Quenching impurity

Quenching Impurities in the mobile phase, particularly oxygen, may entirely quench the signal from low concentrations of fluorescent compounds (see solvent degassing). 

One further complication should be noted as well namely, a sensitizer that contains a quenching impurity will display identical kinetics, since the impurity concentration will be proportional to the sensitizer concentration. 

Solvent quenching Self-quenching Impurity quenching Electronic energy... 

The benzene triplet has not been observed to phosphoresce in either the gas or liquid phase, as noted previously but in view of the lifetime measured In glassy media at low temperature this is not surprising, since very small amounts of quenching impurities would reduce emission to undetectable levels. Some detailed investigations have shown that there is an intramolecular process which Induces radiationless decay of the benzene triplet state, other than impurity quenching. 

Quantitative fluorimetric analysis on real samples usually requires a separation of the fluorescent analyte from its matrix because of the wide occurrence of fluorescent and quenching impurities. Occasionally, simple solvent extraction will do the trick. More often, chromatographic separation is necessary, and the fluo-rimeter becomes merely a detector for the chromatographic eluates. Recently, however, the application of immunochemistry to analytical chemistry has permitted in-situ analysis on a scale never before possible. Although the earliest immunochemical analyses utilized radioisotopes, the most popular ones used today employ fluorescent probes or labels. 

Termination reactions in anionic polymerization, particularly with nonpolar monomers and in nonpolar solvent, are not common. If carbanion quenching impurities are absent, many polymerization reactions may not terminate after the complete disappearance of the monomer. Styryl anion (one of the most stable ones), for instance, can persist for a long time, such as weeks, after the monomer is consumed. Addition of more monomer results in a continuation of the reaction and a further increase in the molecular weight. The anionic living polymers retain their activities for considerably longer periods of time than do the cationic living ones. ... 

Tan, B.Q., Li, J.-F., and Viehland, D. (1997) Ferroelectric behaviours dominated by mobile and randomly quenched impurities in modified lead zirconate titanate ceramics. Philos. Mag. B, 76 (1), 59-74. 

MICHEAU - From the experimental point of view, you have observed non exponential decays and variations of the fluorescence lifetime with temperature. Have you taken a special care of concentration effects, reactivity of probes molecules, presence of quenching impurities in the solvent and also of the occurrence of possible intermolecular interactions giving rise to exciplexes formation ... 

W. Gac, M. Kruk, A. Patrykiejew, S. Sokolowski, Effects of random quenched impurities on layering transitions A Monte Carlo study, Langmuir 12 (1996) 159-169. 

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