Dissolution 
711
—
Medium:
0.1 N hydrochloric acid; 1000 mL.
Apparatus 2:
75 rpm.
Time:
60 minutes.
Chromatographic system (see Chromatography 621)—
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 2 mL per 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 Suitability under
Chromatography 621).
Procedure—
Inject an accurately measured volume (about 20 µL) 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
2 dissolved in comparison with a Standard solution having a known concentration of
USP Oxazepam RS in 0.1 N hydrochloric 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 C15H11ClN2O2 is dissolved in 60 minutes.
Assay—
Remove, as completely as possible, the contents of not less than 20 Capsules, and weigh. Transfer an accurately weighed portion of the mixed powder, equivalent to about 50 mg of oxazepam, to a medium-porosity, sintered-glass funnel that is fitted into a small suction flask. Add 25 mL of alcohol, mix with the aid of a stirring rod, and after about 5 minutes apply gentle suction to remove the extract. Repeat the extraction with four additional 25-mL portions of alcohol, transfer the extracts to a 250-mL volumetric flask, dilute with alcohol to volume, and mix. Transfer 2.0 mL of this solution to a 100-mL volumetric flask, dilute with alcohol to volume, and mix. Concomitantly determine the absorbances of this solution and of a Standard solution of
USP Oxazepam RS in the same medium having a known concentration of about 4 µg per mL in 1-cm cells at the wavelength of maximum absorbance at about 229 nm, with a suitable spectrophotometer, using alcohol as the blank. Calculate the quantity, in mg, of C
15H
11ClN
2O
2 in the portion of Capsules taken by the formula:
12.5C(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Oxazepam RS in the Standard solution, and
AU and
AS are the absorbances of the solution from the Capsules and the Standard solution, respectively.
