Quinine, also known as 6′-Methoxycinchonidine is a fluorescent reagent. The quantum yield of Quinine is 23% higher at 390 mµ excitation wavelength than at 313 mµ. The fluorescence polarization in the emission band of quinine in a rigid medium arises from two singlet states simultaneously. The emission spectra of quinine or 6-methoxyquinoline shifts towards the red zone when excited at 390 mµ.
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