Test Method Technical Information


Tests For: Nitrite in Cooling Water
Tests Range: 0–1500 mg/L
Reagent Chemistry Used: Catalysed Iodide
Method Detection Limit*: 2.67 mg/L
Limit of Quantification**: 8.9 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 Nitrite

Nitrites and nitrite-based formulations are widely used for corrosion control in cooling water systems. The Palintest Nitriphot test provides a simple means of measuring nitrite for the control of such treatment products in cooling water. The test covers the range 0–1500 mg/I NaNO2.

Reagent Chemistry

The Palintest Nitriphot method is based on a colorimetric procedure using an iodide containing reagent system. Nitrites catalyse the oxidation of the iodide to iodine under mildly acid conditions to produce a brown coloration. Over the range of the test a series of colours from colourless through yellow to brown are produced.

The intensity of the colour produced in the test is proportional to the nitrite concentration and is measured using a Palintest Photometer.


Chlorine in excess of 30 mg/l may give slight positive interference. However, nitrite and chlorine are incompatible and do not normally co-exist.

The solution should be cooled to below 30°C before testing for the most accurate analytical results.

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”).