Patent ID: 7038199
Filing Date: 2006-05-02
Classification: H01J

Abstract:
1. A mass spectrometer for elemental analysis of a sample comprising: source means for atomising a portion of the sample, said source means being a plasma ion source; means for extracting a beam of particles from the source means, wherein the beam contains elemental sample ions and interfering polyatomic or doubly charged ions; means for providing a population of electrons in a region through which the beam of particles is passed and which defines a predetermined path length for the particles through the electron population, said region being located within an evacuable chamber of the mass spectrometer whereby a low pressure is establishable in said region, the population of electrons having an electron number density and free electron energy which, together with said predetermined path length and low pressure, provide for interfering polyatomic or doubly charged ions preferentially to undergo ion-electron recombination and thus dissociation thereby removing a significant number of the interfering ions from the beam of particles, said means for providing a population of electrons comprising a device for providing a magnetic field axially of the beam of particles for confining said population of electrons from the plasma within said region further defined by the magnetic field; and a mass analyser and an ion detector for receiving ions from the beam of particles after it has passed through the population of electrons for spectrometric analysis whereby concentrations of different elements in the sample are determinable.