Complex fluorescence decay of quinine bisulphate in aqueous sulphuric acid solution

Fluorescence of quinine bisulphate is shown to be two-component. In 1.0 N H₂SO₄ solution the major component has a decay time ≈20 ns, but there is a minor component with decay time ≈2 ns with a different fluorescence spectrum. It is recommended that the compound not be used as a standard for decay-time measurements.