the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Development of accurate and stable primary standard gas mixtures for global atmospheric acetonitrile monitoring: evaluating adsorption loss and long-term stability
Abstract. Acetonitrile plays an important role in atmospheric processes and serves as a key tracer of biomass burning, the major emission source of primary carbonaceous particles and trace gases in the global atmosphere. Recognizing its significance, the World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) has designated acetonitrile as one of the target volatile organic compounds for global atmospheric monitoring, aiming for data quality better than 20 % accuracy and 15 % precision. Meeting the objectives of the WMO GAW program requires accurate and stable calibration standards with uncertainties of less than 5 %. In this study, we explored the feasibility of gravimetry for developing primary standard gas mixtures (PSMs) in three different types of aluminium cylinders, each with distinct internal surface treatments, at nmol mol-1 and µmol mol-1 levels with a relative expanded uncertainty of less than 5 %. We found that all three types of cylinders were inadequate, without further passivation, for developing acetonitrile PSMs below 10 nmol mol-1 due to significant adsorption losses (6 %–49 %) onto the cylinder's inner surface. To overcome this challenge, we prepared acetonitrile gas mixtures at 100 nmol mol-1 using a modified gravimetric method and at 10 µmol mol-1 using a conventional gravimetric method and then evaluated their long-term stability. Results showed that the effect of the adsorption loss at 100 nmol mol-1 and 10 µmol mol-1 was negated and negligible, respectively. Stability results show that we can disseminate acetonitrile calibration standards at both 100 nmol mol-1 and 10 µmol mol-1 with a relative expanded uncertainty of 3 % and 1 %, respectively (with an expiration period of 3 years), meeting the target uncertainty of the WMO GAW program. Further research is still needed to develop accurate and stable acetonitrile calibration standards below 10 nmol mol-1 that are closer to atmospheric levels.
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RC1: 'Comment on amt-2024-132', Maitane Iturrate-Garcia, 29 Oct 2024
The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2024-132/amt-2024-132-RC1-supplement.pdf
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AC1: 'Reply on RC1', Baigali Tsogt, 14 Nov 2024
Dear Dr. Maitane Iturrate-Garcia
Your kind contribution of time to our study and your insightful comments were greatly appreciated. It appears that your recommendations really help a wider audience understand and make sense of our work. Every suggestion and feedback you provided was taken into account when we revised our manuscript.
Citation: https://doi.org/10.5194/amt-2024-132-AC1
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AC1: 'Reply on RC1', Baigali Tsogt, 14 Nov 2024
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RC2: 'Comment on amt-2024-132', Anonymous Referee #1, 31 Oct 2024
General Comments
Tsogt et al. describe the development and evaluation of primary gas standard mixtures of acetonitrile at µmol mol-1 and nmol mol-1 levels in different cylinder passivation treatments in support of global monitoring efforts within the WMO GAW program. The work is important and novel and the experimental work appears to be of good quality. I recommend publishing after some minor errors have been address as outlined below:
Minor comments
In the methods section (Page 3, lines 80-87) there appears to be some errors in the assignment of references in this paragraph as follows:
- Page 3, line 81: the text “…and the modified gravimetric method (Brewer, 2011).” Brewer 2011 is not correct here and this should actually be Brewer et al., 2019 (Anal. Chem 91(8), 5310-5315).
- Page 3, line 81: the text “…known to be stable in aluminium cylinders (Rhoderick, 2013, Brewer, 2019)….”, the reference to Brewer, 2019 is not correct here. An additional reference that should be included here instead is Rhoderick et al., 2019 (doi: 1525/elementa.366) as this paper demonstrates stability for hexane in the nmol mol-1 range in the Experis cylinder being used in this study.
Page 3, line 23: It was not clear to me what the reference was that is referred to here? It looks like from the plots that one mixture has been chosen as the reference and the other results have been normalised to that selected mixture. This was not clear and the choice for the reference was not clear. Some specific text needs to be included to address this.
Technical corrections
Figure 4: I suggest removing the ACN and hexane labels from the figure replacing them with A and B labels for the two panels and refer to each in the caption with reference to hexane or ACN.
There is an inconsistent use of nmol mol-1 (also µmol mol-1) and nmol/mol (also µmol/mol) throughout the paper, the mol mol-1 is preferred but usage should be consistent throughout. Currently both formats are used in the paper.
Citation: https://doi.org/10.5194/amt-2024-132-RC2 -
AC2: 'Reply on RC2', Baigali Tsogt, 14 Nov 2024
Thank you so much for taking the time to look at our work. The comments you made were carefully studied and edited, and the manuscript is revised accordingly.
Citation: https://doi.org/10.5194/amt-2024-132-AC2
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