Brief Method Summary

An aqueous sample is filtered through a 0.45 um filter and the filtrate is adjusted to a pH of 9-9.5 with a concentrated buffer solution. A measured volume of the sample is introduced into the ion chromatograph. A guard column removes organics from the sample before the Cr(VI), as CrO₄^2-, is separated on a high capacity anion exchange separator column. Postcolumn derivatization of the Cr(VI) with diphenylcarbazide is followed by detection of the colored complex using an in-series spectrophometer.

Scope and application 

This method determines dissolved hexavalent chromium as (CrO₄^2-) in ambient waters at EPA water quality criteria (WQC) levels using ion chromatography (IC).