A system, device and apparatus for measuring electrolytes, where an electrical charge is applied to a measurement portion to draw ions from a liquid to a gel-solution via at least one electric field. The gel-solution containing the extracted ions is excited with light of a predetermined wavelength from an emitter. A receiver detects the illumination of the ions as a result of the excited gel-solution, and a processor converts the detected intensities of the illumination to a biologically useful value representing ionic concentration.