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Influence of interfering co-appearing container peaks on the accuracy of direct quantitative Raman measurement of a sample in a plastic container.
Analyst ( IF 4.2 ) Pub Date : 2020-06-08 , DOI: 10.1039/d0an00741b Yoonjeong Lee 1 , Pham Khac Duy 1 , Lawan Sriphong 2 , Nattha Kaewnopparat 3 , Hoeil Chung 1
Analyst ( IF 4.2 ) Pub Date : 2020-06-08 , DOI: 10.1039/d0an00741b Yoonjeong Lee 1 , Pham Khac Duy 1 , Lawan Sriphong 2 , Nattha Kaewnopparat 3 , Hoeil Chung 1
Affiliation
The axially perpendicular offset (APO) scheme was previously demonstrated as a versatile scheme able to minimize or eliminate the glass background in the direct and non-sampling Raman measurement of an ethanol sample housed in a glass bottle. Alternatively, when directly analyzing a sample housed in a plastic container, another typical container yielding strong Raman peaks itself, the Raman peaks of both the container and the housed sample are unavoidably present together in a collected spectrum. Therefore, a crucial issue to investigate under this situation is how the magnitude of the co-appearing container peaks influences the accuracy for quantitative analysis of the housed sample. For the evaluation, a non-sampling Raman spectroscopic measurement of the urea concentration in a urea gel housed in a circular polypropylene (PP) container was attempted by employing two axially perpendicular offset (APO) schemes with detection windows of different sizes (25.4 and 10.0 mm, referred to as the wide-window APO (WW-APO) and narrow-window APO (NW-APO), respectively), and transmission and back-scattering schemes incorporating a 25.4 mm detection window. The intensity ratios between the container and urea peaks in the collected spectra were different depending on the adopted measurement scheme. The intensity ratio was greatest (smallest container peak) in the NW-APO measurement due to the narrowed detection window, making the generated container Raman photons at the side-wall less detectable to the bottom-positioned detector. A spectral acquisition scheme allowing the maximal suppression of the container peaks, while still maintaining the sample features, was a key requirement to secure an accurate measurement of the sample concentration. In addition, a Monte Carlo simulation was used to visualize the distributions of the container and urea photons inside the sample-housed container.
中文翻译:
共同出现的容器峰干扰对塑料容器中样品的直接定量拉曼测量精度的影响。
以前,轴向垂直偏移(APO)方案已被证明是一种通用方案,能够在玻璃瓶中所装乙醇样品的直接和非采样拉曼测量中最小化或消除玻璃背景。或者,当直接分析容纳在塑料容器中的样品时,另一个典型的容器本身会产生很强的拉曼峰,所以容器和所容纳样品的拉曼峰不可避免地会同时出现在收集的光谱中。因此,在这种情况下要研究的关键问题是共同出现的容器峰的大小如何影响所容纳样品定量分析的准确性。为了评估,通过采用两个轴向垂直偏移(APO)方案,检测窗口大小不同(分别为25.4和10.0 mm,称为(分别是宽窗口APO(WW-APO)和窄窗口APO(NW-APO)),以及包含25.4 mm检测窗口的传输和反向散射方案。根据所采用的测量方案,收集的光谱中容器峰和尿素峰之间的强度比是不同的。由于检测窗口变窄,在NW-APO测量中强度比最大(最小的容器峰),从而使底部位置的检测器无法检测到侧壁处产生的容器拉曼光子。光谱采集方案能够最大程度地抑制容器峰,同时仍保持样品特征,这是确保准确测量样品浓度的关键要求。另外,使用蒙特卡洛模拟来可视化容器以及样本容纳容器内尿素光子的分布。
更新日期:2020-08-10
中文翻译:
共同出现的容器峰干扰对塑料容器中样品的直接定量拉曼测量精度的影响。
以前,轴向垂直偏移(APO)方案已被证明是一种通用方案,能够在玻璃瓶中所装乙醇样品的直接和非采样拉曼测量中最小化或消除玻璃背景。或者,当直接分析容纳在塑料容器中的样品时,另一个典型的容器本身会产生很强的拉曼峰,所以容器和所容纳样品的拉曼峰不可避免地会同时出现在收集的光谱中。因此,在这种情况下要研究的关键问题是共同出现的容器峰的大小如何影响所容纳样品定量分析的准确性。为了评估,通过采用两个轴向垂直偏移(APO)方案,检测窗口大小不同(分别为25.4和10.0 mm,称为(分别是宽窗口APO(WW-APO)和窄窗口APO(NW-APO)),以及包含25.4 mm检测窗口的传输和反向散射方案。根据所采用的测量方案,收集的光谱中容器峰和尿素峰之间的强度比是不同的。由于检测窗口变窄,在NW-APO测量中强度比最大(最小的容器峰),从而使底部位置的检测器无法检测到侧壁处产生的容器拉曼光子。光谱采集方案能够最大程度地抑制容器峰,同时仍保持样品特征,这是确保准确测量样品浓度的关键要求。另外,使用蒙特卡洛模拟来可视化容器以及样本容纳容器内尿素光子的分布。