SiREM’s Waterloo Membrane Sampler (WMS) was featured on the cover and in an article entitled “Experimentally validated mathematical model of analyte uptake by permeation passive samplers” in Environmental Science, Processes and Impacts magazine on pages 1363 – 1373 in Issue 11 of the November 2017 edition.
The mathematical model, which was applied to the WMS sampler provides a valuable tool to predict changes in uptake rates during sampling, to assign suitable exposure times at different analyte concentration levels, and to optimize the dimensions of the sampler in a manner that minimizes these changes during the sampling period.
Hester Groenevelt and Todd McAlary provided useful discussions about the sampler for the creation of this paper, authored by F. Salim and co-authored by M. Ioannidis, and T. Górecki.
The cover has a picture of Todd doing some drilling, and the sampler.
A mathematical model describing the sampling process in a permeation-based passive sampler was developed and evaluated numerically. The model was applied to the Waterloo Membrane Sampler (WMS), which employs a polydimethylsiloxane (PDMS) membrane as a permeation barrier, and an adsorbent as a receiving phase. Samplers of this kind are used for sampling volatile organic compounds (VOC) from air and soil gas. The model predicts the spatio-temporal variation of sorbed and free analyte concentrations within the sampler components (membrane, sorbent bed and dead volume), from which the uptake rate throughout the sampling process can be determined. A gradual decline in the uptake rate during the sampling process is predicted, which is more pronounced when sampling higher concentrations. Decline of the uptake rate can be attributed to diminishing analyte concentration gradient within the membrane, which results from resistance to mass transfer and the development of analyte concentration gradients within the sorbent bed. The effects of changing the sampler component dimensions on the rate of this decline in the uptake rate can be predicted from the model. Performance of the model was evaluated experimentally for sampling of toluene vapors under controlled conditions. The model predictions proved close to the experimental values. The model provides a valuable tool to predict changes in the uptake rate during sampling, to assign suitable exposure times at different analyte concentration levels, and to optimize the dimensions of the sampler in a manner that minimizes these changes during the sampling period.
Environmental Science: Processes & Impacts publishes high quality papers in all areas of the environmental chemical sciences, including chemistry of the air, water, soil and sediment. They welcome studies on the environmental fate and effects of anthropogenic and naturally occurring contaminants, both chemical and microbiological, as well as related natural element cycling processes.
Learn more about the article: http://pubs.rsc.org/en/content/articlelanding/2017/em/c7em00315c#!divAbstract.
Read about the WMS sampler: http://www.siremlab.com/pages/wms/.
For consultation regarding WMS sampler, contact Hester Groenevelt at HGroenevelt@Siremlab.com or Todd McAlary at TMcAlary@Geosyntec.com.
Learn more about Hester at: https://www.linkedin.com/in/hester-groenevelt-6140b174/
Learn more about Todd at: https://www.geosyntec.com/people/todd-mcalary