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Chlorine Dioxide

Chlorine dioxide is a deep yellow, toxic gas. Used primarily as a disinfectant in drinking water and in various industrial processes, chlorine dioxide is a highly effective, environmentally friendly microbiocide. Chlorine dioxide is safe, potent, and does not produce trihalomethanes, the disinfection byproduct characteristic of chlorine use.

There are two methods that can be used to measure chlorine dioxide levels in water, the chlorophenol red method and the DPD-Glycine method. In the chlorophenol red method, chlorine dioxide combines with chlorophenol red at pH 5.2 to form a colorless complex. The resulting decrease in color is proportional to the chlorine dioxide concentration in the sample. In the DPD-Glycine method, chlorine dioxide reacts with DPD (N, N-diethyl-p-phenylenediamine) forming a pink color, the intensity of which is proportional to the chlorine dioxide concentration in the sample. Glycine is also added to the sample to remove the interference of chlorine.

Hanna Instruments offers a range of instrumentation for measuring chlorine dioxide. From portable and benchtop photometers to reagents, Hanna has an accurate and affordable solution for many chlorine dioxide related applications.

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Solutions for chlorine dioxide measurement include the CAL Check standards for verifying and, if needed, the calibration of our portable photometers. Each CAL Check standard is supplied with a Certificate of Analysis stating the accuracy and traceability of the standard.


Accessories include spare cuvettes and caps for photometers. Cuvette cleaning solution and microfiber cleaning cloths are also available.

Portable Photometers

Portable photometers are available using both a regular and rapid methods. The portable photometers have a CAL Check feature that allows for performance verification and if needed, recalibration using the CAL Check standards. The portable meters are available as a meter only option or as a kit. The kit version include a rugged carrying case and CAL Check standards

Benchtop Photometers

Benchtop photometers include multi-parameter versions for water treatment, wastewater treatment, swimming pools and boilers and cooling tower. Each photometer is customized to have the parameters used by a specific industry. All benchtop have a digital pH electrode input allowing it to be used as a traditional pH meter.


Spectrophotometers are available that have both rapid and regular chlorine dioxide methods pre-programmed into the meter. The spectrophotometer offers the highest precision due to the quality of the optical system that has a wavelength accuracy of +/- 1.5 nm. The spectrophotometer allows for custom methods to be used.


Reagents include the reagents used with portable and benchtop photometers. They can also be used in the spectrophotometer.