A: Shake well a quantity of the contents of Capsules, equivalent to about 100 mg of quinine sulfate, with 100 mL of dilute sulfuric acid (1 in 350), and filter. An appropriate dilution of the filtrate exhibits a vivid blue fluorescence. On the addition of a few drops of hydrochloric acid the fluorescence disappears.

B: In the test for Chromatographic purity, the RF value of the principal spot obtained from the Test preparation corresponds to that from the Standard preparation.

C: Shake a quantity of the contents of Capsules, equivalent to about 20 mg of quinine sulfate, with 10 mL of dilute hydrochloric acid (1 in 100), and filter: the filtrate responds to the tests for Sulfate 191.

D: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, obtained as directed in the Assay.

Medium: 0.1 N hydrochloric acid; 900 mL.

Apparatus 1: 100 rpm.

Time: 45 minutes.

Procedure— Determine the amount of (C20H24N2O2)2·H2SO4·2H2O dissolved by employing UV absorption at the wavelength of maximum absorbance at about 248 nm on filtered portions of the solution under test, suitably diluted with Dissolution Medium, in comparison with a Standard solution having a known concentration of USP Quinine Sulfate RS in the same Medium.

Tolerances— Not less than 75% (Q) of the labeled amount of (C20H24N2O2)2·H2SO4·2H2O is dissolved in 45 minutes.

Procedure for content uniformity— Transfer the contents of 1 Capsule to a 250-mL volumetric flask, add about 175 mL of dilute hydrochloric acid (1 in 100), and shake by mechanical means for 30 minutes. Add dilute hydrochloric acid (1 in 100) to volume, and mix. Filter a portion of the mixture, discarding the first 20 mL of the filtrate. Concomitantly determine the absorbances of this solution, quantitatively diluted, if necessary, and a Standard solution of USP Quinine Sulfate RS in dilute hydrochloric acid (1 in 100) having a known concentration of about 40 µg per mL, in 1-cm cells, at the wavelength of maximum absorbance at about 345 nm, with a suitable spectrophotometer, using water as the blank. Calculate the quantity, in mg, of active ingredients, calculated as quinine sulfate [(C20H24N2O2)2·H2SO4·2H2O], in the Capsule taken by the formula: in which T is the labeled quantity, in mg, of quinine sulfate in the Capsule, D is the concentration, in µg per mL, of quinine sulfate in the solution from the Capsule, based on the labeled quantity per Capsule and the extent of dilution, C is the concentration, in µg per mL, of USP Quinine Sulfate in the Standard solution, and AU and AS are the absorbances of the solution from the Capsule and the Standard solution, respectively.

(Official January 1, 2007)

Methanesulfonic acid solution, Diethylamine solution, Mobile phase, System suitability preparation, and System suitability test— Proceed as directed in the test for Limit of dihydroquinine sulfate under Quinine Sulfate.

Standard preparation— Transfer about 20 mg of USP Quinine Sulfate RS, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix.

Assay preparation— Transfer the contents of not less than 20 Capsules to a container, and mix. Transfer an accurately weighed portion of the powder, equivalent to about 160 mg of quinine sulfate, to a 100-mL volumetric flask, add 80 mL of methanol, and shake the flask by mechanical means for 30 minutes. Dilute with methanol to volume, and filter, discarding the first 10 mL of the filtrate. Transfer 3.0 mL of the filtrate to a 25-mL volumetric flask, dilute with Mobile phase to volume, and mix.

Procedure (see Chromatography 621)—Inject equal volumes (about 50 µL) of the Standard preparation and the Assay preparation into a chromatograph equipped with a 235-nm detector and a 3.9-mm × 30-cm column that contains packing L1. Calculate the quantity, in mg, of the sum of quinine sulfate and dihydroquinine sulfate in the portion of Capsules taken by the formula: in which C is the concentration, in mg per mL, of USP Quinine Sulfate RS in the Standard preparation, rb,U and rb,S are the peak area responses of quinine obtained from the Assay preparation and the Standard preparation, respectively, and rd,U and rd,S are the peak area responses of dihydroquinine obtained from the Assay preparation and the Standard preparation, respectively.