Othman Ahmed M, Elsayed Ahmed A, Sabry Yasser M, Khalil Diaa, Bourouina Tarik
Université Gustave Eiffel, CNRS ESYCOM UMR 9007, Noisy-le-Grand, ESIEE, Paris 93162, France.
Si-Ware Systems, 3 Khalid Ibn Al-Waleed St., Heliopolis, Cairo 11361, Egypt.
ACS Omega. 2023 Mar 9;8(11):10335-10341. doi: 10.1021/acsomega.2c07998. eCollection 2023 Mar 21.
Microplastics are particulate water contaminants that are raising concerns regarding their environmental and health impacts. Optical spectroscopy is the gold standard for their detection; however, it has severe limitations such as tens of hours of analysis time and spatial resolution of more than 10 μm, when targeting the production of a 2D map of the microparticle population. In this work, through a single spectrum acquisition, we aim at quickly getting information about the whole population of identical particles, their chemical nature, and their size in a range below 20 μm. To this end, we built a compact setup enabling both attenuated total reflection Fourier transform infrared (ATR-FTIR) and Raman spectroscopy measurement on the same sample for comparison purposes. We used monodisperse polystyrene and poly(methyl methacrylate) microplastic spheres of sizes ranging between 6 and 20 μm, also measured collectively using a bench-top FTIR spectrometer in ATR mode. The ATR-FTIR technique appears to be more sensitive for the smallest particles of 6 μm, while the opposite trend is observed using Raman spectroscopy. We use theoretical modeling to simulate and explain the ripples observed in the measured spectra at the shortest wavelength (higher wavenumber) region, which appears as an indicator of the microparticle dimension. The latter finding opens new perspectives for ATR-FTIR for the identification and classification of populations of nearly identical micro-scale bodies, such as bacteria and other micro-organisms, where the same measured spectrum embeds dual information about the chemical nature and the size.
微塑料是水中的颗粒污染物，其对环境和健康的影响引发了人们的关注。光谱学是检测微塑料的金标准；然而，当以生成微颗粒群体的二维图为目标时，它存在严重的局限性，比如分析时间长达数十小时，空间分辨率超过10μm。在这项工作中，我们旨在通过单次光谱采集，快速获取关于相同颗粒的整个群体、它们的化学性质以及尺寸在20μm以下范围内的信息。为此，我们构建了一个紧凑的装置，能够对同一样品进行衰减全反射傅里叶变换红外光谱（ATR-FTIR）和拉曼光谱测量，以便进行比较。我们使用了尺寸在6至20μm之间的单分散聚苯乙烯和聚甲基丙烯酸甲酯微塑料球，也使用台式傅里叶变换红外光谱仪在ATR模式下对它们进行了集体测量。ATR-FTIR技术对于6μm的最小颗粒似乎更敏感，而使用拉曼光谱时则观察到相反的趋势。我们使用理论模型来模拟和解释在最短波长（更高波数）区域的测量光谱中观察到的波纹，这似乎是微颗粒尺寸的一个指标。后一发现为ATR-FTIR在识别和分类几乎相同的微观物体群体（如细菌和其他微生物）方面开辟了新的前景，在这些群体中，相同的测量光谱嵌入了关于化学性质和尺寸的双重信息。
