Identification—
Dissolve a portion of finely powdered Tablets in methanol to obtain a test solution containing about 2.5 mg of molindone hydrochloride per mL. Separately apply 5 µL of the test solution and 5 µL of a Standard solution of
USP Molindone Hydrochloride RS in methanol containing 2.5 mg per mL to a thin-layer chromatographic plate (see
Chromatography 
621
) coated with a 0.25-mm layer of chromatographic silica gel mixture. Allow the spots to dry, protect the chromatogram from light, and develop in a solvent system consisting of a mixture of alcohol and 1 N hydrochloric acid (95:5). Remove the plate from the developing chamber, mark the solvent front, and allow the solvent to evaporate. Locate the spots on the plate by spraying with Dragendorff's reagent, prepared as directed for
Visualization Technique 3 under
Ordinary Impurities 466: 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.
Solvent A—
Mix 300 mL of methanol and 700 mL of 0.1 N hydrochloric acid.
Solvent B—
Mix 75 mL of methanol and 25 mL of 0.1 N hydrochloric acid.
Standard solution—
Transfer about 100 mg of
USP Molindone Hydrochloride RS, accurately weighed, to a 250-mL volumetric flask, and dissolve in and dilute with
Solvent A to volume. Pipet 5.0 mL of this stock solution into a 250-mL volumetric flask, and dilute with
Solvent A to volume. Pipet 15.0 mL of the diluted stock solution into a 50-mL volumetric flask, and dilute with
Solvent A to volume.
Test solution—
Withdraw a portion of the solution under test, and filter, discarding the first 3 mL of filtrate. Pipet 15.0 mL of this solution into a 25-mL volumetric flask, and dilute with Solvent B to volume.
Mobile phase—
Dissolve 1.08 g of sodium 1-octanesulfonate in 480 mL of water. Add 520 mL of methanol, 2.0 mL of acetic acid, and 0.4 mL of triethylamine, and mix. Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 254-nm UV detector and a 4.6-mm × 25-cm column that contains packing L11. The flow rate is about 1.5 mL per minute.
Procedure—
Separately inject equal volumes (about 100 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the peak heights. Determine the amount of molindone hydrochloride (C16H24N2O2·HCl) dissolved.
Tolerances—
Not less than 80% (Q) of the labeled amount of C16H24N2O2·HCl is dissolved in 30 minutes.
Assay—
Mobile phase
,
Solvent mixture,
Internal standard solution,
Standard preparation, and
Chromatographic system—Proceed as directed in the
Assay under
Molindone Hydrochloride.
Assay preparation—
Accurately weigh not less than 20 Tablets, grind the Tablets to a homogeneous mixture, and transfer an accurately weighed portion, equivalent to about 50 mg of molindone hydrochloride, to a 250-mL conical flask. Add 10.0 mL of Internal standard solution and 90.0 mL of Solvent mixture, shake for 30 minutes, and filter.
Procedure—
Proceed as directed for
Procedure in the
Assay under
Molindone Hydrochloride. Calculate the quantity, in mg, of molindone hydrochloride (C
16H
24N
2O
2·HCl) in the portion of Tablets taken by the formula:
100C(RU / RS),
in which
C is the concentration, in mg per mL, of
USP Molindone Hydrochloride RS in the
Standard preparation, and
RU and
RS are the ratios of the peak response of molindone to that of butylparaben obtained from the
Assay preparation and the
Standard preparation, respectively.
