AIR SAMPLING AND ANALYSIS OF POLYCYCLIC AROMATIC-HYDROCARBONS

Polycyclic aromatic hydrocarbons (PAHs) occur in particles or in vapou r phase. The size of the particles is affected by the season: in the w inter there is a shift from large to small particles. PAHs, which are associated with particulate matter, are usually collected on filters a nd are then vaporized from the filter, or exist in the vapour phase an d are trapped by a back-up solid sorbent. Many PAHs can react with oth er environmental pollutants. Benzo[a]pyrene deposited on a filter was reported to undergo chemical reactions with ozone and nitric acid. The loss of benzo[a]pyrene can be as high as 85%. The most common samplin g method applied is integration of the sample by pumping the air strea m through a sample device (active sampling). Passive sampling relies o n the diffusion-controlled gradients towards a surface. Passive sampli ng is more often used for vapour-phase PAHs in occupational environmen ts. Sample clean-up is increasingly performed by solid-phase extractio n and is also applied to air samples. The samples are traditionally de sorbed using Soxhlet apparatus, ultrasonication and various organic so lvents, but supercritical fluid extraction is getting more popular. Th e analysis of PAH samples is usually carried out by high-performance l iquid chromatography equipped with a fluorescence detector or gas chro matography-mass spectrometry with electron and negative chemical ioniz ation methods. For quantitative analysis the correlation of these two methods have shown to be good. In qualitative analysis mass spectromet ry lacks the ability to resolve the isomeric structures and high-perfo rmance liquid chromatography with time programming fluorescence seems to be the detection method of choice.