TITLE:
Electrochemical Study of Cadmium (II) Complexation with Cysteine
AUTHORS:
Sheriban Ramani, Biserka Raspor, Tahir Arbneshi
KEYWORDS:
Cysteine; Cadmium-Cysteinate Complex; Prepeak; Mass Balance Equations; Stoichiometric Stability Constants; Differential Pulse (DP) Excitation Mode
JOURNAL NAME:
American Journal of Analytical Chemistry,
Vol.4 No.10,
October
11,
2013
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℃.