Dissolution á711ñ—
Medium:
0.1Nhydrochloric acid;1000mL.
Apparatus 2:
75rpm.
Time:
60minutes.
Chromatographic system(see Chromatography á621ñ)—
The liquid chromatograph is fitted with a 232-nm detector and a 4-mm ×15-cm column that contains packing L7.The mobile phase is a degassed mixture of methanol,water,and glacial acetic acid (60:40:1),and the flow rate is about 2mLper minute.Chromatograph the Standard solution,and record the peak response as directed for
Procedure:the tailing factor for the oxazepam peak is not more than 1.5,and the relative standard deviation observed following replicate injections is not more than 3.0%.Make adjustments if necessary (see
System Suitabilityunder
Chromatography á621ñ).
Procedure—
Inject an accurately measured volume (about 20µL)of a filtered portion of the solution under test into the chromatograph,record the chromatogram,and measure the response for the major peak.Calculate the quantity of C
15H
11ClN
2O
2dissolved in comparison with a Standard solution having a known concentration of
USP Oxazepam RSin 0.1Nhydrochloric acid [
NOTE—a volume of methanol not to exceed 10%of the final total volume may be used to dissolve the Oxazepam reference standard]and similarly chromatographed.
Tolerances—
Not less than 75%(Q)of the labeled amount of C15H11ClN2O2is dissolved in 60minutes.
Assay—
Remove,as completely as possible,the contents of not less than 20Capsules,and weigh.Transfer an accurately weighed portion of the mixed powder,equivalent to about 50mg of oxazepam,to a medium-porosity,sintered-glass funnel that is fitted into a small suction flask.Add 25mLof alcohol,mix with the aid of a stirring rod,and after about 5minutes apply gentle suction to remove the extract.Repeat the extraction with four additional 25-mLportions of alcohol,transfer the extracts to a 250-mLvolumetric flask,dilute with alcohol to volume,and mix.Transfer 2.0mLof this solution to a 100-mLvolumetric flask,dilute with alcohol to volume,and mix.Concomitantly determine the absorbances of this solution and of a Standard solution of
USP Oxazepam RSin the same medium having a known concentration of about 4µg per mLin 1-cm cells at the wavelength of maximum absorbance at about 229nm,with a suitable spectrophotometer,using alcohol as the blank.Calculate the quantity,in mg,of C
15H
11ClN
2O
2in the portion of Capsules taken by the formula:
12.5C(AU/AS),
in which
Cis the concentration,in µg per mL,of
USP Oxazepam RSin the Standard solution,and
AUand
ASare the absorbances of the solution from the Capsules and the Standard solution,respectively.