Microplastics (MPs) have been reported in various environmental compartments and their number is continuously increasing because of degradation into smaller fragments down to nanoplastics. Humans are exposed to these small-sized MPs through food and air with potential health consequences that still need to be determined. This requires, in the first place, efficient and detailed visualization, relocalization, and characterization of the same MPs with complementary analytical methods. Here, we show the first application of a correlative microscopy and spectroscopy workflow to MPs that meets these demands. For this purpose, standard MP particles on aluminum-coated polycarbonate membrane filters were investigated by an optical zoom microscope and a hyphenated scanning electron microscopy (SEM)-Raman system. By merging the obtained data in one software, it is possible to navigate on the entire filters’ surface and correlate at identical locations MP morphology at the spatial resolutions of electron (1.6 nm at 1 kV for the used SEM, ∼100 nm minimum MP size in this study) and optical (∼1–10 µm) microscopies with chemical identification by micro-Raman spectroscopy. Moreover, we observed that low-voltage SEM works without a conductive coating of MPs, causes no detectable charging and structural changes, and provides high-resolution surface imaging of single and clustered MP particles, thus enabling subsequent Raman measurements. We believe that further work on the accurate identification and quantification of micro- and nanoplastics in real samples can potentially profit from this workflow.

中文翻译：

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EXPRESS：微塑料的相关显微镜和光谱工作流程

微塑料 (MPs) 已在各种环境隔间中被报道，并且由于降解成更小的碎片直至纳米塑料，它们的数量不断增加。人类通过食物和空气接触这些小型 MP，其潜在的健康后果仍需确定。首先，这需要使用互补的分析方法对相同的 MP 进行有效和详细的可视化、重新定位和表征。在这里，我们展示了相关显微镜和光谱工作流程在满足这些需求的 MP 中的首次应用。为此，通过光学变焦显微镜和连接扫描电子显微镜 (SEM)-拉曼系统研究了镀铝聚碳酸酯膜过滤器上的标准 MP 颗粒。通过将获得的数据合并到一个软件中，可以在整个过滤器的表面上导航，并在电子的空间分辨率（对于使用的 SEM，在 1 kV 下为 1.6 nm，本研究中最小 MP 尺寸为 ~100 nm）和光学（~1 –10 µm) 显微镜，通过显微拉曼光谱进行化学鉴定。此外，我们观察到低压 SEM 在没有 MP 导电涂层的情况下工作，不会引起可检测的充电和结构变化，并提供单个和成簇 MP 颗粒的高分辨率表面成像，从而实现后续的拉曼测量。我们相信，在实际样品中准确识别和量化微塑料和纳米塑料的进一步工作可能会从该工作流程中受益。