Passive Diffusion Sampling
According to the Interstate Technical Regulatory Council's (ITRC) Passive Diffusion Team, passive sampling of groundwater refers to collecting a representative sample of the aquifer immediately adjacent to a specific position in a well without active media transport induced by pumping or purging techniques.
Passive sampling significantly reduces the field costs and time associated with groundwater well monitoring, reduces field sampling variability, can provide vertical profiling of contaminate concentrations, and has no known depth limit. Passive samplers are easy to deploy and retrieve and may be used in conjunction with one another.
Columbia Analytical manufactures two of the available passive samplers on the market:
- The Passive Diffusion Bag Sampler which may be used to collect samples of groundwater for analysis of volatile organic compounds
- The Rigid Porous Polyethylene Samplers which may be used to collect samples for inorganic constituents and water-soluble organic compounds
Passive Diffusion Bag (PDB) Samplers
PDB samplers are made of low density polyethylene (LDPE), which acts as a semi-permeable membrane. VOCs, excluding certain ketones, ethers and alcohols, diffuse readily through the membrane. An equilibrium is established between the VOCs in the bag and those in the groundwater. The PDB Sampler is filled with analyte-free water and is in the shape of a long cylindrical tube. Upon retrieval, usually 14 days after deployment, bags are opened to fill vials and returned to the laboratory for analysis.
Columbia Analytical has been granted a license to manufacture, use and provide the bags by the US Geological Survey (USGS) and The General Electric Company (GE), both co-patent holders on the product (US #5,804,743). The downhole passive water sampler and method of sampling was invented by Don Vroblesky (USGS) and Thomas Hyde (GE).
PDB Sampler Benefits
- Available in both field-ready and field-filled versions
- Simple to deploy
- Eliminates the collection and disposal of purged water
- Significantly reduces the cost of sampling
The standard size PDB Sampler is 24" long and 1 ¼" in diameter. It is manufactured from 4 Mil-thick, 2" wide, "lay flat", low-density polyethylene. All seams and connections are made by heat-seals only. The field-ready PDB Sampler holds approximately 220 mL of certified, laboratory-grade, analyte-free, deionized water. After retrieval, simply cut the top and pour water into 40 mL vials.
The field-filled PDB Sampler must be filled with water prior to deployment. It is fitted at one end with a threaded screw cap for filling and a snap-on spout for pouring water into vials. When ready to sample, just open the snap top and pour.
Different sizes are available with advance notice. If there is a chance of abrasion or tearing due to the well’s physical condition, we recommend the use of a protective polyethylene mesh cover.
Columbia Analytical is a leader in passive diffusion sampler (PDS) technology and has been since March 2000 when it began manufacturing and distributing samplers for Volatile Organic Compounds (VOCs). Wide acceptance of these samplers has spurred Columbia Analytical to partner with USGS to develop passive diffusion samplers for common LTM inorganic parameters. Both laboratory and field demonstration studies are currently underway to determine feasibility of nylon-screen (NS) and rigid porous polyethylene (RPP).
Pricing for Passive Diffusion Bag Samplers
| Passive Diffusion Bags, each | Field-Ready Price | Field-Filled Price |
|---|---|---|
| 1-9 | $35.00 | $22.00 |
| 10-24 | $32.00 | $20.00 |
| 25-99 | $28.50 | $19.00 |
| 100 and over | $25.00 | $18.00 |
| 36" length - 1-1/4" diameter | $40.00 | $40.00 |
| 48" length - 3/4" diameter | $40.00 | $40.00 |
| Other non-standard size bags are available | Call for quote | Call for quote |
Pricing for Passive Diffusion Bag Sampler Accessories
| Storage Pouches, each |
Price |
|---|---|
| zip-lock type (storage < 14 days before deployment) | FREE |
| foil barrier type (storage > 14 days before deployment) | $15.00 |
| Protective Mesh Cover, EACH (optional and reusable) |
PRICE |
| One unit | $2.00 |
Rigid Porous Polyethylene (RPP) Samplers
RPPs were invented by Don Vroblesky, Ph.D., of the United States Geological Survey (USGS). Columbia Analytical manufactures a prototype that will soon be licensed with the USGS for production under the US Patent Application Serial #10/767,496, entitled "Porous Polyethylene Diffusion Sampler for Groundwater."
RPPs are made of thin sheets of foam-like porous polyethylene with pore sizes of 6-20 microns. When completely filled with water the pores allow a water-water interface, facilitating the equilibrium of water-soluble analytes in the aquifer adjacent to the well screen with the deionized water of the RPP. Like the majority of passive samplers, it is recommended that they remain deployed for a minimum of 14 days, though the analytes of interest may equilibrate sooner.
The RPPs are deployed with the plug end down and are kept in this position until the contents are placed into sample bottles for transport to the laboratory. This is to avoid leakage from the pores of the sampler.
RPP Sampler Benefits
- Samples all water soluble analytes, such as:
- Perchlorate
- 1,4-dioxane
- Inorganic anions and cations
- Metals
- MEE parameters
- MTBE
- Hexavalent chromium
- Explosives
- Dissolved gases
- Long term groundwater monitoring situations, especially when purged water must be collected and disposed of off-site
- Well fields in porous/permeable formations with good groundwater recovery
- Very useful in deep wells where submersible pumps may not function
Rigid Porous Polyethylene (RPP) Samplers
| Rigid Porous Polyethylene Samplers (RPPS) | PRICE |
|---|---|
| One unit | $65.00 |
Accessories for both PDBs and RPPs
| Hanging assemblies and supplies, EACH (reusable) |
PRICE |
|---|---|
| lines, weights, clips, safety caps, reels | Call for quote |
| Weights alone | $12.50 |
To order, call: 1.800.695.7222
Columbia Analytical also provides air quality sampling equipment and media for lease or purchase. More information can be found in our air quality testing and consulting service section.
We actively participate in the Interstate Technology Regulatory Council (ITRC) and have been instrumental in technological and regulatory advancements in this field.
