Fluorescence properties of carminic acid in relation to aggregation, complex formation and oxygen activation in aqueous food models

摘要: Abstract The fluorescence of carminic acid is moderately dependent on pH in acidic and neutral aqueous solution has, at 2·0 1·0 m NaCl 25°C, a quantum yield 0·00133 ± 0·00019 an emission lifetime 0·093 0·010 ns, as determined by the phase modulation method. quenched iodide (diffusion controlled reaction), decreases for increasing concentration, suggesting molecular stacking fast equilibrium, further evidenced pressure quenching emission. dilute increased aluminium result formation 1:1 complex with stability constant (6·8 1·8) × 10 3 litres mol −1 (1·0 4, 25°C), 0·022 0·004 2·1 0·1 ns. An excited state kinetic analysis based photophysical characterization shows electronic deactivation path which does not involve oxygen activation. acid, declines rapidly alkaline concomitant increase photooxidation photoreactive triplet state, capable activation, becomes importance higher pH.