Principle : The spectroscopy of absorption or emission is probably the oldest analytical method used in the world. it includes two methods of quantitative analysis that can be used to measure the concentrations of approximately 70 elements (metals, metalloids and non-metals). the principle behind these methods of analysis of elements depends on the measurements made in an analyte that is transformed in the form of an atom, the free (atomization). once the atoms cannot rotate or vibrate as molecules, only in this case, the electronic transitions take place when the energy is absorbed. because the transitions are quantized, one obtains a spectrum of lines and elements are detected by spectrometry with optical or mass. this technique is based on the absorption of the radiation to be monochromatic by a cloud of atoms. the atoms in the ground state absorb energy in a certain wavelength produced by a source composed by the same atoms to be analyzed from a source (lamp with hollow cathode). this source produces an electromagnetic radiation intense with a wavelength similar to that absorbed by the atoms. the sensitivity of this technique is proportional to the number of atoms in the ground state.
When an atom absorbs energy from this source, an electron jumps from the ground state to a state less stable « excited state ». returning to the ground state, a photon of light energy is emitted with an intensity proportional to the concentration of the element to be analyzed. the efficiency and reproducibility of the atomization determine the sensitivity, accuracy and reproducibility of this technique. the sensitivity is in the range of parts per million (ppm) and parts per billion (ppb), with additional benefits including speed, high sensitivity and the moderate costs of the instrument.