Microdroplets rev up reactions

Abstract

Electrospray ionization (ESI) is best known as a way to introduce chemical compounds and mixtures into mass spectrometers. The machines apply a voltage to a stream of liquid containing a sample, creating an aerosol of charged, microsized droplets that then fly into the detector for analysis. But what ESI might one day be just as well-known for is as a tool to accelerate chemical reactions, enabling scientists to test out catalysts, reagents, and conditions faster and more efficiently. Under the right conditions, the microdroplets generated by ESI can serve as reaction vessels. Chemists don’t yet know exactly why the tiny droplets accelerate the reaction of chemical reagents contained within, but they do know the microdroplets sometimes even allow chemical transformations to proceed that wouldn’t normally occur in bulk solutions—in flasks and other larger vessels. R. Graham Cooks’s group at Purdue University stumbled upon microdroplet reaction acceleration while trying to analyze