US EPA Method 7199: Determination of hexavalent chromium in drinking water, groundwater and industrial wastewater effluents by ion chromatography
This method provides procedures for the determination of hexavalent chromium in drinking water, groundwater, and industrial wastewater effluents.
An aqueous sample is filtered through a 0.45 µm filter and the filtrate is adjusted to a pH of 9 to 9.5 with a buffer solution. A measured volume of the sample (50-250 µL) is introduced into the ion chromatograph. A guard column removes organics from the sample before the Cr(VI) as CrO42- is separated on an anion exchange separator column. Post-column derivatization of the
Cr(VI) with diphenylcarbazide is followed by detection of the colored complex at 530 nm.