QEPAS sensor for breath analysis: a behavior of pressure

Abstract

The measurement of trace gases has increasingly become a key technique in healthcare and other medical applications. Quartz-enhanced photoacoustic spectroscopy (QEPAS) is a suitable method that can provide the required characteristics in such applications for a comparatively low cost and small size. The quantitative detection and a low detection limit are also required by applications. In this paper, we present new results on sensing biomedically relevant gases using the on-beam QEPAS technique with some newly developed tunable high-power single-mode laser diodes based on GaSb material. The data processing and detection limit determination are done by a field programmable gate array device, as well as an automatic measurement of the resonance frequency.

Comparison of the spectral excitation behavior of methane according to InP, GaSb, IC, and QC lasers as excitation source by sensor applications

“…In this paper, we decided not to display the absorption spectra and the RF curves because the reader should be adequately familiar with them. Examples of those figures can be seen in the abovementioned references [11,13]. At the end of each subsection, a weighting will take place to estimate the use of these absorption regions and their lasers.…”

Review of Recent Advances in QEPAS-Based Trace Gas Sensing

“…The high Q-factor (~100,000 in a vacuum and~10,000 in a standard atmosphere pressure) and narrow resonance frequency band (<1 Hz) of QTF improve the QEPAS selectivity and immunity to environmental acoustic noise [13][14][15][16][17][18][19]. Due to the merits of high selectivity and sensitivity, low cost, compactness, and a large dynamic range, QEPAS sensors have been widely applied in gas detection for atmospheric monitoring [20][21][22][23][24][25][26][27], chemical analysis [28][29][30][31][32], biomedical diagnostics [33][34][35][36], and trace gas sensing [37][38][39][40][41][42][43][44]. Different QEPAS sensor architectures were developed to meet the requirements of a large number of applications.…”

Advances in Mid-Infrared Spectroscopy-Based Sensing Techniques for Exhaled Breath Diagnostics

“…On the other hand, broadband sources matching with broadband spectra of species of interest can be used, which allows low power based multiple-gas sensing. Recently, QEPAS based on quartz tuning forks (QTF) as a sound transducer for the PAS technique has been increasingly used for selective and sensitive sensing [81][82][83][84][85][86][87][88][89][90][91][92]. The general architecture of a QEPAS system is shown in Figure 5.…”