Seghers John, Cella Claudia, Pequeur Emmy, La Spina Rita, Roncari Francesco, Valsesia Andrea, Mehn Dora, Gilliland Douglas, Trapmann Stefanie, Emteborg Håkan
European Commission, Joint Research Centre (JRC), Geel, Belgium.
European Commission, Joint Research Centre (JRC), Ispra, Italy.
Anal Bioanal Chem. 2025 May;417(12):2589-2602. doi: 10.1007/s00216-024-05726-7. Epub 2025 Jan 25.
When performing effect studies to investigate the impact of microplastic (MP) on cell lines, algae, or daphnia, it is advantageous if such experiments can be performed without the use of surfactants. The need for surfactants arises from the fact that finely milled pristine MP particles generally are hydrophobic. Methods for the preparation of larger amounts of hydrophilic and hence artificially aged MP particles and approaches for their characterization are of high importance. Here we present methods to artificially age polyethylene terephthalate (PET) and low-density polyethylene (PE) using alkaline and acidic treatments that reproducibly result in large quantities of particles below 5 µm with considerably increased hydrophilicity. The artificially aged MP particles were characterized using particle counting by single-particle extinction and scattering (SPES), particle size by laser diffraction measurements, zeta potential using electrophoretic light scattering, hydrophobicity index (Hy) through dark-field (DF) microscopy, chemical composition by inductively coupled plasma-mass spectrometry (ICP-MS), Fourier transform infrared (FTIR) microscopy, and Raman microscopy. The hydrophobicity index values obtained should allow the aged MP particles to be characterized as qualitative reference materials (RMs) with an ordinal property. Evidence for the maintained integrity and hydrophilicity of the artificially aged MP particles (in powder form) over time was obtained by measurements of zeta potential with a 33-month interval. Uniformity of subsampling with respect to particle number concentration in suspensions within a 10-day period was also investigated. It provided evidence for the possibility of reproducible spiking of a specific number of hydrophilic MP particles with relative standard deviations (RSDs) from 6.2 to 13.6%. For the development of future reference materials of artificially aged microplastics, they should be characterized for an ordinal property (artificial age as Hy-index) and nominal property (identity of PET or PE based on spectral matching).
在进行效应研究以调查微塑料（MP）对细胞系、藻类或水蚤的影响时，如果能在不使用表面活性剂的情况下进行此类实验将更具优势。使用表面活性剂的需求源于这样一个事实，即精细研磨的原始MP颗粒通常具有疏水性。制备大量亲水性且因此经过人工老化的MP颗粒的方法及其表征方法至关重要。在此，我们介绍了使用碱性和酸性处理对聚对苯二甲酸乙二酯（PET）和低密度聚乙烯（PE）进行人工老化的方法，这些处理可重复性地产生大量粒径小于5微米且亲水性显著增加的颗粒。通过单颗粒消光和散射（SPES）进行颗粒计数、激光衍射测量粒径、电泳光散射测量zeta电位、暗场（DF）显微镜测量疏水性指数（Hy）、电感耦合等离子体质谱（ICP-MS）分析化学成分、傅里叶变换红外（FTIR）显微镜和拉曼显微镜对人工老化的MP颗粒进行了表征。所获得的疏水性指数值应能将老化的MP颗粒表征为具有序次特性的定性参考物质（RMs）。通过间隔33个月测量zeta电位，获得了人工老化的MP颗粒（粉末形式）随时间保持完整性和亲水性的证据。还研究了在10天内悬浮液中颗粒数浓度的二次采样均匀性。这为以6.2%至13.6%的相对标准偏差（RSD）可重复添加特定数量的亲水性MP颗粒提供了证据。对于未来人工老化微塑料参考物质的开发，应根据序次特性（作为Hy指数的人工老化程度）和标称特性（基于光谱匹配的PET或PE的身份）对其进行表征。
