Measuring air pollutants

There are many different pollutants in the air, most of which require an adapted analytical method for their determination. For some substance classes - such as volatile organic compounds (VOCs) - methods exist that allow simultaneous determination of compounds even in complex mixtures ("screening").

Various analytical methods exist for the determination of compounds in the air, which allow the determination of the type of compounds ("qualitative") and the level of concentration ("quantitative"). A distinction is made between continuous and discontinuous methods, which allow an air sample to be taken and subsequently analyzed.

Continuous monitoring devices enable direct determination of the substance concentration in the air ("online monitoring") and are generally used to measure concentration profiles with a high temporal resolution or to determine peak values.

In discontinuous methods, the target substances are collected onto a carrier material (adsorber) and then qualitatively and quantitatively analyzed in the laboratory. Air sampling can be either active or passive. In active air sampling, a defined volume of air is passed over the collection phase (adsorber) with the aid of a pump. The sampling time varies from a few minutes to several hours. In passive sampling, on the other hand, the collection phase is exposed to room air for several days or weeks. The target substances to be detected must reach the collection phase through the natural air movement.

The compounds accumulated on the collection phase are then released again by heat (thermal) or with a suitable solvent and analyzed. Common determination methods are usually based on gas chromatography (often coupled with mass spectrometry) or high-performance liquid chromatography.