Microfabricated three-electrode on-chip PDMS device with a vibration motor for stripping voltammetric detection of heavy metal ions

Abstract

A microfabricated three-electrode on-chip device with a vibration motor for stripping voltammetric detection of Cd2+ and Pb2+ ions is introduced. Gold electrodes on a glass substrate are utilized as the counter electrode directly, as well as the working electrode with bismuth coating. The reference electrode is achieved by painting silver/silver chloride layer on the gold layer. Polydimethylsiloxane (PDMS) cover is bonded onto the glass substrate, organizing a compact module. A vibration motor in the device provides vibration as the alternate for stirring to improve detection limits and decrease deposition time. Cyclic voltammetry (CV) is performed with the on-chip reference electrode and a commercial liquid electrolyte Ag/AgCl electrode, showing that the potential shift is less than 20mV. Differential pulse stripping voltammetry (DPSV) is used to detect Cd2+ and Pb2+ ions. Linearity is well defined from 10µg/L to 80µg/L for both ions. Detection limits for Cd2+ and Pb2+ ions are 0.7µg/L and 1.2µg/L, respectively, at 325s deposition without vibration; the limits are 0.11µg/L and 0.25µg/L at 120s deposition with vibration. The reliability is verified by detecting Cd2+ and Pb2+ concentrations of natural water samples and comparing with the results obtained from inductively coupled plasma mass spectrometry (ICP-MS).