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Effect of Albumin on Underpotential Lead Deposition and Stripping on Ag‐RDE
Author(s) -
Hepel Maria
Publication year - 2005
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.200503288
Subject(s) - adsorption , chemistry , desorption , bovine serum albumin , analytical chemistry (journal) , gibbs free energy , charge transfer coefficient , molecule , stripping (fiber) , electrode , inorganic chemistry , electrochemistry , cyclic voltammetry , chromatography , materials science , organic chemistry , physics , quantum mechanics , composite material
Abstract The effects of adsorption of bovine serum albumin (BSA) on the electrodeposition and stripping of Pb‐adatoms at a Ag‐RDE in acetate buffer solutions have been studied. The adsorbed BSA molecules have been found to inhibit the lead adsorption process. A decrease in the apparent charge transfer coefficient α for Pb‐adatom desorption from 0.39 to 0.34 in the presence of adsorbed BSA molecules has been attributed to the electric field screening by multiply charged BSA in the adsorption film, since no major lateral interactions between Pb and BSA have been observed. The kinetics of BSA adsorption on a Ag‐RDE was followed by Pb‐adatom probe technique in the range of low BSA coverage, 0< θ BSA <0.4. The adsorption ( k 1 ) and desorption ( k −1 ) rate constants were determined as follows: k 1 =2.42×10 −4 cm/s, k −1 =1.12×10 −14 mol cm −2 s −1 . The equilibrium constant for BSA adsorption on Ag electrode from 3×10 −8 M BSA solution, also determined from the Pb‐adatom probe method, was: K ads =2.17×10 7 L/mol and the corresponding Gibbs free energy of adsorption: Δ G ° ads =−9.99 kcal/mol (−41.85 kJ/mol). The formation of BSA films on Ag electrodes has been confirmed by EQCN mass transients and AFM imaging. It follows from these experiments that BSA molecules adsorb in horizontal orientation and form a film on Ag with 4 nm thickness.