Using electrochemical control to change the chemical environment in liquids is quite challenging because the small surface to volume ratio offered by traditional cells limits the release or modification of chemicals from the electrodes. Here we present the control of proton concentration (acidity) using a combination of a redox active SAM, which allows ease of fabrication, control of the chemical reactions and repeatability, with a microfluidic design that provides large range and stability over time of the set acidity point, quasi-reversibility during several cycles, and capacity of miniaturization and scalability for multiplexing.