Elemental analysis is a process where a sample of some material (e.g., soil, waste or drinking water, bodily fluids,
minerals,
chemical compounds) is analyzed for its
elemental and sometimes
isotopic composition. Elemental analysis can be qualitative (determining what elements are present), and it can be quantitative (determining how much of each are present). Elemental analysis falls within the ambit of
analytical chemistry, the set of instruments involved in deciphering the chemical nature of our world.
For organic chemists, elemental analysis or "EA" almost always refers to CHNX analysis — the determination of the percentage weights of carbon, hydrogen, nitrogen, and heteroatoms (X) (halogens, sulfur) of a sample. This information is important to help determine the structure of an unknown compound, as well as to help ascertain the structure and purity of a synthesized compound.
The most common form of elemental analysis, CHN analysis, is accomplished by combustion analysis. In this technique, a sample is burned in an excess of oxygen, and various traps collect the combustion products — carbon dioxide, water, and nitric oxide. The weights of these combustion products can be used to calculate the composition of the unknown sample.
Other quantitative methods include
