Benefits and Alternatives of the Various Methods for Metals Speciation for Chromium in Soils

Ask the Expert Question:Can you summarize the benefits and alternatives of the various methods for metals speciation for chromium in soils?

Expert Repsonse:
Method 3060A is the primary sample preparation method used to extract the hexavalent chromium (Cr(VI)) from a soil matrix. This sample preparation method must then be followed with an analysis method to determine the Cr(VI) concentration. There are three analytical technique options.

The most common is colorimetry as described in Method 7196A. This test is widely available and low cost. It can suffer from color based and reduction / oxidation chemistry (redox) matrix interferences.

Ion chromatography with colorimetric detection is used in Method 7199. Method 7199 is available from many labs, though it is less common than 7196A and is a bit more expensive. This method resists the color based interferences, but is still affected by the redox chemistry of the soil matrix.

The most sophisticated technique uses ion chromatography coupled with ICP/MS detection and uses isotopically labeled chromium species. This is described in Method 6800. There are only a few labs in the United States with this capability, TestAmerica being one of them. It is much more expensive than either 7196A or 7199. This method compensates for both color based and redox interferences in most samples.

All of the Cr(VI) analysis options are available from TestAmerica. For additional information on these methods, please submit at question at this link: http://www.testamericainc.com/contactus/contactform.aspx.

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