Laser-induced fluorescence of perylene in a microparticle suspension environment

Laser-induced fluorescence (LIF) is one of the most sensitive techniques for analysis of traces of polycyclic aromatic compounds in liquids. Application of this method to on-line monitoring requires solution of problems related to the presence of particulate materials. Thus, understanding the analytical effects associated with the suspension of microparticles is of considerable importance for both environmental and industrial applications. Here, LIF of perylene in acetonitrile solutions was studied for different light-scattering/-absorbing microparticle matrixes. With increasing suspension mass of efficiently light absorbing black-colored particles, the intensity of the associated LIF signals was found to obey an apparently exponential decrease. Their white-colored counterparts, however, have initially produced a sizable, ～20%, signal increase of the respective LIF responses. An exponential decrease then became predominant, too. A model that explains the observations in terms of absorption and scattering coefficients is developed and examined. The quantitative effect of the particulate mass is correctly reproduced by the model, as well as the laser wavelength dependence. A possible application of a calibrating algorithm is addressed.