Application of parallel factor analysis for time-resolved laser fluorescence spectroscopy: implication for metal speciation study

Time-resolved laser fluorescence spectroscopy (TRLFS) is an analytical technique capable of discriminating different chemical species of a fluorescent metal ion such as UO(2)(2+), Cm(3+), and lanthanides. Although TRLFS has been widely used to investigate the speciation of the fluorescent metal ions, extracting quantitative and structural information from multiple TRLFS data measured as a function of chemical and physical parameters is not a simple task. The purpose of this study is to apply parallel factor analysis (PARAFAC) for the interpretation of a series of TRLFS data. PARAFAC is a robust technique because it utilizes the entire information contained in a multiway TRLFS data set. The complexation of Eu(3+) by acetate was studied as a test case for the PARAFAC decomposition. It is shown that three factors are necessary and sufficient to explain the systematic variations in the original data set. The resulting spectra, decay, and relative concentrations of the factors were all in agreement with the fluorescent properties and the complexation behaviors of Eu(3+)-acetate complexes. Based on these results, it was concluded that PARAFAC is a promising data analysis tool for TRLFS used for the speciation studies of fluorescent metal ions.