It is often important to know the composition of volatile organic compounds in an air sample. After sampling or sample preparation, the compounds are transferred from the gas phase onto an adsorption tube. This allows us to sample quite large volumes of air enabling detection of very low concentration of VOC.
Depending on the purpose of the study, results can be checked against different limit values (Odour Threshold Value, Threshold Limit Value,...)
Through thermal desorption, the molecules are desorbed from the adsorbent and sent to the gas chromatograph (GC). The GC then seperates all VOC leading them one by one to the detector which records a mass spectrum. Using a library with mass spectra, a comparison is done to identify the unknown substances in the air sample. The next step is the semi-quantification of the detected compounds by calibrating the device with several common VOC (aromatic hydrocarbons, cyclic hydrocarbons, alifatic hydrocarbons, alcohols, aldehydes, ketones, ethers, esters, organic sulphur compounds, organic nitrogen compounds, organic acids,…). Using the response factor of the compound (or group), the concentration is calculated.