where F0 is the fluorescence intensity without the quencher, F is the fluorescence intensity in the presence of a quencher, KSV is the Stern-Volmer constant and [Q] is the quencher concentration. The Stern-Volmer quenching constants of various anions in pure water were determined by fluorescence measurements using a lucigenin dinitrate salt concentration of 1 μM and increasing concentrations of anions. Data for chloride are shown in Figure and for other anions in the SI. The Stern-Volmer constants obtained and the literature values are listed in Table .