VALUE-ADDED PRODUCTS FROM COTTONSEED
Location: Commodity Utilization Research
Title: Capillary electrophoresis application in metal speciation and complexation characterization
Submitted to: Journal of Capillary Electrophoresis
Publication Type: Book / Chapter
Publication Acceptance Date: January 9, 2012
Publication Date: November 13, 2012
Citation: Wang, Y., He, Z., Waldrip, H.M. 2012. Capillary electrophoresis application in metal speciation and complexation characterization. In: He, Z., editor. Capillary Electrophoresis: Fundamentals, Techniques and Applications. New York, NY:Nova Science. p. 117-130.
Interpretive Summary: The mobility, bioavailability, accumulation and toxicological properties of metals are all very dependent on the chemical forms in which they occur in the environment. Since the 1990’s, metal speciation has rapidly gained importance due to its impact on environmental chemistry, toxicology, and biomedical sciences. Capillary electrophoresis (CE) is amenable to the separation of metal ionic species and the characterization of metal-ligand interactions. This chapter reviews and discusses CE applications in (1) iron (Fe) speciation, (2) reactions of manganese (Mn) with organic compounds, and (3) interaction of lead (Pb) with humic substances (HS). Through these representative case studies, this chapter aims to promote broader applications of CE technology in speciation and reactions of metal with bioactive and natural organic molecules in the environment.
Capillary electrophoresis is amenable to the separation of metal ionic species and the characterization of metal-ligand interactions. This book chapter reviews and discusses three representative case studies in applications of CE technology in speciation and reactions of metal with organic molecules in the environment. As both Fe(II) and Fe(III) are present in nature, CE coupled with pre- and on-column complexation provides an effective means of identification and quantification of both total Fe and the two specific Fe forms in various environmental and industrial samples. Large-volume sample stacking (LVSS) for the on-line preconcentration, such as for Fe[PCDA]22- and Fe[PCDA]2- complexes, is a technology that can enhance the detection sensitivity of metal speciation. The application of CE in metal-ligand reactions is exampled by detailed review of the reactions and dissolution of Mn(III, IV) (hydr)oxides with small organic compounds and on-column complexation of Pb2+ with macromolecular humic substances. With an improved CE approach, a Mn(III/II) citrate autocatalytic cycle was identified, which is the first of its kind proposed for a Mn-based redox system. When HS was used as a background electrolyte, HS-reagent interactions could be characterized, as electropherograms of Pb2+ with HS revealed the formation of two complexes (Pb-HS fractions I and II) that were attributed to structural differences in the fractions. In addition to metal speciation, CE can also be used to explore the reaction kinetics and mechanism of metal-ligand complexation.