Portable Analysis of Environmental Samples for Transition Metals

The Metrohm 797 VA Computrace is a modern PC controlled instrument that is capable of realising sub μg l-1 detection limits for a variety of transition metals. The compact footprint of the 797 means that it can be used for at-line or portable analysis in the back of for example a mobile laboratory. The compact nature allows for instant analyses in the field, important for example if a particular water stream is being examined for breach of

consent limits. Apart from the determination of the total concentration, Voltammetry can also distinguish between the different oxidation stages of various metal ions. Voltammetry is an essential tool for any research group interested in differentiating between the free and bound metal ions to make statements about the biological availability of heavy metals.

Typically detection limits that have been determined for a number of important metals are: Arsenic 100 μg l-1, Chromium 25 μg l-1, Copper 50 μg l-1, Iron 50 μg l-1, Lead 50 μg l-1, Mercury 100 μg l-1, Platinum 0.1 μg l-1, Uranium 25 μg l-1 and Zinc 50 μg l-1.

The power of Voltammetry is evident when the sample is of a high ionic nature; high background conductivity poses no problems unlike with Spectroscopic techniques. Key points include the low price (currently under £12k with intelligent Dosinos for addition of reagents), the size (less than a metre footprint), recognised technique (with many official standard methods), standard addition calibration (that takes into account the particular background matrix) and the outstanding detection limits.