Medium: a solution of water and isopropanol (7:3); 500 mL.

Apparatus 2: 100 rpm.

Time: 60 minutes.

Internal standard solution— Dissolve accurately weighed quantities of 17-methyl testosterone, and dilute quantitatively, and stepwise if necessary, with acetonitrile to obtain a solution having a concentration of about 0.2 mg per mL (for tablets with 2.5-mg label claim) and about 0.8 mg per mL (for tablets with 10-mg label claim).

Standard solution— Dissolve an accurately weighed quantity of USP Oxandrolone RS, and dilute quantitatively, and stepwise if necessary, with acetonitrile to obtain a solution having a concentration of about 1 mg per mL.

Working standard solution— Combine 100 µL of the Standard solution, 400 µL of the Internal standard solution, and 1500 µL of acetonitrile.

Test solution— Withdraw 25 mL of the solution under test from the vessel. Pass through a 0.45-µm polytef filter. Transfer 20 mL of the filtrate to a separatory funnel, add 400 µL of the Internal standard solution, 40 mL of 10% potassium chloride solution, and 8 mL of chloroform. In separate separatory funnels, prepare an extraction blank and an internal standard blank in a similar manner using 20 mL of filtered Medium in place of the solution under test and excluding the Internal standard solution from the extraction blank. Shake each funnel, and allow the layers to separate. Collect the lower chloroform layer. Repeat the extraction procedure one more time. Evaporate the solvents under a stream of nitrogen at 45 until just dry. Reconstitute the dried residue with 2 mL of acetonitrile (for tablets with 2.5-mg label claim) or with 8 mL of acetonitrile (for tablets with 10-mg label claim), and sonicate for 10 minutes.

Chromatographic system (see Chromatography 621)— The gas chromatograph is equipped with a flame-ionization detector and a 0.53-mm × 30-m column coated with a 0.5-µm phase G27. The carrier gas is helium, flowing at a rate of about 16.8 mL per minute. The injection port and detector temperatures are maintained at 190 and 320, respectively. The chromatograph is programmed as follows. Upon injection, the column temperature is increased at a rate of 25 per minute to 280, and maintained at 280 for 3 minutes. Then the column temperature is increased at a rate of 10 per minute to 320, and maintained at 320 for 3 minutes. Chromatograph the acetonitrile, the extraction blank, and the internal standard blank, and record the peak responses as directed for Procedure: the tailing factor is not more than 1.5. Make two injections of the Working standard solution, and record the peak responses. The average oxandrolone/Internal standard solution peak area percent comparison is between 98.0% and 102.0%. The resolution, R, between the oxandrolone peak and the nearest eluting peak is equal to or greater than 1.5.

Procedure— Separately inject equal volumes (0.5 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the percentage of C19H30O3 released by the formula: in which CS is the concentration, in mg per mL, of oxandrolone in the Standard solution; sample ratio is the area ratio of oxandrolone to 17-methyltestosterone in the sample injection for each Test solution; VUF is the final volume, in mL, of the sample after reconstitution of the dry residue; 500 is the volume, in mL, of Medium; 100 is the conversion factor to percentage; standard ratio is the mean area ratio of oxandrolone to 17-methyltestosterone in all injections of the Standard solution; VUI is the initial sample volume, in mL, used in the extraction; and LC is the tablet label claim, in mg.

Tolerances— Not less than 75% (Q) of the labeled amount of oxandrolone (C19H30O3) is dissolved in 60 minutes.

(Official January 1, 2007)

Internal standard solution— Dissolve 100 mg of n-octacosane in 200 mL of chloroform.

Standard preparation— Transfer about 50 mg of USP Oxandrolone RS, accurately weighed, to a 100-mL volumetric flask, dissolve in Internal standard solution, dilute with Internal standard solution to volume, and mix.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 5 mg of oxandrolone, to a suitable container, add 10.0 mL of Internal standard solution, and shake by mechanical means for 30 minutes. Pass through Whatman No. 2 filter paper, or equivalent, discarding the first 5 mL of the filtrate.

Procedure— Inject separately 2-µL portions of the Standard preparation and the Assay preparation into a suitable gas chromatograph equipped with a flame-ionization detector (see Chromatography 621) and a 2-m × 4-mm glass column, packed with 3% methylsilicone oil on 80- to 100-mesh acid-, base-, and water-washed, flux-calcined, silanized siliceous earth. The column is maintained at about 250, the injection port is maintained at about 290, and the detector block is maintained at about 300; helium is used as the carrier gas at a flow rate of about 60 mL per minute. Calculate the quantity, in mg, of oxandrolone (C19H30O3) in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Oxandrolone RS in the Standard preparation; and RU and RS are the ratios of the peak heights of the oxandrolone peak and the internal standard peak from the Assay preparation and the Standard preparation, respectively.