ICP-OES consists of an inductively coupled plasma (ICP) interfaced to an optical emission spectrophotometer (OES) and is used for simultaneous multi-analyte determination of ~78 elements on the periodic table.  ICP-OES utilizes a plasma gas to sequentially desolvate, vaporize, atomize, and ionize samples for elemental analysis.. As the ions produced move into the cooler region of the plasma they return to the ground state by absorbing electrons, simultaneously emitting light at wavelengths characteristic of the element. The emitted light is separated into a spectrum and the intensity of each emission line measured at the detector. Detectors include charge coupled devices (CCD), charge injection devices (CID), and diode arrays. CCDs and CIDs are most common as they have wavelength coverage from the ultraviolet (UV) to infrared (IR) region of the spectrum, and can capture full spectral images allowing simultaneous quantitation of all detected emission. The typical working range is low part per billion (ppb) to percent composition (%).  As with ICP-MS both solid and liquid samples can be analyzed with this technique dependent upon the sample introduction system.  ICP-OES instruments are benchtop models.  The technique is mature and a number of instruments are commercially available.