Passive sampling: Difference between revisions

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=== Microporous polyethylene tubes (MPT) ===

Microporous polyethylene tubes (MPT) attempt to mitigate the flow-dependency of other kinetic passive samplers such as Chemcatcher and POCIS by introducing a thicker membrane.<ref>{{Cite journal|last1=Fauvelle|first1=Vincent|last2=Kaserzon|first2=Sarit L.|last3=Montero|first3=Natalia|last4=Lissalde|first4=Sophie|last5=Allan|first5=Ian J.|last6=Mills|first6=Graham|last7=Mazzella|first7=Nicolas|last8=Mueller|first8=Jochen F.|last9=Booij|first9=Kees|date=2017-03-07|title=Dealing with Flow Effects on the Uptake of Polar Compounds by Passive Samplers|journal=Environmental Science & Technology|volume=51|issue=5|pages=2536–2537|doi=10.1021/acs.est.7b00558|pmid=28225255|bibcode=2017EnST...51.2536F|s2cid=206567423 |issn=0013-936X|doi-access=free}}</ref> The diffusive polyethylene layer prevents the thickness of the water-boundary layer (which is affected by flow) from dominating diffusion.<ref name=":0">{{Cite journal|last1=Fauvelle|first1=Vincent|last2=Montero|first2=Natalia|last3=Mueller|first3=Jochen F.|last4=Banks|first4=Andrew|last5=Mazzella|first5=Nicolas|last6=Kaserzon|first6=Sarit L.|date=2017|title=Glyphosate and AMPA passive sampling in freshwater using a microporous polyethylene diffusion sampler|url=https://pubmed.ncbi.nlm.nih.gov/28886558/|journal=Chemosphere|volume=188|pages=241–248|doi=10.1016/j.chemosphere.2017.08.013|issn=1879-1298|pmid=28886558|bibcode=2017Chmsp.188..241F}}</ref> The tube is filled with sorbents depending on the chemicals or chemical groups being sampled and has been successfully used to sample glyphosate, AMPA, illicit drugs and pharmaceuticals and personal care products.<ref name=":0" /><ref>{{Cite journal|date=2020-02-20|title=Calibration and validation of a microporous polyethylene passive sampler for quantitative estimation of illicit drug and pharmaceutical and personal care product (PPCP) concentrations in wastewater influent|url=https://www.sciencedirect.com/science/article/abs/pii/S0048969719358863|journal=Science of the Total Environment|language=en|volume=704|pagesarticle-number=135891|doi=10.1016/j.scitotenv.2019.135891|issn=0048-9697|last1=McKay|first1=Sarah|last2=Tscharke|first2=Ben|last3=Hawker|first3=Darryl|last4=Thompson|first4=Kristie|last5=O'Brien|first5=Jake|last6=Mueller|first6=Jochen F.|last7=Kaserzon|first7=Sarit|pmid=31838300|bibcode=2020ScTEn.70435891M|s2cid=209386153 |url-access=subscription|hdl=10072/396186|hdl-access=free}}</ref>

===Peepers===

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===Semipermeable membrane devices (SPMDs)===

{{Main|Semipermeable membrane devices}}

Semipermeable membrane devices (SPMDs) passively sample [[Chemical polarity|nonpolar]] organic contaminants with a log octanol-water partition coefficient (K_ow) value greater than 3. Examples of these types of chemicals include [[polycyclic aromatic hydrocarbons]] (PAHs), [[polychlorinated biphenyls]] (PCBs), [[polybrominated diphenyl ethers]] (PBDEs), chlorinated pesticides, [[dioxinPolychlorinated dibenzodioxins|dioxins]]s, and [[furanPolychlorinated dibenzofurans|furans]]s. SPMDs are composed of sealed plastic tubing filled with [[triolein]], in which nonpolar organics are very soluble and which serves as a representation of the fatty tissues of aquatic organisms. The tubing is then weaved between metal rods and enclosed in a metal cage. The sampler can be made in varying lengths of tubing for different applications, since sampling rate depends on the surface area of tubing exposed to the water. As long as the amount of water passing over the sampler is known, nonpolar organic contaminant water concentrations can be calculated after extracting contaminants from a SPMD.<ref name = POCISSPMD />

[[File:Stabilized liquid membrane device (SLMD).jpg|thumb|75px |A 7.5 centimeter SLMD, filled with a 1:1 mixture of Kelex-100 and oleic acid.]]

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==Advantages==

Contaminant concentrations from passive sampling reflect average contamination throughout the sampler deployment time, meaning the sample will capture contaminant concentration fluctuations over the whole deployment period. Traditional grab sampling does not do this, since collected samples only represent a single moment in time and multiple grab samples must be taken to observe variation in contaminant concentrations over time.<ref name = Main /> This integrative sampling method can also can result in the detection of chemicals present at such low concentrations that they would be undetected in a grab sample, due to concentration of the chemicals on the sampler over time. As a result, passive sampling has the potential to be a less time-intensive, less expensive and more accurate sampling method than grab sampling.

In addition, passive samplers are often easy to use and deploy, have no pumps or moving parts, and do not require electricity, since they rely on the [[molecular diffusion]] of contaminants or binding of contaminants to agents within the samplers, unlike active sampling.<ref name = Sigma /> They may also be inexpensive and simple to construct, such as SLMDs, which only require sealed plastic tubing and two chemical components.<ref name = Brumbaugh />