We can not live without water, if a considerable number of organic pollutants exist in the water, will directly affect the quality of the water body, causing harm to our life and production. Therefore, the monitoring of water and wastewater, more and more people’s attention, in which the detection of total organic carbon (TOC) content in the water body, an increasing concern.
TOC analyzer is the laboratory to analyze the carbon content in the water source of the commonly used equipment. Next we understand the working principle of TOC analyzer.

What is a Total Organic Carbon (TOC) Analyzer?

Total Organic Carbon (TOC) analysis is an analytical technique commonly used to determine water quality. It is a comprehensive indicator of the total amount of organic matter in a body of water expressed in carbon content.TOC can be used directly to express the total amount of organic matter. Thus, it is used as an important reference indicator for evaluating the degree of organic matter pollution in a water body.

How does a TOC analyzer work?

A TOC analyzer oxidizes total organic carbon (TOC) in an aqueous solution to carbon dioxide and measures its content. By utilizing the correspondence of carbon content between carbon dioxide and total organic carbon, total organic carbon in aqueous solution can be quantitatively determined.
TOC analyzers can be classified into combustion oxidation-non-dispersive infrared absorption, conductivity, gas chromatography, etc. according to different working principles.

Combustion oxidation-non-dispersive infrared absorption method:

The different principles of determining the TOC value can be subdivided into two kinds differential subtraction method and direct method.

Differential subtraction method: The principle is that the water samples were injected into the high-temperature combustion tube (900 ℃) and low-temperature reaction tube (150 ℃).

The water sample through the high temperature combustion tube by high temperature catalytic oxidation, so that organic compounds and inorganic carbonates are converted into carbon dioxide. The water samples in the reaction tube are acidified to decompose inorganic carbonates into carbon dioxide. The generated carbon dioxide is sequentially introduced into the non-dispersive infrared detector to measure the total carbon (TC) and inorganic carbon (IC) in the water. The difference between total carbon and inorganic carbon is total organic carbon (TOC).

Direct method: The principle is to acidify the water sample after aeration, so that the decomposition of various carbonates to generate carbon dioxide and drive off, and then injected into the high-temperature combustion tubes, can be directly determined by the total organic carbon. However, the aeration process will cause the loss of volatile organic compounds in the water samples and the determination of errors, so the results of its determination are just not blowing out the value of organic carbon.

TOC Conductivity Method

TOC conductivity detection technology is capable of measuring CO2 in the liquid state. There are two main types of conductivity detection technology used in the industry:
One is direct conductivity and the other is thin film conductivity detection (selective conductivity).
TOC analyzers using both conductivity methods have been calibrated to be stable and highly accurate. The main difference between the two technologies is that the direct conductivity method is more susceptible to interference from hetero-acids, halogenated organics, etc. The thin-film conductivity detection technology is more resistant to interference.

Conclusion

A TOC analyzer, or total organic carbon analyzer, is an instrument used to determine total organic carbon (TOC) in solution. It is a comprehensive indicator that expresses the total amount of organic matter in a water body in terms of carbon content.
TOC is a rapid determination of water quality as a comprehensive indicator, usually as an important basis for evaluating the degree of organic pollution of water bodies.