A portable N2O sensor based on quartz-enhanced photoacoustic spectroscopy with a distributed-feedback quantum cascade laser for medical and atmospheric applications

A portable sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS) is reported to analyze trace gases. QEPAS is a high sensitivity and very compact well-established spectroscopic technique for sensitive and selective detection of trace gases. A distributed feedback quantum cascade laser (DFB-QCL) emitting at 4474 nm is utilized as excitation light source. N2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_2$$\end{document}O has been selected as the target molecule, in order to evaluate the performance of the sensor. By analyzing the QEPAS peak signal as a function of the N2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_2$$\end{document}O concentration, the response of the sensor has been investigated and a sensitivity of 0.24 mV/ppb and a linearity of 0.999 have been found. An Allan deviation analysis has been performed to determine the long-term performance of the sensor. A minimum detection limit of 2 ppb for 100 s integration time has been achieved. A precision and stability of 100 ppb (0.5 %\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\%$$\end{document}) have been demonstrated as well.