Abstract:
Passive sampling of air using SPME involves unknown air interaction volumes and may be affected by variations in air current. To control air speed and interaction volume, we constructed a dynamic SPME sampling device that enclosed the SPME fibre in a tube coupled to an air sampling pump. A vapour-dosing system which vaporised methamphetamine from an acetonitrile solution was constructed to test the sampler. Sorption and desorption behaviour of methamphetamine with 100 µm polydimethylsiloxane (PDMS) SPME fibres was then characterised. Dynamic SPME sampling of a 1 L min-1 flow of 4 ng L-1 methamphetamine caused a linear increase in the amount of methamphetamine sorbed to the PDMS fibre from 5 min up to 90 min. Desorption at room temperature was investigated by exposing an SPME fibre in the dynamic sampler to a 1 L min-1 flow of 4 ng L-1 methamphetamine for 40 min, then switching to sampling laboratory air. There was no evidence of desorption occurring up to 60 min after the fibre was exposed to laboratory air. The strong affinity of methamphetamine for PDMS means that the amount of methamphetamine retained on the fibre represents an integration of the concentrations that the SPME device has sampled.