Multiway analysis through direct excitation-emission matrix imaging

Abstract

In this work, a direct in-flow methodology for the acquisition of excitation-emission fluorescence matrices is presented. The system is particularly suited for measurements in the order of tens of milliseconds. A light source operated in continuous mode is dispersed through a grating and focused onto a square-section capillary. Under the spatially resolved excitation, the emission is collected, dispersed through a second grating and further focused onto a CCD array sensor. To allow the wavelength accuracy, a spectral calibration was performed registering the scattering signal of a dispersive element using interference filters ranging from 340 nm to 740 nm. The theoretical performance of the method was analyzed and second-order data obtained for different analyte mixtures are presented and discussed. PARAFAC was applied to evaluate the trilinearity of the obtained data. Mathematical evaluation by means of the criterion of similarity corroborates the agreement between experimental pure spectra and spectral profiles retrieved from PARAFAC. Moreover, the feasibility of the spectrometer to obtain second-order data for analyses with quantitative aims was demonstrated. Finally, fast data acquisition was proved by monitoring a chromatographic analysis of dye mixtures for the generation of third-order LC-EEM data. Here, an improvement in the resolution of the different instrumental modes was demonstrated.