title: Direct determination of tellurium and its redox speciation at the low nanogram level in natural waters by catalytic cathodic stripping voltammetry.
abstract: Tellurium is one of the elements recently identified as technologically critical and is becoming a new emergent contaminant. No reliable method exists for its determination in environmental samples such as natural waters. This gap is filled by the method described here; it allows the rapid detection of trace concentrations of Te(IV) and Te(VI) in surface waters by differential pulse cathodic stripping voltammetry. It is based on the proton reduction catalysed by the absorption of Te(IV) on the mercury electrode. Under our conditions (0.1 mol L(-1) HCl) a detection limit of about 5 ng L(-1) for a deposition time of 300 s is achieved. Organic matter does not represent a problem at low concentrations; higher concentrations are eliminated by adsorptive purification. Tellurium occurs primarily as Te(IV) and Te(VI) in natural waters. Thus, determining total Te requires the reduction of Te(VI) that it is not electroactive. A number of reduction procedures have been carefully evaluated and a method based on the addition of TiCl3 to the acidified samples has been proven to reduce Te(VI) at the trace level to Te(IV) reliably and quantitatively. Therefore, the procedure described allows the direct determination of total Te and its redox speciation. It is flexible, reliable and cost effective compared to any possible alternative method based on the common preconcentration-ICPMS approach. It is readily implementable as a routine method and can be deployed in the field with relative ease.
authors.affiliation: Bibliothèque Nationale de Luxembourg, Annexe Kirchberg, 31, Boulevard Konrad Adenauer, L-1115 Luxembourg, Luxembourg.
authors.forename: Marc
authors.initials: M
authors.lastname: Biver
authors.affiliation: Laboratoire de Chimie Analytique, UMR-CNRS 6521, Université de Bretagne Occidentale, 6 Avenue V. Le Gorgeu, CS 93837, F-29238 Brest Cedex 3, France.
authors.forename: François
authors.initials: F
authors.lastname: Quentel
authors.affiliation: Institute F.-A. Forel, University of Geneva, 10 Route de Suisse, CH-1290 Versoix, Switzerland. Electronic address: montserrat.filella@unige.ch.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Filella
keywords: Differential pulse cathodic stripping voltammetry; Freshwaters; Seawater; Tellurium; Voltammetry