Capillary zone electrophoresis with UV‐scanning detection for the analysis of metal species and their organic binding partners in biological systems

Abstract

SummaryA capillary zone electrophoretic method with UV-scanning detection for the separation and identification of both free ligands and metal species is presented. The electrophoretic behavior of naturally occurring binding partners such as organic acids and amino acids was studied and compared with their metal-complexes. Copper(I1) complexes of citrate and amino acids showed decreased electrophoretic mobilities and altered UV spectra. The optimized method was validated on ultrafiltered cow's milk and human milk samples. In cow's milk six low molecular weight substances, including citrate, orotate, and hippurate, could be separated. Metal supplementation with Cu(II), Ni(II), or Zn(I1) decreased not only the citrate peak but also the orotate signal and in the case of copper(I1) supplementation a new signal for the copper(I1)-citrate complex appeared. In human milk samples various amino acids such as glutamate, phenylalanine, tyrosine, and tryptophan could be identified besides citrate. The electrophoretic mobilities and peak areas of the amino acids were also influenced by the metal supplementation.

Reaction of aqueous Cu–Citrate with MnO2 birnessite: Characterization of Mn dissolution, oxidation products and surface interactions

“…To monitor the oxidation pathway and the oxidation products, we elected to use a capillary electrophoresis unit (Beckman Coulter P/ACE MDQ Capillary Electrophoresis System). The methods by Theobald and Dunemann (1996) for Cu-citrate and by (Wang et al (2003) were slightly modified (see Supporting Information) in this study for the determination of the oxidation intermediates and products.…”

Capillary Zone Electrophoresis of some organic acids in milk whey

“…A recent paper describes orotic acid analysis by an enzymatic microcalorimetric method [6]. CZE has hitherto been applied to only the qualitative study of minor organic species in the whey of cow's and human milk [7]. In a another recent paper [8] the CZE method was used for determination of relevant organic acids in diary products.…”

Bio-inorganic speciation analysis by hyphenated techniques

“…Since speciation of trace elements affects their bioavailability, they should be present in milk not only in appropriate amounts but also in specific forms. 360,365 Milk is analyzed after the elimination of lipids by centrifugation at 3000 rpm for 30 min at 4-5 °C. Speciation of trace elements in human milk has been the subject of three fairly comprehensive multielement studies.…”

“…360 Comparisons between elemental speciation in human and cow milk were made. 365 Casein (a mixture of a-, b-and k-casein) is the major milk protein. The resulting whey is injected on to the column; the precipitation of casein with 1 M acetate is optional.…”