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Mercury compounds in water – a hidden threat?

Analytical method for the determination of mercury compounds in water in the ng/kg range developed

PTBnews 1.2019
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environmental analysis companies and laboratoriesh

Mercury is toxic for many organisms. In the environment, mercury occurs everywhere and in various chemical forms. These mercury compounds are then absorbed by organisms via food, water and air. To assess the risks exhaustively, all forms of mercury as well as their possible conversion products must be known and determined. A traceable analytical method has therefore been developed to enable the quantitative determination of methylmercury and inorganically bound mercury down to the ng/L range.

Taking a water sample from the River Oker in Braunschweig

Mercury occurs in various forms and is very mobile. Most of the mercury comes from natural sources such as volcanic eruptions. But anthropogenic sources such as the combustion of fossil fuels also lead to concentrations that can be very high locally. Due to various conversion processes, the toxicity of mercury can increase further. This is, for example, the case for methylmercury. Methylmercury finds its way into the body via water and food (in particular fish) and may damage the nervous system and the kidneys.

For this reason, the “Minamata Convention on Mercury” was created in 2013, with the aim of reducing worldwide mercury emissions and establishing comparable analytical and control mechanisms.

At PTB, an analytical method has now been developed to determine organic methylmercury and inorganic mercury in water. This method consists in preparing the samples by derivatization into a form that is more easily accessible for separation and extraction into an organic solvent.

This extract is subjected to separation in a gas chromatograph. The analytes are then detected by means of mass spectrometry. With the aid of the species-specific isotope dilution method, the respective concentrations can be determined down to the ng/L range.

In the European Water Framework Directive, mercury compounds are classified as priority hazardous substances, even though the currently valid Environmental Quality Standards (EQS) of 0.07 μg/L in surface waters and 20 μg/ kg in biota (fish, bivalve mollusks, algae, etc.) relate exclusively to the total mercury content.

The new method developed within the scope of the European Metrology Research Programme (Project ENV51) complements the requirements of the directive. It provides a sensitive and comparable measurement method to determine mercury species in water, which can be used to perform a full risk assessment taking the species distribution as well as possible conversion processes into account.


Claudia Swart
Department 3.2
Phone: +49 531 592-3220
Opens window for sending emailclaudia.swart(at)ptb.de