|  | Atomization-excitation source The atomization-excitation source heats the sample in such a way that the sample becomes atomized and that a large proportion of atoms get in the excited state. As the excited gas atoms return to the groundstate, energy is released in the form of light which can be separated into characteristic spectral lines by a monochromator. The two most commonly used forms of atomization-excitation sources in food analysis are: - Flame-AES: this is a nebulizer-burner system. At the flame temperature (2000-3000 K) almost only the alkali elements (such as Li, Na and K) emit light. - Inductively Coupled Plasma-OES: here, the sample is heated to very high temperatures (6000 to 10000 K). At this temperature almost all elements of the periodic system emit light. In this case besides atomic emission lines, also ion lines (ionized atoms) can be measured. |  |

|  | Detector The detector measures the presence and intensity of the emitted light. The presence of particular wavelengths (spectral lines) gives information on the type of minerals present in the sample. The intensity of the emitted light gives information on the concentration of elements. |  |

|  | Monochromator Because the excited atoms return to a lower energy level, energy is released in the form of light. A monochromator or polychromator separates the light into spectral lines characteristic for the element that is being analyzed. |  |

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An other atomic spectrometry method is Atomic Emission Spectrometry (AES). AES differs from AAS, because it uses emission of radiation by a sample, instead of the absorption. Samples have to be heated to a higher temperature so that more elements are getting into an excited state. After a solution of the sample is sprayed into the flame, the heat from the flame evaporates the solvent and breaks chemical bonds to create free atoms. The thermal energy (heat) also excites the atoms into excited electronic states that subsequently emit light when they return to the ground state. Each element emits light at a characteristic wavelength, which is detected in the spectrometer.

For AES a radiation source is not needed, because the sample acts as the radiation source itself: when the atoms fall back to lower levels, light is emitted.

Since all types of atoms in a sample are excited simultaneously, they can be detected simultaneously, because each atom emits light at a specific wavelength. This is the major advantage of AES compared to atomic-absorption spectrometry, because in AAS each element has to be radiated with a specific wavelength. Different wavelength for specific elements cannot be produced simultaneously.

Flame AES

The figure below is a schematic representation of flame-AES. Please move with your mouse over the yellow and white boxes for an explanation of the elements.