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Electrochemical stripping analysis has long been recognizedas a powerful technique for trace heavy metal detectionin environmental samples. Its remarkable sensitivity isattributed to the combination of an effective preconcentrationstep with pulse measurement techniques that generatesan extremely favorable signal-to-background ratio. Twoelectrode systems, the mercury film electrode and the hangingmercury drop electrode, have been traditionallyemployed for achieving high reproducibility and sensitivityof the stripping technique [1–3]. The excellent performancesof mercury-based electrodes are due to their uniqueability to preconcentrate target metals during the accumulationstep [4]. Using anodic stripping voltammetry (ASV),the metals are cathodically preconcentrated into the mercuryelectrode by amalgam formation and then strippedout of the electrode by applying an anodic potential scan(e.g. Cd, Pb, and Zn) [5]. In certain cases, where the metalsform intermetallic compounds, react irreversibly or cannotform an amalgam (e.g. Co and Ni), the adsorptive cathodicstripping protocol is employed. A complexing agent likedimethylglyoxime (DMG) is added to the measuring solution,forming a complex with the target metal. This complexis then subsequently accumulated onto the electrodesurface and stripped off voltammetrically or chronopotentiometrically[6–9]. The growing needs for on-site monitoring of prioritymetal pollutants have led to the development of flow stripping
systems [10–13] and more recently to the introduction
of hand-held metal analysers [14,15]. A more attractive
in situ approach is to immerse the stripping electrode
directly in the natural matrix (e.g. natural waters or industrial
wastes). However, despite the excellent performance of
mercury electrodes, future regulations and occupational
health considerations may severely restrict or even ban
the use of mercury as an electrode material because of its
high toxicity. Indeed, mercury compounds that are characterized
by a high toxicity, like mercuric ions (Hg2+) or
organic compounds (e.g., dimethyl mercury), can be
formed by immersion of metallic mercury (Hg0) in natural
waters in the presence of dissolved oxygen or by the mean
of bacterial activity. A few years ago, Yosypchuk et al. [16]
described the use of ‘‘non-toxic’’ electrodes of solid mercury
amalgams (Ag, Cu, and Au) for stripping analysis.
However, despite these electrode materials can be considered
as ‘‘non-toxic’’ for laboratory use, it is not the case
for environmental on-site monitoring. Indeed, mechanical
and/or bacterial corrosion can lead to mercury release from
amalgams, as mercuric ions or metallic mercury.
New alternative electrode materials are then highly
desired to develop ‘environmentally friendly’ stripping
sensors suitable for on-site heavy metals monitoring.
Numerous solid electrode materials, including gold [17],
carbon-based [9] or iridium [18], have been tested, but
their overall performances have never approached those
of mercury. Recently, Wang et al. [19–21], Hutton et al.
[22], Kro´ licka et al. [23] and Baldo et al. [[24] introduced
the use of bismuth thin films, in situ electrodeposited onto
glassy carbon or platinum substrates, for use in stripping
analysis of trace heavy metals. The behaviour of the bismuth
film electrode (BiFE) was shown to compare
favourably to that of mercury electrodes, with its attractive
properties including high sensitivity, well-defined
stripping signals, good resolution of neighbouring peaks
(e.g. Cd, Pb, and Zn), large cathodic potential range,
and insensitivity to dissolved oxygen in contrast to mercury
electrodes. This latter characteristic is an essential
property for on-site monitoring. In addition, bismuth is
a more ‘environmentally friendly’ material with a low toxicity
and is widely used in medicine and cosmetics. However,
in situ procedure for BiFE preparation, consisting of
Bi3+ addition to the sample and simultaneous deposition
of the bismuth film and target metals on the substrate,
is not suitable for on-site monitoring. In a previous study
[25], we demonstrated that economic bismuth film electrodes
(BiFE) prepared by electrodeposition onto a copper
substrate offer an alternative to mercury electrodes
for anodic stripping analysis of trace heavy metals, such
as cadmium, lead and zinc. In this paper, the application
of BiFE to trace nickel analysis by the adsorptive stripping
voltammetry (AdSV) technique is presented. BiFE
were prepared by electrodeposition of a thin bismuth film
onto a copper substrate that presents several advantages
compared to platinum and glassy carbon substrates, previously
tested in literature reports. Indeed, copper is a
metal far from expensive, easy to manufacture and lends
itself to the realization, by lithography, of microsensors
of various sizes and geometries. It would then be easy
to adapt these
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