Quantification of Poly(vinyl chloride) Microplastics via Pressurized Liquid Extraction and Combustion Ion Chromatography

Quantification of micro- and nano-plastics in atmospheric fine particles by pyrolysis-gas chromatography-mass spectrometry with chromatographic peak reconstruction

The effects of micro- and nano-plastics (MNPs) on human health are of global concern because MNPs are ubiquitous, persistent, and potentially toxic, particularly when bound to atmospheric fine particles (PM2.5). Traditional quantitative analysis of MNPs by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) is often inaccurate because of false positive signals caused by similar polymers and organic compounds. In this study, a reliable analytical strategy combining HNO3 digestion and chromatographic peak reconstruction was developed to improve the precision of pyrolysis-gas chromatography-mass spectrometry analysis of multiple MNPs bound to PM2.5. The optimized HNO3 digestion method using high-pressure oxidation conditions effectively removed organic matter within two hours, giving recovery rates of 64 %-110 % for eight target MNPs. The chromatographic peak reconstruction procedure minimized interferences caused by similar polymers and achieved high accuracy (101 % ± 10 %) for polyvinyl chloride, polyethylene terephthalate, and polystyrene, whose concentrations are often overestimated due to overlapping pyrolysis products. Quantification uncertainties for MNPs in real PM2.5 samples were up to 52 % lower using the new method than using previous methods. The method was validated using PM2.5 from urban Guangzhou. The total concentrations of the eight target MNPs in the PM2.5 samples were 100-990 ng/m3 (median 277 ng/m3) and the dominant MNPs were polyethylene, polyethylene terephthalate, and polyvinyl chloride, which contributed > 90 % of the MNPs. The new method allows the robust and accurate quantification of MNPs in atmospheric fine particles and will be useful in future studies on the environmental behaviors of MNPs and risks they pose.

Microplastics in soils: A comparative review on extraction, identification and quantification methods

Microplastics (MPs) have been continuously accumulating in soil, posing significant environmental concerns due to their potential toxicity and role as pollutant vectors. Effective monitoring of MPs in soils requires appropriate methods for extraction, identification and quantification. This comparative review systematically examined various methods used in MP analysis from solid matrix environments, highlighting the advantages and disadvantages of each technique. Soils are heterogeneous and complex matrices, which can interact differently with MPs, rendering the separation of MPs from soils a significant challenge. Key challenges include the interactions between MPs and soil organic matter and detection limitations of smaller size MP which can interfere with accurate extraction. Specialized techniques and devices are required for precise identification and quantification. Digestion can be effective in removing organic matter, although harsh digestion can degrade MPs. To improve the liability of MP analysis, it is critical to minimize steps that may reduce accuracy such as filtration, harsh digestion and inappropriate sample size. Conversely, adjusting or combining methods can enhance the precision of MP analysis. This review offers a forward-looking perspective by advocating extraction and detection approaches, thus providing a more accurate, reproducible and holistic framework for MP analysis in soils. These insights are anticipated to guide future research promote standardized protocols and enhance environmental monitoring efforts.

Determination of polychlorinated biphenyls in water by CO2-responsive switchable deep eutectic solvent based homogeneous liquid-liquid microextraction

A homogeneous liquid-liquid microextraction technique based on switchable deep eutectic solvent (SDES-HLLME), combined with gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS), was developed for the extraction and analysis of 16 polychlorinated biphenyls (PCBs) in water samples. CO2-responsive switchable deep eutectic solvent (SDES), which consists of monoethanolamine (MEA) being used as a hydrogen bond acceptor (HBA) and 3-methoxyphenol (3-MP) being used as a hydrogen bond donor (HBD), was used as the extractant, thus providing an environmentally friendly alternative to conventional toxic organic solvents. The study systematically investigated the effects of various parameters on extraction efficiency, including the type and volume of SDES, vortexing duration, CO2 bubbling time, centrifugation rate and time, ionic strength. Optimal extraction conditions were identified as follows: 40.0 μL of SDES, vortexing for 40.0 s, CO2 bubbling for 2.0 min, 5.0 % (w/v) salt concentration, a centrifugation rate of 5000 rpm, and a centrifugation duration of 3.0 min. Under these optimal conditions, the method exhibited a linear range of 0.1-300 ng·mL-1, with limits of detection (LODs) and quantification (LOQs) ranging from 0.003 to 0.096 ng·mL-1 and 0.009 to 0.321 ng·mL-1, while the relative standard deviation (RSD) <7.98 %. Finally, this method was successfully applied to determine the concentrations of 16 PCBs in various environmental water samples, yielding satisfactory recovery rates. This method provides a green, convenient and accurate new idea in the field of HLLME research.

Highly selective solid-liquid extraction of microplastic mixtures as a pre-preparation tool for quantitative nuclear magnetic resonance spectroscopy studies

Despite various developments in the application of quantitative nuclear magnetic resonance (qNMR) spectroscopy toward microplastics in recent years, this method still lacks suitable sample preparation and fractionation procedures. As this poses a crucial obstacle for its utilisation on environmental samples, which contain various mixtures of polymers along with other matrix substances, this research aims to address this missing link by presenting an easy-to-apply procedure based on common laboratory equipment. The process selectively separates microplastics from inorganic constituents while performing the necessary fractionation of different types of microplastics prior to qNMR analysis. It allows subsequent quantification of polystyrene (PS), polybutadiene rubber (BR), polymethylmethacrylate (PMMA), polyvinylchloride (PVC), polyethylene terephthalate (PET) and polyamide (PA) from a single sample, establishing recovery rates greater than 88% for all tested polymer types. Additionally, we extended our previous qNMR protocol to include two common polymer types: polymethylmethacrylate (PMMA) and polyacrylonitrile (PAN), achieving limits of detection down to 1.76 μg ml-1 and 12.53 μg ml-1 as well as limits of quantification down to 5.88 μg ml-1 and 41.78 μg ml-1, respectively. Thus, the qNMR method presented herein is now applicable to eight abundant polymer types, allowing the quantification of up to three different types simultaneously.

Microplastic loads in Eurasian otter (Lutra lutra) feces-targeting a standardized protocol and first results from an alpine stream, the River Inn

Microplastics (MP) are omnipresent in a wide range of environments, constituting a potential threat for aquatic and terrestrial wildlife. Effects in consumers range from physical injuries to pathological reactions. Due to potential bioaccumulation of MP, predators are of particular concern for MP induced health effects. The Eurasian otter is an apex predator in (semi-)aquatic habitats feeding primarily on fish. Furthermore, the species is classified as "near threatened" on the IUCN Red List. Thus, the Eurasian otter is of conservation concern and may serve as a bioindicator for MP pollution. Feces can be used to detect pollutants, including MP. Initial studies confirmed the presence of MP in otter feces (= spraints). However, as specific, validated protocols targeting at an efficient and standardized extraction of MP from otter spraints are missing, experimental results reported from different groups are challenging to compare. Therefore, we (i) present steps towards a standardized protocol for the extraction of MP from otter feces, (ii) give recommendations for field sample collection of otter spraints, and (iii) provide a user-friendly step-by-step workflow for MP extraction and analysis. Applying this framework to field samples from five study sites along the River Inn (n = 50), we detected MP of different sizes and shapes (ranging from microfibers to road abrasion and tire wear) in all otter spraint samples.

Riverbed depth-specific microplastics distribution and potential use as process marker

Riverbed sediments have been identified as temporary and long-term accumulation sites for microplastic particles (MPs), but the relocation and retention mechanisms in riverbeds still need to be better understood. In this study, we investigated the depth-specific occurrence and distribution (abundance, type, and size) of MPs in river sediments down to a depth of 100 cm, which had not been previously investigated in riverbeds. In four sediment freeze cores taken for the Main River (Germany), MPs (≥ 100 µm) were detected using two complementary analytical approaches (spectroscopy and thermoanalytical) over the entire depth with an average of 21.7 ± 21.4 MP/kg or 31.5 ± 28.0 mg/kg. Three vertical trends for MP abundance could be derived, fairly constant in top layers (0-‍30 cm), a decrease in middle layers (30-60 cm), and a strong increase in deep layers (60-100 cm). The dominant polymer types were polyethylene (PE), polypropylene (PP), and polystyrene (PS). Polyethylene terephthalate (PET) and PP were also found in deep layers, albeit with the youngest age of earliest possible occurrence (EPO age of 1973 and 1954). The fraction of smaller-sized MPs (100-500 µm) increased with depth in shallow layers, but the largest MPs (> 1 mm) were detected in deep layers. Based on these findings, we elucidate the relationship between the depth-specific MP distribution and the prevailing processes of MP retention and sediment dynamics in the riverbed. We propose some implications and offer an initial conceptual approach, suggesting the use of microplastics as a potential environmental process tracer for driving riverbed sediment dynamics.

Homogenous Oxidizing Oligomerization Coupled with Coagulation for Water Purification

Natural manganese oxides could induce the intermolecular coupling reactions among small-molecule organics in aqueous environments, which is one of the fundamental processes contributing to natural humification. These processes could be simulated to design novel advanced oxidation technology for water purification. In this study, periodate (PI) was selected as the supplementary electron-acceptor for colloidal manganese oxides (Mn(IV)aq) to remove phenolic contaminants from water. By introducing polyferric sulfate (PFS) into the Mn(IV)aq/PI system and exploiting the flocculation potential of Mn(IV)aq, a post-coagulation process was triggered to eliminate soluble manganese after oxidation. Under acidic conditions, periodate exists in the H4IO6- form as an octahedral oxyacid capable of coordinating with Mn(IV)aq to form bidentate complexes or oligomers (Mn(IV)-PI*) as reactive oxidants. The Mn(IV)-PI* complex could induce cross-coupling process between phenolic contaminants, resulting in the formation of oligomerized products ranging from dimers to hexamers. These oligomerized products participate in the coagulation process and become stored within the nascent floc due to their catenulate nature and strong hydrophobicity. Through coordination between Mn(IV)aq and H4IO6-, residual periodate is firmly connected with manganese oxides in the floc after coagulation and could be simultaneously separated from the aqueous phase. This study achieves oxidizing oligomerization through a homogeneous process under mild conditions without additional energy input or heterogeneous catalyst preparation. Compared to traditional mineralization-driven oxidation techniques, the proposed novel cascade processes realize transformation, convergence, and separation of phenolic contaminants with high oxidant utilization efficiency for low-carbon purification.

Microplastic pollution: a review of techniques to identify microplastics and their threats to the aquatic ecosystem

Microplastics (MPs), small synthetic particles, have emerged as perilous chemical pollutants in aquatic habitats, causing grave concerns about their disruptive effects on ecosystems. The fauna and flora inhabiting these specific environments consume these MPs, unwittingly introducing them into the intricate web of the food chain. In this comprehensive evaluation, the current methods of identifying MPs are amalgamated and their profound impacts on marine and freshwater ecosystems are discussed. There are many potential risks associated with MPs, including the dangers of ingestion and entanglement, as well as internal injuries and digestive obstructions, both marine and freshwater organisms. In this review, the merits and limitations of diverse identification techniques are discussed, including spanning chemical analysis, thermal identification, and spectroscopic imaging such as Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and fluorescent microscopy. Additionally, it discusses the prevalence of MPs, the factors that affect their release into aquatic ecosystems, as well as their plausible impact on various aquatic ecosystems. Considering these disconcerting findings, it is imperative that appropriate measures should be taken to assess the potential risks of MP pollution, protect aquatic life and human health, and foster sustainable development.

Quantitative Determination of Poly(methyl Methacrylate) Micro/Nanoplastics by Cooling-Assisted Solid-Phase Microextraction Coupled to Gas Chromatography-Mass Spectrometry: Theoretical and Experimental Insights

Determinations of micro/nanoplastics (MNPs) in environmental samples are essential to assess the extent of their presence in the environment and their potential impact on ecosystems and human health. With the aim to provide a sensitive method with simplified pretreatment steps, cooling-assisted solid-phase microextraction (CA-SPME) coupled to gas chromatography-mass spectrometry (GC-MS) is proposed as a new approach to quantify mass concentrations of MNPs in water and soil samples. The herein proposed CA-SPME method offers the unique advantage of integrating the thermal decomposition of MNPs and enrichment of signature compounds into one step. Poly(methyl methacrylate) (PMMA) was used as a model substance to verify the method performance in this work. Theoretical insights demonstrated that pyrolysis is the rate-determining step during the extraction process and that PMMA is effectively decomposed at 350 °C with an estimated incubation time of 13 min. Eight compounds were identified in the pyrolysis products by CA-SPME-GC-MS with the use of a DVB/CAR/PDMS coating, wherein methyl methacrylate was considered as the best indicator and dimethyl 2-methylenesuccinate was selected as the confirmation compound. Under the optimized conditions, the proposed method exhibited wide linearity (0.5-2000 μg for water and 5-1000 μg for soil) and high sensitivity, with limits of detection of 0.014 and 0.28 μg for water and soil, respectively. Finally, the proposed method was successfully applied for determinations of PMMA MNPs in real water and soil samples with satisfactory recoveries attained. The method only required the employment of a filter membrane for water analysis, while soil samples were analyzed directly without any pretreatment. The solvent-free approach, straightforward operation, and high sensitivity of the proposed method show great potential for the analysis of MNPs in different environmental samples.

Oxidative degradation and possible interactions of coexisting decabromodiphenyl ether (BDE-209) on polystyrene microplastics in UV/chlorine process

This work was to investigate the transformation of coexisting decabromodiphenyl ether (BDE-209) on microplastics and their possible interactions in UV/chlorine process. Compared with pristine microplastics, the highly aged polystyrene (PS) showed an inhibitory effect on degradation of BDE-209. Increasing initial concentration of BDE-209 on PS inhibited degradation, while the chlorine concentration and pH did not affect the final degradation efficiency. Moreover, the presence of NO3-, SO42-, HCO3- and HA in water was unfavorable for BDE-209 degradation. According to the experimental and calculation results, the contribution to the degradation of BDE-209 was ranked as direct photolysis > HO• > •Cl in the UV/ chlorine system. Chlorination products released by PS during UV/chlorination were detected. Four possible reaction pathways of BDE-209 were proposed, which mainly involved debromination, hydroxylation, chlorine substitution, cleavage of ether bond, and intramolecular elimination of HBr. It was worth noting that PS microplastics not only inhibited the degradation of BDE-209, but also affected the type and abundance of its transformation products. Meanwhile, interaction products of PS and BDE-209 were determined, which was attributed to reactions of PS-derived radicals with •Br/•C6Br5 and •Cl. Results of toxicity evaluation showed that the introduction of carbon-halogen bonds, especially C-Br bond, increased the toxicity of chain scission products of PS. This work provides some new insights into transformation, interaction, and associated ecological risks of coexisting microplastics and surface adsorbed contaminants in the UV/chlorine process of drinking water treatment plants (DWTPs) and wastewater treatment plants (WWTPs).