Modeling and characterization of a carbon fiber emitter for electrospray ionization

A novel microscale emitter employing a pointed carbon fiber (CF) can be used for electrospraying in mass spectrometric (MS) analysis. The carbon fiber is located coaxial with a fused silica capillary tube of 360 mu m OD and 75 mu m ID with its sharp tip extending 30 mu m beyond the tube terminus. The electrospray ionization (ESI) process is simulated using a computational fluid dynamics (CFD) code based on the Taylor-Melcher leaky-dielectric fluid model for solving the electrohydrodynamics and the volume of fluid (VOF) approach for tracking the liquid-gas interface. The CFD code is first validated for a conventional geometry and then used to simulate the CF emitter based ESI model. The simulated current-flow and current-voltage results are in good agreement with experimental results for the CF emitter. The effects of emitter geometry, potential difference, flow rate and the physical properties of the liquid on the electrospray behavior of the CF emitter are thoroughly investigated. The spray current and jet diameter are correlated with the flow rate, potential difference and physical properties of the liquid and the correlation results are quantitatively compared with the results reported in the literature.