Methodological and analytical aspects of simple methods for measuring iodine in urine. Comparison with HPLC and Technicon Autoanalyzer II

This work describes an optimization of a simple photometric determination o f iodine concentrations in urine using a modified eerie arsenite method wit h ammonium persulfate as oxidant. By means of this sensitive method iodine concentrations can be determined in very small specimens (50 mu L). Urine s amples (105) collected from a mixed population, were analyzed for urine iod ine content by the optimized ammonium persulfate method a Technicon Autoana lyzer II and a paired-ion-RP HPLC. We found that the precision of this opti mized ammonium persulfate method yields inter assay CVs of <10% for urinary iodine concentrations >10 mu g/dL. Recovery of [I-123]iodide added to urin e in vitro was 100.9 +/- 2.4%. The detection limit was 0.0029 mu g iodine. There was a high correlation between all three methods (r > 0.94 in any cas e) and the interpretation of the results was consistent. We conclude that t his simple, manual ammonium persulfate method is suitable for urinary iodin e analysis and can be performed in any routine clinical laboratory.