An ion chromatography method with post-column reaction and optical detection, according to EPA Method 326.0, for the determination of bromate has been developed and validated in water samples. Optimization of reaction and operating conditions (post-column reagent and sulphuric acid regenerant flow rate) made possible to minimize the background noise and attain low detection limit. Employing a carbonate elluent (9.0 mM Na2CO3) at a flow rate of 1.1 ml/min and a sample loop of 250 mu l, a detection limit for bromate of 0.33 mu g/l and a quantification limit (LOQ) of 0.99 mu g/l were generated. Under these conditions bromate and chlorite were separated (resolution factor >2.5) in an analysis time of less than 6.5 min and the important validation parameters were evaluated. Calibration curve in laboratory-grade water produced excellent regression in the range from LOQ up to 20 mu g/l in the order of r(2)=0.99, whereas a range of applicability of 0.99 mu g/l to 100 mu g/l was confirmed. UV detector response (AU*min/(mu g/l)) was almost constant (+/- 2%) at various concentration levels. The recoveries obtained in the accuracy test for all aqueous matrices studied were in the 93.1-106% range and the intraday and interday precisions (expressed as coefficient of variation, CV) were smaller than 13.5%. Expanded uncertainty (95%) was calculated at various concentration levels according to propagation error theory (1 +/- 0.28 mu g/l, 5 +/- 0.44 mu g/l, 10 +/- 0.60 mu g/l).