A HIGH-PERFORMANCE LOW MAGNETIC-FIELD INTERNAL ELECTROSPRAY-IONIZATION FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE MASS-SPECTROMETER

A new in-magnetic field electrospray ionization (ESI) and Fourier tran sform ion cyclotron resonance mass spectrometer has been constructed a nd evaluated. This system is characterized by the use of multiple conc entric cryopanels to achieve ultrahigh vacuum in the ion cyclotron res onance cell region, a probe-mounted internal ESI source, and a novel i n-field shutter. Initial experiments demonstrate high resolution mass measurement capability at a field strength of 1 T. Mass resolution of 700,000 has been obtained for the 3+ charge state of Met-Lys-bradykini n (at m/z 440) generated by electrospray ionization. When electron imp act ionization was employed, resolution in excess of 9,200,000 was ach ieved for nitrogen molecular ions (N-2(+)). Isotopic resolution for mo lecular ions of bovine ubiquitin (MW = 8565 mu) also was achieved by u sing small ion populations.