The birth of atomic spectrometry began with the first patent of atomic absorption spectrometry by Walsh in 1955. A few of the more relevant discoveries for atomic spectroscopy were the first observations by Newton of the separation of white light into different colors by a prism in 1740, the development of the first spectroscope (a device for studying small concentrations of elements) in 1859 by Kirchhoff and Bunsen, and the first quantitative analysis (of sodium) by flame emission by Champion, Pellet, and Grenier in 1873. Slightly more advanced, but still unexplained observations were responsible for the first development of colorful fireworks in China over 2000 years ago. This color was caused by the relaxation of the 3p electron to a 3s orbital in sodium (refer to the energy level diagram in Figure 1-3 given earlier), and in part by carbene ions. The first observation of atomic emission dates back to at least the first campfire where hominoids/humans observed a yellow color in the flame. AAS is used almost exclusively for quantitative analysis of elements, hence the use of the term " spectrometry " in the name of the technique instead of " spectroscopy ".This last disadvantage makes AAS of very limited use for qualitative analysis. The major disadvantages of AAS are that no information is obtained on the chemical form of the analyte (no " speciation ") and that often only one element can be determined at a time.This is not to say that AAS measurements are completely free from interferences both chemical and spectral interferences do occur and must be compensated for.This results in rapid analysis times and eliminates some sources of error. Therefore it is not necessary to separate the analyte from the rest of the sample (the matrix). Another principal advantage is that a given element can be determined in the presence of other elements, which do not interfere by absorption of the analyte wavelength. Concentrations as low as ppt levels of some elements in solution can be determined and AAS is used routinely to determine ppb and ppm concentrations of most metal elements. It does not matter whether the cadmium exists as the chloride, sulphate, or nitrate, or even if it exists as a complex or an organ metallic compound, if the proper analysis conditions are used. A determination of cadmium in a water sample is a determination of the total cadmium concentration. As an elemental analysis technique, it has the significant advantage in many cases of being practically independent of the chemical form of the element in the sample. AAS is an elemental analysis technique capable of providing quantitative information on 70 elements in almost any type of sample. Theory: AAS was developed in the 1950s by Alan Walsh and rapidly became a widely used analytical tool. Free atoms in the gas phase are formed from the sample by an " atomizer " at high temperature. The basis of atomic absorption spectrometry (AAS) is the absorption of discrete wavelengths of light by ground state, gas phase free atoms.
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