Chromium (VI)


Test Method Technical Information


Tests For: Hexavalent chromium in natural and industrial wastewater
Test Range: 0–1.0 mg/L
Basis of Test Method: Standard Method 3500-Cr-B, US EPA 7196
Method Detection Limit*: 0.02 mg/L
Limit of Quantification**: 0.05 mg/L

*The Method Detection Limit (MDL) is defined as the minimum measured concentration of a substance that can be reported with 99% confidence to be different from the method blank results.
**The Limit of Quantification (LOQ) is the smallest quantity that can be detected with reasonable certainty for a given analytical procedure.

Testing for Chromium

Chlorine and chlorine-release compounds are widely used for the disinfection of drinking water and swimming pools, for the Chromium (VI) may be present in certain industrial waste waters, such as those from the tanning, plating and coating industries. Chromium may occur in hexavalent form as chromates and dichromates, or in trivalent form as chromium salts. In water supplies hexavalent chromium is a particularly objectionable constituent. Trivalent chromium, although relatively inert, is also regarded as undesirable.
The Palintest Chromicol test provides a means of measuring hexavalent chromium over the range 0–1.0 mg/L.

Reagent Chemistry

In the Palintest Chromicol method, hexavalent chromium salts in acidic conditions react with diphenylcarbazide to give a purple-coloured complex. This provides a measure of the hexavalent chromium (CrVI) present in the sample. The reagents are provided in tablet form and the test is simply carried out by adding tablets to a sample of the water.
The intensity of colour produced in the tests is proportional to the chromium concentrations and is measured using a Palintest Photometer.


Levels of dissolved iron above 1 mg/L cause low results. To increase the tolerance, repeat the test using two Chromicol No 1 tablets and one Chromicol No 2 tablet. Tannin causes complexation which prevents a response in the test.

EPA, Definition and Procedure for the Determination of the Method Detection Limit, Revision 2, Dec 2016.
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the “Gold Book”).