The sample to be analysed is weighed accurately to one millionth of a gram inside a small tin capsule.
This capsule is introduced to the analyser's furnace (combustion tube), which is at a temperature of 950 ºC. At this temperature the tin capsule combusts in a high oxygen environment to form tin oxide. This combustion elevates the temperature to well above 1800ºC. At this temperature, the sample is 'vapourised' and then undergoes complete combustion, to form CO2, N2, NxOy, H2O and other by-products. Undesirable by products such as halogens, sulfur, phosphorus, etc. are removed by 'scrubbing' chemicals inside the combustion tube.
After combustion, the sample gases flow through a reduction tube which removes any unused oxygen, and converts oxides of nitrogen to N2.
These gases are then homogenised at a precise temperature, pressure and volume in the mixing area.
A small portion of this mixture, from the sample volume, then flows through a series of thermal conductivity cells (the detector), where the 'quantity' of each gas, CO2, H2O, N2 and He carrier gas, is recorded.
From these readings, and the weight of sample used it is possible to calculate %C, %H, %N.