A: Infrared Absorption á197Mñ—

Test specimen— Transfer a quantity of finely powdered Tablets,equivalent to about 50mg of cyclobenzaprine hydrochloride,to a small flask,add 10mLof methylene chloride,swirl to dissolve,and filter.Evaporate the clear filtrate to about 5mL,transfer to a suitable centrifuge tube,and add 1to 2mLof ether.Evaporate with the aid of a current of air to about 1mL,and agitate until crystallization occurs.Wash the crystals with several portions of ether,and air-dry.

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: 0.1Nhydrochloric acid;900mL.

Apparatus 1: 50rpm.

Time: 30minutes.

Procedure— Determine the amount of C20H21N·HCl dissolved by employing UVabsorption at the wavelength of maximum absorbance at about 290nm 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 Cyclobenzaprine Hydrochloride RSin the same Medium.

Tolerances— Not less than 75%(Q)of the labeled amount of C20H21N·HCl is dissolved in 30minutes.

Mobile phase— Prepare a suitable filtered and degassed mixture of water,acetonitrile,methanol,and methanesulfonic acid (48:28:24:0.2),and adjust with diethylamine to a pHof 3.6.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Cyclobenzaprine Hydrochloride RSin 0.1Nhydrochloric acid,and dilute quantitatively,and stepwise if necessary,with 0.1Nhydrochloric acid to obtain a solution having a known concentration of about 0.05mg per mL.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 10mg of cyclobenzaprine hydrochloride,to a 200-mLvolumetric flask,add 150mLof 0.1Nhydrochloric acid,and shake by mechanical means for 30minutes.Dilute with 0.1Nhydrochloric acid to volume,mix,and filter.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 290-nm detector and a 4.6-mm ×10-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the capacity factor,k¢,for the analyte peak is not less than 2.0;the column efficiency determined from the analyte peak is not less than 1000theoretical plates;the tailing factor for the analyte peak is not more than 2;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 areas for the major peaks.Calculate the quantity,in mg,of C20H21N·HCl in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Cyclobenzaprine Hydrochloride RSin the Standard preparation:and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.