ICP-MS (Inductively Coupled Plasma Mass Spectrometry) is a type of mass spectrometry
that is highly sensitive and capable of simultaneous determination of a range of elements at below one part in 1012
. It is based on coupling together an inductively coupled plasma
as an ion source with a mass spectrometer as a detection system for ions.
The ions generated within the plasma at atmospheric pressure are extracted through a series of cones into the vacuum chamber of a mass spectrometer, usually a quadrupole. Other mass analyzers coupled to ICP systems include double focusing magnetic-electric sector systems with both single and multiple collector, as well as time-of-flight (TOF) systems (both with axial and orthogonal accelerators). In any case the ions are separated on the basis of their mass-to-charge ratio and a detector receives an ion signal proportional to the concentration.
The concentration of a sample can be determined through calibration with elemental standards (external calibration). Accuracy and precision can be enhanced by using internal standards
and rationing the measurements against these. ICP-MS also lends itself to quantitative determinations through isotope dilution analysis
, a single point method based on an isotopically enriched standard.