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Title: Exploring Chemistry in Microcompartments Using Guided Droplet Collisions in a Branched Quadrupole Trap Coupled to a Single Droplet, Paper Spray Mass Spectrometer

Abstract

Recent studies suggest that reactions in aqueous microcompartments can occur at significantly different rates than those in the bulk. Most studies have used electrospray to generate a polydisperse source of highly charged microdroplets, leading to multiple confounding factors potentially influencing reaction rates (e.g., evaporation, charge, and size). Thus, the underlying mechanism for the observed enhancement remains unclear. We present a new type of electrodynamic balance - the branched quadrupole trap (BQT) - which can be used to study reactions in microdroplets in a controlled environment. The BQT allows for condensed phase chemical reactions to be initiated by colliding droplets with different reactants and levitating the merged droplet indefinitely. The performance of the BQT is characterized in several ways. Sub-millisecond mixing times as fast as ~400 μs are measured for low velocity (~0.1 m/s) collisions of droplets with <40 μm diameters. The reaction of o-phthalaldehyde (OPA) with alanine in the presence of dithiolthreitol is measured using both fluorescence spectroscopy and single droplet paper spray mass spectrometry. The bimolecular rate constant for reaction of alanine with OPA is found to be 84 ± 10 and 67 ± 6 M -1s -1 in a 30 μm radius droplet and bulk solution, respectively, whichmore » demonstrates that bimolecular reaction rate coefficients can be quantified using merged microdroplets and that merged droplets can be used to study rate enhancements due to compartmentalization. Products of the reaction of OPA with alanine are detected in single droplets using paper spray mass spectrometry. Finally, we demonstrate that single droplets with <100 pg of analyte can easily be studied using single droplet mass spectrometry.« less

Authors:
ORCiD logo [1];  [2];  [2]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [2]
  1. Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
OSTI Identifier:
1456984
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Analytical Chemistry
Additional Journal Information:
Journal Volume: 89; Journal Issue: 22; Journal ID: ISSN 0003-2700
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Jacobs, Michael I., Davies, James F., Lee, Lance, Davis, Ryan D., Houle, Frances, and Wilson, Kevin R.. Exploring Chemistry in Microcompartments Using Guided Droplet Collisions in a Branched Quadrupole Trap Coupled to a Single Droplet, Paper Spray Mass Spectrometer. United States: N. p., 2017. Web. doi:10.1021/acs.analchem.7b03704.
Jacobs, Michael I., Davies, James F., Lee, Lance, Davis, Ryan D., Houle, Frances, & Wilson, Kevin R.. Exploring Chemistry in Microcompartments Using Guided Droplet Collisions in a Branched Quadrupole Trap Coupled to a Single Droplet, Paper Spray Mass Spectrometer. United States. doi:10.1021/acs.analchem.7b03704.
Jacobs, Michael I., Davies, James F., Lee, Lance, Davis, Ryan D., Houle, Frances, and Wilson, Kevin R.. Thu . "Exploring Chemistry in Microcompartments Using Guided Droplet Collisions in a Branched Quadrupole Trap Coupled to a Single Droplet, Paper Spray Mass Spectrometer". United States. doi:10.1021/acs.analchem.7b03704. https://www.osti.gov/servlets/purl/1456984.
@article{osti_1456984,
title = {Exploring Chemistry in Microcompartments Using Guided Droplet Collisions in a Branched Quadrupole Trap Coupled to a Single Droplet, Paper Spray Mass Spectrometer},
author = {Jacobs, Michael I. and Davies, James F. and Lee, Lance and Davis, Ryan D. and Houle, Frances and Wilson, Kevin R.},
abstractNote = {Recent studies suggest that reactions in aqueous microcompartments can occur at significantly different rates than those in the bulk. Most studies have used electrospray to generate a polydisperse source of highly charged microdroplets, leading to multiple confounding factors potentially influencing reaction rates (e.g., evaporation, charge, and size). Thus, the underlying mechanism for the observed enhancement remains unclear. We present a new type of electrodynamic balance - the branched quadrupole trap (BQT) - which can be used to study reactions in microdroplets in a controlled environment. The BQT allows for condensed phase chemical reactions to be initiated by colliding droplets with different reactants and levitating the merged droplet indefinitely. The performance of the BQT is characterized in several ways. Sub-millisecond mixing times as fast as ~400 μs are measured for low velocity (~0.1 m/s) collisions of droplets with <40 μm diameters. The reaction of o-phthalaldehyde (OPA) with alanine in the presence of dithiolthreitol is measured using both fluorescence spectroscopy and single droplet paper spray mass spectrometry. The bimolecular rate constant for reaction of alanine with OPA is found to be 84 ± 10 and 67 ± 6 M-1s-1 in a 30 μm radius droplet and bulk solution, respectively, which demonstrates that bimolecular reaction rate coefficients can be quantified using merged microdroplets and that merged droplets can be used to study rate enhancements due to compartmentalization. Products of the reaction of OPA with alanine are detected in single droplets using paper spray mass spectrometry. Finally, we demonstrate that single droplets with <100 pg of analyte can easily be studied using single droplet mass spectrometry.},
doi = {10.1021/acs.analchem.7b03704},
journal = {Analytical Chemistry},
issn = {0003-2700},
number = 22,
volume = 89,
place = {United States},
year = {2017},
month = {10}
}

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