Elemental Analysis and Atomic Spectroscopy

Atomic spectroscopy is employed for the qualitative and quantitative determination of around 70 elements primarily for the analysis of a wide range of metals (often for trace analysis). Atomic spectroscopy can provide information regarding the identity and concentration of atoms in a sample irrespective of how these atoms are combined. In contrast, molecular spectroscopy gives qualitative and quantitative information about the molecules (or particular functional groups present in molecules) in a sample. 

Sensitivities of atomic methods lie typically in the parts per million (mg dm ) to parts per billion (pg dm or pg kg ) range, although in some cases in the parts per trillion (ng dm ) range. (You may wish to think about the implications of this ). Additional virtues associated with these methods include speed, convenience, unusually high selectivity and moderate instrument costs (although not for an inductively coupled plasma-mass spectrometry system ). 

The first key step in all atomic spectroscopic techniques is atomisation , a 

Atomic emission spectra are produced when an atom or ion excited by the absorption of energy from a hot source relaxes to its ground state by giving off a photon of radiation (with a characteristic wavelength). In contrast, atomic absorption takes place when a gaseous atom or ion absorbs a photon of radiation (with a characteristic wavelength) from an external source and is thus excited. 

Atomic absoiption spectroscopy (AAS) is probably still the most widely employed of all the atomic methods because of its simplicity, effectiveness and relatively low cost. A Tine source of radiation is required for AAS (they do not employ a continuous source of radiation) hence a complete spectrum is not obtained. The sources (which are changed depending on the element of interest) emit certain lines of radiation that have the same wavelength as that of the absorption peak of the analyte of interest. 

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