Pyranine is particularly effective at distinguishing ranges of cations from the Cu+ ion, even in environments with competing ions. It exhibits a rapid fluorescence response (half-life of 1.66 minutes) toward Cu+ ions, with a detection limit in the micromolar range, making it suitable for environmental monitoring. The stoichiometry of the complex formed between Pyranine and Cu+ is 2:1, indicating that two Pyranine molecules interact with each Cu+ ion^[1].

Pyranine's pH sensitivity has been explored for potential applications such as in vivo studies in the cornea and anterior chamber of the eye. After topical administration, sufficient concentrations of Pyranine are achieved in these areas, and the pH can be accurately measured using fluorophotometry. This involves calculating the ratio of fluorescent intensity at two different excitation wavelengths (I463/I404), a method that is sensitive to pH changes but independent of fluorophore concentration and other variables that might affect intensity^[2].