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Global Journal of Analytical Chemistry 2012, 3: 8
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Research Article
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Free Article
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Multivariate curve resolution of the quenching of excitation-emission matrices of fluorescence: Application to salicylic and fulvic acids
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Maria Cristina G. Antunesa, Joaquim C.G. Esteves da Silvab
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a Centro de Química – Vila Real, Chemistry Department, Universidade de Trás-os-Montes e Alto Douro, 5000-911 Vila Real, Portugal
b Centro de Investigação em Química, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687,4169-007 Porto, Portugal
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Abstract |
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Multivariate curve resolution with alternating least squares (MCR-ALS) is proposed to be used for the analysis of excitation-emission matrices (EEM) of fluorescence. Sets of EEM were obtained for fluorescent substances, salicylic acid (SA) and several fulvic acids (FA) extracted from soil, water and composting livestock waste, as a function of Cu2+ concentration resulting in the quenching of the EEM fluorescence due to the formation of stable complexes between fluorescent binding sites present in the samples and the metal ion. MCR-ALS successfully resolves the EEM into several components successfully separating scatter and background noise signals from the analytically relevant information corresponding to the fluorophores present in the samples. The overlapped spectra of the fluorophores were successfully deconvoluted allowing the calculation of their steady state fluorescence properties (excitation and emission spectra) and quenching profiles. From the corresponding quenching profiles, and by fitting the data to a modified Stern-Volmer equation, conditional stability constants were calculated: SA – Log(K) = 4.97; FA samples – Log(K) between 4.3 to 4.6.
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Keywords |
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Multivariate curve resolution (MCR); Excitation-emission matrix (EEM); Quenching of fluorescence; Copper(II) complexation; Humic substances; Salicylic acid
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