inductively-coupled plasma optical emission spectroscopy 

Initialism: ICP-OES
https://doi.org/10.1351/goldbook.08491
Measurement method of atomic spectroscopy that uses an inductively-coupled plasma to excite and ionize atoms with measurement of the number and kind of ions in the plasma from their emission of electromagnetic radiation (see optical emission spectroscopy).
Source:
PAC, 2021, 93, 647. (Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)) on page 722 [Terms] [Paper]