Microfabricated chip integrating a bismuth microelectrode array for the determination of trace cobalt(II) by adsorptive cathodic stripping voltammetry

Abstract

This work presents the determination of trace Co(II) by adsorptive cathodic stripping voltammetric (AdCSV) using a 3-electrode microdevice featuring an integrated bismuth microelectrodes array (Bi-MEA). The microdevice was fabricated through sputtering and photolithography and consisted of thin Ag and Pt films (serving as reference and counter electrode, respectively), while the working transducer was a microelectrode array composed of 625 bismuth microdisks (10μm in radius and interelectrode distance of 200μm). Exploiting the superior performance of Bi-MEA in quiescent solutions at low supporting electrolyte concentration, the AdCSV determination of Co(II) after its complexion with dimethylglyoxime (DMG) was conducted in the presence of only 1.0×10−3molL−1 ammonia buffer and 30s preconcentration without stirring. The microfabricated Bi-MEAs were characterized by cyclic voltammetry and scanning electron microscopy, while their improved analytical characteristics (low ohmic drop and high mass transport) were revealed after a thorough comparison with bismuth macro-electrodes. Besides, other experimental variables related to Co(II) determination (the DMG concentration, the preconcentration potential, the preconcentration time) were studied in detail. The limit of detection for Co(II) was 0.18μgL−1. These microdevices were successfully applied to the analysis of Co(II) in a spiked mineral water sample and a certified lake water sample. This ready-to-use microsensor overcomes the drawbacks of existing electroplated electrodes, enabling AdCSV determination of trace Co(II) for on-site monitoring.