Temperature-dependent sensitivity of iodide chemical ionization mass spectrometers
<p>Iodide chemical ionization mass spectrometry (CIMS) is a common analytical tool used in both laboratory and field experiments to measure a large suite of atmospherically relevant compounds. Here, we describe a systematic ion molecule reactor (IMR) temperature dependence of iodide CIMS analy...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-07-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/15/4295/2022/amt-15-4295-2022.pdf |
| Summary: | <p>Iodide chemical ionization mass spectrometry (CIMS) is a common analytical
tool used in both laboratory and field experiments to measure a large suite
of atmospherically relevant compounds. Here, we describe a systematic ion
molecule reactor (IMR) temperature dependence of iodide CIMS analyte
sensitivity for a wide range of analytes in laboratory experiments. Weakly
bound iodide clusters, such as HCl, HONO, HCOOH, HCN, phenol, 2-nitrophenol,
and acyl peroxynitrate (PAN) detected via the peroxy radical cluster, all
exhibit strong IMR temperature dependence of sensitivity ranging from <span class="inline-formula">−3.4</span> % <span class="inline-formula"><sup>∘</sup></span>C<span class="inline-formula"><sup>−1</sup></span>
to 5.9 % <span class="inline-formula"><sup>∘</sup></span>C<span class="inline-formula"><sup>−1</sup></span> (from 37 to 47 <span class="inline-formula"><sup>∘</sup></span>C). Strongly
bound iodide clusters, such as Br<span class="inline-formula"><sub>2</sub></span>, N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span>, ClNO<span class="inline-formula"><sub>2</sub></span>, and PAN
detected via the carboxylate anion, all exhibit little to no IMR temperature
dependence ranging from 0.2 % <span class="inline-formula"><sup>∘</sup></span>C<span class="inline-formula"><sup>−1</sup></span> to <span class="inline-formula">−0.9</span> % <span class="inline-formula"><sup>∘</sup></span>C<span class="inline-formula"><sup>−1</sup></span> (from 37 to 47 <span class="inline-formula"><sup>∘</sup></span>C). The IMR temperature relationships of weakly bound clusters
provide an estimate of net reaction enthalpy, and comparison with database
values indicates that these clusters are in thermal equilibrium. Ground site
HCOOH data collected in the summer of 2021 in Pasadena (CA) are corrected
and show a reversal in the diel cycle, emphasizing the importance of this
correction (<span class="inline-formula">35±6</span> % during the day, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M18" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">26</mn><mo>±</mo><mn mathvariant="normal">2</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="39pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="5f68a989a9daf5d6cb167661ad06f8e3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-15-4295-2022-ie00001.svg" width="39pt" height="10pt" src="amt-15-4295-2022-ie00001.png"/></svg:svg></span></span> % at night).
Finally, we recommend two approaches to minimize this effect in the field,
namely heating or cooling the IMR; the latter technique has the added benefit of
improving absolute sensitivity.</p> |
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| ISSN: | 1867-1381 1867-8548 |