Direct Measurement of Microplastics by Carbon Detection via Single Particle ICP-TOFMS in Complex Aqueous Suspensions

Abstract

Multiple analytical techniques to measure microplastics (MPs) in complex environmental matrices are currently under development, and which is most suited often depends on the aim(s) of the research question and the experimental design. Here, we further broaden the suite of possible techniques which can directly detect MPs in suspension while differentiating the carbon contained in MPs from other natural particles and dissolved organic carbon (DOC). Single particle inductively coupled plasma mass spectrometry (sp-ICP-MS) is well suited to measuring particles at trace concentrations, and the use of ICP time-of-flight-MS (ICP-TOFMS) allows one to simultaneously monitor the entire elemental spectrum to assess the full elemental composition of individual particles through developing elemental fingerprints. Because carbon is not detected in a standard operation mode with icp TOF, a dedicated optimization was necessary. Subsequently, to assess the feasibility of monitoring 12C particle pulses for the detection of MPs in more complex natural waters, two proof-of-principle studies were performed to measure MPs in waters with environmentally relevant DOC backgrounds (≤20 mg/L) and in the presence of other carbon containing particles, here, algae. Elevated DOC concentrations did not impact the enumeration of particles in suspension, and individual MPs, single algae, and aggregates of MPs and algae were clearly distinguished. The simultaneous identification of different analytes of interest allows for multiplexed sp-ICP-TOFMS experiments utilizing elemental fingerprinting of particles and is a step forward in quantifying MPs in aqueous environmental samples.

Single-Particle ICP-TOFMS with Online Microdroplet Calibration: A Versatile Approach for Accurate Quantification of Nanoparticles, Submicron Particles, and Microplastics in Seawater

“…Single-particle ICP–MS has previously been applied to the measurement of microplastic particles; − however, the approach has not yet been applied for the analysis of microplastics in seawater. Here, we used uniform polystyrene beads doped with rare-earth elements (Ce, Eu, Ho, and Lu) as model microplastics.…”

Development of single-cell ICP-TOFMS to measure nanoplastics association with human cells

“…It should be noted that as cells also contain carbon, distinguishing between the carbon content in cells and the carbon in nanoplastics adds another level of complexity. While it is possible to distinguish μm-sized plastics from algae cells using multi-element fingerprints, 22 the low intrinsic carbon mass of nanoplastics and limited sensitivity for carbon, prevented their detection and thus reinforces the need to explore alternative approaches such as using metal signals as proxies for the nanoplastics. Consequently, here Pd-signals were used as proxy for individual nanoplastics detection.…”

“…Plastics particles down to the μm-size can be detected by monitoring the carbon content by ICP-MS analysis, however due to the low sensitivity of ICP-MS for carbon, this approach is not sufficient to target nano-sized plastics. [22][23][24] Labelled or doped nanoplastics have been previously used as an approach to trace and characterize nanoplastics in complex media and biological tissues, including the use of fluorescent dyes, isotope labels 25 and trace metals. 26 Fluorescence labeling is a common method due to ease of detection by simple optical methods, but limitations include potential modification of particle properties and biointeractions from incorporated dyes, stability of fluorescence, leakage of dyes from the particle as well as limited sensitivity to detect and quantify individual or small particles.…”

The elemental fingerprint as a potential tool for tracking the fate of real-life model nanoplastics generated from plastic consumer products in environmental systems

“…43,44 Additionally, it has been recently used for the detection of carbon in microplastics. 45–49 The size detection limit of metal(loid)s-bearing nanoparticles varies from few to several hundreds of nanometers 50 whereas that of carbon-bearing particles (microplastics) varies from 0.62 to 1.8 μm, 45–47 depending on instrument sensitivity, target element, and media composition. Additionally, single particle-inductively coupled plasma-time of a flight-mass spectrometry (SP-ICP-TOF-MS) has been recently used for the simultaneous detection of carbon and rare earth elements (REEs) in synthetic REE-doped polystyrene microplastics.…”