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Determination of halogens, with special reference to iodine, in geological and biological samples using pyrohydrolysis for preparation and inductively coupled plasma mass spectrometry and ion chromatography for measurement.

A method for determining iodine, bromine, chlorine and fluorine in geological and biological materials is described. In a quartz tube, solid material was heated to 1100 degrees C under a wet oxygen flow (pyrohydrolysis). By this process the halogens (I, Br, Cl, F) were separated from the matrix and then collected in a receiver solution. The chemical yield of iodine was determined by a radioactive tracer. ICP-MS and ion chromatographic measurements were used for the determination of the halogens. The method was optimized by investigating different experimental conditions. All four halogens can be trapped in the receiver solution from one combustion procedure. Precision and accuracy were evaluated by the analysis of environmental standard reference materials (rock, soil, milk, leaves, marine tissue). The concentrations in the materials analysed were in the ranges 0.006-50 mg kg-1 for I, 0.06-1300 mg kg-1 for Br, 50-1100 mg kg-1 for F and 400-11000 mg kg-1 for Cl. The lower values represent the practical detection limit of this method. The results obtained by the proposed method and the certified values are in good agreement.