{"title":"Performance of Analytical Techniques for Microplastic and Nanoplastic Quantification in the Presence of Clay","authors":"Surya Sujathan, Abbas El-Zein","doi":"10.1016/j.watres.2025.124716","DOIUrl":null,"url":null,"abstract":"Accurate quantification of microplastics (MPs) and nanoplastics (NPs) in laboratory and environmental samples remains challenging, particularly in complex matrices such as clay. While ultraviolet-visible (UV-Vis) and fluorescence spectrophotometry (FS) are widely used due to their simplicity and high throughput, their reliability diminishes in the presence of clay. Existing separation methods are often ineffective for MP/NPs and may introduce additional errors during the measurement process. Advanced analytical techniques have shown high accuracy for monodisperse MP/NP solutions, yet their reliability in clay-rich environments remains untested. This study evaluates two such techniques, flow cytometry (FCM) and nanoparticle tracking analysis (NTA) – in both fluorescence and non-fluorescence modes, alongside UV-Vis and FS, assessing their performance in measuring polystyrene (PS) MP/NPs (0.1–5 µm) at varying concentrations, in the presence of kaolinite, montmorillonite and bentonite clays. Tests with clay-free monodisperse MP solutions indicated that UV-vis and FS can measure wide range of MP size and concentrations, while NTA and FCM showed effective detection within narrower size range, < 0.5 µm and > 0.5 µm, respectively. The presence of clay adversely affected all methods to varying extents. UV-Vis was the most susceptible, with errors exceeding 10% at PS/clay mass ratios above ∼ 1. In contrast, FCM was the least affected due to its ability to distinguish particles based on size, shape, and granularity. Fluorescence-based detection offered a clear advantage in separating MPs from clay interference, allowing FS, NTA, and FCM to show improved measurement accuracy compared to non-fluorescent based measurements. However, FS accuracy declined as PS/clay ratio dropped below 0.01 due to autofluorescence from clays. Overall, FCM emerged as the most suitable method for rapid and reliable quantification of MP/NPs in clay-rich matrices, using both fluorescent and non-fluorescent detection modes. These findings provide direct practical advantage for laboratory-scale investigations and a foundation for developing protocols for fast, accurate MP/NP quantification in clay rich environmental matrices.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"9 1","pages":""},"PeriodicalIF":12.4000,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Water Research","FirstCategoryId":"93","ListUrlMain":"https://doi.org/10.1016/j.watres.2025.124716","RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, ENVIRONMENTAL","Score":null,"Total":0}
引用次数: 0
Abstract
Accurate quantification of microplastics (MPs) and nanoplastics (NPs) in laboratory and environmental samples remains challenging, particularly in complex matrices such as clay. While ultraviolet-visible (UV-Vis) and fluorescence spectrophotometry (FS) are widely used due to their simplicity and high throughput, their reliability diminishes in the presence of clay. Existing separation methods are often ineffective for MP/NPs and may introduce additional errors during the measurement process. Advanced analytical techniques have shown high accuracy for monodisperse MP/NP solutions, yet their reliability in clay-rich environments remains untested. This study evaluates two such techniques, flow cytometry (FCM) and nanoparticle tracking analysis (NTA) – in both fluorescence and non-fluorescence modes, alongside UV-Vis and FS, assessing their performance in measuring polystyrene (PS) MP/NPs (0.1–5 µm) at varying concentrations, in the presence of kaolinite, montmorillonite and bentonite clays. Tests with clay-free monodisperse MP solutions indicated that UV-vis and FS can measure wide range of MP size and concentrations, while NTA and FCM showed effective detection within narrower size range, < 0.5 µm and > 0.5 µm, respectively. The presence of clay adversely affected all methods to varying extents. UV-Vis was the most susceptible, with errors exceeding 10% at PS/clay mass ratios above ∼ 1. In contrast, FCM was the least affected due to its ability to distinguish particles based on size, shape, and granularity. Fluorescence-based detection offered a clear advantage in separating MPs from clay interference, allowing FS, NTA, and FCM to show improved measurement accuracy compared to non-fluorescent based measurements. However, FS accuracy declined as PS/clay ratio dropped below 0.01 due to autofluorescence from clays. Overall, FCM emerged as the most suitable method for rapid and reliable quantification of MP/NPs in clay-rich matrices, using both fluorescent and non-fluorescent detection modes. These findings provide direct practical advantage for laboratory-scale investigations and a foundation for developing protocols for fast, accurate MP/NP quantification in clay rich environmental matrices.
期刊介绍:
Water Research, along with its open access companion journal Water Research X, serves as a platform for publishing original research papers covering various aspects of the science and technology related to the anthropogenic water cycle, water quality, and its management worldwide. The audience targeted by the journal comprises biologists, chemical engineers, chemists, civil engineers, environmental engineers, limnologists, and microbiologists. The scope of the journal include:
•Treatment processes for water and wastewaters (municipal, agricultural, industrial, and on-site treatment), including resource recovery and residuals management;
•Urban hydrology including sewer systems, stormwater management, and green infrastructure;
•Drinking water treatment and distribution;
•Potable and non-potable water reuse;
•Sanitation, public health, and risk assessment;
•Anaerobic digestion, solid and hazardous waste management, including source characterization and the effects and control of leachates and gaseous emissions;
•Contaminants (chemical, microbial, anthropogenic particles such as nanoparticles or microplastics) and related water quality sensing, monitoring, fate, and assessment;
•Anthropogenic impacts on inland, tidal, coastal and urban waters, focusing on surface and ground waters, and point and non-point sources of pollution;
•Environmental restoration, linked to surface water, groundwater and groundwater remediation;
•Analysis of the interfaces between sediments and water, and between water and atmosphere, focusing specifically on anthropogenic impacts;
•Mathematical modelling, systems analysis, machine learning, and beneficial use of big data related to the anthropogenic water cycle;
•Socio-economic, policy, and regulations studies.