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 biol ogical 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-focu sing sector field ICP-MS an apparatus for introducing elemental iodine via the gas phase into the argon plasma is tested. The influence of t he 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 o ut 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 bi ological standard reference materials.