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TOC - What is Total Organic Carbon?


Total Organic Carbon (TOC) instrumentation measure water quality by analysing the organic contamination within a water sample. The Protoc 300 analyser may be configured to rapidly report TOC, TC (Total Carbon) or DOC (Dissolved Organic Carbon) and include MCERTS accreditation. MCERTS certifies instrumentation for continuous on-line water quality measurement.


A filtered sample is pumped into a sparge vessel with acid and agitated with gas, to remove the inorganic carbon typically present as carbonates. The prepared sample is then delivered to a reaction vessel, containing a high intensity UV light source and oxidising reagent. The organic carbon is oxidised to form CO2, which is liberated by a carrier gas and delivered to an infrared detection system. The controller compares the output from the detector against automatic calibration data, to report the measured Total Organic Carbon concentration.

Different Configurations

PPM Protoc TOC total organic carbon parameter MCERTS analyserAnalysers may be configured (at the time of delivery) for TC - Total Carbon, TOC - Total Organic Carbon and TOC by difference (a combined measurement of the volatile and dissolved organic components). Typically, TC mode is used to give optimum speed of response. TOC measurement configuration may be required for low concentrations where relatively significant inorganic carbon (present as carbonates and dissolved CO2), must be initially removed from the sample. TOC by difference enables volatile fractions to be included within the analysis, by continuously monitoring the TC of the sample and subtracting the IC component, which is intermittently analysed.

Important Features Of Test

The recognised UV-persulphate Total Organic Carbon method can be used on-line for continuous measurement providing real time data with a response time from under 3 minutes. The Protoc measurement is repeatable and when used with the correct sample preparation and delivery system, is very reliable even in demanding waste-water applications. It is therefore suitable for monitoring / control applications and often be used to predict oxygen demands such as BOD and COD.