ICP-OES
/ EYE-see-pee oh-ee-ess /
ICP-OES is atomic emission done in a plasma instead of a flame — a multi-element workhorse that reads the colours many elements shine at once. Feed a sample into a torch far hotter than any flame and almost every metal lights up with its own lines; a spectrometer fans those colours out and measures them all in a single run.
More precisely, the sample mist enters an inductively coupled plasma at several thousand kelvin, which atomizes and excites the elements; the light they emit is dispersed by wavelength and recorded by a detector. The intensity at each element's chosen line, compared with standards, gives its concentration, and modern instruments watch dozens of elements simultaneously.
It matters because that hot, even plasma handles refractory metals a flame cannot and gives a wide working range with good speed — ideal for environmental, geological, and industrial labs. The honest limits are cost, heavy argon use, and a busy spectrum where many lines crowd together, raising the chance of spectral interference; for the lowest trace levels, ICP-MS goes lower still.
A geology lab dissolves a rock and runs it on ICP-OES; in one ninety-second measurement it reports iron, magnesium, calcium, aluminium, and a dozen trace metals at once, each from its own emission line.
One plasma, many elements at once — read by light.
OES (optical emission) and AES (atomic emission) name the same thing in this context; the older name ICP-AES and the newer ICP-OES are interchangeable. ICP-OES reads the light atoms emit; ICP-MS instead counts the ions by mass, reaching far lower concentrations.