Passive Sampling Using SPMDs and POCIS

Two of the most commonly used passive samplers for organic contaminants are the semipermeable membrane device (SPMD) and the polar organic chemical integrative sampler (POCIS). These samplers can provide information on the concentration, occurrence, transport, and fate of a wide range of organic chemicals. The SPMD and POCIS sample chemicals in the dissolved phase (not bound to particulate or other matter) and therefore mimic the organismal exposure of bioavailable chemicals. Extracts from these samples can also be screened by in vitro and in vivo tests to determine the biological importance of chemicals sampled by the device.

A semipermeable membrane device (SPMD).

(Public domain.)

Semipermeable Membrane Devices (SPMDs)

SPMDs are constructed of a non-porous lay-flat polyethylene membrane containing an ultra-high purity lipid (triolein). SPMDs sample neutral organics with a log octanol-water partition coefficient (log K_ow) greater than 3. SPMD have been used for sampling both water and air; however, their primary use is in surface water monitoring studies.  

Chemicals frequently sampled by SPMDs include:

• Polycyclic Aromatic Hydrocarbons (PAHs)
• Polychlorinated Biphenyls (PCBs)
• Organochlorine Pesticides
• Polybrominated Diphenyl Ethers (PBDEs)
• Dioxins and Furans
• Fragrances
• Triclosan

A polar organic chemical integrative sampler (POCIS).

(Public domain.)

Polar Organic Chemical Integrative Samplers (POCIS)

POCIS consist of two microporous (0.1 micron pore) polyethersulfone membranes enveloping a solid-phase extraction resin. Oasis HLB is the general resin of choice for use in the POCIS due to its ability to sample and retain a wide range of chemicals; however, other types of resins such as carbaneous and ion-exchange resins have been used for specific applications. The POCIS generally samples organic chemicals with a log K_ow less than 3; however, chemicals with log K_ows between 4 and 5 are frequently reported. The POCIS is primarily used in surface water studies and can be used for groundwater studies.

Chemicals frequently sampled by POCIS include:

• Current-use Pesticides
• Hormones
• Pharmaceuticals
• Phosphate flame retardants
• Surfactants
• Per- and Polyfluoroalkyl Substances (PFAS)
• Metabolites and degradation products

Tools and Resources

SPMD and POCIS How-To Guide

The following guide provides suggestions and best-practices that can help users have a successful study.  This guide covers aspects of study design, field deployments, laboratory work, and data handling.

Alvarez, D.A., 2010, Guidelines for the Use of the Semipermeable Membrane Device (SPMD) and the Polar Organic Chemical Integrative Sampler (POCIS) in Environmental Monitoring Studies: U.S. Geological Survey, Techniques and Methods 1–D4, 28 p.

(Chapter 4 of Section D, Water Quality Book 1, Collection of Water Data by Direct Measurement)

Passive Sampling Devices for Environmental Monitoring: Tips for a Successful Study  

SPMD Calculators

The mathematical models used to convert a concentration of a chemical in an SPMD extract into a time-weighted average water concentration can be complex.  To simplify this process, two customizable Microsoft Excel spreadsheets have been created.  Selection of which calculator to use depends on whether PRC data is available for the SPMDs or not.  Both of these spreadsheets have an Instructions tab that provide information on how to use and modify the spreadsheet.

SPMD Water Concentration Estimator v4-1.xls

Use for estimating water concentrations in cases where no PRCs were used in conjunction with the SPMDs.

SPMD Water Concentration Estimator v5-2.xlsx

Use for estimating water concentrations when PRCs were used. This version allows for the use for up to 5 PRCs at a time.

Read more about Passive and Field Sampling