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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

  09 Sep 2019

09 Sep 2019

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This preprint is currently under review for the journal AMT.

Technical note: Common glitch affecting the EC/OC split point determination in the Sunset Thermal-Optical Analyzerand recommendations to reduce its occurrence

Stéphanie Gagné, Brett Smith, Gregory J. Smallwood, and Joel C. Corbin Stéphanie Gagné et al.
  • Metrology Research Centre, National Research Council Canada, Ottawa, K1A 0R6, Canada

Abstract. We identified a common and relatively frequent glitch in the light transmittance/reflectance measurement during thermal-optical analysis in the Sunset Laboratory bench top thermal-optical analyzer models. In the instrument studied, the glitch is observed for one in three punch analyses when using the default analysis parameters. The occurrence of this glitch can invalidate the split point and thus the OC and EC fractions and absolute quantities reported. The glitch was observed in data from at least three independent laboratories using different thermal protocols. We describe this glitch as a “discontinuity” (rapid increase or decrease occurring over a few seconds) in the laser transmittance or reflectance which happens relatively frequently and whose behaviour varies in amplitude, timing and direction. We use over 2,200 filter-punch analyses to expose the factors that contribute to the risk of such a discontinuity occurring. We demonstrate that these discontinuities are due to the movement of filter punches within the instrument, and can therefore be minimized by decreasing the blower speed of the instrument and, if possible, by ensuring a tighter fit of the filter punch in its holder (by testing different spoons). The decrease in blower speed has a negligible effect on the measured temperature program during analysis and is the single most effective way to reduce the risk of discontinuity occurrence. We recommend these modifications for all Sunset instruments.

Stéphanie Gagné et al.

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Stéphanie Gagné et al.

Stéphanie Gagné et al.


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Latest update: 27 Nov 2020
Publications Copernicus
Short summary
We identified a common glitch in the Sunset Laboratory Thermal-Optical Analyzer which invalidates the differentiation between organic and elemental carbon i.e. what the instrument is designed to do. This glitch happened 33% of the time in our own instrument. The occurrence was reduced to around 5% when following the recommendations set out in this paper. The glitch was also observed in other Sunset instruments used worldwide for air quality monitoring and regulated emissions measurements.
We identified a common glitch in the Sunset Laboratory Thermal-Optical Analyzer which...