Elemental analysis is one of the most common procedures used to characterize a sample. It is useful in most areas of human endeavor and is commonly applied to samples of importance in toxicology, geology, forensic science, prospecting, health, nanotechnology, materials science, industrial process control, semiconductor processing, automobile manufacturing, and others. Because of this importance and range of application, a broad suite of methods for elemental analysis has been devised. These methods range from long-established procedures such as those based on precipitation and titration to more modern ones that rely as much on physical principles as on chemistry.