A microfluidic cell system to measure proton concentration in a fluid sample. The microfluidic cell system includes: a first microchip and a second microchip dimensioned to permit electron beam scanning of a fluid sample; a first membrane attached to the first microchip; a second membrane attached to the second microchip, the first membrane and the second membrane being disposed adjacent to one another with a space for the fluid sample therebetween, and the first membrane and the second membrane including a region of the fluid sample in which an electron beam is scanned; a first electrode patterned onto the first membrane and positioned a first distance from the region; a second electrode patterned onto the first microchip and positioned a second distance from the region, the first distance being less than the second distance; and a potentiostat in communication with the first electrode and the second electrode.