Flexing the electrified meniscus: the birth of a jet in electrosprays.

Spraying of liquids through an electrified meniscus has become a method of choice to produce ions from large biomolecules. Using mass spectrometry, the generated ions can be analyzed to provide detailed information on their composition and structure. This technique enables high-throughput protein analysis that is a prerequisite for answering the questions presented by proteomics. In this report, Taylor cone deformations are shown to play a central role in the mechanism of electrostatic spraying. Spontaneous spray current oscillations are known to exist in most electrospray regimes and affect the stream of ions introduced into the mass spectrometer. Fast time-lapse imaging of the Taylor cone throughout its evolution indicates the presence of a nodal line and standing waves on its surface. Four phases of the cone pulsation cycle (liquid accumulation, cone formation, ejection of a jet, relaxation) are established. Based on image analysis, apex velocities, curvatures, and opening angles are determined. During...