Polar organic chemical integrative sampler

Last updated

A polar organic chemical integrative sampler (POCIS) is a passive sampling device which allows for the in situ collection of a time-integrated average of hydrophilic organic contaminants developed by researchers with the United States Geological Survey in Columbia, Missouri. [1] POCIS provides a means for estimating the toxicological significance of waterborne contaminants. [2] The POCIS sampler mimics the respiratory exposure of organisms living in the aquatic environment and can provide an understanding of bioavailable contaminants present in the system. [3] POCIS can be deployed in a wide range of aquatic environments and is commonly used to assist in environmental monitoring studies.

Contents

Background

The first passive sampling devices were developed in the 1970s to determine concentrations of contaminants in the air. In 1980 this technology was first adapted for the monitoring of organic contaminants in water. [4] The initial type of passive sampler developed for aquatic monitoring purposes was the semipermeable membrane device (SMPD). [4] SPMD samplers are most effective at absorbing hydrophobic pollutants with an octanol-water partition coefficient (Kow) ranging from 4-8. [5] As the global emission of bioconcentratable persistent organic pollutants (POPs) was shown to result in adverse ecological effects, industry developed a wide range of increasing water-soluble, polar hydrophilic organic compounds (HpOCs) to replace them. These compounds generally have lower bioconcentration factors. However, there is evidence that large fluxes of these HpOCs into aquatic environments may be responsible for a number of adverse effects to aquatic organisms, such as altered behavior, neurotoxicity, endocrine disruption, and impaired reproduction. [5] In the late 1990s research was underway to develop a new passive sampler in order to monitor HpOCs with a log Kow value of less than 3. [4] In 1999 the POCIS sampler was under development at the University of Missouri-Columbia. It gathered more support in the early 2000s as concern increased regarding the effects of pharmaceutical and personal care products in surface waters. [4]

The United States Geological Survey (USGS) has been heavily involved in the development of passive samplers and has articles in their database regarding the development of POCIS as early as 2000. The USGS Columbia Environmental Research Center (CERC) is a self-proclaimed international leader in the field of passive sampling. [1] There have been recent efforts by the USGS to connect people who have an interest in passive sampling. An international workshop and symposium on passive sampling was held by the USGS in 2013 to connect developers, policy makers and end users in order to discuss ways of monitoring environmental pollution. [6]

Fundamentals

The POCIS device was developed and patented by Jimmie D. Petty, James N. Huckins, and David A. Alvarez, of the Columbia Environmental Research Center. [1] Integrative passive samplers are an effective way to monitor the concentration of organic contaminants in aquatic systems over time. Most aquatic monitoring programs rely on collecting individual samples, often called grab samples, at a specific time. [7] The grab sampling method is associated with many disadvantages that can be resolved by passive sampling techniques. When contaminants are present in trace amounts, grab sampling may require the collection of large volumes of water. Also, lab analysis of the sample can only provide a snapshot of contaminant levels at the time of collection. This approach therefore has drawbacks when monitoring in environments where water contamination varies over time and episodic contamination events occur. [4] Passive sampling techniques have been able to provide a time-integrated sample of water contamination with low detection limits and in situ extraction of analytes. [8]

POCIS set-up

The POCIS sampler consists of an array of sampling disks mounted on a support rod. Each disk consists of a solid sorbent sandwiched between two polyethersoulfone (PES) microporous membranes which are then compressed between two stainless steel rings which expose a sampling area. [8] A standard POCIS disk consists of a sampling surface area to sorbent mass ratio of approximately 180 cm2g. Because the amount of chemical sampled is directly related to the sample surface area, it is sometimes necessary to combine extracts from multiple POCIS disks into one sample. Stainless steel rings, or other rigid inert material, are essential to prevent sorbent loss as the PES membranes are not able to be heat sealed. [5] The POCIS array is then inserted and deployed within a protective canister. This canister is usually made of stainless steel or PVC and works to deflect debris that may displace the POCIS array during its deployment. [3]

The PES membrane acts as a semipermeable barrier between the sorbent and surrounding aquatic environment. It allows dissolved contaminants to pass through the sorbent while selectively excluding any particles larger than 100 nm. [5] The membrane resists biofouling because the polyethersulphone used in the design is less prone than other materials. [3] The POCIS is versatile in that the sorbents can be changed to target different classes of contaminants. However, only two sorbent classes are considered as standards of all POCIS deployments to date. [2]

Theory and modeling

Each POCIS disk will sample a certain volume of water per day. The volume of water sampled varies from chemical to chemical and is dependent on the physical and chemical properties of the compound as well as the duration of sampling. The sampling rate of POCIS can vary with changes in the water flow, turbulence, temperature, and the buildup of solids on the sampler’s surface. [3] The accumulation of contaminants into a POCIS device is the result of three successive process occurring at the same time. First, the contaminants have to diffuse across the water boundary layer. The thickness of this layer is dependent on water flow and turbulence around the sampler and can significantly alter sampling rates. Second, the contaminant must transport across the membrane either through the water-filled pores or through the membrane itself. Finally, contaminants transfer from the membrane into the sorbent material mainly through adsorption. These last two steps make the modeling, understanding, and prediction of accumulation by a POCIS device challenging. To date, a limited number of chemical sampling rates have been determined. [8]

Accumulation of chemicals by a POCIS device generally follows first order kinetics. The kinetics are characterized by an initial integrative phase, followed by an equilibrium partitioning phase. During the integrative phase of uptake, a passive sampling device accumulates residues linearly relative to time, assuming constant exposure concentrations. Based on current results, the POCIS sampler remains in a linear phase for at least 30 days, and has been observed up to 56 days. Therefore, both laboratory and field data justify the use of a linear uptake model for the calculation of sample rates. [5] In order to estimate the ambient water concentration of contaminants sampled by a POCIS device, there must be available calibration data applicable for in situ conditions regarding the target compound. Currently, this information is limited. [3]

Applicability

POCIS can be deployed in a wide range of aquatic environments including stagnant pools, rivers, springs, estuarine systems, and wastewater streams. [9] However, there has been little research into the use of POCIS in strictly marine environments. [8] Prior to deployment of a POCIS device, it is essential to select a study site that will maximize the effectiveness of the sampler. Selecting an area that is shaded will help prevent light sensitive chemicals from being degrading. The site should also allow the sampler to be submerged in the water without being buried in the sediment. [9] It is ideal to place the sampler in moving water in order to increase sampling rates, however, areas with an extremely turbulent water flow should be avoided as to prevent damage to the POCIS device. Passive samplers are very vulnerable to vandalism and it is therefore important to secure the sampler in areas that are not easily visible and that are away from areas frequently used by people. [9]

POCIS samplers can be deployed for a period of time ranging from weeks to months. The shortest deployment lengths are typically 7 days but average 2–3 months. [8] It is important to have a long enough deployment period to allow for adequate detection of contaminants at ambient environmental concentrations. Often, the two different types of POCIS devices will be deployed together in order to provide the greatest understanding of contamination. [8] It is also important to deploy enough POCIS devices to ensure a large enough sample of contaminant is recovered for chemical analysis. An estimate or the number of samplers needed at a given site can be determined by the following equation. [10]

Rs x t x n x Cc x Pr x Et > MQL x Vi
where
  • Cc is the predicted environmental concentration of the contaminant
  • t is the deployment time in days
  • Rs is sampling rate in liters of water extracted by the passive sampler per day(L/day)
  • Pr is the overall method recovery for the analyte (expressed as a factor of one; ::therefore 0.9 is used for 90 percent recovery),
  • n is the number of passive samplers combined into a single sample,
  • Et is the fraction of the total sample extract which is injected into the ::instrument for quantification
  • MQL is the method quantification limit
  • Vi is the volume of standard injection (commonly 1 μL).

Relevant contaminants

Any compound with a log Kow of less than or equal to 3 can concentrate in a POCIS sampler. [5] Applicable classes of contaminants measured by POCIS are pharmaceuticals, household and industrial products, hormones, herbicides, and polar pesticides (Table 1). Currently, there are two POCIS configurations that are targeted for different classes of contaminants. A general POCIS design contains a sorbent that is used to collect pesticides, natural as well as synthetic hormones, and wastewater related chemicals. The pharmaceutical POCIS configuration contains a sorbent that is designed to specifically target classes of pharmaceuticals. [11]

Applicable contaminants that concentrate in a POCIS device. Not to be considered a complete list. [5]
Chemical ClassExamples
Pharmaceuticalsacetaminophen, azithromycin, carbamazepine, ibuprofen, propranolol, sulfa drugs, tetracycline antibiotics
Household and industrial productsalkyl phenols, benzophenone, caffeine, DEET, fire retardants, indole, triclosan
Hormones17β-estradiol, 17α-ethynlestradiol, estrone, estriol
Herbicidesatrazine, cyanazine, hydroxyatrazine, tertbutylazine
Polar pesticidesalachlor, chlorpyrifos, diainon, dichlorvos, diuron, isoproturon, metolachlor
OtherUrobilin

POCIS processing

Before the POCIS is constructed, all the hardware as well as the sorbents and membrane must be thoroughly cleaned so that any potential interference is removed. During and after sampling the only cleaning necessary is the removal of any sediment that has adhered to the surface of the sampler. After assembly, and prior to deployment, the samplers are stored in frozen airtight containers to avoid any contamination. The samplers should be kept in airtight containers during transportation both to and from the sampling site so that airborne contaminants do not contaminate the sampler. It is ideal to keep the samplers cold while transporting them in order to preserve the integrity of the samples. [3]

After the POCIS is retrieved from the field, the membrane is gently cleaned to reduce the possibility of any contamination to the sorbent. [5] The sorbent is placed into a chromatography column so that the chemicals that samples can be recovered using an organic solvent. The solvent used is specifically chosen based on the type of sorbent and chemicals sampled. The sample can go through further processing such as cleanup or fractionation depending on the desired use of the sample. [3]

Data analysis

After the sample has been processed, the extract can be analysed using a variety of data analysis techniques. [8] The chemical analysis and analytical instrumentation used depends on the goal of the study. Many analyses require multiple samples, although in some cases a single POCIS sample can be used for multiple analyses. [10]

It is vital to use quality control (QC) procedures when using passive samplers. [5] It is common practice for 10% to 50% of the total number of samples to be used for QC purposes. The number of QC samples depends on the study objectives. [10] The QC samples are used to address issues such as sample contamination and analyte recovery. [5] The types of QC samples commonly used include; reagent blanks, field blanks, matrix spikes, and procedural spikes. [5]

A large number of studies have been performed in which POCIS data was combined with bioassays to measure biological endpoints. Testing POCIS extracts in biological assays is useful as a POCIS device samples over its entire deployment period, and biologically active compounds can be effectively monitored. It can also be argued that the use of POCIS is a more relevant from an ecotoxicological perspective as the use of a passive sampler mimics the uptake of compounds by organisms. Another strength in using bioassays to test environmental samples is that they can provide an integrative measure of the toxic potential of a group of chemical compounds, rather than a single contaminant. [8]

Other passive samplers

There are many types of passive samplers used that specialize in absorbing different classes of aquatic contaminants found in the environment. [3] Chemcatcher and SMPD are two types of passive samplers that are also commonly used. [4] Monitoring programs use SMPDs to measure to hydrophobic organic contaminants. SPMDs are designed to mimic the bioconcentration of contaminants in fatty tissues (ITRC, 2006). Contaminants applicable to the use of an SPMD include, but are not limited to, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides, dioxins, and furans. [3]

The SPMD consist of a thin-walled, nonporous, polyethylene membrane tube that is filled with high molecular weight lipid. [2] These tubes are approximately 90 cm long and wrap around the inside of a stainless steel deployment canister. [9] SMPDs are efficient at absorbing pollutants with a log Kow of 4-8. This slightly overlaps with the range of contaminants absorbed by POCIS. Because of this, SMPDs and POCIS devices are often used together in monitoring studies to achieve a more representative understanding of contamination. [2]

Future development

The POCIS system is continually evaluated for the potential to sample a wide range of contaminants. Calibration data and analyte recovery methods are currently being generated by researchers around the world. Techniques to merge the POCIS device with bioassays are also under development. [3] The POCIS sampler already serves as a versatile, economical, and robust tool for monitoring studies and observing trends in both space and time. However, sampling rates are not yet robust enough to supply reliable contaminant concentrations, particularly when regarding environmental quality standards. [8] A limited number of sampling rates have been determined for chemicals and the determination of additional sampling rate data is necessary for the advancement of passive sampling technology. [3]

Related Research Articles

<span class="mw-page-title-main">Water quality</span> Assessment against standards for use

Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through treatment of the water, can be assessed. The most common standards used to monitor and assess water quality convey the health of ecosystems, safety of human contact, extent of water pollution and condition of drinking water. Water quality has a significant impact on water supply and oftentimes determines supply options.

Contamination is the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical body, natural environment, workplace, etc.

<span class="mw-page-title-main">Biochemical oxygen demand</span> Oxygen needed to remove organics from water

Biochemical oxygen demand is an analytical parameter representing the amount of dissolved oxygen (DO) consumed by aerobic bacteria growing on the organic material present in a water sample at a specific temperature over a specific time period. The BOD value is most commonly expressed in milligrams of oxygen consumed per liter of sample during 5 days of incubation at 20 °C and is often used as a surrogate of the degree of organic water pollution.

<span class="mw-page-title-main">Environmental chemistry</span> Scientific study of the chemical and phenomena that occur in natural places

Environmental chemistry is the scientific study of the chemical and biochemical phenomena that occur in natural places. It should not be confused with green chemistry, which seeks to reduce potential pollution at its source. It can be defined as the study of the sources, reactions, transport, effects, and fates of chemical species in the air, soil, and water environments; and the effect of human activity and biological activity on these. Environmental chemistry is an interdisciplinary science that includes atmospheric, aquatic and soil chemistry, as well as heavily relying on analytical chemistry and being related to environmental and other areas of science.

A fecal coliform is a facultatively anaerobic, rod-shaped, gram-negative, non-sporulating bacterium. Coliform bacteria generally originate in the intestines of warm-blooded animals. Fecal coliforms are capable of growth in the presence of bile salts or similar surface agents, are oxidase negative, and produce acid and gas from lactose within 48 hours at 44 ± 0.5°C. The term "thermotolerant coliform" is more correct and is gaining acceptance over "fecal coliform".

A particle counter is used for monitoring and diagnosing particle contamination within specific clean media, including air, water and chemicals. Particle counters are used in a variety of applications in support of clean manufacturing practices, industries include: electronic components and assemblies, pharmaceutical drug products and medical devices, and industrial technologies such as oil and gas.

Groundwater remediation is the process that is used to treat polluted groundwater by removing the pollutants or converting them into harmless products. Groundwater is water present below the ground surface that saturates the pore space in the subsurface. Globally, between 25 per cent and 40 per cent of the world's drinking water is drawn from boreholes and dug wells. Groundwater is also used by farmers to irrigate crops and by industries to produce everyday goods. Most groundwater is clean, but groundwater can become polluted, or contaminated as a result of human activities or as a result of natural conditions.

<span class="mw-page-title-main">Environmental monitoring</span> Monitoring of the quality of the environment

Environmental monitoring describes the processes and activities that need to take place to characterize and monitor the quality of the environment. Environmental monitoring is used in the preparation of environmental impact assessments, as well as in many circumstances in which human activities carry a risk of harmful effects on the natural environment. All monitoring strategies and programs have reasons and justifications which are often designed to establish the current status of an environment or to establish trends in environmental parameters. In all cases, the results of monitoring will be reviewed, analyzed statistically, and published. The design of a monitoring program must therefore have regard to the final use of the data before monitoring starts.

Water chemistry analyses are carried out to identify and quantify the chemical components and properties of water samples. The type and sensitivity of the analysis depends on the purpose of the analysis and the anticipated use of the water. Chemical water analysis is carried out on water used in industrial processes, on waste-water stream, on rivers and stream, on rainfall and on the sea. In all cases the results of the analysis provides information that can be used to make decisions or to provide re-assurance that conditions are as expected. The analytical parameters selected are chosen to be appropriate for the decision making process or to establish acceptable normality. Water chemistry analysis is often the groundwork of studies of water quality, pollution, hydrology and geothermal waters. Analytical methods routinely used can detect and measure all the natural elements and their inorganic compounds and a very wide range of organic chemical species using methods such as gas chromatography and mass spectrometry. In water treatment plants producing drinking water and in some industrial processes using products with distinctive taste and odours, specialised organoleptic methods may be used to detect smells at very low concentrations.

Chemcatcher® is a passive sampling device for monitoring a variety of pollutants in water.

Pollution-induced community tolerance (PICT) is an approach to measuring the response of pollution-induced selective pressures on a community. It is an eco-toxicological tool that approaches community tolerance to pollution from a holistic standpoint. Community Tolerance can increase in one of three ways: physical adaptations or phenotypic plasticity, selection of favorable genotypes, and the replacement of sensitive species by tolerant species in a community.

Analytical thermal desorption, known within the analytical chemistry community simply as "thermal desorption" (TD), is a technique that concentrates volatile organic compounds (VOCs) in gas streams prior to injection into a gas chromatograph (GC). It can be used to lower the detection limits of GC methods, and can improve chromatographic performance by reducing peak widths.

<span class="mw-page-title-main">Groundwater pollution</span> Ground released seep into groundwater

Groundwater pollution occurs when pollutants are released to the ground and make their way into groundwater. This type of water pollution can also occur naturally due to the presence of a minor and unwanted constituent, contaminant, or impurity in the groundwater, in which case it is more likely referred to as contamination rather than pollution. Groundwater pollution can occur from on-site sanitation systems, landfill leachate, effluent from wastewater treatment plants, leaking sewers, petrol filling stations, hydraulic fracturing (fracking) or from over application of fertilizers in agriculture. Pollution can also occur from naturally occurring contaminants, such as arsenic or fluoride. Using polluted groundwater causes hazards to public health through poisoning or the spread of disease.

<span class="mw-page-title-main">Diffusive gradients in thin films</span> Environmental chemistry technique

The diffusive gradients in thin films (DGT) technique is an environmental chemistry technique for the detection of elements and compounds in aqueous environments, including natural waters, sediments and soils. It is well suited to in situ detection of bioavailable toxic trace metal contaminants. The technique involves using a specially-designed passive sampler that houses a binding gel, diffusive gel and membrane filter. The element or compound passes through the membrane filter and diffusive gel and is assimilated by the binding gel in a rate-controlled manner. Post-deployment analysis of the binding gel can be used to determine the time-weighted-average bulk solution concentration of the element or compound via a simple equation.

SPMDs, or semipermeable membrane devices, are a passive sampling device used to monitor trace levels of organic compounds with a log Kow > 3. SPMDs are an effective way of monitoring the concentrations of chemicals from anthropogenic runoff and pollution in the marine environment because of their ability to detect minuscule levels of chemical. The data collected from a passive sampler is important for examining the amount of chemical in the environment and can therefore be used to formulate other scientific research about the effects of those chemicals on the organisms as well as the environment. Examples of commonly measured chemicals using SPMDs include: PAHs, PCBs, PBDEs, dioxins and furans as well as hydrophobic waste-water effluents like fragrances, triclosan and phthalates.

The stabilized liquid membrane device (SLMD) is a passive, integrative sampler that provides an alternative or complementary approach to the conventional water sampling of aqueous metals. The simple device is composed of nonporous low-density plastic lay-flat tubing, which is filled with a chemical mixture containing a chelating agent (metal-binding agent) and a long chain organic acid. The water-insoluble chelating agent-organic acid mixture diffuses in a controlled manner to the exterior surface of the sampler membrane and binds to environmental metals. In practice, the SLMD provides for continuous sequestration of bioavailable forms of trace metals, such as, cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn). The SLMD can also be utilized for in-laboratory preconcentration and speciation of bioavailable trace metals from grab water samples.

<span class="mw-page-title-main">Stabilized liquid membrane devices</span>

A stabilized liquid membrane device or SLMD is a type of passive sampling device which allows for the in situ, integrative collection of waterborne, labile ionic metal contaminants. By capturing and sequestering metal ions onto its surface continuously over a period of days to weeks, an SLMD can provide an integrative measurement of bioavailable toxic metal ions present in the aqueous environment. As such, they have been used in conjunction with other passive samplers in ecological field studies.

<span class="mw-page-title-main">Passive sampling</span>

Passive sampling is an environmental monitoring technique involving the use of a collecting medium, such as a man-made device or biological organism, to accumulate chemical pollutants in the environment over time. This is in contrast to grab sampling, which involves taking a sample directly from the media of interest at one point in time. In passive sampling, average chemical concentrations are calculated over a device's deployment time, which avoids the need to visit a sampling site multiple times to collect multiple representative samples. Currently, passive samplers have been developed and deployed to detect toxic metals, pesticides, pharmaceuticals, radionuclides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and other organic compounds in water, while some passive samplers can detect hazardous substances in the air.

Within the environmental sciences, screening broadly refers to a set of analytical techniques used to monitor levels of potentially hazardous organic compounds in the environment, particularly in tandem with mass spectrometry techniques. Such screening techniques are typically classified as either targeted, where compounds of interest are chosen before the analysis begins, or non-targeted, where compounds of interest are chosen at a later stage of the analysis. These two techniques can be organized into at least three approaches: target screening, using reference standards that are analogous to the target compound; suspect screening, which uses a library of cataloged data such as exact mass, isotope patterns, and chromatographic retention times in lieu of reference standards; and non-target screening, using no pre-existing knowledge for comparison before analysis. As such, target screening is most useful when monitoring the presence of specific organic compounds—particularly for regulatory purposes—which requires higher selectivity and sensitivity. When the number of detected compounds and associated metabolites needs to be maximized for discovering new or emerging environmental trends or biomarkers for disease, a more non-targeted approach has traditionally been used. However, the rapid improvement of mass spectrometers into more high-resolution forms, with increased sensitivity, has made suspect and non-target screening more attractive, either as stand-alone approaches or in conjunction with more targeted methods.

Workplace exposure monitoring is the monitoring of substances in a workplace that are chemical or biological hazards. It is performed in the context of workplace exposure assessment and risk assessment. Exposure monitoring analyzes hazardous substances in the air or on surfaces of a workplace, and is complementary to biomonitoring, which instead analyzes toxicants or their effects within workers.

References

  1. 1 2 3 "Passive Sampling". United States Geological Society (USGS) Columbia Environmental Research Center. May 2004. Retrieved 24 May 2014.
  2. 1 2 3 4 Alvarez, DA; Petty JD; Huckins JN; Jones-Lepp TL; Getting GT; Goddard JP; Manahan SE (2004). "Development of a passive. in situ sampler for hydrophobic organic contaminants in aquatic environments". Environmental Toxicology and Chemistry. 23 (7): 1640–1648. doi:10.1897/03-603. PMID   15230316.
  3. 1 2 3 4 5 6 7 8 9 10 11 Interstate Technology & Regulatory Council, Authoring Team. "Technology Overview of Passive Sampler Technologies". ITRC (Interstate Technology & Regulatory Council).
  4. 1 2 3 4 5 6 Alvarez, D. (2013). "Development of Semipermeable Membrane Devices (SPMDs) and Polar Organic Integrative Samplers (POCIS) for Environmental Monitoring". Environmental Toxicology and Chemistry. 23: 2179–2181. doi: 10.1002/etc.2339 . PMID   24006333.
  5. 1 2 3 4 5 6 7 8 9 10 11 Alvarez, D. A.; Huckins,J. N.; Petty, J.D.; Jones-Lepp, T.; Stuer-Lauridsen, F.; Getting, D.T.; Goddard, J.P.; Gravel A. (2007). Comprehensive Analytical Chemistry: Passive Sampling Techniques in Environmental Monitoring. Netherlands: Elsevier. pp. 171–197. ISBN   978-0-444-52225-2.
  6. http://ipsw.eu/2013/ International Passive Sampling Workshop and Symposium (IPSW)[ dead link ]
  7. Chimuka L, Cukrowska E. 2008. Monitoring of Aquatic Environments Using Passive Samplers. Open Analytical Chemistry Journal 2:1-9.
  8. 1 2 3 4 5 6 7 8 9 Harman C, Allan IJ, Vermeirssen ELM. 2012. Calibration and Use of the Polar Organic Chemical Integrative Sampler- A Critical Review. Environmental Toxicology and Chemistry 14:2724-2738.
  9. 1 2 3 4 Polar Organic Chemical Integrative Sampler (POCIS) United States Geological Society (USGS) Columbia Environmental Research Center.
  10. 1 2 3 Alvarez DA. 2010. Guidelines for the Use of the Semipermeable Membrane Device (SPMD) and the Polar Organic Chemical Integrative Sampler (POCIS) in Environmental Monitoring Studies.Section D, Water Quality Book 1, Collection of Water Data by Direct Measurement.
  11. USGS: POCIS: Polar Organic Chemical Integrative Sampler (POCIS) National Environmental Methods Index (NEMI).