Identification of Pyrene in Complex Sample Matrix Using Time-Resolved Fluorescence Measurement Coupled with PARAFAC Analysis

Abstract This article reports an approach to use pyrene time-resolved fluorescence decay coupled with parallel factor analysis (PARAFAC) as an indicator of the presence of pyrene in complex and interfering sample matrix. Pyrene is selectively excited using 340 nm LED and the fluorescence decay is collected at 390 nm with a cut-off filter at 350 nm; pyrene reports through its long excited-state fluorescence lifetime. Humic acid (HA), a component of fluorescent dissolved organic matter, and diesel samples, consisting of PAHs at unknown concentration levels are used as interfering analytes in this study. Compared to previous reported methods (which used time-delayed technique with the help of delay generators or low temperature fluorescence decay measurement), this method uses a proven multivariate data analysis tool (PARAFAC) to segregate fluorescence decay profile of background intense and short-lived chromophores; it is verified that PARAFAC model effectively resolves the interfering decay components. Data are analysed by two approaches: in the first method, decay data are directly subjected to PARAFAC to extract pyrene contribution. In the second method, the decay curves are first globally analysed using separate curve fitting software and then the resultant relative amplitudes or fractional intensities are subjected to PARAFAC analysis. The second method provides better decomposition in terms of relative fluorescence decay contributions of pyrene.