Background
Today there are two common colorimetric techniques using a Diphenylcarbazide (DPC) solution for determining Hexavalent Chromium (Cr+6) in RCRA site water samples. EPA Method 7196, a colormetric method, analyzes the untreated or filtered sample as is. EPA Method 7199, an ion chromatographic method, separates the Cr+6 ion from interferences and is then followed by post column reaction with DPC. Therefore, colored matrices or matrices containing chemical interferences may be better analyzed by ion chromatography as shown in the following example.

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