POTENTIOMETRIC STRIPPING ANALYSIS OF COPPER USING CYSTEINE MODIFIED MERCURY FILM ELECTRODE

Cysteine modified mercury film electrode is prepared by electrochemica l in situ co-deposition of mercury and cysteine on glassy carbon, and its application in potentiometric stripping analysis (PSA) of copper(I I) is presented. Copper is potentiometrically deposited at -0.9 V (ver sus Ag/AgCl) on cysteine modified mercury film electrode and yields tw o 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 whic h adsorbs at the mercury electrode surface. Copper(I)-cysteine adsorpt ion on mercury film adheres to a Langmuir model. The relative standard deviation of the stripping times at copper(II) concentration of 1 x 1 0(-6) M is 1.5% (n = 15) using the same electrode, and is 2.9% when us ing six modified electrodes prepared at different times. With a deposi tion time of 2 min, the detection limit of copper(II) is 5 x 10(-10) M using dissolved oxygen as the oxidant. (C) 1998 Elsevier Science B.V. All rights reserved.