Vapor Intrusion Passive Sampler

Origin of the Waterloo Membrane Sampler

The origin, advantages, and benefits of our passive sampler

The Waterloo Membrane Sampler™ (WMS™), a passive sampler for monitoring volatile organic compound (VOC) vapor concentrations, was developed at the University of Waterloo by Drs. Tadeusz Górecki and Suresh Seethapathy. The researchers had identified a need for a passive sampler with resistance to water vapor, which can saturate the sorbent present in passive samplers, for sampling in environmental vapor matrices where water vapor concentrations can be high, such as in soil gas, and they believed that the unique design of the WMS™ gave it an exclusive position in the marketplace for passive samplers.

The WMS™ design incorporates a polydimethylsiloxane (PDMS) membrane across the face of a vial filled with a sorbent medium. Volatile organic compound (VOC) vapors partition into and permeate through the membrane. The sorbent then traps the vapors, and the mass of each compound is determined by gas chromatography–mass spectrometry (GC-MS). The uptake rate has been experimentally measured for many common VOCs and can easily be calculated for other compounds because it is directly proportional to the gas chromatographic retention index, a property that is readily available in the scientific literature. Thus, the WMS™ sampler can be used to measure time-weighted average concentrations for virtually any VOC.

Advantages & Benefits

Advantages of passive sampling compared to conventional active sampling methods (e.g., Summa™ canisters)

Lower cost
Simpler sampling protocols
Lower reporting limits without a premium price
Longer time-integrated samples
Very small size (discrete to deploy and easy to ship)

Benefits of WMS™ compared to other quantitative passive air samplers

Predictable uptake rates for less common compounds
Ability to measure Total Petroleum Hydrocarbon/Gasoline Range Organic compounds
Minimal effect of moisture (very advantageous for subsurface monitoring)
Insensitive to wind velocity (very advantageous for outdoor and vent-pipe monitoring)
Ability to modify configuration to avoid the "starvation effect" when collecting subsurface samples
Small diameter (easy to put in vent pipes or sub-slab probes)
Competitive pricing

PATENT FOR QUANTITATIVE SOIL GAS SAMPLING

The unique design of the WMS™ sampler allows it to collect soil gas samples quantitatively by manipulating the uptake rate to alleviate starvation. This innovation has been granted USA patent number 9399912.

Read the patent.

WATERLOO MEMBRANE SAMPLER PRODUCTS

The Waterloo Membrane Sampler™ (WMS™) comes in several configurations, described below. Choosing the best configuration for your application may require consultation with SiREM, or with an approved analytical laboratory.

WMS-SE™

The solvent-extraction version of the WMS™ is an excellent choice for monitoring VOC vapor concentrations in indoor air, outdoor air, and vent pipes. Samples can be collected for extended periods of time due to the strong sorbent employed in this configuration, and can be analyzed multiple times to quantify analytes present at different concentrations within the calibration range.

Learn More »

WMS-LU™

The low-uptake rate version of the WMS™ is a great choice for monitoring VOC vapor concentrations in soil gas. The lower uptake rates mitigate the effect of sampler starvation that may occur when collecting soil gas samples, and allow for quantitative soil gas sampling in drier subsurface conditions.

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WMS-TM™

The thick-membrane version of the WMS™ is a unique sampler designed for quantitatively monitoring VOC vapor concentrations in soil gas in low permeability or very wet soils. This sampler has the lowest uptake rates of the configurations available.

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HOW DOES THE WMS™ WORK?

The Waterloo Membrane Sampler™ (WMS™) contains a sorbent in an inert container with an opening of known dimensions covered with a membrane. VOC vapors pass through the membrane at a constant rate, called the uptake rate, over time.

Passive samplers can be classified into two general types based on the how the VOC uptake is controlled: (1) those that rely on diffusion through a stagnant air region (passive diffusion samplers) and; (2) those that rely on permeation through a nonporous membrane (passive permeation samplers). In the latter, VOCs permeate through the uptake-rate limiting membrane before they are collected by the sorbent.

The Waterloo Membrane Sampler™ is a permeation-type passive sampler. When it is exposed to air (e.g., indoor or outdoor air, soil gas, vent pipes), VOCs in the air permeate through the membrane covering the top of the sampler vial, driven by a concentration gradient. The sorbent inside the sampler then traps the vapors, and the mass of each compound on the sorbent is determined in an analytical laboratory by GC-MS.

Learn more in the technical memorandum our staff produced for the United States Navy. »

Calculation of Concentration

Concentrations in the sampled air are calculated according to Equation 1, where:

C = concentration in sampled air (μg/m3)
M = mass on sampler (picograms)
t = sampling time (min)
UR = known analyte-specific uptake rate (mL/min)

Equation 1

Reporting Limits and Sampling Time

The sampling time required to meet a desired reporting limit can be calculated by rearranging Equation 1, and using the minimum mass on the sampler that can be detected by the analytical method (MM) to replace M, and the reporting limit required (RL) to replace C. This results in Equation 2, where:

t = sampling time required to achieve the reporting limit (min)
MM = minimum mass on sampler that analytical method can measure (picograms)
RL = reporting limit required (μg/m3)
UR = known analyte-specific uptake rate (mL/min)

Equation 2

Passive Sampling Publications

Articles Published in Peer-Reviewed Journals

BenIsrael, M., P. Wanner, R. Aravena, B. L. Parker, E. A. Haack, D. T. Tsao, K. E. Dunfield, 2019. Toluene biodegradation in the vadose zone of a poplar phytoremediation system identified using metagenomics and toluene-specific stable carbon isotope analysis. Int. J. Phytoremediat., 2019, 1, 60. DOI: 10.1080/15226514.2018.1523873

Salim, F., T. Górecki, 2019. Theory and modelling approaches to passive sampling. Environ. Sci.: Processes Impacts, 2019, 21, 1618. DOI: 10.1039/C9EM00215D

Salim, F., M. Ioannidis, A. Penlidis, T. Górecki, 2019. Modelling permeation passive sampling: intra-particle resistance to mass transfer and comprehensive sensitivity analysis. Environ. Sci.: Processes Impacts, 2019, 21, 469. DOI: 10.1039/C8EM00565F

Salim, F., T. Górecki, M. Ioannidis, 2019. New applications of mathematical model of a permeation passive sampler: prediction of the effective uptake rate and storage stability. Environ. Sci.: Processes Impacts, 2019, 21, 113. DOI: 10.1039/C8EM00397A

Huang, C., W. Shan, H. Xiao, 2018. Recent advances in passive air sampling of volatile organic compounds. Aerosol Air Qual. Res., 2018, 18, 602. DOI: 10.4209/aaqr.2017.12.0556

Salim, F., M. Ioannidis, T. Górecki, 2017. Experimentally validated mathematical model of analyte uptake by permeation passive samplers. Environ. Sci.: Processes Impacts, 2017, 19, 1363. DOI: 10.1039/C7EM00315C

Goli, O., T. Górecki, H. T. Mugammar, M. Marchesi, R. Aravena, 2017. Evaluation of the suitability of the Waterloo Membrane Sampler for sample preconcentration before compound-specific isotope analysis. Environ. Technol. Inno., 2017, 7, 141. DOI: 10.1016.j.eti.2017.02.001

McAlary, T. H. Groenevelt, S. Disher, J. Arnold, S. Seethapathy, P. Sacco, D. Crump, B. Schumacher, H. Hayes, P. Johnson, T. Górecki, 2015. Passive sampling for volatile organic compounds in indoor air-controlled laboratory comparison of four sampler types. Environ. Sci.: Processes Impacts, 2015, 17, 896. DOI: 10.1039/C4EM00560K

Marć, M., M. Tobiszewski, B. Zabiegała, M. de la Guardia, J. Namieśnik, 2015. Current air quality analytics and monitoring: A review. Anal. Chim. Acta, 2015, 853, 116. DOI: 10.1016/j.aca.2014.10.018

McAlary, T., H. Groenevelt, S. Seethapathy, P. Sacco, D. Crump, M. Tuday, B. Schumacher, H. Hayes, P. Johnson, L. Parker, T. Górecki, 2014. Quantitative passive soil vapor sampling for VOCs – Part 4: Flow-through cell. Environ. Sci.: Processes Impacts, 2014, 16, 1103. DOI: 10.1039/C4EM00098F

McAlary, T., H. Groenevelt, P. Nicholson, S. Seethapathy, P. Sacco, D. Crump, M. Tuday, B. Schumacher, P. Johnson, T. Górecki, I. Rivera-Duarte, 2014. Quantitative passive soil vapor sampling for VOCs – Part 3: Field experiments. Environ. Sci.: Processes Impacts, 2014, 16, 501. DOI: 10.1039/C3EM00653K

McAlary, T., H. Groenevelt, S. Seethapathy, P. Sacco, D. Crump, M. Tuday, B. Schumacher, H. Hayes, P. Johnson, T. Górecki, I. Rivera-Duarte, 2014. Quantitative passive soil vapor sampling for VOCs – Part 2: Laboratory experiments. Environ. Sci.: Processes Impacts, 2014, 16, 491. DOI: 10.1039/C3EM00128H

McAlary, T., X. Wang, A. Unger, H. Groenevelt, T. Górecki, 2014. Quantitative passive soil vapor sampling for VOCs – Part 1: Theory. Environ. Sci.: Processes Impacts, 2014, 16, 482. DOI: 10.1039/C3EM00652B

Seethapathy, S., T. Górecki, 2012. Applications of polydimethylsiloxane in analytical chemistry: A review. Anal. Chim. Acta, 2012, 750(31), 48. DOI: 10.1016/j.aca.2012.05.004

Seethapathy, S., T. Górecki, 2011. Polydimethylsiloxane-based permeation passive air sampler. Part I: Calibration constants and their relation to retention indices of the analytes. J. Chromatogr. A, 2011, 1218(1), 143. DOI: 10.1016/j.chroma.2010.11.003

Seethapathy, S., T. Górecki, 2010. Polydimethylsiloxane-based permeation passive air sampler. Part II: Effect of temperature and humidity on the calibration constants. J. Chromatogr. A, 2010, 1217(50), 7907. DOI: 10.1016/j.chroma.2010.10.057

ARTICLES PUBLISHED IN BOOK CHAPTERS

Armenta, S., M. del la Guardia, F. A. Esteve-Turrillas, 2020. Chapter 24 – Environmental applications (air). Solid-Phase Extraction. 2020, 647. DOI: 10.1016/B978-0-12-816906-3.00024-8

Marć, M., M. Śmiełowska, B. Zabiegała, 2017. Chapter 13 – Green Sample Collection. The Application of Green Solvents in Separation Processes. 2017, 379. DOI: 10.1016/B978-0-12-805297-6.00013-9

Reports Produced for the United States Department of Defense

NAVFAC, 2015. Passive Sampling for Vapor Intrusion Assessment. Technical Memo TM-NAVFAC EXWC-EV-1503

Geosyntec, 2015. Cost and report for development of more cost-effective methods for long-term monitoring of soil vapor intrusion to indoor air using quantitative passive diffusive-adsorptive sampling techniques. ESTCP project ER-200830, May 2015.

Geosyntec, 2014. Development of more cost-effective methods for long-term monitoring of soil vapor intrusion to indoor air using quantitative passive diffusive-adsorptive sampling. ESTCP Project ER-200830, June 2014.

Geosyntec, 2011. Demonstration of improved assessment strategies for vapor intrusion – passive samplers. SPAWAR Systems Center Pacific.

PAPER PRODUCED FOR THE UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

U.S. EPA, 2015. Engineering Issue Paper. Passive samplers for investigation of air quality: method description, implementation, and comparison to alternative sampling methods.

ADADEMIC THESES

Faten Salim, 2019. Modelling Permeation Passive Sampling, Ph.D., 2019, University of Waterloo.

Todd McAlary, 2014. Demonstration and Validation of the Use of Passive Samplers for Monitoring Soil Vapor Intrusion to Indoor Air, Ph.D., 2014, University of Waterloo.

Faten Salim, 2013. Novel Applications of the Waterloo Membrane Sampler (WMS) in Volatile Organic Compounds Sampling from Different Environmental Matrices, M.Sc., 2013, University of Waterloo.

Oana Goli, 2013. Compound Specific Isotope Ratio Analysis in Vapour Intrusion Studies using Waterloo Membrane Sampler (WMS), M.Sc., 2013, University of Waterloo.

Suresh Seethapathy, 2009. Development, Validating, Uptake Rate Modeling and Field applications of a New Permeation Passive Sampler, Ph.D., 2009, University of Waterloo.

What's New

Origin of the Waterloo Membrane Sampler

The origin, advantages, and benefits of our passive sampler

Advantages & Benefits

Advantages of passive sampling compared to conventional active sampling methods (e.g., Summa™ canisters)

Benefits of WMS™ compared to other quantitative passive air samplers

PATENT FOR QUANTITATIVE SOIL GAS SAMPLING

WATERLOO MEMBRANE SAMPLER PRODUCTS