Inductively Coupled Plasma
Optical Emission Spectroscopy (ICP-OES)

ICP-OES is a destructive, optical spectroscopy technique to determine the elemental composition of a material.

ICP-OES systems use an inductively coupled plasma to decompose a sample into its constituent elements, which are subsequently ionized. Through a variety of processes, the sample atoms and ions within the plasma chamber will undergo excitation, in which inner shell electrons will jump to a higher energy level. As these electrons relax, they emit a photon with characteristic kinetic energy, unique to the elemental species from which it came. These emitted photons escape the plasma chamber and are detected by a signal analyzer.

Most ICP-OES tools incorporate a polychromator analyzer, which can detect the optical emission from multiple elemental species at once. The measured intensities of each elemental signal are correlated to the quantity of that element in the sample.

ICP-OES is distinct from ICP-MS methods in that it tolerates a much higher content of total-dissolved-solids in an aqueous sample. This allows for ready analysis of fluid composition without dilution or substantial preparation. It is also typically faster and cheaper to execute than ICP-MS, at the expense of some sensitivity for trace elements, and reduced compatibility with pure solid materials.

Application Areas for ICP-OES

ICP-OES is a highly standardized measurement in regulatory compliance analyses of ground water, wastewater, soil, and chemical / solid wastes. Due to its high throughput, efficiency, and aqueous-analyte compatibility, this technique is excellent for identifying environmental contaminants and chemical safety hazards.

Measurements from ICP-OES

  • Elemental composition (liquid)
  • Isotope analysis


  • What it is great for:
    • Identification and measurement of trace elements (detection threshold to ppm)
    • Minimal sample prep for aqueous samples
  • Limitations:
    • Accurate quality assays require parallel analysis of control sample


ICP-OES Calibration Curve
Strong agreement between measured intensity of optical emission signal vs. known concentration of Calcium ions in H2O solution.
From Sigma Aldrich.