Fluorescent pH probes are useful tools for the measurement of pH changes within cells. They provide improved sensitivity and spatial sampling as compared to the application of microelectrodes. Changes in intracellular pH values play a role in the investigation of diverse physiological processes like muscle contraction, endocytosis, cell proliferation, apoptosis, and ion transport. Sigma-Aldrich offers a broad range of fluorophores sensitive to pH including the commonly used pH indicators.
Fluoresceins and carboxyfluoresceins: useful for pH 6.0-7.2 and typically measured by excitation ratio at 490 versus 450 nm BCECF (2′,7′-Bis(3-carboxypropyl)-5(6)-carboxyfluorescein): useful for pH 6.5-7.5 and typically measured by excitation ratio at 490 versus 440 nm HPTS (8-Hydroxypyrene-1,3,6-trisulfonic acid trisodium salt): useful for pH 7.0-8.0 and typically measured by excitation ratio at 450 versus 405 nm