AJAC  Vol.4 No.10 , October 2013
Electrochemical Study of Cadmium (II) Complexation with Cysteine
Abstract: The complexation of Cd with cysteine has been investigated at pH ~9, and in constant ionic medium 0.59 M NaNO3 and borate buffer. Reduction signals of the hydrated Cd2+ and Cd-cysteinate complex were resolved on the potential scale during amperometric titration of 2 × 10-6 M Cd2+ with cysteine and cysteine with Cd2+, in a differential pulse (DP) mode on HMDE. The 1:1 molar ratio of Cd2+ to cysteine, and cysteine to Cd2+, was defined for Cd-cysteinate complex formed under the defined conditions. The appearance of the prepeak on the Cd-cysteinate reduction signal is showed, as the result of cysteine adsorption in reduced form. From the mass balance equations, the stoichiometric stability constants of Cd-cysteinate complex were calculated. Under various experimental conditions, comparable log K values were obtained. The grand average log K = 7.83 M-1 refers to 0.59 M ionic strength and 23℃.
Cite this paper: S. Ramani, B. Raspor and T. Arbneshi, "Electrochemical Study of Cadmium (II) Complexation with Cysteine," American Journal of Analytical Chemistry, Vol. 4 No. 10, 2013, pp. 577-583. doi: 10.4236/ajac.2013.410068.

[1]   A. Cole, C. Furnival, Z. X. Huang, D. Cerijones, P. M. May, G. L. Smith, J. Whittaker and D. R Williams, “Computer Simulation Models for the Low-Molecular-Weight Complex Distribution of Cadmium (II) and Nikel (II) in Human Blood Plasma,” Inorganica Chimica Acta, Vol. 108, No. 3, 1958, pp. 165-171.

[2]   D. Hynek, L. Krejcova, J. Sochor, J. Natalia Cernei, J. Kynicky, V. Adam, L. Trnkova, J. Hubalek, R. Vrba and R. Kizek, “Study of Interactions between Cysteine and Cadmium(II) Ions using Automatic Pipetting System OffLine Coupled with Electrochemical Analyser,” International Journal of Electrochemical Science, Vol. 7, No. 3, 2012, pp. 1802-1819.

[3]   R. G. Pearson, “Hard and Soft Acids and Bases,” Journal of the American Chemical Society, Vol. 85, No. 22, 1963, pp. 3533-3539.

[4]   T. E. Creighton, “Proteins Structures and Molecular Properties,” 2nd Edition, Freeman, W. H. and Co., New York, 1993.

[5]   M. D. Walker and D. R. Williams, “Thermodynamic Considerations In Co-Ordination. Formation Constants for Cadmium (II)-Amino-acid Complexes as Determined by Glass and Soil-State Cadmium-Electrode Potentiometry,” Journal of the Chemical Society, Dalton Transactions, Vol. 1186, 1974, pp. 1186-1189.

[6]   L. Wagner-Roos, H. Zahn, J. M. Séquaris and P. Valenta, “Polarographic Investigations on the Complexation of Cadmium and Zinc by Thiol Peptides,” Toxicological and Environmental Chemistry, Vol. 22, No. 1-4, 1989 pp. 77-90.

[7]   M. Calvin, “Mercaptans and Disulfides,” In Glutathione, Academic Press, Inc., New York, 1954, pp. 8-11.

[8]   NIST Standard Reference Database 46 Version 5.0. NIST Critically Selected Constants of Metal Complexes, 1995.

[9]   S Nyberg and L. Zhou, “Polarography as a Tool in Peptide and Protein Analysis: Studies on Metal-Chelating Substances Included by Cadmium in the Algae Pheodactylum tricornutum and the Graminae Agrosits Capillaries,” Ecotoxicology and Environmental Safety, Vol. 32, No. 2, 1995, pp. 147-153.

[10]   J. Buffle, “Complexation Reactions in the Aquatic Systems,” An Analytical Approach, Wiley and Sons, New York, Chapter 9, 1988, pp. 467-563

[11]   M. Esteban, C. Arino and J. M. Díaz-Cruz, “Metal Complexation by Electroanalytical Techniques: Hard- and Soft-Modelling Approaches,” Contributions to Science, Vol. 2 No. 3, 2003, pp. 359-373.

[12]   H. P. Van Leeuwen, J. Buffle and M. Lovric, “Reactant Adsorption in Analytical Pulse Voltammetry,” Pure and Applied Chemistry, Vol. 64. No. 7, 1992, pp. 1015-1028.

[13]   F. Montserrat and M. Raewyn, “Town, Determination of Metal Ion Binding Parameters for Humic Substances Part 1. Application of a Simple Calculation Method for Extraction of Meaningful Parameters from Reverse Pulse Polarograms,” Journal of Electroanalytical Chemistry, Vol. 485, No. 1, 2000, pp. 21-33.

[14]   R. C. Kapoor and B. S. Aggarwal, “Principles of Polarography,” John Wiley and Sons, 1991.

[15]   T. Vilarino, I. Brandariz, S. Fiol, J. Lopez-Fonseca and M. Sastre de Vicente, “Complexation of Cd2+ by cysteine at ionic strength of 0.7 M studied by differential pulse polarography,” Bulletin des Sociétés Chimiques Belges, Vol. 102, No. 11/12, 1993, pp. 699-707.