Polydimethylsiloxane (PDMS) has interesting sorption and diffusion properties towards many organic compounds and is highly hydrophobic. Due to these features, various analytical techniques utilizing PDMS have been successfully employed in the field of analytical sample preparation (e.g. SPME, stir bar sorptive extraction, membrane extraction with a sorbent interface, etc.,) and separation (e.g. as a stationary phase in capillary gas chromatography). A simple and cost effective permeation passive sampler utilizing these excellent properties of PDMS has been developed in our laboratory to further simplify sample handling and reduce sample contamination during the sample preparation step.

The PDMS-based sampler is expected to be insensitive to humidity variations as the membrane is highly hydrophobic. Further, theoretical considerations of the mechanism of analyte transport across PDMS membranes indicate that the calibration constant (reciprocal of the sampling rate) should be only slightly affected by temperature variations. This is because the permeability of the polymer towards a particular analyte (the product of the analytes diffusivity in the polymer and its partition coefficient between PDMS and air) defines the uptake rates. While the diffusivity of a particular analyte increases with increasing temperature, the partition coefficient decreases. This trade-off between the two parameters defining the permeability of the polymer results in the uptake rate being only slightly affected by temperature.

Experiments were performed with various model compounds with a wide polarity range to test the hypothesis. The calibration constants were determined at different temperatures, and the energy of activation of permeation (which defines the variation of permeability with variation in temperature) was deduced from the experimental results. In the seminar, the new sampling device, sample preparation methodology, the theory and experimental results obtained will be discussed.