Ion flux assays are cell-based functional assays. They trace ionic flux through channels by radioisotopes, or detect ionic flux using highly sensitive flame atomic absorption spectrometers (AAS) or using fluorescence ion-specific probes/biosensors. Ion flux assays use a radioactive species in combination with a scintillation counter or use a tracer ion measured by atomic absorption/emission spectrometry.

In the 1980’s the development of ion-selective fluorescent dye-based indicators