Medium: 0.1Nhydrochloric acid;750mL.

Apparatus 1: 100rpm.

Time: 60minutes.

Procedure— Determine the amount of C10H13NO3dissolved from UVabsorbances at the wavelength of maximum absorbance at about 274nm of filtered portions of the solution under test,suitably diluted with Medium,if necessary,in comparison with a Standard solution having a known concentration of USP Metyrosine RSin the same medium.

Tolerances— Not less than 75%(Q)of the labeled amount of C10H13NO3is dissolved in 60minutes.

Standard preparation— Dissolve a suitable quantity of USP Metyrosine RS,accurately weighed,in dilute hydrochloric acid (1in 100)to obtain a solution having a known concentration of about 100µg per mL.

Assay preparation— Combine the contents of not less than 20Capsules,and transfer an accurately weighed portion of the combined contents,equivalent to about 100mg of metyrosine,to a 100-mLvolumetric flask.Add 50mLof dilute hydrochloric acid (1in 100),shake by mechanical means for 45minutes,dilute with dilute hydrochloric acid (1in 100)to volume,mix,and filter.Transfer 10.0mLof the filtrate to a 100-mLvolumetric flask,dilute with dilute hydrochloric acid solution (1in 100)to volume,and mix.Concomitantly determine the absorbances of this solution and the Standard preparationat the wavelength of maximum absorbance at about 274nm,with a suitable spectrophotometer,using dilute hydrochloric acid solution (1in 100)as the blank.Calculate the quantity,in mg,of metyrosine (C10H13NO3)in the portion of Capsules taken by the formula: in which Cis the concentration,in µg per mL,of USP Metyrosine RSin the Standard preparation,and AUand ASare the absorbances of the solutions obtained from the Assay preparationand the Standard preparation,respectively.