Dual mode ionization device

A mass and/or mobility spectrometer comprising:

• a spray device having a bore through which liquid sample is prayed, in use, into a spray region;
• a vacuum region configured to be maintained at a lower pressure than the spray region;
• an impact surface arranged as an interface between the spray region and the vacuum region, wherein the impact surface is an inlet cone comprising an aperture;
• a power supply configured to:
• (i) maintain the spray device at a reference electrical potential;
• (ii) maintain the impact surface at a voltage of a first polarity relative to the reference potential, during a first ionization mode, so as to generate an electrical potential difference in the spray regain and produce analyte ions by electrospray ionization;
• (iii) maintain the impact surface at a voltage of a second polarity relative to the reference potential, during a second ionization mode, so that the sample is sprayed onto the impact surface to produce analyte ions by impact ionization, wherein the second polarity is opposite the first polarity relative to the reference potential;
• and
• (iv) alternate the polarity of the voltage at which the impact surface is maintained so as to switch between the first and second ionization modes;
• wherein the mass and/or mobility spectrometer is configured to urge ions generated in the first and second ionization modes through the aperture in the impact surface and into the vacuum region;
• and
• further comprising a mass and/or ion mobility analyser for mass and/or ion mobility analysing ions produced by the first and second ionization modes.