An Artifact in the Paper Chromatography of Radioiodide

Abstract

Various preparations of Oak Ridge radioiodide were diluted with glass-distilled water and applied to filter paper strips for chromatography. Spontaneous drying of the applied samples for 10–20 min before the papers were placed in the chromatography jar resulted in variable, and sometimes very marked (up to 70%), transformation of the radioiodide. At least 3 different non-iodide components were formed. These changes were largely prevented by drying in a nitrogen atmosphere, and were completely inhibited by 3 ×l0^-4 M methimazole. An oxidative mechanism is therefore suggested. Addition of 3×l0^-4 M carrier iodide also greatly reduced the chemical changes occurring on drying. This, coupled with the variability of the effect, suggests that a trace component of the atmosphere, whose concentration varied from day to day, was involved in the reaction. These findings raise the possibility that other labile compounds, in addition to iodide, may also undergo oxidative changes when very dilute solutions are dried on filter paper.