Submersible voltammetric probes for in situ real-time trace element measurements in surface water, groundwater and sediment-water interface

Abstract

A summary of the state of the art in the development of two submersible voltammetric probes performed by us to allow continuous, real-time monitoring of trace elements (Cu(II), Pb(II), Cd(II), Zn(II) and Mn(II), Fe(II)) in natural aquatic ecosystems is given. The first one, called the voltammetric in situ (VIP) profiling system, allowed in situ measurements in surface water and groundwater down to 500 m. Its construction required the development of: (i) a gel-integrated, either single or interconnected, array microsensor, (ii) a submersible probe and (iii) hardware, firmware and software for control of the whole system: i.e. data transmission and acquisition, data processing and maintenance operations. The second system, called the sediment-water interface voltammetric in situ profiling (SIVIP) system, has been developed to allow real-time, high spatial resolution trace elements concentration profile measurements at the sediment-water interface. Its construction required the development of: (i) a gel-integrated microsensor array with 64 individually addressable lines, (ii) a voltammetric probe based on powerful double multiplexing system and single potentiostat allowing simultaneous measurements over the 64 sensor lines, and (iii) hardware, firmware and software for control of the whole system. A general description of both systems as well as examples of laboratory characterization and/or field applications are reported.

Voltammetric procedure for trace metal analysis in polluted natural waters using homemade bare gold-disk microelectrodes

“…Luther and co-workers demonstrated that the use of mercury-plated gold microelectrodes allows the in situ determination of, among others, Mn(II), Fe(II) and S(-II) in sediment porewaters [5][6][7][8][9][10]. In the same period, Buffle and co-workers focussed their micro-captors on Ir microelectrodes also plated with mercury for Zn, Pb, Cd and Cu analysis [11][12][13][14][15]. In this case, a monitoring system is introduced in the water column, though the voltammetric measurements are not really performed in situ because of the necessity for removing oxygen from the sample before analysis.…”

Detecting marine hazardous substances and organisms: sensors for pollutants, toxins, and pathogens

“…Voltammetric instruments are a promising tool for in situ measurements of trace metals (Howell et al, 2003). A commercially available voltammetric in situ profiling system (VIP) (Tercier et al, 1998;Tercier-Waeber et al, 1999) has been successfully applied for autonomous, continuous monitoring in estuarine and coastal marine waters for up to one week (Tercier et al, 1998;Howell et al, 2003) with detection limits for dynamic fractions of Cu(II), Pb(II), Cd(II), and Zn(II) at ppb level, for Mn(II) at ppt level. Based on the VIP, Tercier-Waeber et al (2005) have presented a Multi Physical-Chemical Profiler (MPCP) employing on gelintegrated voltammetric microsensors and a multi-channel voltammetric probe as well as advanced microprocessor.…”

Electrochemical techniques and sensors for ocean research

“…This film may range from a single molecular layer to several mm thick. Examples of materials used to modify electrodes include mercury for the polarographic determination of trace metals (Devitre et al, 1991), probably the most common electrode modification, conducting polymers (Dhawan et al, 1997), gels (Tercier-Waeber et al, 1998;Tercier-Waeber et al, 1999), polymers loaded with enzymes and redox mediators (Grundig et al, 1995;Bartlett et al, 1998;Cosnier et al, 1999), doped polymers (Trojanowicz et al, 1996), molecular constructions tethered to the electrode surface and nanostructured materials (Evans et al, 2002;Imokawa et al, 2006). The electrodes may be passive as in potentiometry or active as in amperometry and impedimetry.…”

“…labile Fe (Mikkelsen et al, 2006), Co (Vega and van den Berg, 1997), Ni, Sb, V, Se, Sn, U (van den Berg et al, 1991) and the list of species detected with electrochemical sensors will grow beyond H + (Reimers, 2007), dissolved oxygen, heavy metals where some of the sensors are at a technology readiness level of 7 with the detection of Cu, Pb and Cd concentrations at sub nM levels (Tercier-Waeber et al, 1999), carbonates (Choi et al, 2002), silicates (Lacombe et al, 2007), in situ speciation of Mn, Fe and in S compounds (Luther et al, 1998;Rozan et al, 1999Rozan et al, , 2000.…”