ICP-MS (inductively coupled plasma mass spectrometry) is an analytical technique for measuring elements in biological fluids at trace levels. Although some laboratories still employ earlier techniques like atomic absorption and atomic emission, there has been a gradual trend toward ICP-MS, notably in the last decade. Clinical scientists should be aware of the analytical characteristics of Agilent 7900 ICP-MS, as well as the possibility for both spectroscopic and non-spectroscopic interference, and measures that can be used to avoid or reduce these concerns, as this transition is expected to continue.
ICP-MS instruments are highly expensive, and for some laboratories, this cost may be prohibitive. A graphite furnace apparatus may be more cost-effective for a low-volume laboratory, whereas an ICP-MS is more cost-effective for a high-volume laboratory.
The sample introduction system
Inductively coupled plasma (ICP), interface, ion optics, mass analyser, and detector are the six fundamental compartments of a single quadrupole ICP-MS.
Liquid samples are nebulized first in the sample introduction system, resulting in a fine aerosol that is then delivered to the argon plasma. The high-temperature plasma atomises and ionizes the material, resulting in ions that are extracted through the interface region and into the ion optics, a collection of electrostatic lenses. The quadrupole mass analyser’s ion optics focuses and guides the ion stream. The mass analyzer separates ions based on their mass-charge ratio (m/z), and these ions are then analyzed.
Plasma that is inductively coupled
A plasma is an ionized gas made up of positively charged ions and free (unbound) electrons. In ICP-MS, the plasma (ICP) is used to ionize the material. The ICP is termed a ‘hard’ ionisation technique since it completely atomises most molecules in the sample, in contrast to so-called ‘soft’ ionisation sources employed in other forms of mass spectrometry (such as electrospray), which contribute very little energy to the analyte.
Ion Optics is the science of ionization.
The ion optics refers to the collection of electrostatic lenses placed beneath the skimmer cone. The ion optics system’s job is to direct the ion beam toward the mass analyser while keeping photons and other neutral species out of the detector (such non-ionised matrix components).
Ions come at the mass analyser after passing via the ion optics system. ICP-MS has been performed using a variety of mass analyzers, including quadrupole, magnetic sector, and (rarely) time-of-flight (TOF).
An electron multiplier is the most common detector for ICP-MS (EM). The first dynode of the detector, which is kept at a high negative voltage, is struck by positively charged analyte ions. The ion’s impact with the detector causes the surface to emit numerous electrons, which then strike the next dynode, releasing more electrons.