Preparation of Durable Emitter of Electrospray Mass Spectrometry by Covalently Coating the Fused‐Silica Capillary Tip with Carbon‐Nanotube Sol‐Gel Composite Material

A simple approach for the preparation of emitter of electrospray ionization mass spectrometry by covalently coating the fused-silica capillary tip with the conductive carbon-nanotube sol-gel composite material (CNTSCM) is described. The CNTSCM was prepared by dispersing single-walled carbon nanotubes in the sol composed of a mixture of 3-glycidoxypropyltrimethoxysilane and 3-aminopropyltrimethoxysilane, and ethanol. The long-term stability of the prepared ESI emitters was demonstrated by at least 180 h of continuous use. Signal intensity obtained by the prepared emitter was mass-flux sensitive when the flow rate was lower than 500 nL/min, while the signal intensity performed a concentration dependence when the flow rate was in the range of 500-800 nL/min. The usefulness of such a prepared emitter was demonstrated by the analysis of various types of samples such as organic small molecular drugs, oligosaccharide, peptide, and protein.