Sunscreens are an important source of TiO₂ nanoparticles in surface waters. The fate and toxicity of these particles have not been fully addressed due to the gap between model nanoparticles usually used in studies and the more complex particles found in commercial products. Therefore, mild extraction methods for TiO₂ nanoparticles from sunscreens were evaluated for providing more realistic nanoparticle samples for future studies. We propose two methods based on ultrafiltration and ultracentrifugation, respectively, for extracting TiO₂ nanoparticles from sunscreens using a surfactant solution as the solvent. These methods were tested on eleven commercial sunscreens with differing compositions. The ultracentrifugation variant allows extracting 250 mg from approximately 5 g of sunscreen in one day. Recoveries for ultrafiltration and ultracentrifugation were 52–96% and 78–98%, respectively. Purification efficiency was determined for the ultracentrifugation variant by determining the avobenzone concentration in sunscreen extracts using UV-spectrometry and was high for all tested sunscreens. Transmission electron microscopy and dynamic light scattering revealed a high diversity in particle shape, although size parameters were comparable (average hydrodynamic diameter: 19–34 nm). Isoelectric points were below 4.6 for all sunscreen extracts. Time-of-flight secondary ion mass spectrometry revealed that probably all TiO₂ particles were coated; most of them with PDMS, some others with Al- and Si-based materials. Comparison of images of particles inside the sunscreens using cryogenic transmission electron microscopy and of extracted particles showed that while the shape of the primary nanoparticles was not affected by the extraction, they were agglomerated inside the sunscreens. These agglomerates could be completely disrupted using ultrasonication. Therefore, the particles extracted in the present study can be considered as more environmentally relevant in terms of size, shape, surface charge and coating than model TiO₂ nanoparticles.

中文翻译：

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从商品化防晒霜中提取和表征二氧化钛纳米颗粒的方法†

防晒剂是地表水中TiO ₂纳米颗粒的重要来源。由于通常在研究中使用的模型纳米颗粒与在商业产品中发现的更复杂的颗粒之间存在间隙，因此尚未完全解决这些颗粒的命运和毒性问题。因此，评估了从防晒霜中提取TiO ₂纳米粒子的温和方法，以提供更实际的纳米粒子样品，以供将来研究。我们提出两种分别基于超滤和超离心的方法萃取TiO ₂使用表面活性剂溶液作为溶剂的防晒霜中的纳米颗粒。这些方法在11种成分不同的商业防晒霜上进行了测试。超速离心变型可以在一天之内从大约5 g的防晒霜中提取250 mg。超滤和超速离心的回收率分别为52–96％和78–98％。通过使用紫外线光谱法测定防晒霜提取物中的阿伏苯宗浓度，可以确定超速离心方法的纯化效率，并且对于所有测试的防晒霜都具有很高的纯化效率。透射电子显微镜和动态光散射揭示了颗粒形状的高度多样性，尽管尺寸参数是可比较的（平均流体动力学直径：19–34 nm）。所有防晒霜提取物的等电点均低于4.6。涂覆_2个颗粒；其中大多数使用PDMS，另一些使用Al和Si基材料。使用低温透射电子显微镜比较防晒霜内部颗粒和提取颗粒的图像，结果表明，虽然初级纳米颗粒的形状不受提取影响，但它们在防晒霜内部聚集。这些附聚物可以使用超声波完全破坏。因此，与TiO ₂纳米颗粒相比，在尺寸，形状，表面电荷和涂层方面，本研究中提取的颗粒与环境的相关性更高。