Atomic emission spectroscopy
Encyclopedia
Atomic emission spectroscopy (AES) is a method of chemical analysis that uses the intensity of light emitted from a flame
, plasma
, arc
, or spark
at a particular wavelength to determine the quantity of an element
in a sample. The wavelength of the atomic spectral line
gives the identity of the element while the intensity of the emitted light is proportional to the number of atom
s of the element.
A frequent application of the emission measurement with the flame is the regulation of alkali metals for pharmaceutical analytics.
to produce excited atoms and ions that emit electromagnetic radiation
at wavelengths characteristic of a particular element
.
Advantages of ICP-AES are excellent limit of detection and linear dynamic range, multi-element capability, low chemical interference and a stable and reproducible signal. Disadvantages are spectral interferences (many emission lines), cost and operating expense and the fact that samples typically must be in solution.
or arc
atomic emission spectroscopy is used for the analysis of metallic elements in solid samples. For non-conductive materials, the sample is ground with graphite
powder to make it conductive. In traditional arc spectroscopy methods, a sample of the solid was commonly ground up and destroyed during analysis. An electric arc or spark is passed through the sample, heating it to a high temperature to excite the atoms within it. The excited analyte atoms emit light at characteristic wavelengths that can be dispersed with a monochromator and detected. As the spark or arc conditions are typically not well controlled, the analysis for the elements in the sample is qualitative. However, modern spark sources with controlled discharges under an argon atmosphere can be considered quantitative. Both qualitative and quantitative spark analysis are widely used for production quality control in foundries and steel mills.
Flame
A flame is the visible , gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone...
, plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
, arc
Electric arc
An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge. An arc discharge is characterized by a lower voltage than a glow discharge, and relies on...
, or spark
Electric spark
An electric spark is a type of electrostatic discharge that occurs when an electric field creates an ionized electrically conductive channel in air producing a brief emission of light and sound. A spark is formed when the electric field strength exceeds the dielectric field strength of air...
at a particular wavelength to determine the quantity of an element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
in a sample. The wavelength of the atomic spectral line
Atomic spectral line
In physics, atomic spectral lines are of two types:* An emission line is formed when an electron makes a transition from a particular discrete energy level of an atom, to a lower energy state, emitting a photon of a particular energy and wavelength...
gives the identity of the element while the intensity of the emitted light is proportional to the number of atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
s of the element.
Flame emission spectroscopy
A sample of a material (analyte) is brought into the flame as a gas or sprayed solution. The heat from the flame evaporates the solvent and breaks chemical bonds to create free atoms. The thermal energy also excites the atoms into excited electronic states that subsequently emit light when they return to the ground electronic state. Each element emits light at a characteristic wavelength, which is dispersed by a grating or prism and detected in the spectrometer.A frequent application of the emission measurement with the flame is the regulation of alkali metals for pharmaceutical analytics.
Inductively coupled plasma atomic emission spectroscopy
Inductively coupled plasma atomic emission spectroscopy (ICP-AES) uses an inductively coupled plasmaInductively coupled plasma
An inductively coupled plasma is a type of plasma source in which the energy is supplied by electric currents which are produced by electromagnetic induction, that is, by time-varying magnetic fields.-Operation:...
to produce excited atoms and ions that emit electromagnetic radiation
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...
at wavelengths characteristic of a particular element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
.
Advantages of ICP-AES are excellent limit of detection and linear dynamic range, multi-element capability, low chemical interference and a stable and reproducible signal. Disadvantages are spectral interferences (many emission lines), cost and operating expense and the fact that samples typically must be in solution.
Spark and arc atomic emission spectroscopy
SparkElectrostatic discharge
Electrostatic discharge is a serious issue in solid state electronics, such as integrated circuits. Integrated circuits are made from semiconductor materials such as silicon and insulating materials such as silicon dioxide...
or arc
Electric arc
An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge. An arc discharge is characterized by a lower voltage than a glow discharge, and relies on...
atomic emission spectroscopy is used for the analysis of metallic elements in solid samples. For non-conductive materials, the sample is ground with graphite
Graphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...
powder to make it conductive. In traditional arc spectroscopy methods, a sample of the solid was commonly ground up and destroyed during analysis. An electric arc or spark is passed through the sample, heating it to a high temperature to excite the atoms within it. The excited analyte atoms emit light at characteristic wavelengths that can be dispersed with a monochromator and detected. As the spark or arc conditions are typically not well controlled, the analysis for the elements in the sample is qualitative. However, modern spark sources with controlled discharges under an argon atmosphere can be considered quantitative. Both qualitative and quantitative spark analysis are widely used for production quality control in foundries and steel mills.
See also
- Inductively coupled plasma atomic emission spectroscopy
- Atomic absorption spectroscopyAtomic absorption spectroscopyAtomic absorption spectroscopy is a spectroanalytical procedure for the qualitative and quantitative determination of chemical elements employing the absorption of optical radiation by free atoms in the gaseous state. In analytical chemistry the technique is used for determining the concentration...
- Atomic spectroscopyAtomic spectroscopyAtomic spectroscopy is the determination of elemental composition by its electromagnetic or mass spectrum. Atomic spectroscopy is closely related to other forms of spectroscopy. It can be divided by atomization source or by the type of spectroscopy used. In the latter case, the main division is...
- Laser-induced breakdown spectroscopy