Bresch Harald, Hodoroaba Vasile-Dan, Schmidt Alexandra, Rasmussen Kirsten, Rauscher Hubert
Federal Institute for Materials Research and Testing (BAM), D-12200 Berlin, Germany.
Joint Research Centre (JRC), European Commission, 21027 Ispra, Italy.
Nanomaterials (Basel). 2022 Jun 29;12(13):2238. doi: 10.3390/nano12132238.
Electron microscopy (EM) is the gold standard for the characterisation of the morphology (size and shape) of nanoparticles. Visual observation of objects under examination is always a necessary first step in the characterisation process. Several questions arise when undertaking to identify and count particles to measure their size and shape distribution. In addition to challenges with the dispersion and identification of the particles, more than one protocol for counting particles is in use. This paper focuses on precise rules for the counting of particles in EM micrographs, as this influences the measurement accuracy of the number of particles, thus implicitly affecting the size values of the counted particles. We review and compare four different, commonly used methods for counting, which we then apply in case studies. The impact of the selected counting rule on the obtained final particle size distribution is highlighted. One main aim of this analysis is to support the application of a specific, well-defined counting approach in accordance with regulatory requirements to contribute to achieving more reliable and reproducible results. It is also useful for the new harmonised measurement procedures for determining the particle size and particle size distribution of nanomaterials.
电子显微镜（EM）是表征纳米颗粒形态（尺寸和形状）的金标准。在表征过程中，对被检查物体进行目视观察始终是必要的第一步。在识别和计数颗粒以测量其尺寸和形状分布时会出现几个问题。除了颗粒分散和识别方面的挑战外，目前使用的颗粒计数方法不止一种。本文重点关注电子显微镜显微照片中颗粒计数的精确规则，因为这会影响颗粒数量的测量准确性，从而间接地影响所计数颗粒的尺寸值。我们回顾并比较了四种不同的常用计数方法，然后将其应用于案例研究。突出了所选计数规则对最终获得的颗粒尺寸分布的影响。该分析的一个主要目的是根据监管要求支持应用特定的、定义明确的计数方法，以有助于获得更可靠和可重复的结果。这对于确定纳米材料的粒度和粒度分布的新的统一测量程序也很有用。
