Versatile, ultra-low sample volume gas analyzer using a rapid, broad-tuning ECQCL and a hollow fiber gas cell
Versatile, ultra-low sample volume gas analyzer using a rapid, broad-tuning ECQCL and a hollow fiber gas cell
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多功能、超低样品量气体分析仪，采用快速、宽调谐 ECQCL 和中空纤维气室
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发表时间：
2017
期刊：
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通讯作者：
J. Kelly
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作者：
J. Kriesel;Camille N. Makarem;M. Phillips;J. Moran;M. Coleman;L. Christensen;J. Kelly
我们描述了一种多功能中红外 (Mid-IR) 光谱系统，该系统旨在以超低样品量测量各种气体的浓度。该系统将快速扫频外腔量子级联激光器 (ECQCL) 与中空光纤气室结合在一起。 ECQCL 具有足够的光谱分辨率和再现性来测量具有窄特征的气体（例如水、甲烷、氨等），并且还具有测量挥发性有机化合物 (VOC)（例如醛、酮、碳氢化合物）、硫化合物、氯化合物等所需的光谱调谐范围。中空纤维是具有内部反射涂层的毛细管，经过优化，可将中红外激光束传输到探测器。引入光纤中的样气（例如，内部体积 = 0.6 ml）与激光束发生强烈相互作用，尽管路径长度相对适中（例如，L ~ 3 m），但灵敏测量所需的样品量可能明显少于使用传统红外激光光谱系统所需的样品量。给出的测量示例包括与人体呼吸分析相关的 VOC 定量，在 1 Hz 数据速率下灵敏度约为 2 皮摩尔。
We describe a versatile mid-infrared (Mid-IR) spectroscopy system developed to measure the concentration of a wide range of gases with an ultra-low sample size. The system combines a rapidly-swept external cavity quantum cascade laser (ECQCL) with a hollow fiber gas cell. The ECQCL has sufficient spectral resolution and reproducibility to measure gases with narrow features (e.g., water, methane, ammonia, etc.), and also the spectral tuning range needed to measure volatile organic compounds (VOCs), (e.g., aldehydes, ketones, hydrocarbons), sulfur compounds, chlorine compounds, etc. The hollow fiber is a capillary tube having an internal reflective coating optimized for transmitting the Mid-IR laser beam to a detector. Sample gas introduced into the fiber (e.g., internal volume = 0.6 ml) interacts strongly with the laser beam, and despite relatively modest path lengths (e.g., L ~ 3 m), the requisite quantity of sample needed for sensitive measurements can be significantly less than what is required using conventional IR laser spectroscopy systems. Example measurements are presented including quantification of VOCs relevant for human breath analysis with a sensitivity of ~2 picomoles at a 1 Hz data rate.