electrospray ionisation mass spectrometry extractive electrospray ionisation mass spectrometry EESI/MS EESI-MS extractive electrospray ionization mass spectroscopy extractive electrospray ionization mass spectrometry CHMO:0000717 extractive electrospray ionisation mass spectroscopy Mass spectrometry where a neutral sample, in the form of a gas or aerosol flow, is ionised by directing it into a plume of charged droplets, generated by forcing a solution of pure solvent through a small heated capillary (at a flow rate of 1-10 microlitres per minute) into an electric field.