The determination of iodine in aqueous solutions suffers from several serious problems, caused by the formation of iodine species, derived from the oxidative pretreatment of biological materials. For the determination of these iodine species an ion chromatograph was coupled with an ICP-mass spectrometer. Because of the possible interconversion of the iodine species depending on the pH-value, different eluent-column combinations were used for acidic or alkaline sample solutions, respectively. Iodide, iodate, and several not identified, presumably organo-iodine species could be separated and detected. Unfortunately, the iodine (I₂) itself could not be determined with the method proposed. The reaction products of pretreatment are influenced strongly by the matrix. Mixtures of different iodine containing components are received, dependent on the matrix composition and particularly on the pH-value.