AhStlWt A sensltlve and rapld single-sweep polarographlc assay was developed for the determrnatlon of estradlol or estrlol The assay Involves a controlled mtratlon usmg 0 4 M sodmm mtnte solution at 100Β°C m a water-bath for 30 mm The mtrated estradlol or estrlol IS determmed directly m the reaction mixture by polarography Because of the strong adsorption abdlty of ndro denvatwes, the senntwlty m smgle-sweep polarography IS extremely high The detectlon hmlts are as low as 6 X 10e8 and 4 X 10m8 M, respectwely The procedure was apphed to the determmatlon of estrlol m the urme of pregnant women Keywords Polarography, Estradlol, Estnol, Steroids, Urme Estradrol and estnol (Fig 1) are important steroid hormones, the concentrations of which and their changes m women are closely related to ferdlty, mfertlhty and many diseases The determination of steroid hormones has mainly been accomphshed by spectrophotometxx and more recently by chromatographlc techniques [l-4] Because these two compounds generally show no electrochenucal reduction behavlour m a 0 01 M borate electrolyte, it IS difficult to determine them directly at a droppmg mercury electrode by polarography Recent work 15-71 has demonstrated that mtrated phenyl and phenohc compounds give well defined waves for the reduction of the mtro group m the potential range -300 to -800 mV (vs SCE) Therefore, the prmclple of controlled mtratlon can be applied to analyses for a wide variety of phenyl-ring-containing drugs which may