Microplastics have become emblematic of modern pollution, but their impact extends beyond the particles themselves. As they drift through rivers and oceans, these polymer fragments can accumulate a suite of hydrophobic contaminants – from polycyclic aromatic hydrocarbons (PAHs) to widely used pesticides – potentially reshaping how such chemicals move through ecosystems. As environmental monitoring expands to address emerging contaminants, analytical chemists face a dual challenge: measuring complex pollutant interactions while minimizing the footprint of the measurement process itself.
In a recent study, Achille Cappiello and colleagues present a miniaturized SPME-MOI-LEI-MS platform designed to monitor pollutant adsorption on microplastics with minimal solvent use and high throughput. Here, Cappiello discusses the motivation behind developing a greener, gas-phase ionization strategy, the analytical refinements needed to ensure robustness, and the implications for more sustainable environmental monitoring.
What initially motivated your team to develop a rapid, greener analytical approach for studying organic pollutants associated with microplastics?
My team and I decided to study this topic because there remains insufficient information on the adsorption of pollutants onto microplastic surfaces under real-world environmental conditions. At the same time, several studies have shown that the toxicity of microplastics contaminated with heavy metals or organic pollutants can be significantly higher than that of pristine particles. In our view, this underscores the importance of the subject, as the toxicity of microplastic exposure extends well beyond the particles themselves to include the chemicals they transport.
The use of a green, rapid, and versatile analytical technique was fundamental to the study’s implementation – and to the potential, low-impact future extension to other environmental pollutants. Compared with existing methods, our gas-phase ionization approach is unaffected by matrix effects, thereby consistently improving quantitative LC-MS data in real-world applications.
Could you explain, in a nutshell, how your platform works?
This technique is useful for monitoring a chemical process in near-real time, as demonstrated in our recent studies. The platform operates by desorbing the SPME fiber into 2.5 µL of solvent, leading to high enrichment of analytes within the microfluidic open interface (MOI) chamber, followed by injection into the MS via a liquid electron ionization (LEI) interface at nL/min flow rates. This interface enables proper vaporization and efficient transport of analytes in the gas phase to the EI ion source.
We decided to use this platform to monitor PAHs and pesticide concentrations over time, as SPME-MS requires minimal analysis time and solvent consumption. We considered this aspect fundamental in complying with the principles of green analytical chemistry. SPME fibers can be selected based on the analyte’s chemical properties, while LEI is particularly suitable for the analysis of PAHs and most pesticides.
Were there any results in particular that surprised you?
A surprising result was the high adsorption capacity of chlorpyrifos – a neurotoxic pesticide – on LDPE. More than 90 percent of the initial mass was recovered, indicating strong adsorption and suggesting a phenomenon that warrants monitoring in future environmental studies. LDPE is more hydrophobic than PP, and thus exhibits greater adsorption capacities for most of the targeted analytes – PAHs in particular – for which hydrophobic interactions mainly drive adsorption.
That said, we did observe some deviations from this trend for pesticide adsorption. For example, in the case of dichlorvos – an organophosphate insecticide – adsorption on PP was significantly higher than on LDPE. Conversely, metalaxyl – an acylalanine fungicide – showed comparable adsorption capacities on both microplastics. These results indicate that pesticides with different functional groups can have markedly distinct interactions with microplastic surfaces, sometimes exhibiting nonintuitive or unpredictable trends.
What were the main analytical or technical challenges you faced – and how did you overcome them?
One of the main challenges we initially encountered was optimizing the conditioning and cleaning steps for the SPME fiber between consecutive analyses. As desorption in the MOI is partial rather than exhaustive, a fraction of the analytes remains adsorbed on the fiber after each run – potentially leading to carryover effects and reduced reproducibility.
Initially, we had combined conditioning and cleaning into a single step to minimize solvent consumption and align with green analytical chemistry principles. However, this approach proved challenging to implement effectively as residual analytes were not completely removed, resulting in signal variability across extractions. A significant improvement in reproducibility was achieved by performing conditioning and cleaning as two distinct steps before subsequent extractions. This strategy ensured more consistent fiber performance, reduced memory effects, and ultimately enhanced the analytical method’s robustness and reliability.
More broadly, how does this approach improve our ability to understand microplastics as vectors for hazardous chemicals?
Our study aimed to quantify microplastic adsorption and assess their viability as vectors for hazardous chemicals across the environment and biota, with a focus on pollutants frequently detected in surface and groundwater. We hope that this work can contribute to research in this field by supporting the assessment of environmental and human health risks associated with microplastic exposure, including the often-overlooked co-exposure to toxic chemicals transported by these particles.
This study can be extended in several ways. This could be by monitoring additional classes of hazardous chemicals, or evaluating the effects on biota arising from the combined exposure to microplastics and the contaminants investigated. In this context, a new project is currently underway to examine the adsorption of benzodiazepines – a widely used class of pharmaceuticals – onto micro- and nanoplastics. This work is motivated by evidence that particle size has a dramatic influence on adsorption capacity. In parallel, we’re also assessing the influence of key environmental factors – such as photodegradation (plastic aging) and biofilm formation on plastic surfaces – on adsorption behavior and contaminant transport.
Looking ahead, what are the next steps for this platform?
Environmental monitoring at the global level remains a subject of active debate, and much greater effort is still required. As new and emerging pollutants continue to be identified, analytical scientists must develop innovative solutions that generate increasingly comprehensive and reliable data. Green analytical methods are essential for extending chemical monitoring to a global scale, both sustainably and practically.
At present, a significant disparity persists in chemical pollution monitoring between the Global North and the Global South, as well as among different regions worldwide. In this context, miniaturized analytical devices and in situ monitoring technologies represent promising solutions for environmental surveillance. They may also help improve the global availability of information on pollution levels and the environmental impacts of chemical contaminants.
Achille Cappiello is a Professor of Analytical Chemistry at the University of Perugia, Italy.
Newsletters
Receive the latest analytical science news, personalities, education, and career development – weekly to your inbox.
