Analysis of trimethylselenonium ion in urine by high-performance liquid chromatography

A rapid and simple method for the separation of trimethylselenonium ion and other cationic forms of selenium in urine by HPLC on a strong cation exchanger is described. Most of the inorganic salts in urine are removed prior to chromatography by means of ethanolic precipitation, thus minimizing interferences. Following sample loading and elution with 0.003 M ammonium phosphate (pH 4), a linear gradient to 0.33 M ammonium phosphate (pH 4) is employed. Complete separation of the trimethylselenonium ion from four other selenonium compounds was achieved, and good recovery of the compounds was obtained for the desalting and chromatographic procedures. The procedure was successfully employed to demonstrate that dimethylselenocysteineselenonium iodide and Se-methylselenomethionineselenonium iodide are extensively metabolized when administered to rats, and that trimethylselenonium ion is a major urinary metabolite of both compounds.