When it comes to the analysis of trace amounts of rare earth elements (REEs) in a sample such as drinking water, ICP-MS is becoming an industry standard. The technique uses 5.0 grade argon gas to both carry the sample and form a plasma flame which exists at between 6,000 and 10,000°C. The sample is passed into the plasma where it is ionised. The ensuing ions are then measured in a mass spectrometer.
The ICP-MS technique has superior detection capability to its sister technique ICP-AES where an atomic emission spectrometer is used instead of the mass spectrometer for ion characterisation. ICP-MS has a higher throughput than a graphite furnace atomic adsorption spectrometer (GFAAS) at similar, or better detection limits. It is also less vulnerable to matrix effects than these alternative techniques due to the very high plasma flame temperature.
The main limitation of the technique is that the plasma tends to produce positive ions, so species that predominantly form negative ions such as chlorine, iodine and fluorine are difficult to detect with ICP-MS.
Another notable technique for similar work is the flame atomic adsorption spectrometer for flame AAS. Similar to the ICP, it has earned its place in environmental and food testing laboratories to detect metals in water, soil and food samples.