Removal of Inorganic Iodide in the Automated Serum Protein-Bound Iodine Determination

Values for serum protein-bound iodine (PBI) concentration obtained by the Auto-Analyzer method are too high becauseof the failure of the batch (Technicon) process to completely remove inorganic iodide. The Technicon method removes about 98% of the inorganic iodide; this incomplete adsorption of inorganic iodide would give falsely elevated PBI values in serumswith high iodide concentrations. A rapid, economical method for removing serum inorganic iodide to the extent of 99.8 % by a single pass of serum through a small column packed with an anion-exchange resin is described. Using Dowex-1 X 8, 20-50 mesh, 2 ml. of serum is filtered in 30 sec. directly into an AutoAnalyzer sample cup. Filtration through the column eliminates all possibilityof clogging the sample probe with either resin beads or serumclots. The column method requiresa little lessserum than the batch process. ljHE AUTOMATED METHOI) for PB1 devised by Riley and Gochman (1) for the AutoAnalyzer is widely used. In this method, the total amount of iodine in serum is measured after removal of inorganic iodide by manually shaking the serum with a small amount of anion-exchang