Apparatus for inductively coupled plasma mass spectrometry

A sampling interface for use in mass spectroscopy apparatus, the sampling interface being arranged to enable the sampling of ions in a mass spectrometer for subsequent spectroscopic analysis, the sampling interface comprising:

• an inlet for receiving a quantity of particles from an ion source, the quantity of particles including ions for spectroscopic analysis;
• a skimmer arranged downstream of the inlet, the skimmer comprising an aperture through which particles from the inlet pass;
• an extraction lens arranged downstream of the skimmer, the extraction lens being configured for extracting ions from the particles passed through the aperture at the skimmer;
• an adjustable voltage source for applying a bias voltage to the extraction lens so as to generate an electric field in at least a region between the extraction lens and the skimmer;
• and
• a controller configured to:
• receive a measured value of a system parameter representative of the number density in a region immediately downstream of the skimmer;
• determine a magnitude of the bias voltage to be applied by the adjustable voltage source based on the measured value of the system parameter;
• and
• control the adjustable voltage source to apply the bias voltage of the determined magnitude to the extraction lens, in order to control the reduced electric field in the region immediately downstream of the skimmer.