Correction of fluorescence inner filter effects and the partitioning of pyrene to dissolved organic carbon

The ability of dissolved organic carbon (DOC) to bind pyrene can be monitored by fluorescence quenching. Inner filter effects, caused by DOC, complicate the interpretation of the partitioning coefficient of DOC to pyrene. Since DOC absorbs and fluoresces at the excitation wavelength of pyrene, by fitting the DOC self-quenching curve to a simple empirical model that quantifies the absorbance in the spectrofluorimeterʹs interrogation zone, one can obtain the necessary information to correct for the inner filter effects. This model can be combined with the Stern-Volmer equation to give a single equation that models the total fluorescence of a quenching experiment, and from which a value for the linear Stern-Volmer quenching constant, corrected for the inner filter effects, may be obtained. The mechanisms of inner filter effects are discussed and then quantified, leading to a mathematical model of a self-quenching curve. This is then reduced to the empirical model of DOC self-quenching.