Quinaldine red R.

2-(p-Dimethylaminostyryl)quinoline ethiodide; C₂₁H₂₃IN₂.

Description. A dark blue-black powder.

Solubility. Sparingly soluble in water; freely soluble in ethanol (~750 g/l) TS.

Melting temperature. About 260°C with decomposition.

Quinaldine red/ethanol TS.

Procedure. Dissolve 0.1 g of quinaldine red R in 100 mL of ethanol (~750 g/l) TS.

Quinaldine red/methanol TS.

Procedure. Dissolve 1.0 g of quinaldine red R in sufficient methanol R to produce 100 mL.

Quinhydrone R.

p-Benzoquinone compound with hydroquinone (1:1); C₁₂H₁₀O₄.

Description. Dark green, lustrous crystals or a crystalline powder.

Melting point. About 171 °C.

Quinhydrone/methanol TS

Procedure. Dissolve 2.5 g of quinhydrone R in sufficient methanol R to produce 100 mL.

Quinine R.

C₂₀H₂₄N₂O₂.

Description. A white, microcrystalline powder; odourless.

Solubility. Very slightly soluble in water; slightly soluble in boiling water; very soluble in ethanol (~750 g/l) TS; soluble in ether R and benzene R.

Melting temperature. About 175°C.

Identification. Very dilute solutions containing sulfuric acid (~100 g/l) TS show a blue fluorescence. Acid solutions are levorotatory. Dissolve about 5 mg in a mixture of 5 mL of water and 0.3 mL of hydrochloric acid (~70 g/l) TS. Mix the solution with 0.2 mL of bromine TS1 and add 1 mL of ammonia (~35 g/l) TS; an emerald green colour is produced.

Quinine sulfate R

Quinine sulfate of a suitable quality should be used.