Passive Sampling Method for Analyzing Water Contaminants

A team of scientists from Universitat Rovira i Virgili in Tarragona, Spain, is investigating a new approach to monitoring water samples for contaminants of emerging concern, with their work being published in the Journal of Chromatography A (1).

Contaminants of emerging concern (CECs) in water is 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. Monitoring contaminants in environmental waters can be done in numerous ways. One approach that has recently grown in popularity is the use of passive sampling. Although most analytical methods for contaminant detection are based on discrete grab sampling, passive sampling combines sampling with sample treatment steps, which can provide time-weighted average (TWA) concentration values. This, along with low cost, ease of deployment, capacity for performing multi-site screening, no requirements for power or supervision, easy maintenance, and a reduction of matrix interferences, among other factors, makes passive sampling a good option for monitoring contaminants in water.

To test this method, the scientists used ceramic passive samplers (CPSs) using mixed-mode strong cation-exchange sorbent (Oasis MCX) as retention phase for the determination of 21 different drugs and their metabolites in river water samples, which were previously determined with liquid chromatography-tandem mass spectrometry. The CPSs were calibrated using 10 samplers in a 4L beaker with bottled water spiked at 20 μg/L with a mixture of analytes, before repeating the process with the same conditions, only with river water instead. The team used bottled water because “its pH and mineral content better simulates natural waters as compared to ultrapure water, and compounds are hardly present in bottled water samples,” said Núria Fontanals, Senior Researcher in the Analytical and Organic Chemistry Department at the Universitat Rovira i Virgili.

According to the researchers, bottled water was used for calibration since it proved more like the river water than Mili-Q ultrapure water. The CPSs were calibrated for 9 days with bottled water and river water, obtaining, for the 19 stable compounds, sample rates (R_s) ranging between 0.180 and 1.767 mL/day and diffusion coefficients (D_e) between 2.02E-8 and 2.81E-7 cm²/s. After calibration, CPSs were deployed into the Ebre River, located in Spain. Reproducibility was achieved, and multiple analytes were determined, including, but not limited to, gabapentin at 76 ng/L, caffeine at 203 ng/L and diclofenac amine at 57 ng/L.

The stability and calibration studies, despite using different types of water, disclosed similar results, in addition to proving effective in the experiment. “The passive method presented here is simple and feasible for the monitoring of CECs at trace levels in river water. This study opens the possibility of using other mixed-mode sorbents or other types of sorbents as retaining phase on CPSs or other passive samplers,” the scientists wrote in the study (1). Furthermore, the scientists believe the design can be improved “so that the diffusion of the compounds from sample to reach the sampler might be improved”. They also agree there is always room to test compound retention with other materials, from different bodies of water to biological source or food samples.

Reference

(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

(2) Loop. Núria Fontanals. Frontiers Media SA 2023. https://loop.frontiersin.org/people/53798/bio (accessed 2023-09-29)