Evolving Factor Analysis of Synchronous Fluorescence Spectra of Fulvic Acids in the Presence of Aluminum

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Abstract
The variations observed in synchronous fluorescence spectra of aqueous solutions (pH = 4) of three fulvic acids (fua) upon variation of the concentration of Al3+ were analyzed by evolving factor analysis (EFA). The three fua samples were extracted from materials present in a pine-wood soil: dry pine needles and the upper and lower soil horizons. The presence of Al3+ induces quenching and enhancement of bands in the synchronous fluorescence spectra, and concentration constraints are proposed for the EFA analysis that allow the calculation, on a self-modeling curve resolution basis, of the number of components that show linearly independent variations, their spectra, and corresponding concentration profiles. Simulated and experimental data sets of simple known compounds (catechol, caffeic acid, salicylic acid, and morin) were also studied as the first validation of the experimental and data treatment procedures.