An In-Depth Look at Passive Sampling to Determine Contaminants of Emerging Concern

A team of investigating a new approach to monitoring water samples for contaminants of emerging concern (1).

Scientists from the Universitat Rovira i Virgili in Tarragona, Spain, in collaboration with the Department of Environmental Chemistry, IDAEA-CSIC in Barcelona, conducted the study, which was published in the Journal of Chromatography A, to find a more efficient means of contaminant detection than discrete grab sampling. Contaminants of emerging concern (CECs) in water are one of the most vital issues in environmental studies, partly because they can stem from many compound groups, including pharmaceuticals, flame retardants, hormones, and plastic additives, amongst others. The passive sampling method presented is simple and feasible and allows the time-integrated analysis of pharmaceuticals and drugs at trace levels in river water.

LCGC spoke with Núria Fontanals, senior researcher in the Analytical and Organic Chemistry Department at the Universitat Rovira i Virgili in Tarragona, Spain, about the inner workings of this method and how it can be developed further.

Can you explain the passive sampling method that you used in this study?

Passive sampling combines the sampling and sample treatment steps in one as it enables the in-situ enrichment of contaminants, and, therefore, it is not necessary to sample, handle, and extract large volume of samples. Moreover, as it yields time-weight-average (TWA) concentration, it provides a high level of sensitivity since the compounds accumulate over the deployment period. Interferences from matrix might be reduced due to the diffusion layer of the device. In addition, as the passive sampler is left during the deployment period in contact with the sample and the compounds, the representativeness of the sample is enhanced. As passive sampling combines sampling and sample treatment saves time and money. Moreover, it does not require power and supervision, it is easy to use and maintain, and the sampler device is low cost.

In your study, you tested river water for trace amounts of drugs. How do these drugs typically end up in river water?

Drugs are constantly emitted into the environmental samples due to their widespread use and consumption. They are not completely metabolized in the organism and are excreted unchanged or as metabolites through urine. They reach wastewater treatment plants and because of the limited capacity of the treatment process to eliminate these types of compounds, they are finally discharged into surface waters.

Can this approach be adjusted for other bodies of water? How so?

Passive sampling can be applied to different types of water samples after successful calibration with this type of water. In fact, there are several examples reported in literature where passive sampling is effectively applied to different type of water such as mineral water, tap water, surface water and sewage water.

Why did you select bottled water as the means of initially calibrating ceramic passive samplers (CPSs)?

In a first instance, calibration was performed in bottled water rather than ultrapure water as its pH and mineral content better simulates natural waters as compared to ultrapure water, and compounds are hardly present in bottled water samples. Nevertheless, in one study, calibration was performed in bottled water and river water and the constants were comparable (1).

Are there any ways this method can be improved on in the future?

The design of the sampler can be improved so that the diffusion of the compounds from sample to reach the sampler might be improved. In addition, there is always room to test other materials to improve the retention of the compounds.

What other types of analysis can passive sampling be used for?

Passive sampling can be used in other type of liquids other than water for instance from biological source or food samples. However, the passive sampling fully exploits its advantages when large volume of sample should be sampled. For instance, passive samplers can be used for analysis of water quality in food processing industries.

Was there anything surprising you found during this study?

The sampler design developed did not involve fouling during deployment period and how influent is to select a suitable material to successfully retain the studied compounds.

What’s the most important part of this research that you’d like readers to know?

One of the main advantages of the passive sampling is yielding time-weight average concentration as well as the high-level of sensitivity provided since the analytes accumulate over their deployment period. Reporting TWA concentration provide an average contaminant concentration that is more representative of exposure rather than reporting punctual concentrations.

Passive sampling is an undiscovered sampling and sample treatment approach for most laboratories involved in environmental analysis. We encourage them to test it. Once you start using there is no chance to come back again to grab sampling and the tedious sample treatment techniques in laboratory. There are lots of unexplored issues in passive sampling, so there is room for research!

This interview has been lightly edited for length and clarity.

References

(1) Clivillé-Cabré, P.; Lacorte, S.; Borrull, F.; Fontanals, N.; Marcé, R. M. Evaluation of ceramic passive samplers using a mixed-mode strong cation-exchange sorbent to monitor polar contaminants in river water. J. Chromatogr. A. 2023, 1708, 464348. DOI: https://doi.org/10.1016/j.chroma.2023.464348