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Volume 10, issue 12 | Copyright
Atmos. Meas. Tech., 10, 4613-4621, 2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 01 Dec 2017

Research article | 01 Dec 2017

Validation of spectroscopic gas analyzer accuracy using gravimetric standard gas mixtures: impact of background gas composition on CO2 quantitation by cavity ring-down spectroscopy

Jeong Sik Lim, Miyeon Park, Jinbok Lee, and Jeongsoon Lee Jeong Sik Lim et al.
  • Center for Gas Analysis, Chemical and Medical Metrology Division, Korea Research Institute of Standards and Science (KRISS), Gajeong-ro 267, Yuseong-gu, Daejeon 34113, Republic of Korea

Abstract. The effect of background gas composition on the measurement of CO2 levels was investigated by wavelength-scanned cavity ring-down spectrometry (WS-CRDS) employing a spectral line centered at the R(1) of the (3 00 1)III ← (0 0 0) band. For this purpose, eight cylinders with various gas compositions were gravimetrically and volumetrically prepared within 2σ = 0.1%, and these gas mixtures were introduced into the WS-CRDS analyzer calibrated against standards of ambient air composition. Depending on the gas composition, deviations between CRDS-determined and gravimetrically (or volumetrically) assigned CO2 concentrations ranged from −9.77 to 5.36µmolmol−1, e.g., excess N2 exhibited a negative deviation, whereas excess Ar showed a positive one. The total pressure broadening coefficients (TPBCs) obtained from the composition of N2, O2, and Ar thoroughly corrected the deviations up to −0.5 to 0.6µmolmol−1, while these values were −0.43 to 1.43µmolmol−1 considering PBCs induced by only N2. The use of TPBC enhanced deviations to be corrected to ∼ 0.15%.

Furthermore, the above correction linearly shifted CRDS responses for a large extent of TPBCs ranging from 0.065 to 0.081cm−1atm−1. Thus, accurate measurements using optical intensity-based techniques such as WS-CRDS require TPBC-based instrument calibration or use standards prepared in the same background composition of ambient air.

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Short summary
Effect of background gas composition on the spectroscopic measurement of CO2 concentration at ambient levels has been investigated. The wavelength-scanned cavity ring-down spectroscopy was employed to explore the spectral line shape of CO2 at 1603 nm. It is revealed that the instrument response should be corrected with respect to a total pressure broadening coefficient given by a matrix composition. The correction method is validated by high accurate gravimetric standard gas mixture.
Effect of background gas composition on the spectroscopic measurement of CO2 concentration at...