Liquid extraction surface analysis (“LESA”) is a known technique whereby samples are extracted from a surface into a small liquid junction for further analysis by an Electrospray ionisation (“ESI”) ion source. Liquid extraction surface analysis has been used for imaging of tissue sections at fairly modest spatial resolution.
According to a known arrangement a crystallised Matrix Assisted Laser Desorption Ionisation matrix is provided and desorbed ions or particles are ionised or further ionised by an Electrospray ionisation ion source.
US2014/0070088 (Otsuka) discloses an Electrospray ionisation device.
It is desired to provide an improved ion source and an improved method of ionising a sample.