DETERMINATION OF FREE IODIDE IN HUMAN SERUM - SEPARATION FROM OTHER I-SPECIES AND QUANTIFICATION IN SERUM POOLS AND INDIVIDUAL-SAMPLES

A method for the determination of free iodide in human serum was devel oped. For this purpose iodide from pooled serum samples was separated from the organic manner by SEC. The iodide fraction subsequently was f reeze-dried and analyzed by ion chromatography for quantification. Inv estigations for recovery and precision were carried out and were found to show sufficient results. For quality assurance ICP-MS was taken ad ditionally as an total I-detector [1], using native and iodide-spiked serum samples. The iodide results of ICP-MS as well as those of IC wer e well corresponding. Iodine containing SEC-fractions from iodide-spik ed samples showed no increased I-values except that in the iodide frac tions, proving that there was no iodide conversion into other I-specie s (and vice versa) during the whole procedure. Free iodide from two se rum pools of different healthy persons was determined as 2.25 and 2.43 mu g I-/L, respectively. The values are related to total iodine level s determined by ICP-MS. For comparative reasons a table of individual iodine and iodide values is presented.