Mass spectrometry apparatus and method

摘要

A mass spectrometer in which a substance is introduced into a plasma ( 28 ) which contains analyte ions as the plasma ( 28 ) is passing through an aperture ( 42 ), for example in a skimmer cone ( 40 ) between two vacuum regions ( 38 ) and ( 44 ) so that the substance interacts with the plasma ( 28 ) thereby reducing the concentration of interfering polyatomic or multicharged ions in the plasma by reactive or collisional interactions. The substance may be supplied via passage ( 60 ) having an outlet ( 63 ) in skimmer cone ( 40 ). The invention gives improved attenuation of interfering ions because the substance is supplied directly into the plasma ( 28 ) as it is substantially radially confined by aperture ( 42 ) and before an ion beam ( 58 ) is extracted. Alternatively or additionally a substance may be supplied directly into the plasma within aperture ( 36 ) in sampling cone ( 34 ).