Binding capacity of casein to lead and voltammetric speciation of lead in milk with a nafion coated electrode

The complexation of lead with casein (CS) was studied by several voltammetric methods, as was the selective determination and speciation of lead in milk. First, cyclic voltammetry (CV) was used to examine the influence of adsorbed casein and complexation on the electrochemical response of lead at neutral and alkaline pHs. Second, by titrating solutions of CS with lead, two mathematical methods based on differential-pulse anodic stripping voltammetry (DPASV) for evaluating the binding properties of CS to lead were compared with a hanging mercury drop electrode (HMDE) and a Nafion-covered mercury film electrode (Nf-MFE). In all cases, the conditional stability constants for the Pb-CS complex agreed well and were close to log β′ = 5.5 at pH 7.0. Finally, lead was directly determined with the chemically modified electrode in acidified samples (≈pH 0.3) of whole and skim milk at the ng/ml level, with no need for preliminary acid digestion.

[1]  G. S. Wilson,et al.  Pulsed amperometric detection of glucose in biological fluids at a surface-modified gold electrode. , 1989, Analytical chemistry.

[2]  S. Mannino,et al.  Studies on the complexation properties of casein with lead by potentiometric stripping analysis. , 1988, The Analyst.

[3]  T. Florence,et al.  Application of polymer-coated glassy carbon electrodes to the direct determination of trace metals in body fluids by anodic stripping voltammetry. , 1987, Analytical chemistry.

[4]  Graeme E. Batley,et al.  Application of polymer-coated glassy carbon electrodes in anodic stripping voltammetry , 1987 .

[5]  S. Mannino,et al.  Measurement of the binding capacity of casein for copper by potentiometric stripping analysis , 1987 .

[6]  J. Wang,et al.  Selectivity and sensitivity improvements at perfluorinated ionomer/cellulose acetate bilayer electrodes. , 1986, Analytical chemistry.

[7]  T. Florence,et al.  Electrochemical approaches to trace element speciation in waters , 1986 .

[8]  C. Eckhert.  Isolation of a protein from human milk that enhances zinc absorption in humans. , 1985, Biochemical and biophysical research communications.

[9]  R. B. Smart,et al.  Differential pulse anodic stripping voltammetry of cadmium(II) with a rotating membrane-covered mercury film electrode , 1984 .

[10]  B. Lönnerdal,et al.  Iron, copper, zinc, calcium, and magnesium in human milk fat. , 1984, The American journal of clinical nutrition.

[11]  B. Lönnerdal,et al.  Distribution of Trace Elements and Minerals in Human and Cow's Milk , 1983, Pediatric Research.

[12]  G. Marletta,et al.  Preliminary investigation on the balance of lead and cadmium content in milk and its by-products , 1983, Zeitschrift fur Lebensmittel-Untersuchung und -Forschung.

[13]  L. Hurley,et al.  Zinc and copper binding proteins in human milk. , 1982, The American journal of clinical nutrition.

[14]  B. Lönnerdal,et al.  Zinc, copper, calcium, and magnesium in human milk. , 1982, The Journal of pediatrics.

[15]  I. Ruzic.  THEORETICAL ASPECTS OF THE DIRECT TITRATION OF NATURAL WATERS AND ITS INFORMATION YIELD FOR TRACE METAL SPECIATION , 1982 .

[16]  G. Harzer,et al.  Binding of zinc to casein. , 1982, The American journal of clinical nutrition.

[17]  M. Shuman,et al.  Chemical constants of metal complexes from a complexometric titration followed with anodic stripping voltammetry , 1973 .

[18]  Richard S. Nicholson,et al.  Theory and Application of Cyclic Voltammetry for Measurement of Electrode Reaction Kinetics. , 1965 .