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Fluorescence quenching titration for determination of complexing capacities and stability constants of fulvic acid

Fluorescence quenching titration for determination of complexing capacities and stability constants of fulvic acid,10.1021/ac00243a033,Analytical Chem

Fluorescence quenching titration for determination of complexing capacities and stability constants of fulvic acid   (Citations: 49)
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We describe a fluorescence tltration technique which can be used to determine complexing Capacities (C,) and 1:l con- ditlonai stability constants (K) of fluorescing ligands with paramagnetlc metal Ions at the micromolar level. An equa- tion, which we derive, allows calculation of the amount of ligand bound for fluorescence quenching curves. Further analysis of the data and fitting to a theoretical equation by a nonilnear regression computer program results in the best fit K and CL. Fluorescence results for soil fulvic acid (SFA) wlth Cu2+ at pH 5,6, and 7 compare well wlth results for the same material uslng different technlques. Titrations of the model compound L-tyroslne prove the validity of the technlque. The average CL value Is withln 7.5% of the experlmental con- centration and the average K value is wlthin 1.5% of the theoretical value under the conditions used. Rayieigh scat- tering data collected slmultaneously with fluorescence indi- cates preclpHate formatlon during compiexlng capacity tltra- tions. The combined fluorescence and scattering measure- ments result in a powerful method that can distingulsh be- tween solution phase complexatlon and processes that may be Occurring at the solid-solution Interface. These phenom- ena must be consMered for better Interpretation of compiexing capacity results.
Journal: Analytical Chemistry - ANAL CHEM , vol. 54, no. 6, pp. 986-990, 1982
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    • ...Thus, metal ion-binding parameters such as the binding constant and capacity of HSs for binding can be calculated from the quenching data by assuming a stoichiometric relationship [15]...

    Motoki Terashimaet al. Europium-binding abilities of dissolved humic substances isolated from...

    • ...This technique has also been used to determine complexing capacities of HAs and stability constants of metal-ion-humic acids complexes (Ryan and Weber, 1982; Cabaniss, 1992; Evanglou and Marsi, 2001; Elkin and Nelson, 2002; Provenzano et al, 2004)...

    Achour Terboucheet al. Characterization and Complexing Capacity of Humic Acid Extracted from ...

    • ...DOM plays a key role in constraining the form, toxicity, transport and conversion of trace metallic ions in aquatic environments because of the strong interaction between DOM and contaminants (Ryan and Weber, 1982; Yin et al., 1997; Esteves da Silva et al., 1998; Lu and Jaffe, 2001; Ravichandran, 2004; Wu Fengchang et al., 2004)...
    • ...and Weber, 1982; Ravichandran, 2004), of which fluorescence quenching titration is an approach employed internationally (Ryan and Weber, 1982; Esteves da Silva et al., 1998; Lu and Jaffe, 2001; Wu Fengchang et al., 2004)...
    • ...Expressions (11) and (12) are called the modified Stern-Volmer linear model equations for fluorescence quenching titration, expression (13) is the Ryan-Weber non-linear model equation (Ryan and Weber, 1982; Esteves da Silva et al., 1998)...
    • ...The variation of Rayleigh scattering intensity may indicate variations in the number of microns in the solution (Ryan and Weber, 1982; Wu Fengchang et al., 2004)...
    • ...This indicates that in the process of titration there occurred no obvious precipitation (Ryan and Weber, 1982; Wu Fengchang et al., 2004), and variations in UV absorbance and fluorescence intensity are caused by complexation...

    Yingchen Baiet al. Ultraviolet absorbance titration for the determination of conditional ...

    • ...These parameters can be determined using the fluorescence titration technique combined with the mathematical approach introduced by Ryan and Weber (1982)...
    • ...To reach these objectives, fluorescence titration and the single site model of Ryan and Weber (1982) were used...
    • ...The Cu(II) and Zn(II) complexing capacities of HAs and the stability constants of Cu(II) and Zn(II) complexes with HAs were determined by the single site fluorescence quenching model of Ryan and Weber (1982)...
    • ...According to Ryan and Weber (1982), the measured fluorescence intensity (I) varies linearly with the fraction of the total ligand bound yielding the following relationship...
    • ...The experimental values (dots) of the fluorescence intensity of the main HA fluorophore as a function of Cu(II) and Zn(II) concentrations and the nonlinear regressions generated by best fitting these data in the model of Ryan and Weber (1982) are shown inFig. 3. The corresponding best-fit parameters obtained for each HA, i.e., the correlation coefficients of predicted vs. measured fluorescence intensity (r), the fluorescence intensities ...
    • ... vs. measured fluorescence intensity (r), the fluorescence intensities (IML)ofmetal-saturatedeHAcomplexes,thestability constants (log K)ofmetaleHAcomplexes,andthemetal complexingcapacities (CC) of HAs, are listed in Table 3. The large values found for the correlation coefficients (r) indicate that the model fitsverywell totheexperimentaldata setsforHAsexamined,as it was previously demonstrated in other works on similar systems (Ryan and Weber, ...

    Diana Hern√°ndezet al. Detection of Copper(II) and zinc(II) binding to humic acids from pig s...

    • ... speciation of metal ions in soil and natural water is dependent on the quantity and quality of FA. Molecular fluorescence spectroscopy is a particularly useful technique for the study of the chemical equilibrium properties of fluorescent FA molecules because it is a highly sensitive analytical technique, allowing measurements to be made at natural environmental concentrations, and measurements are nondestructive (Saar and Weber, 1980; Ryan and ...
    • ...When paramagnetic metal ions, like for example Cu(II), are brought into contact with FA its fluorescence is quenched as consequence of the formation of stable complex species and quantitative information about the complexation phenomena can be obtained (Ryan and Weber, 1982; Machado et al., 1994; Esteves da Silva et al., 1998c)...

    C. G. Esteves da Silvaet al. Multivariate curve resolution of multidimensional excitation-emission ...

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