The determination of ClNO<sub>2</sub> via thermal dissociation–tunable infrared laser direct absorption spectroscopy
<p>Nitryl chloride (ClNO<span class="inline-formula"><sub>2</sub></span>) is a reservoir species of chlorine atoms and nitrogen oxides, both of which play important roles in atmospheric chemistry. To date, all ambient ClNO<span class="inline-formula&qu...
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| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-08-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/18/3799/2025/amt-18-3799-2025.pdf |
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| Summary: | <p>Nitryl chloride (ClNO<span class="inline-formula"><sub>2</sub></span>) is a reservoir species of chlorine atoms and nitrogen oxides, both of which play important roles in atmospheric chemistry. To date, all ambient ClNO<span class="inline-formula"><sub>2</sub></span> observations have been obtained by chemical ionization mass spectrometry (CIMS). In this work, thermal dissociation–tunable infrared laser direct absorption spectrometry (TD-TILDAS) is shown to be a viable method for quantifying ClNO<span class="inline-formula"><sub>2</sub></span> in laboratory and field settings. This technique relies on the thermal dissociation of ClNO<span class="inline-formula"><sub>2</sub></span> to create chlorine radicals, which undergo fast reactions with hydrocarbons to produce hydrogen chloride (HCl) that is detectable by the TILDAS instrument. Complete quantitative conversion of ClNO<span class="inline-formula"><sub>2</sub></span> to HCl was achieved at temperatures <span class="inline-formula">></span> 400 °C, achieving 1 Hz measurement precision of 11 <span class="inline-formula">±</span> 1 pptv (3<span class="inline-formula"><i>σ</i></span> limits of detection of 34 <span class="inline-formula">±</span> 2 pptv) during laboratory comparisons with other ClNO<span class="inline-formula"><sub>2</sub></span> detection methods. After blank and line loss corrections, method accuracy is estimated to be within <span class="inline-formula">±</span> 5 %. Performance metrics of TD-TILDAS during ambient sampling were a 1 Hz precision of 19 <span class="inline-formula">±</span> 1 pptv and 3<span class="inline-formula"><i>σ</i></span> limits of detection of 57 <span class="inline-formula">±</span> 3 pptv, which is directly comparable to previously reported ClNO<span class="inline-formula"><sub>2</sub></span> detection by quadrupole CIMS. Thus, TD-TILDAS can provide an alternative analytical approach for a direct measurement of ClNO<span class="inline-formula"><sub>2</sub></span> that can complement existing datasets and future studies. The quantitative nature of TD-TILDAS also makes it a potentially useful tool for the calibration of CIMS instruments. However, interpretation of ambient data may be complicated by potential interferences from unaccounted-for sources of thermolabile chlorine, such as ClNO, chloramines, and organochlorides.</p> |
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| ISSN: | 1867-1381 1867-8548 |