of meprobamate to a 5-mLvolumetric flask,add 1mLof acetonitrile,and shake to dissolve.Add 1mLof Phenacetin stock solution,dilute with water to volume,and mix.

Assay preparation— Weigh and finely powder not less than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 250mg of meprobamate,to a 50-mLvolumetric flask,add 15mLof acetonitrile,and shake to dissolve.Dilute with water to volume,mix,and filter,discarding the first 10mLof the filtrate.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 200-nm detector and a 3.9-to 4.6-mm ×25-to 30-cm column that contains packing L1.The flow rate is about 1mLper minute.Chromatograph the Resolution solution,and record the peak responses as directed for Procedure:the resolution,R,between the meprobamate and the phenacetin peaks is not less than 2.0,and the area of the phenacetin peak is not less than 65.0%and not more than 100.0%of the meprobamate peak area.The relative retention times are about 0.7for meprobamate and 1.0for phenacetin.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C9H18N2O4in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Meprobamate RSin the Standard preparation,and rUand rSare the meprobamate peak responses obtained from the Assay preparationand the Standard preparation,respectively.