Abstract: A mass spectrometer has an ion source (10) with a plurality of atmospheric pressure sample ioniser (20) mounted in a front face (15) thereof. Each sample ioniser (20) extends into a corresponding sample region (30) and the tip of each sample ioniser is mounted at right-angles to a corresponding one of a plurality of entrance cones (50) each having an entrance orifice (40) therein. Each entrance cone (50) in turn opens into an inlet channel having first and second parts (60, 70). The two parts of the inlet channel are separated by an electrical gate (65). The inlet channels corresponding to each entrance cone (50) all merge into a common exit channel (90) to a mass spectrometer. By appropriate operation of the gates (65) dividing the inlet channels, rapid switching between the samples that are analysed in the mass analyser can be achieved.

Abstract: A mass spectrometer has an ion source (10) with a plurality of atmospheric pressure sample ioniser (20) mounted in a front face (15) thereof. Each sample ioniser (20) extends into a corresponding sample region (30) and the tip of each sample ioniser is mounted at right-angles to a corresponding one of a plurality of entrance cones (50) each having entrance orifice (40) therein. Each entrance cone (50) in turn opens into an inlet channel having first and second parts (60, 70). The two parts of the inlet channel are separated by an electrical gate (65). The inlet channels corresponding to each entrance cone (50) all merge into a common exit channel (90) to a mass spectrometer. By appropriate operation of the gates (65) dividing the inlet channels, rapid switching between the samples that are analysed in the mass analyser can be achieved.