Asymmetrical flow field‐flow fractionation as a method to study the behavior of humic acids in solution

Asymmetrical flow field-flow fractionation (AsFlFFF) is used to measure the size distributions of humic acids in solution. Shifts in the size distribution are used to study the behavior of these amphiphilic macromolecules in solution with changes in pH, ionic strength, and humic acid concentration. Humic acid concentrations are increased by on-channel focusing of the injected samples. As the concentration is increased, the humic acids aggregate, but the effect varies with solution conditions. As the concentration of calcium chloride is increased, size distributions broaden and become multimodal. The decrease in size is consistent with reports that divalent cations induce conformational changes by the formation of intramolecular bridges between carboxylate moieties; multimodality indicates intermolecular interactions as well. Lowering the pH also promotes intermolecular interactions, with severe aggregation occurring below pH 4. The work demonstrates the utility of AsFlFFF in studies of the hydrodynamic behavior of amphiphilic macromolecules. © 1997 John Wiley & Sons, Inc. J Micro Sep9: 535–543, 1997

[1]  E. O’Loughlin,et al.  Molecular weight, polydispersity, and spectroscopic properties of aquatic humic substances. , 1994, Environmental science & technology.

[2]  R. Engebretson,et al.  Micro-organization in dissolved humic acids. , 1994, Environmental science & technology.

[3]  J. Zachara,et al.  Interaction of hydrophobic organic compounds with mineral-bound humic substances. , 1994, Environmental science & technology.

[4]  R. Wershaw.  MODEL FOR HUMUS IN SOILS AND SEDIMENTS , 1993 .

[5]  James J. Morgan,et al.  Effects of aqueous chemistry on the binding of polycyclic aromatic hydrocarbons by dissolved humic materials , 1993 .

[6]  A. Litzen.  Separation speed, retention, and dispersion in asymmetrical flow field-flow fractionation as functions of channel dimensions and flow rates , 1993 .

[7]  N. Funasaki.  Gel filtration chromatographic study on the self-association of surfactants and related compounds. , 1993, Advances in colloid and interface science.

[8]  P. Gschwend,et al.  The abundance, distribution, and configuration of porewater organic colloids in recent sediments , 1991 .

[9]  J. Giddings,et al.  Accurate molecular weight distribution of polymers using thermal field‐flow fractionation with deconvolution to remove system dispersion , 1989 .

[10]  K. Hunter,et al.  Competitive adsorption of phosphate on goethite in marine electrolytes , 1989 .

[11]  C. T. Chiou,et al.  Water solubility enhancement of some organic pollutants and pesticides by dissolved humic and fulvic acids. , 1986, Environmental science & technology.

[12]  R. Summers,et al.  Diffusion of humic acid in dilute aqueous solution , 1986 .

[13]  M. N. Myers,et al.  Extension of thermal field-flow fractionation to ultra-high (20 .times. 106) molecular weight polystyrenes , 1985 .

[14]  K. Tsutsuki,et al.  Molecular size distribution of humic acids as affected by the ionic strength and the degree of humification , 1984 .

[15]  James A. Davis,et al.  Adsorption of natural dissolved organic matter at the oxide/water interface , 1982 .

[16]  E. Thurman,et al.  Molecular size of aquatic humic substances , 1982 .

[17]  H. L. Ong,et al.  COAGULATION OF HUMIC COLLOIDS BY METAL IONS , 1968 .

[18]  J. B. Mooney,et al.  Pyrolytic Graphite Spectrographic Electrodes. , 1964 .

[19]  Helene Dérand,et al.  Aggregation Behavior of an Amphiphilic Graft Copolymer in Aqueous Medium Studied by Asymmetrical Flow Field-Flow Fractionation , 1996 .

[20]  D. Bursill,et al.  Gel permeation chromatography of humic acid Problems associated with sephadex gel , 1984 .

[21]  E. Tipping,et al.  The effects of adsorbed humic substances on the surface charge of goethite (α-FeOOH) in freshwaters , 1982 .

[22]  S. Waksman.  Humus: origin, chemical composition, and importance in nature , 1936 .