Inductively Coupled Plasma Optical Emission Spectroscopy
This one is super rough, but the exact type of topic that is most important.
ICP-OES is used to identify the chemical constituents of a sample. The sample is often digested using strong acids (HCL + HNO3) into a homogenous solution. It is then diluted and quantified by comparing it to standards of known concentration.
Standards often contain between ~0.1-30 ppm of the desired elements. These are run through the ICP, and should display a linear relationship between concentration and signal intensity. At high concentrations, the response becomes non-linear, and this non-linear regime can't be used. Minimum concentrations can be identified in https://www.inorganicventures.com/periodic-table.
Will add more detail on best practices for making standards later.