Abstract: There is disclosed a double-focusing mass spectrometer in which ions are generated from a sample in a microwave-induced or inductively-coupled plasma (3). Ions are sampled from the plasma (3) through an aperture in a sampling cone (19) and pass through a skimmer cone (28) and several electrostatic lenses (30,33) to the entrance slit of the mass analyzer. The sampling cone (19) and skimmer cone (28) are maintained by a power supply (40) at a potential approximately equal to the accelerating potential required by the mass analyzer. It is found that the plasma potential may be maintained at such a value that a substantial proportion of the ions generated in the plasma (3) have energies lying within the energy passband of the mass analyzer, so that a high sensitivity, high resolution mass spectrometer especially suitable for the elemental analysis of solid or liquid samples is provided.

Abstract: The invention comprises a mass spectrometer wherein a sample is ionized in a plasma (14), especially an inductively-coupled or microwave-induced plasma. Ions are sampled from the plasma (14) through an orifice (16) in a sampling member (15), a second orifice (37) in a hollow tapered member (19) and a third orifice (53) in a tubular electrode (43). The hollow tapered member (19) comprises a portion (35) both externally and internally tapered with an interior included angle greater than 60.degree., and preferably a shorter externally tapered portion (38) with an external included angle of less than 60.degree.. A tubular extraction electrode 43, preferably comprising a conical end-portion (47) , is disposed within the member (19) for efficiently transmitting the ions into a mass analyzer.