Universal control of protons concentration using electrochemically generated acid compatible with miniaturization

Controlling locally produced acidity in miniaturized spaces is of high importance yielding to manage simultaneous chemical reactions. Here we present a platform that hosts miniaturized micro reactors, each one enabling electrochemical control of the acidity in ~nL volumes. We demonstrated the local control of chemical reactions with the deprotection of strong acid labile groups in a region of 150 μm of diameter of an upstanding glass using high proton concentrations (~10-1M) and the acidity contrasts between the cell region and the outside. We demonstrated an accurate control of the proton concentration in aqueous and organic solvents and the control of chemical reactions in organic electrolytes achieved with a sulfonated tetrafluoroethylene-based membrane, that isolates the acid generating electrodes from the reagents in the solution. The quantitative control of the acidity by the Faradaic currents was demonstrated by the calibration of carboxyfluorescein adjusted with external titrations, and with a tautomer transition occurring at pH 4.2. To the best of our knowledge, this platform shows the best control of acidity in the smallest volume reported so far.