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

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 (BiMEA). 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 (10 pin in radius and interelectrode distance of 200 lam). 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 x 10(-3) mol L-1 ammonia buffer and 30 s 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 0.18 mu g L-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. (C) 2016 Elsevier B.V. All rights reserved.