Fig. 7.

Fluorescence sensitivity measured using fluorescein at pH 9.5. (a) Measured fluorescence signal (upper panel) with log-scaled fluorescence image (lower panel) of four glass capillary tubes filled with decreasing concentrations of fluorescein. Inset: magnified plot of signal from 10 nM and 5 nM fluorescein filled tubes (blue line) compared to the same tubes with no fluorescein (black line). In the fluorescence colourbar, dB is measured relative to maximum measured fluorescence signal. (b) Plot of maximum fluorescence signal from each tube (blue circles) with line of best fit (blue line) compared to the RMS noise floor (red dashed line).