A new laser-based and ultra-portable gas sensor for indoor and outdoor formaldehyde (HCHO) monitoring

Shutter, Joshua D.; Allen, Norton; Hanisco, T. F.; Wolfe, G. M.; Clair, J. M. St; Keutsch, Frank N.

doi:10.5194/amt-12-6079-2019

Cited by 15 publications

(20 citation statements)

References 26 publications

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“…The methods used to estimate each instrumental precision are listed in the table notes. It should be noted that although the precision here was used to indicate the detection capability, − ,, it was not calculated strictly according to the IUPAC recommended method. For a clear comparison, the precision of HCHO IBBCEAS based on both HCHO standard measurements and the IUPAC method is listed in Table .…”

Section: Resultsmentioning

confidence: 99%

“…In contrast, the Hantzsch method also has a sensitive HCHO detection capacity albeit with a much shorter time resolution (i.e., 50 pptv at a 60 s time resolution), and online-measuring instruments based on this approach have been widely used for HCHO detection indoors and outdoors, − exhibiting chemical interference only in rare instances . Nonetheless, numerous spectroscopic methods have been developed to achieve sub-ppbv detection of HCHO or lower, such as tunable diode laser absorption spectroscopy (TDLAS), differential optical absorption spectroscopy (DOAS), quantum cascade laser spectroscopy (QCLS), laser-induced fluorescence (LIF), and incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS). ,− …”

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confidence: 99%

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Sensitive Detection of Ambient Formaldehyde by Incoherent Broadband Cavity Enhanced Absorption Spectroscopy

Liu

Yang

et al. 2020

Anal. Chem.

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Formaldehyde (HCHO) is the most abundant atmospheric carbonyl compound and plays an important role in the troposphere. However, HCHO detection via traditional incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) is limited by short optical path lengths and weak light intensity. Thus, a new light-emitting diode (LED)-based IBBCEAS was developed herein to measure HCHO in ambient air. Two LEDs (325 and 340 nm) coupled by a Y-type fiber bundle were used as an IBBCEAS light source, which provided both high light intensity and a wide spectral fitting range. The reflectivity of the two cavity mirrors used herein was 0.99965 (1 − reflectivity = 350 ppm loss) at 350 nm, which corresponded with an effective optical path length of 2.15 km within a 0.84 m cavity. At an integration time of 30 s, the measurement precision (1σ) for HCHO was 380 parts per trillion volume (pptv), and the corresponding uncertainty was 8.3%. The instrument was successfully deployed for the first time in a field campaign and delivered results that correlated well with those of a commercial wet-chemical instrument based on Hantzsch fluorimetry (R 2 = 0.769). The combined light source based on a Y-type fiber bundle overcomes the difficulty of measuring ambient HCHO via IBBCEAS in near-ultraviolet range, which may extend IBBCEAS technology to measure other atmospheric trace gases with high precision.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Sensitive Detection of Ambient Formaldehyde by Incoherent Broadband Cavity Enhanced Absorption Spectroscopy

Liu

Yang

et al. 2020

Anal. Chem.

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“…Strong absorption lines in the UV region allow the sensitive detection of formaldehyde by differential absorption (DOAS) instruments with either high or low spectral resolution (Dorn et al, 1995;Platt and Stutz, 2008) and cavitybased absorption spectroscopy (Washenfelder et al, 2016;Liu et al, 2019). Detection by absorption in the IR region is also possible by either Fourier transformation infrared spectroscopy (FTIR), tunable diode laser spectroscopy (TDLS) (Weibring et al, 2007;Shutter et al, 2019), quantum cascade laser spectroscopy (QCLS) (McManus et al, 2010), photoacoustic spectroscopy (Dugheri et al, 2021) or cavity ringdown spectroscopy (Picarro, Inc.). Absorption spectroscopy has the advantage that it does not need regular calibrations with a gas standard, but it does require knowledge of absorption cross-sections and careful characterization of instrument properties to avoid or correct for possible spectral interferences and signal offsets.…”

Section: Introductionmentioning

confidence: 99%

“…Formaldehyde measurements by a LIF instrument were compared to Hantzsch measurements in the SAPHIR chamber in 2014 (Kaiser et al, 2014), and to those provided by a recently developed commercial TDLAS system from Aeris Technology in ambient air (Shutter et al, 2019). The agree-ment between the measurements from the LIF and TDLAS instruments was better than 8 % for formaldehyde mixing ratios higher than 1 ppbv.…”

Section: Introductionmentioning

confidence: 99%

Comparison of formaldehyde measurements by Hantzsch, CRDS and DOAS in the SAPHIR chamber

Glowania¹,

Rohrer²,

Dorn³

et al. 2021

Atmos. Meas. Tech.

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Abstract. Three instruments that use different techniques to measure gaseous formaldehyde (HCHO) concentrations were compared in experiments in the atmospheric simulation chamber SAPHIR at Forschungszentrum Jülich. One instrument (AL4021, Aero-Laser GmbH) detects HCHO using the wet-chemical Hantzsch reaction (for efficient gas-phase stripping), chemical conversion and fluorescence measurement. An internal HCHO permeation source allows for daily calibrations. This instrument was characterized by sulfuric acid titration (overall accuracy 8.6 %) and yields measurements with a time resolution of 90 s and a limit of detection (3σ) of 0.3 ppbv. In addition, a new commercial instrument that makes use of cavity ring-down spectroscopy (CRDS) determined the concentrations of HCHO, water vapour, and methane (G2307, Picarro, Inc.). Its limit of detection (3σ) is specified as 0.3 ppbv for an integration time of 300 s, and its accuracy is limited by the drift of the zero signal (manufacturer specification 1.5 ppbv). A custom-built high-resolution laser differential optical absorption spectroscopy (DOAS) instrument provided HCHO measurements with a limit of detection (3σ) of 0.9 ppbv and an accuracy of 7 % using an optical multiple reflection cell. The measurements were conducted from June to December 2019 in experiments in which either ambient air flowed through the chamber or the photochemical degradation of organic compounds in synthetic air was investigated. Measured HCHO concentrations were up to 8 ppbv. Various mixtures of organic compounds, water vapour, nitrogen oxides and ozone were present in these experiments. Results demonstrate the need to correct the baseline in measurements performed by the Hantzsch instrument to compensate for drifting background signals. Corrections were equivalent to HCHO mixing ratios in the range of 0.5–1.5 ppbv. The baseline of the CRDS instrument showed a linear dependence on the water vapour mixing ratio with a slope of (-11.20±1.60) ppbv %−1 below and (-0.72±0.08) ppbv %−1 above a water vapour mixing ratio of 0.2 %. In addition, the intercepts of these linear relationships drifted within the specification of the instrument (1.5 ppbv) over time but appeared to be equal for all water mixing ratios. Regular zero measurements are needed to account for the changes in the instrument zero. After correcting for the baselines of measurements by the Hantzsch and the CRDS instruments, linear regression analysis of measurements from all three instruments in experiments with ambient air indicated good agreement, with slopes of between 0.98 and 1.08 and negligible intercepts (linear correlation coefficients R2>0.96). The new small CRDS instrument measures HCHO with good precision and is accurate if the instrument zero is taken into account. Therefore, it can provide measurements with similar accuracy to the DOAS instrument but with slightly reduced precision compared to the Hantzsch instrument.

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“…In recent years, several 65 commercially available instruments have been developed towards that goal, including a cavity ring down spectroscopy (CRDS) instrument from Picarro, a photoacoustic gas analyser from Gasera, and Tunable Diode Laser Spectroscopy (TDLS) instruments from Aeris Technologies and Aerodyne Research, Inc. Here, we focus on the Aeris MIRA and Picarro CRDS G2307 instruments, which have been compared against other instruments in a small number of informal (Whitehill et al, 2018;Furdyna, 2020) and peer-reviewed (Shutter et al, 2019;Glowania et al, 2021) intercomparison efforts. Since those efforts, the Picarro G2307 instrument implemented updates to its spectral fitting algorithm, and the Aeris MIRA instrument has offered improved thermal stabilization.…”

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confidence: 99%

Evaluation of Aeris MIRA, Picarro CRDS G2307, and DNPH-based sampling for long-term formaldehyde monitoring efforts

Mouat

Siegel

Kaiser

2023

Preprint

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Abstract. Current formaldehyde measurement networks rely on the TO-11A offline chemical derivatization technique, which can be resource intensive and limited in temporal resolution. In this work, we evaluate the field performance of three new commercial instruments for continuous in-situ formaldehyde monitoring: the Picarro cavity ringdown spectroscopy (CRDS) G2307 gas concentration analyzer and Aeris Technologies’ mid-infrared absorption (MIRA) Pico and Ultra gas analyzers. All instruments require regular drift correction, with baseline drifts over a 1-week period of ambient sampling of 1 ppb, 4 ppb, and 20 ppb for the G2307, Ultra, and Pico, respectively. Baseline drifts are easily corrected with frequent instrument zeroing using DNPH scrubbers, while Drierite, molecular sieves, and heated hopcalite fail to remove all incoming HCHO. Drift-corrected 3σ limits of detection (LOD) determined from regular instrument zeroing were relatively comparable at 0.055 ppb (Picarro G2307), 0.065 ppb (Aeris Ultra), and 0.08 ppb (Aeris Pico) for a 20 min integration time. We find that after correcting for a 30–40 % bias in the Pico measurements, all instruments agree within 5 % and are well correlated with each other (all R2≥0.70). Picarro G2307 HCHO observations are more than 50 % higher than co-located TO-11A HCHO measurements (R2 = 0.92, slope = 1.47, int = 1 ppb HCHO), which is in contrast to previous comparisons where measurements were biased low by 1–2 ppb. We attribute this discrepancy to the previous versions of the spectral fitting algorithm as well as the zeroing method. The temperature stabilization upgrade of the Ultra offers improved baseline stability over the previously described Pico version, reducing the maximum drift rate by a factor of 13 and improves precision of a 10 min average by 13 ppt. Using a 6-month deployment period, we demonstrate that all instruments provide a reliable measurement of ambient HCHO concentrations in an urban environment and, when compared with previous observations, find that midday summertime HCHO concentrations have reduced by approximately 50 % in the last two decades.

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A new laser-based and ultra-portable gas sensor for indoor and outdoor formaldehyde (HCHO) monitoring

Cited by 15 publications

References 26 publications

Sensitive Detection of Ambient Formaldehyde by Incoherent Broadband Cavity Enhanced Absorption Spectroscopy

Sensitive Detection of Ambient Formaldehyde by Incoherent Broadband Cavity Enhanced Absorption Spectroscopy

Comparison of formaldehyde measurements by Hantzsch, CRDS and DOAS in the SAPHIR chamber

Evaluation of Aeris MIRA, Picarro CRDS G2307, and DNPH-based sampling for long-term formaldehyde monitoring efforts

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