ELECTROSPRAY-IONIZATION FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE MASS-SPECTROMETRY AT 11.5 TESLA - INSTRUMENT DESIGN AND INITIAL RESULTS

Initial results obtained using a new electrospray ionization (ESI) Fou rier transform ion cyclotron resonance (FTICR) mass spectrometer opera ted at a magnetic field 11.5 tesla are presented. The new instrument u tilized an electrostatic ion guide between the ESI source and FTICR tr ap that provided up to 5% overall transmission efficiency for Light io ns and up to 30% efficiency for heavier biomolecules. The higher magne tic field in combination with an enlarged FTICR ion trap made it possi ble to substantially improve resolving power and operate in a more rob ust fashion for large biopolymers compared to lower field instruments. Mass resolution up to 10(6) has been achieved for intermediate size b iopolymers such as bovine ubiquitin (8.6 kDa) and bovine cytochrome c (12.4 kDa) without the use of frequency drift correction methods. A ma ss resolution of 370,000 has been demonstrated for isotopically resolv ed molecular ions of bovine serum albumin (66.5 kDa). Comparative meas urements were made with the same spectrometer using a lower field 3.5- tesla magnet allowing the performance gains to be more readily quantif ied. Further improvements in pumping capacity of the vacuum system and efficiency of ion transmission from the source are expected to lead t o further substantial sensitivity gains. (C) 1998 American Society for Mass Spectrometry.