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How does the PeCOD system work? How does it compare to other methods?

The PeCOD system for COD analysis has attracted international attention as provides a faster and safer method of COD testing.

Unfortunately the PeCOD system is no longer available. You can click here to view our COD range.
But just how does the system work? How is it different to traditional COD tubes or vials methods?

And most importantly, how do the results compare?

PeCOD COD test being performed
The PeCOD system being used to test COD in water samples

How does PeCOD work?

The PeCOD uses a photoelectrical reaction method.

When an organic molecule in the sample hits the UV-activated nanoparticle Titanium Dioxide catalyst it is oxidised and an electron is given off.

This electron moving produces a current, which is related back to the final reported COD value.

PeCOD photoelectrical reaction
PeCOD reaction scheme

This reaction is fast and doesn’t require any harmful chemicals.

Results are given in 15 minutes.


How do COD vials work?

When testing by the traditional COD vials method, a mixture of chemicals are required to achieve the oxidation of the organic molecules.

Samples are pipetted into COD vials (also known as COD tubes or LCK’s) which contain corrosive Sulphuric Acid (H2SO4), carcinogenic Potassium Dichromate (K2Cr2O7), toxic Mercury Sulphate (HgSO4) and irritant Silver Sulphate (Ag2SO4).

COD vials
COD vial

The vials then need to be heated in a reactor, left to cool, and then read in a photometer.

Overall results are achieved in a minimum of around 2 hours.


How do the results of PeCOD and COD vials compare?

When comparing the same samples tested by PeCOD and COD vials, results are seen to be very close – as shown in the graph below;

PeCOD vs COD vials results
Plot of PeCOD COD, soluble dichromate COD and total dichromate COD for surface water samples from Alberta, Canada

This strong correlation was seen in both surface water (correlation R2 value of 0.84) and waste water  samples (correlation R2 values of 0.95, 0.98 and 0.92 seen in separate studies).

Unfortunately the PeCOD system is no longer available. You can click here to view our COD range.

To find out more, follow the links above or see the full presentation comparing dichromate and PeCOD anaylsis here.

Contact us to find out more about PeCOD analysis for COD