Radiation chemistry
Encyclopedia
Radiation chemistry is a subdivision of nuclear chemistry
which is the study of the chemical effects of radiation on matter; this is very different from radiochemistry
as no radioactivity needs to be present in the material which is being chemically changed by the radiation. An example is the conversion of water into hydrogen
gas and hydrogen peroxide
.
an inorganic chloride. This is because the solvated electron
s react with the organic compound to form a radical
anion, which decomposes by the loss of a chloride
anion. If a deoxygenated mixture of PCBs in isopropanol or mineral oil
is irradiated with gamma rays, then the PCBs will be dechlorinated to form inorganic chloride
and biphenyl
. The reaction works best in isopropanol if potassium hydroxide
(caustic potash) is added. The base deprotonates the hydroxydimethylmethyl radical to be converted into acetone and a solvated electron, as the result the G value (yield for a given energy due to radiation deposited in the system) of chloride can be increased because the radiation now starts a chain reaction, each solvated electron formed by the action of the gamma rays can now convert more than one PCB molecule. If oxygen
, acetone
, nitrous oxide
, sulfur hexafluoride
or nitrobenzene
is present in the mixture, then the reaction rate is reduced. This work has been done recently in the USA, often with used nuclear fuel
as the radiation source.
In addition to the work on the destruction of aryl chlorides it has been shown that aliphatic chlorine and bromine
compounds such as perchloroethylene, Freon (1,1,2-trichloro-1,2,2-trifluoroethane) and halon-2402
(1,2-dibromo-1,1,2,2-tetrafluoroethane) can be dehalogenated by the action of radiation on alkaline isopropanol solutions. Again a chain reaction has been reported.
In addition to the work on the reduction of organic compounds by irradiation, some work on the radiation induced oxidation of organic compounds has been reported. For instance the use of radiogenic hydrogen peroxide (formed by irradiation) to remove sulfur from coal
has been reported. In this study it was found that the addition of manganese
dioxide to the coal increased the rate of sulfur removal. The degradation of nitrobenzene
under both reducing and oxidising conditions in water has been reported.
solution, at pH 4.1 is converted to a colloid
of technetium dioxide. Irradiation of a solution at pH 1.8 soluble Tc(IV) complexes are formed. Irradiation of a solution at 2.7 forms a mixture of the colloid and the soluble Tc(IV) compounds. Gamma irradiation has been used in the synthesis of nanoparticles of gold
on iron oxide (Fe2O3).
It has been shown that the irradiation of aqueous solutions of lead
compounds leads to the formation of elemental lead, when an inorganic solid such as bentonite
and sodium formate are present then the lead is removed from the aqueous solution.
s to polymer
s, to crosslink polymers, and to break polymer chains. Both man-made and natural polymers (such as carbohydrate
s) can be processed in this way.
and acute radiation injuries
) and the useful effects of radiotherapy involve the radiation chemistry of water. The vast majority of biological molecules are present in an aqueous medium; when water is exposed to radiation, the water absorbs energy, and as a result forms chemically reactive species that can interact with dissolved substances (solutes
). Water is ionized to form a solvated electron
and H2O+, the H2O+ cation can react with water to form a hydrated proton (H3O+) and a hydroxyl radical (HO.). Furthermore, the solvated electron can recombine with the H2O+ cation to form an excited state of the water, this excited state then decomposes to species such as hydroxyl radical
s (HO.), hydrogen atoms (H.) and oxygen atoms (O.). Finally, the solvated electron can react with solutes such as solvated protons or oxygen molecules to form respectively hydrogen atoms and dioxygen radical anions. The fact that oxygen changes the radiation chemistry might be one reason why oxygenated tissues are more sensitive to irradiation than the deoxygenated tissue at the centre of a tumor. The free radicals, such as the hydroxyl radical, chemically modify biomolecules such as DNA
, leading to damage such as breaks in the DNA strands. Some substances can protect again radiation-induced damage by reacting with the reactive species generated by the irradiation of the water.
It is important to note that the reactive species generated by the radiation can take part in following reactions, this is similar to the idea of the non-electrochemical reactions which follow the electrochemical event which is observed in cyclic voltammetry
when a non-reversible event occurs. For example the SF5 radical formed by the reaction of solvated electrons and SF6 undergo further reactions which lead to the formation of hydrogen fluoride
and sulfuric acid
.
In water the dimerisation reaction of hydroxyl radicals can form hydrogen peroxide
, in saline systems the reaction of the hydroxyl radicals with chloride
anions form hypochlorite
anions.
It has been suggested that the action of radiation upon underground water
is responsible for the formation of hydrogen which was converted by bacteria into methane
.http://deepbio.princeton.edu/samp/papers/LinetalGCA69-893.pdf. A series of papers on the subject of bacteria living under the surface of the earth which are fed by the hydrogen generated by the radiolysis
of water can be read on line.
s from a LINAC. After the pulse of radiation, the concentration of different substances within the material are measured by emission spectroscopy or Absorption spectroscopy
, hence the rates of reactions can be determined. This allows the relative abilities of substances to react with the reactive species generated by the action of radiation on the solvent (commonly water) to be measured. This experiment is known as pulse radiolysis which is closely related to Flash photolysis
.
In the latter experiment the sample is excited by a pulse of light to examine the decay of the excited states by spectroscopy
http://www.chem.uic.edu/chem343/Flash-Photolysis.pdf; sometimes the formation of new compounds can be investigated.http://nobelprize.org/nobel_prizes/chemistry/laureates/1967/porter-lecture.pdf Flash photolysis experiments have led to a better understanding of the effects of halogen
-containing compounds upon the ozone layer
.
is nonionic and nonspecific. It directly measures the total mass of each chemical compound as it exits the gas chromatography
column and condenses on the crystal surface, thus causing a change in the fundamental acoustic frequency of the crystal. Odor concentration is directly measured with this integrating type of detector. Column flux is obtained from a microprocessor that continuously calculates the derivative of the SAW
frequency.
Nuclear chemistry
Nuclear chemistry is the subfield of chemistry dealing with radioactivity, nuclear processes and nuclear properties.It is the chemistry of radioactive elements such as the actinides, radium and radon together with the chemistry associated with equipment which are designed to perform nuclear...
which is the study of the chemical effects of radiation on matter; this is very different from radiochemistry
Radiochemistry
Radiochemistry is the chemistry of radioactive materials, where radioactive isotopes of elements are used to study the properties and chemical reactions of non-radioactive isotopes...
as no radioactivity needs to be present in the material which is being chemically changed by the radiation. An example is the conversion of water into hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
gas and hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
.
Reduction of organics by solvated electrons
A recent area of work has been the destruction of toxic organic compounds by irradiation; after irradiation, "dioxins" (polychlorodibenzo-p-dioxins) are dechloroinated in the same way as PCBs can be converted to biphenylBiphenyl
Biphenyl is an organic compound that forms colorless crystals. It has a distinctively pleasant smell. Biphenyl is an aromatic hydrocarbon with a molecular formula 2...
an inorganic chloride. This is because the solvated electron
Solvated electron
A solvated electron is a free electron in a solution. Solvated electrons occur widely although they are often not observed directly. The deep colour of solutions of alkali metals in ammonia arises form the presence of solvated electrons: blue when dilute and copper-colored when more concentrated...
s react with the organic compound to form a radical
Radical (chemistry)
Radicals are atoms, molecules, or ions with unpaired electrons on an open shell configuration. Free radicals may have positive, negative, or zero charge...
anion, which decomposes by the loss of a chloride
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
anion. If a deoxygenated mixture of PCBs in isopropanol or mineral oil
Mineral oil
A mineral oil is any of various colorless, odorless, light mixtures of alkanes in the C15 to C40 range from a non-vegetable source, particularly a distillate of petroleum....
is irradiated with gamma rays, then the PCBs will be dechlorinated to form inorganic chloride
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
and biphenyl
Biphenyl
Biphenyl is an organic compound that forms colorless crystals. It has a distinctively pleasant smell. Biphenyl is an aromatic hydrocarbon with a molecular formula 2...
. The reaction works best in isopropanol if potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
(caustic potash) is added. The base deprotonates the hydroxydimethylmethyl radical to be converted into acetone and a solvated electron, as the result the G value (yield for a given energy due to radiation deposited in the system) of chloride can be increased because the radiation now starts a chain reaction, each solvated electron formed by the action of the gamma rays can now convert more than one PCB molecule. If oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
, acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
, nitrous oxide
Nitrous oxide
Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...
, sulfur hexafluoride
Sulfur hexafluoride
Sulfur hexafluoride is an inorganic, colorless, odorless, and non-flammable greenhouse gas. has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom. It is a hypervalent molecule. Typical for a nonpolar gas, it is poorly soluble in water but soluble in...
or nitrobenzene
Nitrobenzene
Nitrobenzene is an organic compound with the chemical formula C6H5NO2. It is a water-insoluble pale yellow oil with an almond-like odor. It freezes to give greenish-yellow crystals. It is produced on a large scale as a precursor to aniline. Although occasionally used as a flavoring or perfume...
is present in the mixture, then the reaction rate is reduced. This work has been done recently in the USA, often with used nuclear fuel
Nuclear fuel
Nuclear fuel is a material that can be 'consumed' by fission or fusion to derive nuclear energy. Nuclear fuels are the most dense sources of energy available...
as the radiation source.
In addition to the work on the destruction of aryl chlorides it has been shown that aliphatic chlorine and bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
compounds such as perchloroethylene, Freon (1,1,2-trichloro-1,2,2-trifluoroethane) and halon-2402
Dibromotetrafluoroethane
1,2-Dibromotetrafluoroethane is a haloalkane. It is also known under codenames R-114B2 and Halon 2402. It is a colorless liquid with a boiling point of 47.2 °C. R-114B2 is occasionally used in fire suppression systems. It is also used as a tracer chemical in Praxair's Seep Sense leak detection...
(1,2-dibromo-1,1,2,2-tetrafluoroethane) can be dehalogenated by the action of radiation on alkaline isopropanol solutions. Again a chain reaction has been reported.
In addition to the work on the reduction of organic compounds by irradiation, some work on the radiation induced oxidation of organic compounds has been reported. For instance the use of radiogenic hydrogen peroxide (formed by irradiation) to remove sulfur from coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
has been reported. In this study it was found that the addition of manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
dioxide to the coal increased the rate of sulfur removal. The degradation of nitrobenzene
Nitrobenzene
Nitrobenzene is an organic compound with the chemical formula C6H5NO2. It is a water-insoluble pale yellow oil with an almond-like odor. It freezes to give greenish-yellow crystals. It is produced on a large scale as a precursor to aniline. Although occasionally used as a flavoring or perfume...
under both reducing and oxidising conditions in water has been reported.
Reduction of metal compounds
In addition to the reduction of organic compounds by the solvated electrons it has been reported that upon irradiation a pertechnetatePertechnetate
The pertechnetate ion is an oxoanion with the chemical formula TcO4−. It is often used as a convenient water-soluble source of isotopes of the radioactive element technetium...
solution, at pH 4.1 is converted to a colloid
Colloid
A colloid is a substance microscopically dispersed evenly throughout another substance.A colloidal system consists of two separate phases: a dispersed phase and a continuous phase . A colloidal system may be solid, liquid, or gaseous.Many familiar substances are colloids, as shown in the chart below...
of technetium dioxide. Irradiation of a solution at pH 1.8 soluble Tc(IV) complexes are formed. Irradiation of a solution at 2.7 forms a mixture of the colloid and the soluble Tc(IV) compounds. Gamma irradiation has been used in the synthesis of nanoparticles of gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
on iron oxide (Fe2O3).
It has been shown that the irradiation of aqueous solutions of lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
compounds leads to the formation of elemental lead, when an inorganic solid such as bentonite
Bentonite
Bentonite is an absorbent aluminium phyllosilicate, essentially impure clay consisting mostly of montmorillonite. There are different types of bentonite, each named after the respective dominant element, such as potassium , sodium , calcium , and aluminum . Experts debate a number of nomenclatorial...
and sodium formate are present then the lead is removed from the aqueous solution.
Polymer modification
Another key area uses radiation chemistry to modify polymers. Using radiation, it is possible to convert monomerMonomer
A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...
s to polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
s, to crosslink polymers, and to break polymer chains. Both man-made and natural polymers (such as carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
s) can be processed in this way.
Water chemistry
Both the harmful effects of radiation upon biological systems (induction of cancerCancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
and acute radiation injuries
Radiation Sickness
Radiation Sickness is a VHS by the thrash metal band Nuclear Assault. The video is a recording of a concert at the Hammersmith Odeon, London in 1988. It was released in 1991...
) and the useful effects of radiotherapy involve the radiation chemistry of water. The vast majority of biological molecules are present in an aqueous medium; when water is exposed to radiation, the water absorbs energy, and as a result forms chemically reactive species that can interact with dissolved substances (solutes
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
). Water is ionized to form a solvated electron
Solvated electron
A solvated electron is a free electron in a solution. Solvated electrons occur widely although they are often not observed directly. The deep colour of solutions of alkali metals in ammonia arises form the presence of solvated electrons: blue when dilute and copper-colored when more concentrated...
and H2O+, the H2O+ cation can react with water to form a hydrated proton (H3O+) and a hydroxyl radical (HO.). Furthermore, the solvated electron can recombine with the H2O+ cation to form an excited state of the water, this excited state then decomposes to species such as hydroxyl radical
Hydroxyl radical
The hydroxyl radical, •OH, is the neutral form of the hydroxide ion . Hydroxyl radicals are highly reactive and consequently short-lived; however, they form an important part of radical chemistry. Most notably hydroxyl radicals are produced from the decomposition of hydroperoxides or, in...
s (HO.), hydrogen atoms (H.) and oxygen atoms (O.). Finally, the solvated electron can react with solutes such as solvated protons or oxygen molecules to form respectively hydrogen atoms and dioxygen radical anions. The fact that oxygen changes the radiation chemistry might be one reason why oxygenated tissues are more sensitive to irradiation than the deoxygenated tissue at the centre of a tumor. The free radicals, such as the hydroxyl radical, chemically modify biomolecules such as DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
, leading to damage such as breaks in the DNA strands. Some substances can protect again radiation-induced damage by reacting with the reactive species generated by the irradiation of the water.
It is important to note that the reactive species generated by the radiation can take part in following reactions, this is similar to the idea of the non-electrochemical reactions which follow the electrochemical event which is observed in cyclic voltammetry
Cyclic voltammetry
Cyclic voltammetry or CV is a type of potentiodynamic electrochemical measurement. In a cyclic voltammetry experiment the working electrode potential is ramped linearly versus time like linear sweep voltammetry. Cyclic voltammetry takes the experiment a step further than linear sweep voltammetry...
when a non-reversible event occurs. For example the SF5 radical formed by the reaction of solvated electrons and SF6 undergo further reactions which lead to the formation of hydrogen fluoride
Hydrogen fluoride
Hydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers . HF is widely used in the...
and sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
.
In water the dimerisation reaction of hydroxyl radicals can form hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
, in saline systems the reaction of the hydroxyl radicals with chloride
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
anions form hypochlorite
Hypochlorite
The hypochlorite ion, also known as chlorate anion is ClO−. A hypochlorite compound is a chemical compound containing this group, with chlorine in oxidation state +1.Hypochlorites are the salts of hypochlorous acid...
anions.
It has been suggested that the action of radiation upon underground water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
is responsible for the formation of hydrogen which was converted by bacteria into methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
.http://deepbio.princeton.edu/samp/papers/LinetalGCA69-893.pdf. A series of papers on the subject of bacteria living under the surface of the earth which are fed by the hydrogen generated by the radiolysis
Radiolysis
Radiolysis is the dissociation of molecules by nuclear radiation. It is the cleavage of one or several chemical bonds resulting from exposure to high-energy flux...
of water can be read on line.
Radiation Chemistry applied in Industrial processing equipment
To process materials, either a gamma source or an electron beam can be used. The international type IV (wet storage) irradiator is a common design, of which the JS6300 and JS6500 gamma sterilizers (made by 'Nordion International'http://www.mds.nordion.com/, which used to trade as 'Atomic Energy of Canada Ltd') are typical examples. In these irradiation plants, the source is stored in a deep well filled with water when not in use. When the source is required, it is moved by a steel wire to the irradiation room where the products which are to be treated are present; these objects are placed inside boxes which are moved through the room by an automatic mechanism. By moving the boxes from one point to another, the contents are given a uniform dose. After treatment, the product is moved by the automatic mechanism out of the room. The irradiation room has very thick concrete walls (about 3 m thick) to prevent gamma rays from escaping. The source consists of 60Co rods sealed within two layers of stainless steel, the rods are combined with inert dummy rods to form a rack with a total activity of about 12.6PBq (340kCi).Research equipment
While it is possible to do some types of research using an irradiator much like that used for gamma sterilization, it is common in some areas of science to use a time resolved experiment where a material is subjected to a pulse of radiation (normally electronElectron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s from a LINAC. After the pulse of radiation, the concentration of different substances within the material are measured by emission spectroscopy or Absorption spectroscopy
Absorption spectroscopy
Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating field. The intensity of the absorption varies as a...
, hence the rates of reactions can be determined. This allows the relative abilities of substances to react with the reactive species generated by the action of radiation on the solvent (commonly water) to be measured. This experiment is known as pulse radiolysis which is closely related to Flash photolysis
Flash photolysis
Flash photolysis is a pump-probe laboratory technique, in which a sample is firstly excited by a strong pulse of light from a laser of nanosecond, picosecond, or femtosecond pulse width or by a short-pulse light source such as a flash lamp...
.
In the latter experiment the sample is excited by a pulse of light to examine the decay of the excited states by spectroscopy
Spectroscopy
Spectroscopy is the study of the interaction between matter and radiated energy. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, e.g., by a prism. Later the concept was expanded greatly to comprise any interaction with radiative...
http://www.chem.uic.edu/chem343/Flash-Photolysis.pdf; sometimes the formation of new compounds can be investigated.http://nobelprize.org/nobel_prizes/chemistry/laureates/1967/porter-lecture.pdf Flash photolysis experiments have led to a better understanding of the effects of halogen
Halogen
The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...
-containing compounds upon the ozone layer
Ozone layer
The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone . This layer absorbs 97–99% of the Sun's high frequency ultraviolet light, which is potentially damaging to the life forms on Earth...
.
Chemosensor
The SAW chemosensorChemosensor
A chemoreceptor, also known as chemosensor, is a sensory receptor that transduces a chemical signal into an action potential. In more general terms, a chemosensor detects certain chemical stimuli in the environment.- Classes :...
is nonionic and nonspecific. It directly measures the total mass of each chemical compound as it exits the gas chromatography
Chromatography
Chromatography is the collective term for a set of laboratory techniques for the separation of mixtures....
column and condenses on the crystal surface, thus causing a change in the fundamental acoustic frequency of the crystal. Odor concentration is directly measured with this integrating type of detector. Column flux is obtained from a microprocessor that continuously calculates the derivative of the SAW
SAW
A saw is a cutting tool.Saw or SAW may also refer to:-In Film:*Saw , a series of horror films**"Saw" , a 2003 short film by James Wan, upon which the series of films was originally based**Saw...
frequency.