Effects of aerosol size and coating thickness on the molecular detection using extractive electrospray ionization
<p>Extractive electrospray ionization (EESI) has been a well-known technique for high-throughput online molecular characterization of chemical reaction products and intermediates, detection of native biomolecules, in vivo metabolomics, and environmental monitoring with negligible thermal and i...
Main Authors: | , , , , , , , , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2021-09-01
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Series: | Atmospheric Measurement Techniques |
Online Access: | https://amt.copernicus.org/articles/14/5913/2021/amt-14-5913-2021.pdf |
Summary: | <p>Extractive electrospray ionization (EESI) has been a well-known
technique for high-throughput online molecular characterization of chemical
reaction products and intermediates, detection of native biomolecules, in
vivo metabolomics, and environmental monitoring with negligible thermal and
ionization-induced fragmentation for over two decades. However, the EESI
extraction mechanism remains uncertain. Prior studies disagree on whether
particles between 20 and 400 nm diameter are fully extracted or if the
extraction is limited to the surface layer. Here, we examined the analyte
extraction mechanism by assessing the influence of particle size and coating
thickness on the detection of the molecules therein. We find that particles
are extracted fully: organics-coated NH<span class="inline-formula"><sub>4</sub></span>NO<span class="inline-formula"><sub>3</sub></span> particles with a
fixed core volume (156 and 226 nm in diameter without coating) showed
constant EESI signals for NH<span class="inline-formula"><sub>4</sub></span>NO<span class="inline-formula"><sub>3</sub></span> independent of the shell coating
thickness, while the signals of the secondary organic molecules comprising
the shell varied proportionally to the shell volume. We also found that the
EESI sensitivity exhibited a strong size dependence, with an increase in
sensitivity by 1–3 orders of magnitude as particle size decreased
from 300 to 30 nm. This dependence varied with the electrospray (ES)
droplet size, the particle size and the residence time for coagulation in the
EESI inlet, suggesting that the EESI sensitivity was influenced by the
coagulation coefficient between particles and ES droplets. Overall, our
results indicate that, in the EESI, particles are fully extracted by the ES
droplets regardless of the chemical composition, when they are collected by
the ES droplets. However, their coalescence is not complete and depends
strongly on their size. This size dependence is especially relevant when
EESI is used to probe size-varying particles as is the case in aerosol
formation and growth studies with size ranges below 100 nm.</p> |
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ISSN: | 1867-1381 1867-8548 |