Chemical optical sensing based on luminescence lifetime measurements: a caveat

Optical sensors based on the luminescence lifetime quenching are often cons idered as being more attractive than luminescence intensity-based sensors. However, depending on the nature of the luminophore-matrix system considere d, the relative positions of the I-0/I and tau(0)/tau curves as a function of the quencher concentration can vary considerably. With a view to rationa lize these observations, numerical computations of the I-0/I and tau(0)/tau ratios have been performed in a two-site model. It is shown that this simp le model can explain the various observations and that lifetime measurement s performed by phase fluorometry are sometimes not suitable for analytical application. (C) 1999 Elsevier Science S.A. All rights reserved.