Product: Semipermeable Membrane Device (SPMD) and
its Deployment
Semipermeable Membrane Devices (SPMDs) are used as bioaccumulators of lipophilic environmental contaminants in aqueous, sediment, and atmospheric media in a large number of research and monitoring studies throughout the world. These devices mimic biological systems to provide a measure of bioavailable pollutants in both fresh and salt water. It's passive transport mechanism is similar to that of fish gills and human lungs. The SPMD, however, unlike the typical biota used in pollution testing, does not metabolize the sequestered compounds, is site-specific, is much easier to extract, and will not overdose and die from the contamination it is supposed to be monitoring.
The SPMD tubing as shown on its spider carrier.
The Semipermeable Membrane Device (SPMD) is composed of lay flat, low density polyethylene tubing containing a thin film of a pure, high-molecular weight lipid (triolein). The polymer, often thought to be non-permeable, actually consists of transport corridors of less than 10 Å in diameter. These pores allow for the selective diffusion of hydrophobic organic chemicals, which are then sequestered in the lipid phase. These chemicals can be assessed or analyzed by a variety of techniques. Screening can be accomplished using biomarker tests such as MICROTOX, MUTATOX, EROD and VITELLGENIN. Analytical data can be acquired by using HPLC, GC (FID/PID/ECD) or GC-MS. The SPMD as a sampler in conjunction with sensitive analytical techniques, allows the analyst to achieve accurate, reproducible data in the parts per quadrillion level. Mathematical modeling of SPMD uptake has been accomplished with respect to ambient environmental concentrations of dissolved organic contaminants. Thus water concentrations of some contaminants can be accurately assessed. Through the use of SPMDs, it is feasible to estimate the time-integrated dose of waterborne bioavailable pollutants to aquatic organisms.
The entire spider is pictured here with the SPMD.
Field deployment of SPMD's is usually accomplished on a stainless steel "spider" in a canister which can be deployed rapidly to minimize exposure to atmospheric contaminants. Field blanks or trip controls are always recommended for simultaneous exposure during deployment. Recommended monitoring times vary depending on the anticipated level of contaminants and water temperatures, but generally 28 days has afforded the best results
The cost, ease of usage, sensitivity, reproducibility, and application to water concentrations make SPMD's the best available passive environmental sampler. The published research and current on-going investigations enhance the monitoring usage of SPMD's.
Semipermeable Membrane Device (SPMD) technology, covering both assembly and dialytic recovery, is the subject of two US Government patents and one Canadian patent that are exclusively licensed to Environmental Sampling Technologies, Inc.
Specifications of Standard Semipermeable Membrane Device (SPMD:
- Length: (between the welds) 91.4cm
- Width: 2.5cm
- Wall thickness: 70-95µm
- Tubing: lay flat low density polyethylene, additive free
- Triolein: 99% purity (l.0mL used for standard 91.4cm length)
-
Membrane: surface area to total SPMD volume
(SA-V) ratio
≈90cm2/mL or ≈460cm2/mL of triolein - Lipid-to-membrane: mass ratio ≈0.2
- Weight of standard SPMD: 4.4 to 4.6 grams
SPMDs can be made at custom lengths upon request.
Deployment Options
The deployment device is a stainless steel canister, available in four sizes (small, large, well and disposable), and depending on your needs and style of canister, it can hold from one to five carriers. The deployment device allows for a fixed sampling location eliminating the migration and mortality problems connected with aquatic organisms.
Small
Description: Holds one to two spider carriers which uses standard length (91.4 cm) SPMDs.
Dimensions: 15 cm high x 16 cm wide. Two "D" rings on the body of the canister and one "D" ring on the lid. The distance between the "D" ring on the lid and the one on the body is 6.5 cm. The "D" rings are 25 mm wide and 19 mm deep.
Large
Description: Holds one to five spider carriers which use standard length (91.4 cm) SPMDs.
Dimension: 30 cm high x 16 cm wide. Two "D" rings on the body of the canister and one "D" ring on the lid. The distance between the "D" ring on the lid and the one on the body is 6.5 cm. The "D" rings are 25 mm wide and 19 mm deep.
Well
Description: Holds one to two standard lengths (91.4 cm) SPMDs.
Dimensions: 73 cm length x 4.5 cm wide.
Disposable
Description: Holds one or two six-inch SPMDs.
Dimensions: 9.5 cm length x 4.5 cm wide.
Additional Considerations
The Semipermeable Membrane Device (SPMD) can be combined with the Polar Organic Chemical Integrative Samplers (POCIS). Please view our POCIS page for information on sampling water soluble contaminants.