Organic matter is abundantly present in the soils and sediments of natural water bodies around the world. They consist of an array of organic elements such as simple carbohydrates and sugars as well as relatively complex waxes, fats, proteins and organic acids. From a geological perspective, the presence of these elements facilitate the release and absorption of plant nutrients by forming water soluble and insoluble complexes which interact with the clay minerals in the water bodies.
Consequently, the measurement of total organic carbon in water helps in determining the presence or absence of these matters and the influence of these elements on the chemical reactions that take place in the water, soil or sediment in question. Total organic carbon analysis is frequently conducted for industrial applications, site characterization and to gather ecological risk assessment data.
There are a number of qualitative and quantitative techniques for effective TOC measurement. The quantitative methods typically require the preparation of a sample from which the water and the inorganic carbonates can be separated. The most common laboratory based measurement techniques tend to follow the same three stages of acidification; oxidation; and detection & quantification.
I. Acidification
In this stage of the TOC measurement process, the Purgeable Organic Carbon (POC) and Inorganic Carbon (IC) is separated from the water sample. The gases from the total carbon -inorganic carbon analysis are typically captured and released into a detector for further measurement and the gases generated from the non-purgeable organic carbon analysis are released into the air.
II. Oxidation
In this stage, carbon in the form of carbon dioxide and other gases is released into the chamber cell of the TOC analyzer where the residual water sample remains. This is commonly conducted by employing the High Temperature Combustion or the High Temperature Catalytic Oxidation techniques.
III. Detection and Quantification
Considered the most crucial stage in the entire total organic carbon analysis exercise, this stage is quintessentially performed by employing conductivity or non-dispersive infrared techniques with modernized TOC analyzers.
Furthermore, there are two ways in which one can conduct detection and quantification using the conductivity technique. The direct conductor is a relatively easier and cost-effective method to measure carbon levels. While the membrane conductivity process employs the same TOC analyzer technology, it is a little more time consuming.
