Off-resonant photoacoustic spectroscopy for analysis of multicomponent gas mixtures at high concentrations using broadband vibrational overtones of individual gas species

Selvaraj, Ramya; Vasa, Nilesh J.; Nagendra, S.M. Shiva

doi:10.1364/ao.58.004118

Cited by 13 publications

(8 citation statements)

References 24 publications

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“…The acoustic resonance of a sample cell depends sensitively on the speed of sound. Due to the significant mass difference, doubling or tripling a methane concentration of 25% in an N 2 matrix considerably changes the speed of sound resulting in a large shift of the cell's resonance frequency (Selvaraj et al, 2019). Over a large range, the PA signal is proportional to the concentration of the absorbing molecules.…”

Section: Measurement Proceduresmentioning

confidence: 99%

PAS-based isotopologic analysis of highly concentrated methane

Bahr

Wolff

2022

Front. Environ. Chem.

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Photoacoustic spectroscopy (PAS) is typically used for the detection of trace gases. In this way, mixtures of short-chain hydrocarbons such as methane, ethane or propane can be analyzed with detection limits in the range of parts per million (ppm) or parts per billion (ppb) or even below. However, there are a number of applications where highly concentrated mixtures need to be analyzed. In some cases even the isotopologic composition of certain hydrocarbons needs to be determined. Examples can be found in natural gas production and planetary research. We present PAS-based isotopologic analyses of two digit percentage-level methane concentrations in nitrogen. The investigation allows conclusions to be drawn about the extent to which PAS is suitable for an isotopologic analysis of undiluted natural gas-like mixtures.

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Section: Measurement Proceduresmentioning

confidence: 99%

PAS-based isotopologic analysis of highly concentrated methane

Bahr

Wolff

2022

Front. Environ. Chem.

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“…A broadband photoacoustic technique for CH 4 detection in the 1.65 µm region was developed, where multiple absorption lines of methane were utilized to produce the photoacoustic signal. A bandpass filter with a full width at half maximum (FWHM) of 12 nm was chosen with a centre wavelength at 1.65 µm where the interference owing to moisture is minimal, as shown in Figure 6 [119]. A multi-wavelength algorithm can be used to estimate the cumulative PA signal amplitude analytically and a least detection limit of 0.05 ppm was reported [120].…”

Section: Methane (Ch 4 )mentioning

confidence: 99%

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

et al. 2020

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Human exhaled breath consists of more than 3000 volatile organic compounds, many of which are relevant biomarkers for various diseases. Although gas chromatography has been the gold standard for volatile organic compound (VOC) detection in exhaled breath, recent developments in mid-infrared (MIR) laser spectroscopy have led to the promise of compact point-of-care (POC) optical instruments enabling even single breath diagnostics. In this review, we discuss the evolution of MIR sensing technologies with a special focus on photoacoustic spectroscopy, and its application in exhaled breath biomarker detection. While mid-infrared point-of-care instrumentation promises high sensitivity and inherent molecular selectivity, the lack of standardization of the various techniques has to be overcome for translating these techniques into more widespread real-time clinical use.

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“…The PA cell consisting of a resonating tube and two buffer volumes with quartz windows similar to that described elsewhere, was used . This design reduced the interference from the windows heating up.…”

Section: Experimental Setupmentioning

confidence: 99%

“…The PA cell consisting of a resonating tube and two buffer volumes with quartz windows similar to that described elsewhere, was used. 25 This design reduced the interference from the windows heating up. A microphone (Ono Sokki MI 1235) with a preamplifier (Ono Sokki, MI 3111) was located at the antinode of the fundamental mode of vibration of the PA resonator.…”

Section: ■ Experimental Setupmentioning

confidence: 99%

Off-Resonance Photoacoustic Spectroscopy Technique for Multi-Gas Sensing in Biogas Plants

2019

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An off-resonance broadband photoacoustic spectroscopy (PAS) technique with a supercontinuum laser (SCL) in the near-infrared range is demonstrated for biogas measurements with different biomass matrices. The PAS sensor system has been calibrated with known concentrations of methane (CH4), carbon dioxide (CO2), water vapor (H2O vapor), and hydrogen sulfide (H2S). A laboratory-scale bioreactor was set up to monitor CH4 and CO2 generation using the SCL-PA sensor system. The obtained results show the suitability of the PAS sensor to be employed in a fully operational large scale biogas plant for online monitoring. The periodic variations in concentration for CH4, CO2, and H2O vapor were monitored in a large scale cattle dung based biogas plant in real-time, and the operating ranges were measured to be around 50–65%, 34–48%, and 0–1%, respectively. The SCL-PA sensor was also employed at two different Sewage Treatment Plants in Chennai, Tamilnadu, India, where along with CH4 (60–63%), CO2 (34–38%), and H2O vapor (0.8–1%), trace concentration levels of H2S were found to be around 0.04–1%.

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Off-resonant photoacoustic spectroscopy for analysis of multicomponent gas mixtures at high concentrations using broadband vibrational overtones of individual gas species

Cited by 13 publications

References 24 publications

PAS-based isotopologic analysis of highly concentrated methane

PAS-based isotopologic analysis of highly concentrated methane

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

Off-Resonance Photoacoustic Spectroscopy Technique for Multi-Gas Sensing in Biogas Plants

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