Cavity ring-down spectroscopy sensor for detection of hydrogen chloride

Abstract

Abstract.A laser-based cavity ring-down spectroscopy (CRDS) sensor for measurement of hydrogen chloride (HCl) has been developed and characterized. The instrument uses light from a distributed-feedback diode laser at 1742 nm coupled to a high finesse optical cavity to make sensitive and quantifiable concentration measurements of HCl based on optical absorption. The instrument has a (1σ ) limit of detection of <20 pptv in 1 min and has high specificity to HCl. The measurement response time to changes in input HCl concentration is <15 s. Validation studies with a previously calibrated permeation tube setup show an accuracy of better than 10 %. The CRDS sensor was preliminarily tested in the field with two other HCl instruments (mist chamber and chemical ionization mass spectrometry), all of which were in broad agreement. The mist chamber and CRDS sensors both showed a 400 pptv plume within 50 pptv agreement. The sensor also allows simultaneous sensitive measurements of water and methane, and minimal hardware modification would allow detection of other near-infrared absorbers.

Comment on amt-2021-6

“…Increase in HCl had a similar response time. The response time is comparable to Webster et al, 1994 andHagen et al, 2014, who both took similar steps to ensure their instruments were suitable for HCl measurements (Hagen et al made their cell out of Teflon instead of coating a stainless-steel cell with an inert silicon layer).…”

“…However, these commercial HCl instruments are designed more for ground-based industrial applications, and their response times are relatively slow (around 1 minute). The only cavityenhanced HCl spectrometer reported in peer-reviewed scientific literature relies on cavity-ringdown spectroscopy (CRDS) rather than ICOS to realize the desired precision (Hagen et al, 2014). The 90 % response time of this instrument is 10 seconds, with a 1 60s precision of 20 parts per trillion by volume (pptv).…”

Simultaneous detection of ethanol, ether and acetone by mid-infrared cavity ring-down spectroscopy at 3.8 μm

“…Their influence on the mirror reflectivity is not noticeable in our experiment. For detecting VOCs that could cause mirror reflectivity degradation, gas (nitrogen or clean air) purging to the mirror surface can be employed to protect the mirrors from VOC contaminations [30,31]. In addition, the influence of adsorption and memory effects can be decreased by measuring the baseline regularly…”

Double-looped Mach-Zehnder interferometry for achieving simultaneous spectral ring-down information

“…[1][2][3] Cavity ring-down spectroscopy (CRDS) is a representative tool for accurately measuring the concentration of trace samples. 4 Recently, numerical research on fiberloop ring-down spectroscopy (FLRDS) has been reported due to the advantages of optical fiber sensors, such as miniaturization feasibility and remote sensing potential.…”