Institute of Biomedical Engineering, Chinese Academy of Medical Sciences & Peking Union Medical College, No.236 Baidi Road, Tianjin, 300192, China.
Institute of Biomedical Engineering, Chinese Academy of Medical Sciences & Peking Union Medical College, No.236 Baidi Road, Tianjin, 300192, China.
Anal Chim Acta. 2020 Sep 22;1131:18-24. doi: 10.1016/j.aca.2020.07.056. Epub 2020 Jul 28.
Breath analysis offers a promising method of noninvasive analyses of volatile metabolites and xenobiotics present in human body. Isoprene is one of the highest abundant volatile organic compounds (VOCs) present in human exhaled breath. Breath isoprene (50-200 part per billion by volume (ppbv) or higher) can be analyzed by using mass spectroscopy-based methods, yet laser absorption spectral detection of breath isoprene has not been much reported, partially due to its ultraviolet (UV) absorption wavelength and the spectral overlap with other breath VOCs such as acetone in the same wavelength region. These facts make it challenging to develop a spectroscopy-based breath isoprene analyzer for a potential portable instrument. Here we report on the development of a cavity ringdown spectroscopy (CRDS) system for detection of breath isoprene in the UV region near 226 nm. First, we investigated spectral absorption interferences near 226 nm and selected an optimal detection wavelength at 226.56 nm with minimum to no spectral interference. We then measured absorption cross-sections of isoprene at 225.5-227.4 nm under controlled cavity pressures, and the measured absorption cross-section 1.93 × 10 cm/molecule at 226.56 nm was used to quantify isoprene in different cases including human breath gas samples. Finally, we validated the CRDS system by measuring breath gas samples from 19 human subjects using proton transfer reaction mass spectrometry (PTR-MS). The CRDS system shows good linear response (R = 0.999), high stability (0.2%), and high accuracy (R = 0.906 with PTR-MS). The limit of detection of the system was 0.47 ppbv, with average over 100 ringdown events (equivalent to 5 s). This work represents the first exploratory study of the detection of breath isoprene using CRDS. The results demonstrate the potential of developing a CRDS-based breath analyzer for online, near-real time, sensitive analysis of breath isoprene for further research that would help to elucidate its physiological and clinical significance.
呼气分析提供了一种有前途的非侵入性分析方法，可用于分析人体中存在的挥发性代谢物和外源性化合物。异戊二烯是人体呼出气体中含量最高的挥发性有机化合物 (VOC) 之一。可以使用基于质谱的方法分析呼气中的异戊二烯（体积浓度为 50-200 十亿分之一 (ppbv) 或更高），但激光吸收光谱法对呼气异戊二烯的检测却鲜有报道，部分原因是其紫外 (UV) 吸收波长以及与其他呼吸 VOC（如同波长区域内的丙酮）的光谱重叠。这些事实使得开发用于潜在便携式仪器的基于光谱的呼气异戊二烯分析仪具有挑战性。在这里，我们报告了一种用于检测近 226nm 紫外区域内呼气异戊二烯的腔衰荡光谱 (CRDS) 系统的开发。首先，我们研究了近 226nm 处的光谱吸收干扰，并选择了一个最佳的检测波长 226.56nm，该波长的光谱干扰最小或没有。然后，我们在受控腔压下测量了异戊二烯在 225.5-227.4nm 处的吸收截面，在 226.56nm 处测量的吸收截面为 1.93×10-19cm2/分子，用于量化不同情况下（包括人体呼吸气体样本）的异戊二烯。最后，我们使用质子转移反应质谱 (PTR-MS) 测量了来自 19 名人类受试者的呼吸气体样本，验证了 CRDS 系统的性能。CRDS 系统显示出良好的线性响应 (R=0.999)、高稳定性 (0.2%) 和高精度 (R=0.906 与 PTR-MS)。该系统的检测限为 0.47ppbv，平均超过 100 次衰荡事件（相当于 5s）。这项工作代表了使用 CRDS 检测呼气异戊二烯的首次探索性研究。结果表明，开发基于 CRDS 的呼吸分析仪用于在线、近实时、敏感分析呼气异戊二烯具有潜力，这将有助于阐明其生理和临床意义。
