Total hydrocarbon analysis converted to methane
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Total hydrocarbon analysis in air separation is sometimes converted into methane analysis – does that mean it’s sufficient to use a methane analyzer to conduct the analysis? But usually, total carbon is analyzed. Why is it always mentioned in terms of converted methane?
To be precise, this is called total hydrocarbon analysis, although it is sometimes written as total hydrocarbons (TCH). When analyzing total hydrocarbons, it is necessary to convert hydrocarbons with different molecular structures into a simple substance that is easier to represent. Methane is the simplest hydrocarbon; ethane, then, corresponds to 2 molecules of methane. The same applies to ethylene – hydrocarbons with a certain number of carbon atoms are used to represent those with more than 2 carbon atoms, with automatic conversion taking place (this conversion can be carried out by standard chromatography programs). Due to the structural complexity of total hydrocarbons, it is difficult to accurately express the amounts of specific hydrocarbons; converting them into methane allows for a simple and clear representation of all the detected hydrocarbons, making it easier to describe hydrocarbon compounds in gases or water. When analyzing total hydrocarbons, non-methane total hydrocarbons are sometimes measured simultaneously; this can generally be done using gas chromatography equipped with a FID detector, allowing both measurement values to be obtained in a single analysis.