Hexavalent Chromium in Drinking Water
EPA Recommends Nationwide Drinking Water Tests for Hexavalent Chromium
January 11, 2011: See EPA Guidance Memo
A 2010 study of drinking water in 35 U.S. cities found hexavalent chromium in 31 of them, each being above California's current Public Health Goal (PHG) of 0.06 parts per billion (ppb). California’s PHG is the most stringent in the United States as of January 2011. They are also proposing an even stricter goal of 0.02 ppb.
Hexavalent chromium can enter waterways through the erosion of natural deposits or from industrial discharges. Such discharges may come from the manufacturers of stainless steel, metal plating, wood products or textiles. It can also be found in dyes, paints, and inks. Chromium may be added as anti-corrosive agents for primers and paints.
EPA has required water systems to test for total chromium since 1991- the maximum contaminate level for total chromium is 100 ppb. Total chromium includes the toxic hexavalent chromium, or chromium+6, as well as chromium+3, the beneficial nutrient.
Hexavalent Chromium is a chemical compound containing the element chromium in the +6 oxidation state.
An effective method for testing drinking water for hexavalent chromium is by EPA Method 218.6 using ion chromatography. In this method, an aqueous sample is filtered through a 0.45 µm filter and the filtrate is adjusted to a pH of 9-9.5 with a concentrated 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 hexavalent chromium, as CrO4 2-, is separated on a high capacity anion exchange separator column. Post-column derivatization of the hexavalent chromium with diphenylcarbazide is followed by detection of the colored complex at 530 nm. Samples must be buffered to extend the holding time from 24 hours to 5 days. The buffering agent must be present in the sample bottle at the time the sample is taken.
Hexavalent Chromium Detection Limits
For hexavalent chromium, the EPA's current recommended goal is 0.06 ppb. California’s new proposed public health goal is 0.02 ppb.
The lab analysis required for EPA Method 218.6 is not uncommon in drinking water laboratories, however, many laboratories may not be set-up to offer this analysis or be able to reach the recommended detection limit.
ALS Environmental is set up and currently detects hexavalent chromium at 0.02 ppb in drinking water by EPA Method 218.6. Please call 585-288-5380 for a quote.
Learn more about Hexavalent Chromium Testing...
View methods for Hexavalent Chromium...
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Learn more about Colorimetric Techniques for Hexavalent Chromium...