Chromatographic purity
Solution A
Prepare a mixture of water, methanol, acetonitrile, and glacial acetic acid (500:350:150:3), and degas.
Solution B
Prepare a mixture of acetonitrile, methanol, and water (550:500:3), and degas.
Mobile phase
Use variable mixtures of
Solution A and
Solution B as directed for
Chromatographic system. Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Test solution
Dissolve an accurately weighed quantity of Isoflupredone Acetate in Solution A to obtain a solution having a concentration of about 0.3 mg per mL. Sonicate, if necessary, to dissolve. Use this solution within 16 hours.
Chromatographic system (see Chromatography 621)
The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm column that contains packing L7. The flow rate is about 1 mL per minute. Protect the column from temperature fluctuations. The chromatograph is programmed as follows.
Time (minutes) |
Solution A
(%) |
Solution B
(%) |
Elution |
0 |
100 |
0 |
equilibration |
032.5 |
100 |
0 |
isocratic |
32.547.5 |
100®0 |
0®100 |
linear gradient |
47.550.5 |
0 |
100 |
isocratic |
50.551.5 |
0®100 |
100®0 |
linear gradient |
51.561.5 |
100 |
0 |
isocratic |
Chromatograph the
System suitability solution, and record the peak areas as directed for
Procedure: the retention time for isoflupredone acetate is between 21 and 26 minutes; the relative retention times are about 1.1 for prednisolone acetate and 1.0 for isoflupredone acetate; the resolution,
R, between isoflupredone acetate and prednisolone acetate is not less than 1.2; and the column efficiency determined from isoflupredone is not less than 6000 theoretical plates.
Procedure
Inject a volume (about 50 µL) of the
Test solution into the chromatograph, record the chromatogram, and measure the areas for the major peaks. Calculate the percentage of each impurity in the portion of Isoflupredone Acetate taken by the formula:
100(ri / rs),
in which
ri is the peak response for each impurity; and
rs is the sum of the responses of all the peaks: not more than 1.0% of any individual impurity is found; and not more than 2.0% of total impurities is found, excluding those that are present in amounts less than 0.05%.
Assay
Mobile phase
Prepare a mixture of
n-butyl chloride, water-saturated
n-butyl chloride, tetrahydrofuran, methanol, and glacial acetic acid (475:475:70:35:30). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Diluent
Use water-saturated chloroform.
Internal standard solution
Dissolve an accurately weighed quantity of fluoxymesterone in Diluent to obtain a solution having a known concentration of about 0.9 mg per mL.
Standard preparation
Dissolve about 4 mg of
USP Isoflupredone Acetate RS, accurately weighed, in 8.0 mL of
Internal standard solution and 32.0 mL of
Diluent.
Assay preparation
Transfer about 4 mg of Isoflupredone Acetate, accurately weighed, to a suitable container. Dissolve in 8.0 mL of Internal standard solution and 32.0 mL of Diluent, centrifuge, and use the clear chloroform portion.
Chromatographic system (see Chromatography 621)
The liquid chromatograph is equipped with a 254-nm detector and a 4-mm × 30-cm column that contains packing L3. The flow rate is about 0.7 mL per minute. Chromatograph the
Standard preparation, and record the peak areas as directed for
Procedure: the relative retention times are about 1.0 for isoflupredone acetate and 1.2 for fluoxymesterone; the resolution,
R, between isoflupredone acetate and fluoxymesterone is not less than 2.0; and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure
Separately inject equal volumes (about 12 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the areas for the major peaks. Calculate the quantity, in mg, of C
23H
29FO
6 in the portion of Isoflupredone Acetate taken by the formula:
WS(RU / RS),
in which
WS is the weight, in mg, of
USP Isoflupredone Acetate RS taken to prepare the
Standard preparation; and
RU and
RS are the peak area ratios of isoflupredone acetate to fluoxymesterone obtained from the
Assay preparation and the
Standard preparation, respectively.