The Working Principle Of A Total Organic Carbon Analyser

The TOC or Total Organic Carbon is a very popular analytical technique used by laboratories and organisations to determine the suitability of a solution to their processes. simply speaking, TOC, measures the amount of carbon present in pure water or other such aqueous systems. Toc is generally measured to enable process control and satisfy regulatory requirements.

TOC measurement techniques

toc analyzer

Another process adopted by some TOC analysers is to remove the TIC completely from the sample and then measuring the TOC. To enable this method, an acidified sample is purged with either nitrogen or carbon-free air to convert the TIC present into carbon-di-oxide and then measuring it as IC or inorganic carbon. The remaining NPOC or the non-purgeable organic carbon is then oxidised and measured. This is known as the TIC-NPOC process.

Measuring the TOC directly by acidifying the sample so that its pH becomes 2 or even less is another very popular method. Herein the IC gas is released to the atmosphere and not measured. The remaining NPOC remaining within the liquid aliquot undergoes further oxidation to release gases. These are then directed towards the detector to enable its measurement.

TOC measurement process

Irrespective of the TOC measurement method used, the procedure is divided into 3 stages that include:



o HTCO or high-temperature catalytic oxidation,

o Photo-oxidation,

o High-temperature combustion,

o Thermo-chemical oxidation,

o Electrolytic oxidation or

o Photochemical oxidation.

Detection followed by quantification:


Both methods analyse the conductivity of the sample prior to and after its oxidation. The differential measurement is the given sample’s TOC.

Non-dispersive infrared or NDIR:

The presence of several intrusive factors interferes with the readings of the conductivity method. The absence of these process interferences in NDIR makes the TOC calculation more accurate and precise.

Water that has no impurities is said to be ultrapure. Finding such water is nearly impossible. Nevertheless, when using even pure water, understanding the amount of organic impurity present is the key to the success of the processes and systems where it is used. Thus, TOC is an important parameter for monitoring and measuring the organic compound levels present.

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