Differential pulse polarographic determination of iodine in thyroid tablets: collaborative study

A differential pulse polarographic (DPP) method for the determination of iodine in thyroid and thyroid preparations was collaboratively studied by 8 laboratories. The overall concentration of iodine in commercial thyroid tablets containing 1/4, 1,2, and 5 gr. of declared thyroid was 0.196%. The overall repeatability and reproducibility standard deviations were 0.0043 and 0.0067, respectively, and the corresponding coefficients of variation were 2.18 and 3.41%, respectively. The results obtained by the DPP method agreed with those obtained by the U.S. Pharmacopeia XX method at the various concentrations of declared thyroid studied. The DPP method has been adopted official first action.