An electrostatic ion guide interface for combining electrospray with Fourier transform ion cyclotron resonance mass spectrometry

A new interface for coupling electrospray (ES) ionization and Fourier transform ion cyclotron resonance (FTICR) mass spectrometry has been developed based on an electrostatic ion guide (EIG). In these initial studies, the EIG interface has been demonstrated to be a simple but effective means of transmitting ES ions generated outside the magnetic field to the FTICR cell. In the current system, the pressures in the EIG region and front FTICR cell are 10⁻⁵ and 10⁻⁶ Torr, respectively. Under these conditions, ions may be accumulated with low trapping voltages (0.5–0.75 V) and without a high pressure pulse of buffer gas. ES‐FTICR spectra of picomole to femtomole quantities of several peptides, proteins, nucleotides and dinucleotides have been obtained. Modifications currently in progress should enhance performance with respect both to limits of detection and to mass resolution.