A Modified Multisite Stern−Volmer Equation for the Determination of Conditional Stability Constants and Ligand Concentrations of Soil Fulvic Acid with Metal Ions

2004 ◽  
Vol 76 (3) ◽  
pp. 848-854 ◽  
Author(s):  
Michael D. Hays ◽  
David K. Ryan ◽  
Stephen Pennell
Keyword(s):  
Metal Ions ◽  
Fulvic Acid ◽  
Stability Constants ◽  
Conditional Stability ◽  
Conditional Stability Constants

Reactions of gallocyanine methyl ester with gallium(III) and indium(III) ions

1982 ◽  
Vol 47 (7) ◽  
pp. 1950-1963 ◽  
Author(s):  
Milan Kotouček ◽  
Josef Růžička ◽  
Pavla Vaculíková
Keyword(s):  
Methyl Ester ◽  
Stability Constants ◽  
Equilibrium Constants ◽  
Photometric Determination ◽  
Conditional Stability ◽  
Conditional Stability Constants

Reactions of gallocyanine methyl ester with gallium(III) and indium(III) ions in solutions in 15% (m/m) ethanol were studied spectrophotometrically. At pH 1.7-6.5, the GaL, GaL2, and Ga(OH)L3 complexes are formed; in the case of indium, the In(OH)2L2 and In(OH)L3 complexes appear at pH 4-6.5, and InL3B2 in tartrate solutions. The conditional stability constants and the equilibrium constants of the coordination equilibria were calculated, and procedures were worked out for a photometric determination of gallium and for a chelatometric determination of gallium and indium using gallocyanine methyl ester as metallochromic indicator.

Multi-Wavelength Fluorescence-Quenching Model for Determination of Cu2+ Conditional Stability Constants and Ligand Concentrations of Fulvic Acid

2003 ◽  
Vol 57 (4) ◽  
pp. 454-460 ◽  
Author(s):  
Michael D. Hays ◽  
David K. Ryan ◽  
Stephen Pennell
Keyword(s):  
Fulvic Acid ◽  
Data Sets ◽  
Conditional Stability ◽  
Intensity Data ◽  
Fluorescence Excitation ◽  
Ph Values ◽  
Synchronous Fluorescence Spectra ◽  
Multi Wavelength ◽  
Conditional Stability Constants

In this work, a multi-wavelength model (MWM) is developed. It uses fluorescence bands in the fulvic acid (FA) spectrum that quench upon binding of inorganic Cu2+ to FA. Quenching data at pH values of 5, 6, and 7 are placed in sets, containing fluorescence measures at select wavelengths versus added copper ( CM). Intensity data of wavelength set 1 are obtained from 25 nm constant offset synchronous fluorescence spectra (SyF), in which are observed distinct peaks (λex = 415 nm, λem = 440 nm; and λex = 471 nm, λem = 496 nm). Wavelength set 2 intensity data are obtained from the FA fluorescence excitation and emission maxima (λex = 335 nm, λem = 450 nm; and λex = 471 nm, λem = 496 nm). Application of MWM shows that the multi-wavelength data sets characterize ligands of different binding strength (log Kx) and concentration ( CLx). Corresponding to pH values of 5, 6, and 7, mean and standard deviation values for wavelength set 1 are log K415/440 = 4.66 (0.12), 5.03 (0.12), and 5.05 (0.08), log K471/496 = 4.93 (0.06), 5.27 (0.11), and 5.39 (0.09), C415/440 = 3.1 (1.5), 10.9 (4.5), and 7.9 (3.9) μM, C471/496 = 14.3 (3.0), 1.7 (0.6), and 1.4 (0.5) μM. And for wavelength set 2, log K335/450 = 4.50 (0.03), 4.96 (0.27), and 5.22 (0.08), log K471/496 = 5.02 (0.04), 5.42 (0.32), and 5.71 (0.09), C335/450 = 8.8 (0.5), 21.9 (7.9), and 18.7 (0.3) μM, C471/496 = 21.0 (2.5), 7.17 (1.2), and 7.09 (0.3) μM. The ability of the 415/440 nm SyF transect to characterize the main excitation and emission maximum of FA at 335/440 nm is evaluated. Relatively low concentration values returned by the model for this transect (415/440 nm) suggest that it is not entirely illustrative of the maximum. The model predictive capability is verified at pH 6 with two fluorescing Cu2+ chelating organic compounds, L-tyrosine and salicylic acid. This test confirms that the model is capable of providing good estimates of equilibrium binding parameters from multi-wavelength measurements of a mixed ligand system.

Cadmium complexation by soil fulvic acid

1978 ◽  
Vol 56 (17) ◽  
pp. 2331-2336 ◽  
Author(s):  
Bill Brady ◽  
Gordon K. Pagenkopf
Keyword(s):  
Fulvic Acid ◽  
Stability Constants ◽  
Conditional Stability ◽  
Cadmium Complexation ◽  
Conditional Stability Constants

A soil fulvic acid bas been characterized and the complexation stability constants with cadmium have been evaluated. The average gram formula weight of the fulvic acid is 2775. Three complexes of stoichiometry CdFA, Cd2FA, and Cd3FA have been observed. The respective conditional stability constants at pH 5.7 are 105.3, 109.8, and 1014.0; at pH 6.7 they are 105.6, 1010.6, and 1015.5; and at pH 7.7 they are 106.0, 1010.7, and 1015.4.

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