Coupling Droplet Microfluidics with Ion Mobility Spectrometry for Monitoring Chemical Conversions at Nanoliter Scale

Anal Chem. 2021 Oct 12;93(40):13615-13623. doi: 10.1021/acs.analchem.1c02883. Epub 2021 Sep 30.

Abstract

We introduce the coupling of droplet microfluidics and ion mobility spectrometry (IMS) to address the challenges of label-free and chemical-specific detection of compounds in individual droplets. In analogy to the established use of mass spectrometry, droplet-IMS coupling can be also achieved via electrospray ionization but with significantly less instrumental effort. Because IMS instruments do not require high-vacuum systems, they are very compact, cost-effective, and robust, making them an ideal candidate as a chemical-specific end-of-line detector for segmented flow experiments. Herein, we demonstrate the successful coupling of droplet microfluidics with a custom-built high-resolution drift tube IMS system for monitoring chemical reactions in nL-sized droplets in an oil phase. The analytes contained in each droplet were assigned according to their characteristic ion mobility with limit of detections down to 200 nM to 1 μM and droplet frequencies ranging from 0.1 to 0.5 Hz. Using a custom sheath flow electrospray interface, we have further achieved the chemical-specific monitoring of a biochemical transformation catalyzed by a few hundred yeast cells, at single droplet level.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ion Mobility Spectrometry*
  • Mass Spectrometry
  • Microfluidics*