WM-OA-ICOS Based Mid-Infrared Dual-Range Real-Time Trace Sensor for Formaldehyde Detection in Exhaled Breath
Guolin Li, Yimeng Song, Kun Ma, Xuena Zhang, Hao Zhao, Zecheng Zhang, Yajing Liu, Yunhui Wu, Jiarui Li, Shenqiang Zhai, Q. Li, Kaiyuan Zheng, Chuantao Zheng
Abstract
Based on wavelength modulation spectroscopy and off-axis integrated cavity output spectroscopy (WM-OA-ICOS), a highly sensitive dual-range real-time formaldehyde (CH <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{2}}\text{O}$ </tex-math></inline-formula> ) detection trace sensor was developed to detect CH <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{2}}\text{O}$ </tex-math></inline-formula> in human exhaled breath, which can realize the early screening of lung cancer. Also, a 5.85- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> quantum cascade laser (QCL) and an off-axis integrated cavity were adopted. Complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) is applied to improve the signal-to-noise ratio (SNR), and the sensor is embedded with a high-precision concentration inversion algorithm. The reliability of the sensor was verified by experiments with interfering gases in exhaled breath, and the results showed that the sensor has an excellent detection accuracy. The limit of detection (LoD) is ~140 parts per trillion (ppt) with an 88-s integration time by the Allan–Werle deviation analysis. The experimental results of exhaled gas showed that the concentration of CH <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{2}}\text{O}$ </tex-math></inline-formula> exhaled from different subjects was significantly different. Therefore, the sensor provides a promising way for real-time detection of CH <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{2}}\text{O}$ </tex-math></inline-formula> concentration in human exhaled breath.