What is a Passive Sampler?

With a growing concern over the safety of our environment, the governments of countries across the world are imposing ever more strict regulations on the cleanliness of water and air. In order to measure this, samplers are needed to break down the liquid or gas into its components and check for unwanted harmful agents, such as toxic or chemical properties.

Traditionally, sampling of air has been achieved via the use of active samplers, which employ a pump to propel the gas through a filter or other collection device for analysis. However, over the last few decades, the emergence of passive samplers (sometimes known as passive sampling devices (PSDs) or diffusive samplers, since they often rely on the principle of diffusion) has offered an alternative to the active sampler.

Whilst the first passive sampler was pioneered in 1973 by scientists Palmer and Gunnison, the popularity of the method and its widespread commercial availability has exploded over the last 20 years. Instead of using a pump to propel the air, passive samplers utilise unassisted molecular diffusion onto an absorbent. After this process, the analytes are desorbed from the absorbent using thermal desorption or a solvent for further study.

The Advantages of Passive Samplers

Passive samplers offer a number of benefits over active samplers, including the following:

• No need for electricity
• Cheaper running costs
• Ease of use
• No moving parts
• Compact, efficient and highly portable
• Does not need supervision
• Can be used in hazardous environments
• Can reflect pollution evolution over a period of 8 hours or several months
• Is noiseless
• Can be used economically for monitoring several different locations
• Equally adept at indoor and outdoor air analysis

For a more in-depth look at the comparison between the two techniques, read the article Active Versus Passive Air Sampling - Eddie Salter.

Passive Sampling in Water

Just as pollution levels in air are vital to understanding the safety of the air we breathe, monitoring toxicity and chemical corruption of the water which we drink is paramount to safe living, as well. Indeed, as part of the EU's Water Framework Directive, such measures are not only necessary for our safety but actually required by law.

In order to meet these difficult challenges, PSDs are often employed to monitor chemicals levels which may appear to only be present in trace amounts but which are at dangerous toxicity concentrations. This can also work to analyse chemical compounds which may come and go over time, since PSDs can be deployed for months at a time.

The article The Many Faces of a New Versatile Passive Sampler discusses how one particular product, Chemcatcher®, is dominating the field and examines the advantages this particular model offers over the competition.