Identification—
Transfer a portion of powdered Tablets, equivalent to about 100 mg of oxprenolol hydrochloride, to a suitable test tube containing 5 mL of water. Shake this mixture for about 1 minute and allow it to settle. Use the clear supernatant as the test solution. Prepare a Standard solution containing 20 mg of
USP Oxprenolol Hydrochloride RS per mL. Apply separate 1-µL portions of the test solution and of the Standard solution to a suitable thin-layer chromatographic plate (see
Chromatography 
621
) coated with a 0.25-mm layer of chromatographic silica gel mixture. Line a suitable chromatographic chamber with filter paper, saturate the paper with the developing solvent consisting of a mixture of ethyl acetate, glacial acetic acid, and water (15:5:5), and allow to stand for about 30 minutes. Place the plate in the chamber, and develop the chromatogram until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber, and dry at 100
for 15 minutes. Spray the plate uniformly with a detection reagent consisting of a freshly prepared mixture of equal volumes of potassium ferricyanide solution (1 in 100) and ferric chloride solution (1 in 5). Dry the plate in a current of warm air for about 5 minutes. Examine the chromatograms in ordinary light: the
RF value of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.
Dissolution 711—
Medium:
0.1 N hydrochloric acid; 900 mL.
Apparatus 1:
100 rpm.
Time:
30 minutes.
Procedure—
Determine the amount of C
15H
23NO
3·HCl dissolved from UV absorbances at the wavelength of maximum absorbance at about 272 nm of 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 Oxprenolol Hydrochloride RS in the same medium.
Tolerances—
Not less than 80% (Q) of the labeled amount of C15H23NO3·HCl is dissolved in 30 minutes.
Assay—
Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 80 mg of oxprenolol hydrochloride, to a 100-mL volumetric flask. Add 80 mL of a
Diluting solvent, which consists of a mixture of methanol and 0.1 N hydrochloric acid (9:1), and shake by mechanical means for 1 hour. Dilute with
Diluting solvent to volume, and mix. Filter, discarding the first 10 mL of the filtrate, transfer 25.0 mL of the clear filtrate to a 200-mL volumetric flask, dilute with
Diluting solvent to volume, and mix. Concomitantly determine the absorbances of this assay solution and a Standard solution of
USP Oxprenolol Hydrochloride RS in the same solvent having a known concentration of about 0.1 mg per mL at the wavelength of maximum absorbance at about 274 nm and, in addition, at 300 nm, using
Diluting solvent as the blank. Calculate the quantity, in mg, of C
15H
23NO
3·HCl in the portion of Tablets taken by the formula:
800C(AU / AS),
in which
C is the concentration, in mg per mL, of
USP Oxprenolol Hydrochloride RS in the Standard solution, and
AU and
AS are the differences between the absorbances at 274 nm and 300 nm of the assay solution and the Standard solution, respectively.
