Medium: 0.05M,pH6.9phosphate buffer (see Buffer Solutionsin the section Reagents,Indicators,and Solutions)containing 5units of a-amylase per mL;900mL.[NOTE—Use only freshly prepared solutions containing a-amylase;and equilibrate the Dissolution Medium at 37for not more than one hour before beginning the Dissolutiontest.]

Apparatus 2: 75rpm.

Time: 60minutes.

Mobile phase,Resolution solution,and Chromatographic system— Prepare as directed in the Assay.

Standard solution— [NOTE—Avolume of acetonitrile not exceeding 2%of the final total volume of solution may be used to aid in dissolving the carisoprodol.]Prepare a solution of USP Carisoprodol RSin 0.05M,pH6.9phosphate buffer having an accurately known concentration of about 0.4mg per mL.

Procedure— Separately inject equal volumes (about 150µL)of the Standard solutionand a filtered portion of the solution under test into the chromatograph,record the peak responses,and measure the responses for the major peaks.Calculate the amount of C12H24N2O4dissolved.

Tolerances— Not less than 80%(Q)of the labeled amount of C12H24N2O4is dissolved in 60minutes.

Mobile phase— Prepare a filtered and degassed mixture of water and acetonitrile (60:40).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Diluent— Prepare a mixture of methanol and 0.01Nsulfuric acid (60:40).

Standard preparation— Dissolve an accurately weighed quantity of USP Carisoprodol RSin Diluent,using sonication,if necessary,to obtain a solution having a known concentration of about 3.5mg per mL.

Resolution solution— Prepare a solution in Mobile phasecontaining about 2.4mg of 2-methyl-2-propyl-1,3-propanediol and 3.4mg of carisoprodol per mL.

Assay preparation— Weigh and finely powder not less than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 350mg of carisoprodol,to a 100-mLvolumetric flask.Add about 50mLof Diluent,place in an ultrasonic bath for 30minutes,and shake by mechanical means for 60minutes.Dilute with Diluentto volume,and mix.Filter a portion of this solution through a membrane filter of 0.5µm or finer porosity,and use the filtrate as the Assay preparation.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a refractive index detector and a 3.9-mm ×30-cm column that contains packing L1.Maintain the detector and the column at 30±1.The flow rate is about 2mLper minute.Chromatograph the Resolution solutionand the Standard preparation,and record the peak responses as directed for Procedure:the resolution,R,between the 2-methyl-2-propyl-1,3-propanediol and carisoprodol peaks is not less than 2.0,and the relative standard deviation for three replicate injections of the Standard preparationis not more than 2.0%.The relative retention times are about 0.5for 2-methyl-2-propyl-1,3-propanediol and 1.0for carisoprodol.

Procedure— [NOTE—Use peak heights where peak responses are indicated.]Separately inject equal volumes (about 35µL)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 C12H24N2O4in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Carisoprodol RSin the Standard preparation,and rUand rSare the peak responses obtained for carisoprodol from the Assay preparationand the Standard preparation,respectively.