Rapid Identification and Quantification of Microplastics in the Environment by Quantum Cascade Laser-Based Hyperspectral Infrared Chemical Imaging

Abstract

The monitoring of the emerging contaminant, microplastics, in the environment, in water supply, and for food safety is of major interest to science, consumers, and governments. While the chemical analysis of these particles is considered mandatory, a rapid and reliable method for the determination of particle sizes, shapes, and numbers is missing, as existing methods are not fitting into current laboratory measurement routines. In this study, we present an approach for circumventing these issues through the application of quantum cascade laser-based microscopy combined with an automated data analysis. This method allows the measurement of an area of 144 mm2 in 36 min, with a pixel resolution of 4.2 μm, which is an appropriate timeframe and spatial resolution for routine measurements. The performance was compared to the existing state-of-the-art Fourier transform infrared microscopy analyses. Further, the application of the method on various environmental samples was investigated to examine its capacity to provide number and variety of present particles. The described analytical procedure overcomes the last restrictions for schedulable and rapid microplastic monitoring, resulting in a highly detailed data set for particle numbers, particle shapes, and polymer types.

Analysis of microplastics in drinking water and other clean water samples with micro-Raman and micro-infrared spectroscopy: minimum requirements and best practice guidelines

“…For both spectroscopic methods, the description and validation of the spectral identification routine have to be included. At present, it is common practice to report MP numbers in predefined size classes, i.e., in a binned form [10,54,81,128,129]. By this, the details on the size of each MP detected in samples get lost.…”

“…These were subsequently scanned in the region 1800-1184 cm −1 and 1160-1084 cm −1 to identify the targeted polymer types. They compared the QCL-IR system's performance to stateof-the art FTIR imaging and concluded that the results gained using QCL-IR microscopy were in good agreement with those of the reference method, while being about tenfold as fast [81]. QCL-IR, until now, was successfully applied to samples of soil [82,83], river [84], and brackish waters [85].…”

“…The regions of interest are subsequently scanned over a wider wavenumber range to gather enough spectral information to be able to identify the particles. For instance, Primpke et al scanned environmental samples at 1470 cm −1 to identify potential MP particles [81]. These were subsequently scanned in the region 1800-1184 cm −1 and 1160-1084 cm −1 to identify the targeted polymer types.…”

Paradigms to assess the human health risks of nano- and microplastics

“…With regards to innovative technologies addressing the isolation, identification and quantification of NMPs that cause risks for human health, different combinations of methods are currently under research for targeting different size ranges. For MP particles down to 1 μm, techniques employing a correlative combination of light microscopy or hyperspectral imaging with identification by laser confocal Raman and TOF-SIMS are under development [78][79][80]. For plastic particles in the nanoscale, correlative scanning electron microscopy (SEM) -confocal Raman spectroscopy has being explored [81,82].…”

Capture of Toxic Oxoanions from Water Using Metal–Organic Frameworks

“…Oxoanions are a class of pollutants of increasing concern resulting from various industrial processes prevalent today. When discharged into bodies of water, their inherent toxicity harms ecosystems and contaminates potable water. , Oxoanions have been classified as toxic priority pollutants under the Clean Water Act, and because tolerable concentrations are often exceeded, targeted treatment of affected bodies of water becomes necessary. , Several treatment mechanisms have been developed to remediate water sources from these pollutants ranging from the facilitation of degradation processes and use of activated carbon capture to the deployment of sorbents (such as metal–organic and covalent–organic frameworks) for explicit removal of oxoanions. − The latter approach is the focus of this investigation, for which high capacity, porous materials including metal–organic frameworks (MOFs) have found efficient implementation as sorbents. ,− MOFs (nanoporous crystalline materials consisting of metal clusters linked together by organic ligands) exhibit tunable pore sizes, easily functionalizable ligands, and high internal surface areas, making them ideal candidates for small molecule capture and separation. − The vast combinations of metal nodes and organic ligands allow for tuning the chemical and physical properties of MOFs to highly specific applications . This flexibility has led to a wide range of MOF designs, such as zeolitic imidazolate frameworks (ZIFs), cationic MOFs, and neutral MOFs containing open-metal sites. − MOFs hold much promise as highly selective next-generation sorbents by virtue of their diverse structures and finely tunable host–guest interactions.…”