Flame emission spectroscopy is a chemical analysis technique that relies on looking at the energy emitted when excited atoms return to a ground state. Atoms associated with different elements have their own distinct spectral signatures which can be identified with a highly sensitive detector. This method of material analysis is destructive in nature, but can provide important information about the components of an unknown sample of a compound or solution.
The first step is aerosolization of the sample. To accomplish this, a fine spray of the sample material can be pumped through a flame, where the heat excites the atoms, causing them to fall back to a ground state. This causes energy loss and a characteristic emission of energy. A detector notes the wavelengths of light emitted, and records it for the benefit of the operator. This information can be printed and retained digitally in a file.
Some compounds have very characteristic signatures that may be visible with the naked eye in flame emission spectroscopy, especially if the sample is large. In lieu of aerosolization, some test methods require the technician to place a small sample in a holder that can be placed in the flame, which will create a very noticeable emission. Copper, for example, burns bright green to blue, depending on which impurities are present. Chemistry professors may use such recognizable compounds in classroom demonstrations to show students how the process works and to illustrate the varied spectral emissions of different elements.
Differences between other compounds can be more subtle, especially when multiple elements are present in a sample. The flame emission spectroscopy process magnifies the emission and allows the operator to review it at leisure to match it up with known samples. People can look for specific bands of light that can be tell-tale signs of the presence of particular elements. Automated computer systems can also perform this match on their own and return a list of likely candidates to the user.
Charts of flame emission spectroscopy results are available to compare with samples under analysis. These can also be used for equipment calibration. To calibrate, the technician takes a known sample and subjects it to the process, comparing the end result with the chart. If the emissions do not match, there may be something wrong with the equipment. The gear may need servicing, cleaning, or other work to function correctly and return valid results for the user.