Identification—
The UVabsorption spectrum of the solution employed for measurement of absorbance in the
Assayexhibits maxima and minima at the same wavelengths as that of a similar solution of
USP Phenoxybenzamine Hydrochloride RS,concomitantly measured.The ratio
A268/
A272of the maximum at 268±2nm and the minimum at 272±2nm is between 1.75and 1.95.
Dissolution á711ñ—
Medium:
0.1Nhydrochloric acid;500mL.
Apparatus 1:
100rpm.
Time:
45minutes.
Procedure—
Determine the amount of C
18H
22ClNO·HCl dissolved from UVabsorbances at the wavelength of maximum absorbance at about 267nm 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 Phenoxybenzamine Hydrochloride RSin the same
Medium.
Tolerances—
Not less than 75%(Q)of the labeled amount of C18H22ClNO·HCl is dissolved in 45minutes.
Assay—
Remove,as completely as possible,the contents of not fewer than 20Capsules,and weigh.Transfer an accurately weighed portion of the mixed powder,equivalent to about 50mg of phenoxybenzamine hydrochloride,to a 50-mLvolumetric flask,add about 25mLof a 1in 1000solution of hydrochloric acid in alcohol,and shake.Add the alcoholic hydrochloric acid to volume,mix,and filter,discarding the first 10mLof the filtrate.Transfer 15.0mLof the subsequent filtrate to a 100-mLvolumetric flask,dilute with the alcoholic hydrochloric acid to volume,and mix.Concomitantly determine the absorbances of this solution and of a Standard solution of
USP Phenoxybenzamine Hydrochloride RSin the same medium having a known concentration of about 150µg per mLin 1-cm cells at the wavelength of maximum absorbance at about 275nm,with a suitable spectrophotometer,using a 1in 1000solution of hydrochloric acid in alcohol as the blank.Calculate the quantity,in mg,of C
18H
22ClNO·HCl in the portion of Capsules taken by the formula:
0.333C(AU/AS),
in which
Cis the concentration,in µg per mL,of
USP Phenoxybenzamine Hydrochloride RSin the Standard solution,and
AUand
ASare the absorbances of the solution from the Capsules and the Standard solution,respectively.