Iodine Losses in the Alkaline Ashing Method for Determination of Plasma Protein-Bound Iodine

Summary Two different radioisotope procedures were used to determine iodine losses during different steps in the assay for protein-bound iodine in plasma of cattle by the alkaline ashing method. In the first procedure, radioactive iodide was added to the washed precipitated proteins of six blood samples. Losses in iodine between this step and final colorimetry averaged 3.9%. In the second procedure, radioactive thyroxine was added to whole plasma of six cows. Losses in iodine following washing and precipitation of proteins were negligible (0.3%) and were 3.3% for the entire procedure.