Inductively Coupled Plasma (ICP)
Definition
An argon discharge sustained at 6000 to 10000 K by an RF coil at 27.12 MHz wrapped around a quartz torch. Argon flows at roughly 15 litres per minute, the coil's oscillating field induces eddy currents in seed electrons, and the discharge is self-sustaining. The plasma simultaneously nebulises, atomises and ionises the sample aerosol introduced through the central injector.
- Abbreviation
- ICP
- Temperature
- 6000 to 10000 K
- Excitation source
- RF coil at 27.12 MHz
- Argon flow
- Roughly 15 L/min
- Function
- Nebulises, atomises, and ionises the sample aerosol
Common questions
Why is argon used as the plasma gas instead of a cheaper alternative like air or nitrogen?+
Argon is chemically inert so it does not form molecular species with the sample or oxidise the torch components, and its high ionisation energy relative to most elements lets the plasma efficiently excite or ionise analyte atoms without argon itself interfering in the resulting spectrum.
How does the same ICP source support both ICP-OES and ICP-MS in a forensic lab?+
The plasma's role is identical in both, atomising and exciting or ionising the sample, but ICP-OES measures the light emitted as excited atoms relax while ICP-MS extracts the ions themselves into a mass spectrometer, so the same front end feeds two different detection strategies depending on the sensitivity and elemental range needed.
Related terms
- Collision and Reaction Cell (CRC)
- A pressurised cell between the skimmer and the quadrupole, charged with helium for kinetic-energy-discrimination collision mode or with hydrogen, ammonia or oxygen...
- Isotope Ratio Analysis
- Measurement of relative abundances of two or more isotopes of an element to 0.01 to 0.5 percent precision. Lead ratios fingerprint the...
- Optical Emission Spectrometry (OES)
- Detection arm in which excited atoms emit photons at characteristic wavelengths as they relax. A polychromator separates the light by wavelength and...
- Polyatomic Interference
- An ion formed in the plasma at the same nominal mass as a target analyte, for example argon-oxide on iron-56, argon-chloride on...
- Quadrupole ICP-MS
- Detection arm in which positive ions are extracted from the plasma through sampler and skimmer cones into a quadrupole mass filter that...