Electrospray Ionization Fourier Transform Ion Cyclotron Resonance at 9.4 T

We present the first results from a new electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer operated at a magnetic field of 9.4 T (i.e. ⩾2.4 T higher than for any prior FTICR instrument). The 9.4 T instrument provides substantially improved performance for large molecules (⩾50% increase in mass resolving power) and complex mixtures (⩾100% increase in dynamic range) compared to lower‐field (⩽6 T) instruments. The higher magnetic field makes possible larger trapped‐ion population without introduction of significant space–charge effects such as spectral peak shift and/or distortion, and coalescence of closely‐spaced resonances. For bovine ubiquitin (8.6 kDa) we obsrve accurate relative isotopic abundances at a signal‐to‐noise ratio greater than 1000:1, whereas a complete nozzle‐skimmer dissociation electrospray ionization (ESI) FTICR mass spectrum of bovine carbonic anhydrase (29 kDa) is achieved from a single scan with a signal‐to‐noise ratio of more than 250:1. Finally, we are able to obtain mass resolving power, m/Δm>200 000, routinely for porcine serum albumin (67 kDa). The present performance guides further modifications of the instrument, which should lead to significant further improvements.