Abstract: A mass spectrometer and method of mass spectrometry in which polyatomic and doubly charged ion interferences are attenuated by establishing an electron population through which a beam of particles containing elemental sample ions and the interfering ions is passed such that the interfering ions preferentially undergo ion-electron recombination and thus dissociation to remove a significant number of the interfering ions. Means (30 or 32) for providing a population of electrons (34 or 36) in an ICP-MS (22) may comprise a magnetic field means such as an electric coil, or an electron generating device. The population of electrons has an electron number density (>1011 cm?3 to 1014 cm?3), a free electron energy (>0.01 eV to <5 eV) in a region at a low pressure (<10 Torr), such that for a predetermined path length (1–4 cm) of the ions through the electron population, the interfering ions will preferentially be attenuated by the dissociative recombination process.

Abstract: 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).

Abstract: A mass spectrometer and method of mass spectrometry in which polyatomic and doubly charged ion interferences are attenuated by establishing an electron population through which a beam of particles containing elemental sample ions and the interfering ions is passed such that the interfering ions preferentially undergo ion-electron recombination and thus dissociation to remove a significant number of the interfering ions. Means (30 or 32) for providing a population of electrons (34 or 36) in an ICP-MS (22) may comprise a magnetic field means such as an electric coil, or an electron generating device. The population of electrons has an electron number density (>1011 cm?3 to 1014 cm?3), a free electron energy (>0.01 eV to <5 eV) in a region at a low pressure (<10 Torr), such that for a predetermined path length (1-4 cm) of the ions through the electron population, the interfering ions will preferentially be attenuated by the dissociative recombination process.

Abstract: A plasma source mass spectrometer (20) having an ion beam extraction electrode (45) associated with a skimmer cone (40) to restrict the pumping of gas from a region (60) immediately behind the skimmer cone orifice (42) to provide a higher pressure (e.g. 1-10?2 Torr) in the region (60) compared to the pressure downstream of the electrode (45) (e.g. 10?3-1031 4 Torr). This provides a collisional gas volume (60) for plasma (28) for attenuating polyatomic and multicharged interfering ions prior to extraction of an ion beam (49). In one embodiment a substance (e.g. hydrogen) can be supplied into the region (60) to assist attenuation of polyatomic and multicharged interfering ions by reactive or collisional interactions.

Abstract: A mass spectrometer having an ion optics system in a first vacuum region, which diverts ions travelling in a first direction from a source, characterized by an initial pressure, through an angle such that neutral particles and photons from the source continue in the first direction and are removed. The diverted ion beam is then directed into a quadrupole mass analyzer arrangement in a second vacuum region, which comprises a set of fringe electrodes followed by a linear mass analyzer and then an ion detector. The first vacuum region is characterized by a pressure intermediate the initial pressure and a second vacuum region pressure. The set of quadrupole fringe electrodes are configured to divert the ion beam prior to passage of the ion beam into the linear quadrupole mass analyzer and to shield the linear quadrupole mass analyzer entrance from a substantial portion of the trajectory of the ion beam in the first vacuum region.

Abstract: A mass spectrometer having an ion reflecting instead of ion transmissive optics system. The spectrometer includes an ion source (16) for providing a beam of sample particles including ions along an axis (24). Its ion optics system (34-46) establishes a reflecting electrostatic field for reflecting ions along a path (30) from the particle beam and focussing them at an entrance aperture (26) of a mass analyser (25) and ion detector (27) for spectrometric analysis. The invention allows more efficient separation of ions from neutral particles, gives better signal to noise ratios and allows for a compact “optical” path and thus cheaper instrument to be manufacctured. The reflecting electrostatic field can also be used to filter higher energy ions from lower energy ions. An ion optical system as such is also disclosed.

Abstract: A mass spectrometer (10) having an ion optics system (32, 34, 36, 40, 42) in a first vacuum chamber (28) which diverts ions travelling in a first direction from a source (12, 16, 24) through an angle such that neutral particles and photons from the source continue in the first direction and are removed. The diverted ion beam (38) is then directed into a quadrupole mass analyser arrangement (52) in a second vacuum chamber (48) which comprises a configured, for example curved, set of fringe electrodes (56) followed by a linear mass analyser (54) and then an ion detector (46). The configured fringe electrodes (56) again divert the ions prior to their passage into the linear quadrupole mass analyser (54) whereby additional neutral particles possibly created by passage of the ion beam through residual gas in the vacuum chambers (28, 48) are shielded from entering the linear mass analyser (54).