Characterization of humic substances using total luminescence spectroscopy and capillary electrophoresis with fluorescence lifetime detection

Humic substances (HS) are a complex mixture of aliphatic and aromatic compounds found throughout the natural environment. The exact structure of HS is unknown, but the presence of various oxygen functional groups allow HS to interact with a wide range of heavy metals and environmental toxins. We have utilized the intrinsic fluorescence of HS to characterize the heterogeneous humic matrix and probe the interactions of HS with aluminum.; In our first set of studies, a commercial capillary electrophoresis instrument with multi frequency fluorescence lifetime detection was used to characterize five samples from the International Humic Substances Society (IHSS). Our results for the five samples show clear differences in electrophoretic mobility, fluorescence intensity, and fluorescence lifetime components. We were able to distinguish between soil and aquatic derived samples, as well as samples from the same source.; Our second set of studies involved a collaboration with a leading aluminum manufacturer. HS adversely affect the yield of aluminum produced through the Bayer process. We characterized 23 Bayer process samples using Excitation-Emission matrices (EEMs) in which fluorescence intensity (z-axis) is represented as a function of excitation wavelength (y-axis) and emission wavelength (x-axis). Our samples were from three different refineries and from many different points in the Bayer process. We found the EEMs to be useful for differentiating Bayer process samples. Sample EEMs from different points in the Bayer process were visually and mathematically different. Similar samples from different refineries had similar EEM spectra.