Potentiometric stripping analysis of copper using cysteine modified mercury film electrode Original Research Article

Cysteine modified mercury film electrode is prepared by electrochemical in situ co-deposition of mercury and cysteine on glassy carbon, and its application in potentiometric stripping analysis (PSA) of copper(II) is presented. Copper is potentiometrically deposited at −0.9 V (versus Ag/AgCl) on cysteine modified mercury film electrode and yields two highly enhanced potentiometric stripping signals at +0.05 and −0.16 V. The improvement on limits of detection over unmodified mercury film electrode is attributed to the formation of copper(I)–cysteinate which adsorbs at the mercury electrode surface. Copper(I)–cysteine adsorption on mercury film adheres to a Langmuir model. The relative standard deviation of the stripping times at copper(II) concentration of 1×10−6 M is 1.5% (n=15) using the same electrode, and is 2.9% when using six modified electrodes prepared at different times. With a deposition time of 2 min, the detection limit of copper(II) is 5×10−10 M using dissolved oxygen as the oxidant.