Chemical Ion Imaging by Voltammetric Ion Transfer

The use of solid-contact electrodes with membranes of very limited thickness may be probed with dynamic electrochemistry, achieving an electrochemical equilibration step at each applied potential during a linear sweep. In this talk, a novel chemical imaging method is described that does not need a scanning probe or a moving light source. A lipophilic dye is incorporated that optically indicates the electrochemical conversion of a lipophilic redox probe. A local concentration change in the sample gives in a local potential shift of the ion transfer wave, which is detected by a rapid image burst of a camera mounted on a fluorescence microscope. The associated imaging stack within one voltammetric scan is analyzed computationally to find the the point of largest fluorescence change for each pixel position, which gives the peak position. This information is then used in a fully automated procedure to give a concentration image of 250'000 pixels from a voltammetric scan of 3-s duration. The principle will be explained and experimental examples will be given.