Atomic spectroscopy uses the electromagnetic radiation or mass spectrum of a sample to determine elemental composition. The wavelength of energy absorbed or emitted by atoms is characteristic to each element and can be used for element identification and quantification.
Analytical techniques based on atomic spectroscopy are widely used in environmental chemistry, geology and soil science, mining and metallurgy, food sciences, and medicine.
Atomic absorption spectroscopy (AAS) works by measuring the amount of UV/visible light energy absorbed by an element. The wavelength of light absorbed corresponds to the energy needed to promote its electrons from the ground state to a higher energy level. The amount of energy absorbed in this excitation process is proportional to the concentration of the element in the sample.
Flame atomic absorption spectroscopy (FAA) involves vaporization and thermal atomization of a liquid sample by a flame. In this technique, a sample solution is aspirated and sprayed as a fine aerosol into a chamber to combine with fuel and oxidant gases. The resulting mixture is then carried to the burner head, where combustion and sample atomization occurs.
Graphite furnace atomic absorption spectroscopy (GFAA) is the most advanced and sensitive technique to assess atomic absorption. With a graphite furnace atomizer, the atoms are retained in the optical path for a slightly longer time compared with flame atomization, resulting in lower detection limits and sensitivity in the parts per billion (ppb) range.
Inductively coupled plasma optical emission spectroscopy (ICP-OES) measures the light emitted by excited electrons of an element while returning to their stable ground state. The sample is introduced into an argon plasma and high temperature excites the atom’s electrons to higher energy levels. The element is identified by the characteristic wavelength of the light emitted as its electrons return to ground state. The intensity of the light emitted is related to the concentration of the element in the sample.
Inductively coupled plasma mass spectrometry (ICP-MS) is a type of mass spectrometry used for the highly sensitive quantification of various metals and non-metals in the concentration range of below 1 part per trillion (ppt). ICP-MS analyzes elements by their separation in a magnetic field as per their mass to charge (m/z) ratio.
X-ray fluorescence (XRF) spectrometry detects elemental composition by measuring the wavelength and intensity of X-rays emitted by energized atoms in a sample. In this method, a beam of short wavelength x-rays strikes the sample and dislodges innermost shell electrons of the atom, forming a vacant site or “hole”. This causes the atom to rearrange its electronic arrangement with an electron from a higher energy shell jumping to occupy the newly created vacancy and emitting characteristic X-ray light during the process. The X-rays emitted by the atoms during the process of fluorescence are detected and used for sample identification and quantitation.