Ex situ preparation of bismuth film microelectrode for use in electrochemical stripping microanalysis

A study on the preparation and characterisation of ex situ formed bismuth film microelectrodes (BiFMEs) is presented, focusing in particular on their stable and reliable stripping electroanalytical performance. The potentiostatic pre-plating of the bismuth film onto a single carbon fibre substrate microelectrode was investigated and optimised with the aim of achieving long-term electrochemical and mechanical film stability. Several important film preparation parameters, such as plating agent, potential and time, and composition of the plating solution were examined with respect to the current signals of 40 consecutive adsorptive cathodic stripping voltammetry (AdCSV) measurements of trace Co(II) as model analyte. A comparison, also presented, of the stripping performance between bismuth and mercury film microelectrodes revealed a distinct practical advantage of the BiFME. The resulting optimised BiFME exhibited, besides excellent long-term film functional stability, attractive stripping analytical performance. Employing AdCSV with square-wave voltammetric detection, highly linear behaviour was obtained in the examined concentration range, with limits of detection of 70 and 90 ng/l and excellent reproducibility with 2.4 and 2.9% relative standard deviation at the 1 μg/l level (n = 10), for Co(II) and Ni(II), respectively, achieved using only 2 min preconcentration time in the presence of dissolved oxygen. In addition, the performance of the proposed ex situ prepared BiFME in both anodic stripping voltammetry (ASV) of Cd(II) and Pb(II) and in AdCSV of Co(II) and Ni(II) from the same test solution is demonstrated. The ex situ prepared BiFME represents a promising non-toxic, environmentally friendly microsensor for detection at microlocations and in microvolumes, in particular where in situ bismuth film electrode preparation is inappropriate, inconvenient or impossible.