Chromatographic techniques for separation of iodinated thyroid products from human urine

Abstract

The low concentration of iodinated thyroid products in human urine necessitates either the concentration of these compounds or the application of large volumes of urine to papers for the production of paper partition chromatograms. Present day techniques of electrolytic desalting or separations on ion exchange resins are not practicable in this case. Too large a fraction of the low molecular weight iodinated compounds are lost through electrolytic desalting in addition to partial deiodination of some of the compounds. Thicker than ordinary membranes partially eliminates the former effect. The possibility of loss of small quantities of unknown compounds is always present when ion exchange resins are used. Water saturated butanol extraction of urine for concentration of the iodinated compounds is less dangerous when the residual urine or fresh urine is also chromatographed for comparison. Unfortunately, butanol extracts also concentrate many of the organic and inorganic compounds which interfere with the flow of the iodinated thyroid products so they have disadvantages similar to those in applying large volumes of urine to the papers. Two dimensional chromatohraphy diminishes the need for removal of interfering substances such as urea and inorganic salts. Through use of the proper solvents, the iodinated compounds can be chromatographed free of the interfering substances in the first dimension and subsequently separated from each other by the use of a different solvent in the second dimension. Volumes of urine as large as 1 ml have been applied to 18 × 22 in. papers and reasonably good separations obtained. Much oxidation and artifact formation takes place in butanol-dioxane ammonia solvents, but this is partly controlled with cyanide. Pure amino acids and thyroid hormones on paper chromatograms in the presence of iodide are more subject to oxidation and exchange of I 131 for stable iodide than the same compounds on chromatograms of urine.