Optical Emission Spectrometry (OES)
Definition
Detection arm in which excited atoms emit photons at characteristic wavelengths as they relax. A polychromator separates the light by wavelength and a CCD or CID array reads dozens of channels in parallel. Limits of detection sit in the 10 to 100 parts-per-billion range for most metals.
- Detects
- Photons emitted by excited atoms
- Wavelength separator
- Polychromator
- Detector types
- CCD or CID array
- Typical LOD
- 10 to 100 parts per billion for most metals
- Common pairing
- ICP excitation source (ICP-OES)
Common questions
How does OES differ from ICP-MS as a detection method?+
OES measures light emitted as excited atoms relax back to ground state, giving simultaneous multi-element readout across many channels, while ICP-MS measures the mass-to-charge ratio of ionised atoms. ICP-MS generally reaches lower detection limits, but OES is faster for simultaneous multi-element screening and has fewer spectral interference issues for some elements.
Why are multiple channels read in parallel rather than one wavelength at a time?+
Each element emits at several characteristic wavelengths simultaneously, and reading many channels at once lets the instrument quantify dozens of elements from a single sample introduction, which is essential for trace-evidence panels like glass or gunshot residue where turnaround and sample volume are both limited.
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...
- Inductively Coupled Plasma (ICP)
- An argon discharge sustained at 6000 to 10000 K by an RF coil at 27.12 MHz wrapped around a quartz torch. Argon...
- 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...
- 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...