EVALUATION OF SIZE-EXCLUSION AND ION-EXCHANGE CHROMATOGRAPHY FOR METAL-FULVIC ACID STABILITY CONSTANT DETERMINATIONS (TRACE ANALYSIS, GEL-PERMEATION, AAS)
Fulvic acid is a naturally occurring ligand found in soil and water. It is known to complex metal ions and transport them through the environment. The extent of the transport depends on: (1) the strength of the metal-fulvic acid complex, (2) the number of binding sites per fulvic acid molecule, and (3) the dissociation rate of the metal-fulvic acid complex. The strength of the complex and the number of binding sites can be determined through a Scatchard plot model. The determinations are made by measuring the concentrations of free and complexed metal. Of the techniques to measure the free and complexed metal, atomic absorbance spectroscopy is the most versatile but requires a separation of the two metal species. This work evaluates the applicability of size-exclusion and ion-exchange chromatography for the separation. Nonideal influences of ion-exchange, ion exclusion, Donnan exclusion, and hydrophobic and adsorption interactions that influence the separation by size-exclusion chromatography were investigated. Parameters that influence the separation by ion-exchange chromatography were also investigated. An ion-exchange chromatography - atomic absorbance spectroscopy system was developed to make the determinations. The accuracy and reproducibility of the system was evaluated by determining the stability constant of a copper-citric acid complex. The system was optimized and the conditional stability constants and number of binding sites per fulvic acid molecule were determined for a terrestrial and an aquatic fulvic acid.
MARK ROBERT PITLUCK,
"EVALUATION OF SIZE-EXCLUSION AND ION-EXCHANGE CHROMATOGRAPHY FOR METAL-FULVIC ACID STABILITY CONSTANT DETERMINATIONS (TRACE ANALYSIS, GEL-PERMEATION, AAS)"
(January 1, 1985).
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