Waterloo - Model SE -Waterloo Membrane Sampler (WMS)
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 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.
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.
- 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)
- 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