Figure 3.

UV–vis traces of probe 1 (a) in acetonitrile (53 nM, red line), acetonitrile–phosphate buffer 1 mM pH 7.2 1 : 1 (black line), acetonitrile–H₂O 1 : 1 (blue line) and tetrahydrofuran (43 nM, green line); probe 2 (b) in acetonitrile (31 nM, red line), acetonitrile–phosphate buffer 1 mM pH 7.2 1  : 1 (black line) and acetonitrile–H₂O 1 : 1 (blue line); probe 3 (c) in tetrahydrofuran (11 nM, green line); UV–vis spectra of FA (d) in tetrahydrofuran (71 nM, green line), in H₂O pH 1 (35 µM, grey line) and pH 14 (23 µM, grey dashed line).