Determination of iodine using a special sample introduction system coupled to a double-focusing sector field inductively coupled plasma mass spectrometer

A procedure for the determination of iodine (especially I-129) in biological materials using double-focusing sector field mass spectrometry with an inductively coupled plasma ion source is described. To achieve a detection limit of less than 100 pg ml(-1) for I-129 by double-focusing sector field ICP-MS an apparatus for introducing elemental iodine via the gas phase into the argon plasma is tested. The influence of the concentration of various oxidation reagents for oxidizing iodide to iodine and matrix effects on the ion intensity of I-129(+) and I-127(+) are investigated. Quantitative determination of iodide is carried out by the standard additions procedure and isotope dilution analysis. The on-line addition of sample solution to an isotopic tracer solution according to the how injection principle has proved to be efficient. The procedure is discussed by determining I-127 as well as I-129 in biological standard reference materials.