Selaković Miloš, Zenobi Renato, Emmenegger Lukas, Tuzson Béla
Laboratory for Air Pollution/Environmental Technology, Empa, Überlandstrasse 129, 8600 Dübendorf, Switzerland.
Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 3, 8093 Zurich, Switzerland.
Anal Chem. 2025 Jul 1;97(25):13586-13593. doi: 10.1021/acs.analchem.5c02084. Epub 2025 Jun 14.
This study highlights the potential of mid-infrared laser absorption spectroscopy (LAS) for analyzing volatile organic compounds (VOCs) in the gas phase. Using a Vernier-type quantum cascade laser (QCL) in the 9-10 μm spectral region, over 40 different VOCs were systematically investigated with a spectral resolution better than 0.005 cm. It was found that many VOCs, even with more than six heavy atoms, can exhibit significant spectral features at ambient temperature and pressures above 10 mbar, i.e., at conditions well suited for routine analysis. Our observations suggest that in addition to molecular weight and number of atoms, molecular rigidity and symmetry have a decisive impact on the spectral feature content. The high spectral feature content observed in rigid molecules is related to their small number of conformers, while higher molecular symmetry results in fewer nondegenerate vibrational modes, principal rotational axes with different moments of inertia, and a reduced number of nonidentical conformers. Overall, this leads to distinct spectral features that enable the selective and sensitive detection of large VOCs by high-resolution LAS.
本研究突出了中红外激光吸收光谱法（LAS）在分析气相挥发性有机化合物（VOCs）方面的潜力。使用波长在9 - 10μm光谱区域的游标型量子级联激光器（QCL），以优于0.005 cm的光谱分辨率对40多种不同的VOCs进行了系统研究。结果发现，许多VOCs即使含有六个以上重原子，在环境温度和高于10毫巴的压力下，即在非常适合常规分析的条件下，也能表现出显著的光谱特征。我们的观察结果表明，除了分子量和原子数外，分子刚性和对称性对光谱特征含量具有决定性影响。在刚性分子中观察到的高光谱特征含量与其较少的构象异构体数量有关，而较高的分子对称性导致非简并振动模式数量减少、具有不同转动惯量的主旋转轴数量减少以及非相同构象异构体数量减少。总体而言，这导致了独特的光谱特征，使得高分辨率LAS能够选择性且灵敏地检测大型VOCs。
