We showed that Taylor cone deformations 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 (see the movie on the right) indicates the presence of a nodal line and standing waves on its surface. Four phases of the cone pulsation cycle are established:
Based on image analysis, apex velocities, curvatures and opening angles were determined. During jet ejection, the apex velocity and the curvature exhibit singularities. Furthermore, the pulsation frequencies of the Taylor cone deformations are determined using Fourier analysis of light refraction measurements. The oscillation frequency of the electrospray current collected by the counter electrode shows close correlation to the cone deformations, providing the first direct evidence that links spray current oscillations to Taylor cone pulsation.
We suggest two possible applications of these observations:
Last update: November 14, 2006