High‐sensitivity detection and quantification of CHCl₃ vapors in various gas environments based on the photoacoustic spectroscopy

Abstract

In this study, the quality factor and cell constant vs acoustic resonator sizes in the first radial and longitudinal modes were calculated using our homemade simulation. Based on these simulations a photoacoustic (PA) spectroscopy system was designed, optimized, and finally fabricated as a high‐sensitivity gas sensor. The subsequent experiments have been done to online monitoring of the trichloromethane (CHCl3) vapors trace. The sensitivity of system for detection of CHCl3 vapors was measured 488 ppb. Corresponding PA signal for different concentrations of CHCl3 vapors is determined in the presence of N2, synthetic air, He, and Ar in various gas environments. It is shown that the effect of buffer gas and the relevant pressures are substantiated to achieve the minimum detectable concentration. In other words, using heavier gases at the same experimental conditions lead to detection of the lower concentrations. When the buffer gas of system was He, the lowest PA signal was recorded. This faint signal of He is due to vibrational‐translational processes of He, thermodynamic and acoustic properties of system such as cell constant, quality factor, speed of sound, thermal diffusion, thermal boundary layer, and viscous boundary layer for He. These properties for various buffer gases were calculated and discussed.

Study on a photoacoustic spectroscopy trichloromethane gas detection method based on an arched photoacoustic cavity

“…3 Trichloromethane is a colorless transparent liquid with low toxicity that is easy to volatilize, and it gradually oxidizes to a highly toxic phosgene under light. The inhalation of chloroform vapor can paralyze the nervous system, 4 has anesthetic effects, damages the heart, liver and kidneys, and has the possibility of carcinogenicity. Therefore, the development of chloroform gas monitoring systems is of great significance and has received extensive attention.…”

Ppb level detection of carbonyl sulfide and ethene and study resonant frequencies using laser photoacoustic spectroscopy

“…Finally, the QTF will generate an electronic signal based on the piezoelectric effect 20 . While in conventional photoacoustic spectroscopy, microphone is used as acoustic wave transducer 22–28 which is described below Mark Leonidovitch Viengerov first used IR lamp‐based photo‐acoustic spectroscopy to analyze gases in 1938 29 . After the invention of the laser, use of lasers in the photoacoustic spectroscopy setup led to an increase in the sensitivity and efficiency of this optical technique 22–28 .…”

“…Finally, the QTF will generate an electronic signal based on the piezoelectric effect. 20 While in conventional photoacoustic spectroscopy, microphone is used as acoustic wave transducer [22][23][24][25][26][27][28] which is described below Mark Leonidovitch Viengerov first used IR lamp-based photo-acoustic spectroscopy to analyze gases in 1938. 29 After the invention of the laser, use of lasers in the photoacoustic spectroscopy setup led to an increase in the sensitivity and efficiency of this optical technique.…”

“…29 After the invention of the laser, use of lasers in the photoacoustic spectroscopy setup led to an increase in the sensitivity and efficiency of this optical technique. [22][23][24][25][26][27][28] In the photoacoustic spectroscopy the gas sample is exposed to the modulated laser radiation. The absorption of pulsed laser radiation by the sample leads to changes in temperature periodically and then changes in pressure periodically in the longitudinal mode via collisional processes.…”

High Sensitivity Continuous Monitoring of Chloroform Gas by Using Wavelength Modulation Photoacoustic Spectroscopy in the Near-Infrared Range

“…Inhalation of chloroform vapor can paralyze the nervous system. When in an environment of 900 ppm chloroform, people may become dizzy in a very short time [2]. In addition, chloroform is unstable when exposed to light in the air.…”