Patent ID: 7329863

Claim:
A mass spectrometer comprises: a plasma ion source, which provides analyte ions; a mass analyzer; an interface between the plasma ion source and the mass analyzer; and the interface comprising an interface structure being one of a sampling cone and a skimmer cone of the interface, which separates a first region at a relatively high pressure adjacent a first surface of said structure, which receives plasma from the plasma ion source and providing separation from a second region at a relatively low pressure leading to the mass analyzer, said second region adjacent a second surface of said interface structure and, which provides an aperture having axial extension forming a reaction zone between the first surface and the second surface through which the plasma flows from the higher pressure region towards the lower pressure region through said axial extending aperture, the interface structure comprising a passage, which supplies a substance into the reaction zone aperture interacting with the plasma for attenuating polyatomic or multicharged interfering ions by reactive or collisional interactions; wherein the passage is located completely within a cone and leads from an inlet to an outlet at said cone aperture.