Simulation and parametric study of a novel multi-spray emitter for ESI–MS applications
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In this work, we propose a novel carbon nanofiber (CNF) emitter for electrospray ionization (ESI)–mass spectrometry (MS) applications. The proposed emitter comprises an array of CNFs around the orifice of a microscale capillary. The electrospray ionization process is simulated using a CFD code based on Taylor–Melcher leaky-dielectric formulations for solving the electrohydrodynamics and volume-of-fluid (VOF) method for tracking the interface. The code is validated for a conventional multiple electrospray emitter and then applied to simulate the CNF emitter model. The modeling results show that under steady state condition, individual cone-jets are established around each of the CNFs resulting in an array of electrosprays. The approach being taken to fabricate the CNF emitter is briefly discussed. Effects of geometrical parameters including aspect ratio of CNFs, total number of CNFs and distribution pattern of the CNFs on the electrospray performance are studied. The influence of operating parameters such as flow rate, potential difference and physical properties of the solvent on the electrospray behavior is thoroughly investigated. The spray current, ‘onset’ potential and jet diameter are correlated with total number and distribution of CNFs and physical properties of the liquid. The correlation results are compared with the available results in the literature. Higher spray current and lower jet diameter indicate that the device can perform equivalent to nanospray emitters while using a micro-scale orifice. This allows higher sample throughput and eliminates potential clogging problem inherent in nano-capillaries.
KeywordsCarbon nanofiber Electrospray ionization–mass spectrometry Taylor–Melcher leaky-dielectric formulations Electrohydrodynamics Volume of fluid
Supported in part by a grant from the University of South Carolina Research and Productive Scholarship Fund, NIH grant CA86285 and the NHLBI proteomics Initiative via contract N01-HV-28181 (D.R.K.).
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