The selective determination of halogens and sulphur in solution by atmospheric-pressure helium microwave-induced plasma emission spectrometry coupled to an electrothermal introduction system

Instrumentation is described for the direct determination of Cl, Br, I and S in dissolved samples. A tantalum furnace is coupled directly to a TM₀₁₀ cavity, in which a helium microwave plasma is generated at atmospheric pressure. Samples (20 μl) are dried, ashed and atomized; the free atoms are transported by helium to the cavity, where they are excited. Detection limits are in the sub-mg l^-1 region. The effect of counter cations is removed by the addition of 50 mg l^-1 potassium hydroxide, which also helps to suppress interferences by large amounts of matrix constituents, but the standard addition technique remains necessary to permit determinations that are reliable to within 5%.