SPECIATION OF IODO AMINO-ACIDS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRIC DETECTION

High-performance liquid chromatography (HPLC) has been coupled with on-line Inductively coupled plasma mass spectrometry (ICP/MS) for the speciation of iodide ion I- and five iodo amino acids (monolodotyrosine, dilodotyrosine, 3,3',5-and 3,3',5'-trilodothyronine, and thyroxine) commonly found in thyroglobulin. The absolute detection limits were in a range from 35 to 130 pg as iodine: this is roughly 1 order of magnitude lower than those in conventional methods using stable isotope of iodine. The relative standard deviation of peak-ares measurements was less than 6% for each of the six species. Based on these results, the contents of iodine-containing compounds in an enzymatic digest of bovine thyroglobulin were determined.