Abstract

In this paper in situ bismuth, antimony, tin modified electrodes and combinations thereof are explored towards the model target analytes cadmium(II) and lead(II), chosen since they are the most widely studied, to explore the role of the underlying electrode substrate with respect to boron-doped diamond, glassy carbon, and screen-printed graphite electrodes. It is found that differing electrochemical responses are observed, dependent upon the underlying electrode substrate. The electrochemical response using the available range of metallic modifications is only ever observed when the underlying electrode substrate exhibits relatively slow electron transfer properties; in the case of fast electron transfer properties, no significant advantages are evident. Furthermore these bismuth modified systems which commonly employ a pH 4 acetate buffer, reported to ensure the bismuth(III) stability upon the electrode surface can create create a problem when sensing at low concentrations of heavy metals due to its high background current. It is demonstrated that a simple change of pH can allow the detection of the target analytes (cadmium(II) and lead(II)) at levels below that set by the World Health Organisation (WHO) using bare graphite screen-printed electrodes.

Highlights

  • The mercury film and related electrodes were the backbone of early electrochemistry, for the sensing of metal ion species.[1]

  • We reveal that a simple pH change of the electrolyte/sensing solution utilising a bare screen-printed graphite electrodes (SPEs) can give rise to optimal electroanalytical performances and questions the need to modify an electrode substrate in the first place, due to the capability of a bare SPE to sense to below the concentration levels set by the World Health Organisation (WHO) for lead(II) and cadmium(II)

  • Recent work has reported the beneficial modification of electrode materials, such as that reported by Toghill et al.[61] describing the modification of a boron doped diamond electrode (BDDE) with antimony(III) for the sensing of lead(II) and cadmium(II)

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Summary

Introduction

The mercury film and related electrodes were the backbone of early electrochemistry, for the sensing of metal ion species.[1]. Paper by different regulatory agencies indicate that antimony is much less toxic than mercury and antimony-film electrodes are proposed to be more environmentally-friendly than their mercury counterparts.[26,27] Interestingly and most notably, antimony-film electrodes have been constructed utilising a microelectrode as the underlying electrode substrate reporting detection limits of 1.9 and 3.1 μg L−1 for the sensing of cadmium(II) and lead(II) respectively.[28] ESI Table 1† provides a thorough literature overview of the reports of the use of antimony films. In this paper the exploration of the electroanalytical detection of lead(II) and cadmium(II) in aqueous solutions with modifications of the underlying electrode surface with the reported electrocatalytic surfaces of antimony(III), bismuth(III) and tin(II) in situ modified electrodes and their combinations. Such work is of key importance for those concerned with the development of disposable metal sensors

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