Selenium polyatomic anions

The group of the chalcogens sulfur, selenium and tellurium is a typical triad of the more electronegative nonmetals with relatively high-ionization energies, relatively strong element-element bonds and a clear tendency to form mono-and polyatomic anions (Table 1). 

Like their sulfur congener, selenium and tellurium can form polyatomic cations and anions in many compounds. 

It was stressed by the participants using ICP-MS that polyatomic interferences from Cl can be removed to improve the accuracy of selenite determination ways to do so are (i) to dilute the original sample after pre-concentration of the selenite species, (ii) to modify the plasma conditions by adding N2 carrier to the plasma or (iii) to use anion-exchange chromatography to separate chloride from the selenium species. When diluting and pre-concen-trating on a pre-column, care should be taken that selenite is quantitatively recovered. The use of silver nitrate to remove chloride is suspected to affect selenite. 

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