A new fluorescence method for measuring cross-fluctuation fo two non-reactive components in a mixing device

A novel method for measuring local deviations from perfect mixing of two non-reative tracers is presented. It is based on the partially quenched fluorescence of one fluorescent tracer by a second tracer. When the concentration fluctuations are small, the deviation from the linear behaviour yields the cross-correlation of the fluctuating components of the concentrations of both traces from an – easy to record – average value of fluorescence intensity obtained in the focus of a laser beam. The method was proven to be suitable for measuring these quantities in a 1125 cm³ well-stirred tank as a function of location and stirring speed.