Fractionation of Humic Substances by Asymmetrical Flow Field-Flow Fractionation

Asymmetrical flow field-flow fractionation was used to investigate the effects of pH and ionic strength of the buffer, and the binding of polyaromatic hydrocarbons (PAHs) on the particle sizes of humic substances (HSs). Particle sizes were greater when HSs were present in acidic medium with phosphate buffer than when they were present in alkaline medium or in acidic medium with acetate buffer. The association of PAH did not lead to increase sizes of HSs. Bivalent calcium ion had a greater effect on the size than did monovalent sodium ion. Particle sizes in river water and seawater were mostly of the same magnitude of the standards HSs. Some larger particles (30–70 nm) were also found.