Application of self-assembled monolayer-based electrode for voltammetric determination of copper

A gold electrode modified with a self-assembled monolayer (SAM) of 3-mercaptopropionic acid (MPA) was evaluated as a highly sensitive voltammetric sensor for copper ions. As demonstrated by cyclic voltammetric experiments, the SAM-based electrode showed an attractive ability to efficiently preconcentrate trace of copper(II) from solution, allowing a very simple and reproducible method for copper determination at levels down to ppq (parts per quadrillion). The influence of various experimental parameters on the sensor response was investigated (i.e. pH, supporting electrolyte, pre-concentration time). The MPA modified electrode presented a wide linear response range between 1.0 x 10(-12) and 1.0 x 10(-9) mol l(-1) for copper(II), with a detection limit of 1.8 x 10(-14) mol l(-1) (1.1 pg l(-1)) using 10 min of pre-concentration. Moreover, this electrode also presented excellent repeatability, showing a relative standard deviation of 3.2% for a series of nine successive measurements of a 1.0 x 10(-11) mol l(-1) Cu2+ solution. This new sensor was successfully applied for the determination of copper in sugar cane spirits and mineral water samples. (C) 2004 Elsevier Ltd. All rights reserved.