Hexavalent chromium, Cr(VI), is the most toxic form of chromium found in the environment, and requires regulatory monitoring as a primary drinking water contaminant in the U.S. Ion chromatography can determine dissolved Cr(VI) as Chromate (CrO₄^2- ) in drinking water, groundwater, industrial wastewater, and solid waste extracts. U.S. EPA Method 218.6 specifies the use of the IonPac^® AS7 anion-exchange column, postcolumn reaction with diphenlycarbazide, and UV detection at 530 nm. With the conditions described in Dionex Application Update 144, method detection limits (MDLs) of 0.020 µg/L for Cr(VI) (as CrO₄^2-) can be achieved.