Ratiometric probes for hydrogencarbonate analysis in intracellular or extracellular environments using europium luminescence

A series of six, cationic, zwitterionic and anionic Eu complexes has been examined for the analysis of hydrogen-carbonate concentration in the intracellular and extracellular ranges; an anionic complex incorporating three glutarate residues and a sensitising acridone chromophore (lambda(exc) = 410 nm) exhibits a 69% change in the intensity ratio of the 618/588 nm Eu emission bands between 5 and 15 mM HCO3- in a cell lysate medium.