Abstract
(English)
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Two types of novel voltammetric probes, called Voltammetric In situ Profiling System (VIP System) and Sediment-water Interface Voltammetric In situ Profiling System (SIVIP System), have been developed within the project to allow in situ, real-time trace element measurements in the water column and at the sediment-water interface respectively of aquatic ecosystems. Both probes are based on novel gel integrated microsensor arrays which have been specifically developed to enable continuous, reproducible and reliable measurements of analytes in complex media without physical and chemical interferences of the test solution.
Developement of the VIP System has involved : i) a gel integrated Hg-plated microsensor array with 100 interconnected Ir-based microelectrodes build using thin-film and photolitographic technologies (CABE-IMT), ii) a submersible voltammetric probe based on advanced microprocessor and telemetric technologies (Idronaut-CABE), and iii) hardware, firmware and software for control of the whole system (Idronaut-CABE) (e.g. data transmission and acquisition, data processing, autonomous measurements following a pre-programmed cycle, maintenance operations, management and interfacing of an Idronaut Ocean Seven multiparameter probe to measure simultaneously depth, temperature, conductivity, salinity, dissolved O2, pH and Redox E). The VIP System has been thoroughly tested in laboratory (CABE) and in field conditions, i.e. freshwater (CABE), sea water (CABE-AMK) and mining boreholes (CABE) down to 120 m. At its present state, it can be used for real-time in situ measurements of the mobile fraction of Cu(II), Pb(II), Cd(II), Zn(II) at the ppt level as well as Mn(II) and Fe(II) at the ppb level with high reliability (e.g. standard deviation of max. 10 % were observed for unattended autonomous in situ trace metal measurements over 5 days). The VIP System is now commercialised by Idronaut.
Development of the SIVIP System has involve : i) a gel integrated Hg-plated microsensor arrays with 64 individually addressable lines of three Ir-based microelectrodes using technologies similar to those of the VIP microsensor (CABE-IMT), ii) a voltammetric probe based on powerful double multiplexing system and single potentiostat allowing simultaneous measurements over the 64 sensor lines (Idronaut-IMT-CABE), iii) a submersible microprofiler (Idronaut), and iv) hardware, firmware and software for control of the whole system (Idronaut-CABE). Laboratory tests have been performed to characterize and optimize the SIVIP System (CABE). The results have shown that : i) simultaneous measurements over the 64 sensor lines can be performed using a single potentiostat thanks to the powerful multiplexing system developed, ii) behavior of the individually addressable microsensor is in accordance with the theory, iii) good reproducibility and reliability, with standard deviations between 5 and 10%, are observed for the simultaneous mercury layer preparation and SWASV trace metal measurements over the 64 sensor lines, iv) multielement analysis can be performed simultaneously over the 64 sensor lines at the ppt level for Cu(II), Pb(II), Cd(II) and Zn(II). Systematic laboratory tests in sediment cores are now underway to define the optimum analytical conditions for in situ measurements of trace metals as well as Mn(II), Fe(II), S(-II) and O2 at the sediment-water interface.
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