Flow-Through Quantification of Microplastics Using Impedance Spectroscopy

Abstract

Understanding the sources, impacts, and fate of microplastics in the environment is critical for assessing the potential risks of these anthropogenic particles. However, our ability to quantify and identify microplastics in aquatic ecosystems is limited by the lack of rapid techniques that do not require visual sorting or preprocessing. Here, we demonstrate the use of impedance spectroscopy for high-throughput flow-through microplastic quantification, with the goal of rapid measurement of microplastic concentration and size. Impedance spectroscopy characterizes the electrical properties of individual particles directly in the flow of water, allowing for simultaneous sizing and material identification. To demonstrate the technique, spike and recovery experiments were conducted in tap water with 212–1000 μm polyethylene beads in six size ranges and a variety of similarly sized biological materials. Microplastics were reliably detected, sized, and differentiated from biological materials via their electrical properties at an average flow rate of 103 ± 8 mL/min. The recovery rate was ≥90% for microplastics in the 300–1000 μm size range, and the false positive rate for the misidentification of the biological material as plastic was 1%. Impedance spectroscopy allowed for the identification of microplastics directly in water without visual sorting or filtration, demonstrating its use for flow-through sensing.

Using Adhesives to Capture Microplastics from Water

“…In flow cytometry, a sheath fluid is used to hydrodynamically focus a stream of particles in front of a laser where they are subsequently detected, counted, or sorted . This technique is commonly used to analyze single-cell populations and rapidly retrieve data about those cells. , Recently, flow cytometry was utilized for rapid quantification of microplastics using fluorescence or impedance spectroscopies as the output signal. In this work, we deployed a forward scatter detector, a photomultiplier that analyzes events in proportion to their size, for detection.…”

Field-Portable Microplastic Sensing in Aqueous Environments: A Perspective on Emerging Techniques

“…Analysis based on mechanical properties evaluate MP size, density, modulus of elasticity, and acoustic contrast factor [33]. Electrical properties of MPs include relative permittivity, and dielectrophoretic mobility [34,35].…”

“…At low or zero frequency, the impedance change is proportional to particle volume, and is the working principle of a Coulter counter. Impedance changes at high frequency reflect both the material properties and the size of the particle [35,107]. To distinguish between the effects of size and material type, measurements are conducted at high and low frequencies simultaneously [107,111].…”

“…Figure 13A shows how this difference is represented in the impedance spectra of the different particle types. In a recent publication, we demonstrated the use of impedance spectroscopy for flowthrough MP quantification [35]. A flow channel was built from two electrode plates, shown in Figure 13B.…”

Advanced microplastic monitoring using Raman spectroscopy with a combination of nanostructure-based substrates

“…Recently, there has been a large number of scientific reviews promising to elucidate not only the effects of MNP pollution on risks to human health [ 49 ] and the environment [ 50 ], but also many methodologies for the trace detection of MNPs in aquatic [ 51 , 52 ], sedimentary [ 53 , 54 ], freshwater, and coastal ecosystems [ 55 ], as well as other environments [ 56 , 57 ], in wastewater [ 58 ], and on beaches [ 59 ]. Furthermore, several researchers have investigated a variety of analytical technologies for the trace detection of MNPs, including fluorescence microscopy [ 18 , 60 – 62 ], impedance spectroscopy [ 63 ], microwave-based techniques [ 64 ], hyperspectral imaging [ 65 , 66 ], Fourier transform infrared spectroscopy (FTIR) [ 67 , 68 ], near-infrared (NIR) hyperspectral imaging and chemometrics [ 69 ], semi-automated analysis [ 70 ], a thermo analytical method [ 71 ], and mass- or particle-based analysis [ 72 ]. However, these thermal analysis methodologies often require additional procedures to separate analytes in the sample preparation, leading to time-consuming and toxic organic solvents, as well as further adverse effects on the environment.…”