Limitations of quenching as a method of fluorometric analysis of non-fluorescent analytes

It is shown that diffusional quenching of ordinary fluorophores (with decay times no longer than several tens of nanoseconds), a process employed in many fluorescence optical sensors, is rather insensitive as a analytical method having limits of detection no better than about 10−4 M. Longer lived luminophores, such as lanthanides, actinides and phosphorophores, however, can be quenched with substantially lower detection limits for the quencher. Static quenching, on the other hand, is limited by the thermodynamic strength of the complex(es) formed between the fluorophore and quencher rather than by the decay time of the fluorophore and the diffusibility of the quencher and can be quite sensitive as an analytical method for the quencher.