Fourier transform ion cyclotron resonance mass spectrometry electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry electrospray ionisation Fourier transform ion cyclotron resonance mass spectroscopy ESI-FT-ICR-MS Mass spectrometry where the sample is ionised by forcing a solution (usually in an organic solvent) of the sample through a small heated capillary (at a flow rate of 1–10 microlitre min-1) into an electric field to produce a very fine mist of charged droplets. The mass-to-charge ratio of the ions is then determined by measuring their cyclotron frequency (the frequency at which they precesses in a fixed magnetic field) and subjecting it to a Fourier transform. CHMO:0000705