ICP-OES Explained: Revealing the Sample’s Secrets

As indicated by its name, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES or ICP-AES) is a technique that uses a plasma as a source and relies on optical emission for analysis. However, unlike many other spectrometers, the sample is not simply placed in-between source and detector. ICP-OES is mainly used for liquid samples, which first need to be turned into an aerosol (“nebulization”) and then are injected into the plasma. Solid samples can be directly analyzed if a means of vaporization is available, e.g., laser ablation (LA-ICP-OES) or electrothermic vaporization (ETV). The high temperatures in the plasma are sufficient to break down the sample into atoms and provide the energy for ionization and excitation.

For practical analysis with OES, several essential components must be provided:
- An energy source to atomize the test sample and excite the atoms
- A sampling system to introduce the sample into the plasma
- High resolution optics to observe the emissions from the plasma and to separate and isolate the specific emitted wavelengths for the elements to be measured
- A detector system to measure the intensity of the light emissions
- Electronics to acquire the detector signals and to control the functions of the spectrometer
- A computer with software for calculation and display of emission spectra and concentration values

Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) has become the leading technology for routine analysis of liquid samples as well as materials that can be easily turned into a liquid form by dissolution or digestion. Its origin lies in so-called spectroscopes and spectrographs that allow visual evaluation of spectral lines on a film, which required much experience and time in order to obtain reliable results. The developments in electronics and data processing allowed ICP instruments to appear on the market in the middle of the 1970s which helped overcome these obstacles and enable the routine use of optical emission spectroscopy in laboratories.

During the last decades, ICP-OES has seen dramatic improvement. While the first commercially available ICP machines relied on time consuming sequential measurements or had limited availability of emission lines due to the use of Photomultiplier Tubes (PMT), today's ICP instruments are able to capture wide spectral areas simultaneously in a short time thanks to modern solid state detector technology.

This ICP-OES principle video presents an easy-to-understand introduction into the physics and the technology of an optical emission spectrometer with regards to ICP analysis. You can find more detailed information by requesting the featured whitepapers below.