A family of indicators has been developed for fluorescence lifetime-based measurement of oxygen, pH, carbon dioxide, and potassium, all the indicators being derivatives of the same chemical compound and having identical spectral and lifetime properties. The indicators show an absorption accessible to low- cast light sources, a large Stokes shift, and long fluorescence decay time. all indicators can be excited at the same excitation wavelength, monitored at the same emission wavelength, and measured within the same time range. This opens the possibility of building a compact lifetime-based instrument to simultaneously measure blood gases and cations.
Max E. Lippitsch,
"Family of lifetime sensors for medical purposes", Proc. SPIE 2388, Advances in Fluorescence Sensing Technology II, (8 May 1995); doi: 10.1117/12.208472; https://doi.org/10.1117/12.208472