A: A 1 in 2000 solution in dilute sulfuric acid (1 in 350) 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: A solution (1 in 50) made with the aid of a few drops of hydrochloric acid responds to the tests for Sulfate 191.

Test solution: 20 mg per mL, in 0.1 N hydrochloric acid.

Standard preparation— Prepare a solution of USP Quinine Sulfate RS in diluted alcohol to contain 6 mg per mL.

Diluted standard preparation— Dilute a portion of the Standard preparation with diluted alcohol to a concentration of 0.06 mg per mL.

Related substances preparation— Prepare a solution in diluted alcohol containing in each mL 0.05 mg each of USP Quininone RS (corresponding to 0.06 mg of the sulfate), and 0.10 mg of cinchonidine (corresponding to 0.12 mg of the sulfate).

Test preparation— Prepare a solution of Quinine Sulfate in diluted alcohol to contain 6 mg per mL.

Procedure— Apply 10-µL portions of the Test preparation, the Standard preparation, the Diluted standard preparation, and the Related substances preparation to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel. Allow to dry, and develop the chromatogram in a solvent system consisting of a mixture of chloroform, acetone, and diethylamine (5:4:1), the solvent chamber being used without previous equilibration. When the solvent front has moved about 15 cm, remove the plate from the chamber, mark the solvent front, and allow the solvent to evaporate. Spray the chromatogram with glacial acetic acid. Locate the spots on the plate by examination under long-wavelength UV light. Any spot produced by the Test preparation at the RF value of a spot produced by the Related substances preparation is not greater in size or intensity than that corresponding spot. Apart from these spots and from the spot appearing at the RF value of Quinine Sulfate, any additional fluorescent spot is not greater in size or intensity than the spot of the Diluted standard preparation. Spray the plate with potassium iodoplatinate TS. Any spot produced by the Test preparation is not greater in size or intensity than a corresponding spot from the Related substances preparation.

Methanesulfonic acid solution— Add 35.0 mL of methanesulfonic acid to 20.0 mL of glacial acetic acid, dilute with water to 500 mL, and mix.

Diethylamine solution— Dissolve 10.0 mL of diethylamine in water to obtain 100 mL of solution.

Mobile phase— Prepare a suitable filtered and degassed mixture of water, acetonitrile, Methanesulfonic acid solution, and Diethylamine solution (860:100:20:20). Adjust with Diethylamine solution to a pH of 2.6 if found to be lower.

System suitability preparation— Transfer about 10 mg each of quinine sulfate and dihydroquinine to a 50-mL volumetric flask. Dissolve in about 5 mL of methanol, dilute with Mobile phase to volume, and mix.

System suitability test— Chromatograph injections of the System suitability preparation as directed for Procedure: the relative retention times for quinine and dihydroquinine are about 1 and 1.5, respectively. The resolution between the quinine and dihydroquinine peaks is not less than 1.2. The relative standard deviation for the peak response of quinine is not more than 2.0%.

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

Procedure (see Chromatography 621)—Inject about 50 µL of the Test preparation into a chromatograph equipped with a 235-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The response of the dihydroquinine peak is not greater than one-ninth that of the quinine peak (10.0%).