Analysis of microplastics as emerging using single particle ICP-MS

Authors:

Tomoko Vincent, Dhinesh Asogan, Daniel Kutscher

Thermo Fisher Scientific, Germany

Plastics are widely used in many products, electronics and packaging (foils, bottles, foams, etc). Due to their physical formation, plastics often have high strength and are resistant to corrosion. As the overall amount of plastics produced globally continues to increase, so does the amount of waste produced. As a result of incorrect disposal of many plastic products, pollution has become a major threat to the environment.

A surprisingly large amount of the environmental contamination observed today arises from less immediately obvious anthropogenic sources, such as rubber particles from tire wear and other microscale plastic debris, which is then subsequently mobilized. A study conducted in 2019 estimated the contribution of microplastic particles washed off by rain into storm drains in the San Francisco Bay Area to exceed 300 times the amount of plastic pollution that enters the environment through sewers and sewage plants .

Although there is no guidance for a maximum contaminant level yet, the United States Environmental Protection Agency (EPA) has released its Microplastic Beach Protocol, containing a detailed work instruction for volunteers to scientifically collect and analyze microplastic pollution (here with typical sizes in the millimeter range) in the environment.2 This direction has accelerated focus on evaluating the extent of pollution of the environment with microplastics, as well as on research into the degradation of these particles over time and possible ways for protecting environmental and human health on a larger scale.

Inductively coupled plasma mass spectrometry (ICP-MS) has been used for the analysis of nanoparticles, allowing the investigation of a reasonably high number of particles in a short time, and providing an overview on the average size and number composition of a sample. Since there are almost no trace metals intrinsically present in microplastics, direct ICP-MS analysis was for long not considered feasible, as analysis of carbon by ICP-MS is considered difficult due to the low ionization yield for this element and elevated backgrounds due to the ubiquitous presence of carbon as CO2 in the surrounding air and dissolved in all aqueous solutions prepared for analysis. However, for particles of larger size, such as microplastics, the use of ICP-MS operated in time-resolved mode for carbon measurement presents a promising alternative for studying the rate of plastic degradation in environment pollution.4 This application note demonstrates how the iCAP RQ ICP-MS was used to detect the carbon in microplastics in both standard solutions as well as in a drinking water sample fortified with microplastic material.

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