A compact incoherent broadband cavity-enhanced absorption spectrometer for trace detection of nitrogen oxides, iodine oxide and glyoxal at levels below parts per billion for field applications
<p>We present a compact, affordable and robust instrument based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) for simultaneous detection of <span class="inline-formula">NO<sub><i>x</i></sub></span>, IO, CHOCHO and <sp...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-08-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/13/4317/2020/amt-13-4317-2020.pdf |
| Summary: | <p>We present a compact, affordable and robust instrument based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) for simultaneous detection of <span class="inline-formula">NO<sub><i>x</i></sub></span>, IO, CHOCHO and <span class="inline-formula">O<sub>3</sub></span> in the 400–475 nm wavelength region. The instrument relies on the injection of a high-power LED source in a high-finesse cavity (<span class="inline-formula"><i>F</i>∼33 100</span>), with the transmission signal being detected by a compact spectrometer based on a high-order diffraction grating and a charge-coupled device (CCD) camera. A minimum detectable absorption of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">2.0</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">10</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="55pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="c253330af05f9acfa3f592b912e803f1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-4317-2020-ie00001.svg" width="55pt" height="14pt" src="amt-13-4317-2020-ie00001.png"/></svg:svg></span></span> cm<span class="inline-formula"><sup>−1</sup></span> was achieved within <span class="inline-formula">∼22</span> min of total acquisition, corresponding to a figure of merit of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">1.8</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">10</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="55pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="b39a0ddd7bc1f580cf5511ce992fd803"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-4317-2020-ie00002.svg" width="55pt" height="14pt" src="amt-13-4317-2020-ie00002.png"/></svg:svg></span></span> cm<span class="inline-formula"><sup>−1</sup></span> Hz<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><msup><mi/><mrow><mo>-</mo><mn mathvariant="normal">1</mn><mo>/</mo><mn mathvariant="normal">2</mn></mrow></msup></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="21pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="b5319093eda405571bf1c434867fb212"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-4317-2020-ie00003.svg" width="21pt" height="11pt" src="amt-13-4317-2020-ie00003.png"/></svg:svg></span></span> per spectral element. Due to the multiplexing broadband feature of the setup, multi-species detection can be performed with simultaneous detection of <span class="inline-formula">NO<sub>2</sub></span>, IO, CHOCHO and <span class="inline-formula">O<sub>3</sub></span> achieving detection limits of 11, 0.3, 10 ppt (parts per trillion) and 47 ppb (parts per billion) (1<span class="inline-formula"><i>σ</i></span>) within 22 min of measurement, respectively (half of the time is spent on the acquisition of the reference spectrum in the absence of the absorber, and the other half is spent on the absorption spectrum). The implementation on the inlet gas line of a compact ozone generator based on electrolysis of water allows for the measurement of <span class="inline-formula">NO<sub><i>x</i></sub></span> (<span class="inline-formula">NO+NO<sub>2</sub></span>) and therefore an indirect detection of NO with detection limits for <span class="inline-formula">NO<sub><i>x</i></sub></span> and NO of 10 and 21 ppt (1<span class="inline-formula"><i>σ</i></span>), respectively. The device has been designed to fit in a 19 in., 3U (5.25 in.) rack-mount case; weighs 15 kg; and has a total electrical power consumption of <span class="inline-formula"><300</span> W. The instrument can be employed to address different scientific objectives such as better constraining the oxidative capacity of the atmosphere, studying the chemistry of highly reactive species in atmospheric chambers as well as in the field and looking at the sources of glyoxal in the marine boundary layer to study possible implications on the formation of secondary aerosol particles.</p> |
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| ISSN: | 1867-1381 1867-8548 |