Isotopic labeling is a technique for tracking the passage of a sample of substance through a system. The substance is 'labeled' by including unusual isotopes in its chemical composition. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides If these unusual isotopes are later detected in a certain part of the system, they must have come from the labeled substance.
In ordinary isotopic labeling, there are two ways to detect the presence of labeling isotopes. Since isotopes have different masses, they can be separated using mass spectrometry. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object Mass spectrometry is an analytical technique that identifies the chemical composition of a compound or sample based on the Mass-to-charge ratio of charged particles Another consequence of the difference in mass is that molecules containing isotopes have different vibrational modes; these can be detected by infrared spectroscopy. A normal mode of an oscillating system is a pattern of motion in which all parts of the system move sinusoidally with the same frequency Infrared spectroscopy (IR spectroscopy is the subset of Spectroscopy that deals with the Infrared region of the Electromagnetic spectrum.
Isotopic labeling can also be used to study chemical reactions. A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called In this method specific atoms are replaced by an isotope in a reactant molecule which then participates in a chemical reaction. With spectroscopy, nuclear magnetic resonance spectroscopy for example, it is now possible to identify where a particular molecular fragment in the reactant ends up as a particular fragment in one of the reaction products. Spectroscopy was originally the study of the interaction between Radiation and Matter as a function of Wavelength (λ
An example of the use of isotopic labeling is the study of phenol (C6H5OH) in water by replacing common hydrogen (protium) with deuterium (deuterium labeling). Phenol, is a toxic colourless Crystalline Solid with a sweet tarry odor commonly referred to as a "hospital smell" Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 A hydrogen atom is an atom of the chemical element Hydrogen. The electrically neutral Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth Upon adding phenol to deuterated water (water containing D2O in addition to the usual H2O), the substitution of deuterium for the hydrogen is observed in phenol's hydroxyl group (resulting in C6H5OD), indicating that phenol readily undergoes hydrogen-exchange reactions with water. Heavy water is water which contains a higher proportion than normal of the Isotope Deuterium, as deuterium oxide, D2O or ²H2O Hydroxyl in Chemistry stands for a molecule consisting of an Oxygen atom and a Hydrogen atom connected by a Covalent bond. Only the hydroxyl group was affected, indicating that the other 5 hydrogen atoms did not participate in these exchange reactions.
Radioisotopic labelling is a technique for tracking the passage of a sample of substance through a system. The substance is "labelled" by including radionuclides in its chemical composition. A radionuclide is an Atom with an unstable nucleus, which is a nucleus characterized by excess energy which is available to be imparted either to a newly-created When these decay, their presence can be determined by detecting the radiation they emit. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. Particle radiation is the radiation of Energy by means of fast-moving Subatomic particles. Radioisotopic labelling is a special case of isotopic labeling.
For these purposes, a particularly useful type of radioactive decay is positron emission. Positron emission is a type of Beta decay, sometimes referred to as " beta plus " (&beta+ When a positron collides with an electron, it releases two high-energy photons traveling in diametrically opposite directions. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena If the positron is produced within a solid object, it is likely to do this before travelling more than a millimetre. The Millimetre ( American spelling: millimeter, symbol mm) is a unit of Length in the Metric system, equal to If both of these photons can be detected, the location of the decay event can be determined very precisely.
Strictly speaking, radiosotopic labelling includes only cases where radioactivity is artificially introduced by experimenters, but some natural phenomena allow similar analysis to be performed. In particular, radiometric dating uses a closely related principle. Radiometric dating (often called radioactive dating) is a technique used to date materials usually based on a comparison between the observed abundance of a naturally occurring
An isotopic tracer, (also "isotopic marker" or "isotopic label"), is used in chemistry and biochemistry to help understand chemical reactions and interactions. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called In this technique, one or more of the atoms of the molecule of interest is substituted for an atom of the same chemical element, but of a different (often radioactive, such as in radioactive tracing) isotope. History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. A radioactive tracer, also called a radioactive label, is a substance containing a Radioisotope (which is an isotope that has an unstable nucleus and that stabalizes Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides Because the atom has the same number of protons, it will behave in almost exactly the same way chemically as other atoms in the compound, and with few exceptions will not interfere with the reaction under investigation. The difference in the number of neutrons, however, means that it can be detected separately from the other atoms of the same element. This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron.
NMR typically uses this type of technique to investigate the mechanisms of chemical reactions (basically trying to find out which starting atom ends up where after a reaction), because NMR detects not only isotopic differences, but also gives an indication of the position of the atom.
Mass spectrometry can also be used with this technique, since mass spectra recorded with sufficiently high resolution can distinguish among isotopes based on the different masses resulting from the different number of neutrons. Mass spectrometry is an analytical technique that identifies the chemical composition of a compound or sample based on the Mass-to-charge ratio of charged particles
Autoradiographs of gels in gel electrophoresis can also take advantage of this approach. An autoradiograph is an image on an X-ray film or nuclear emulsion produced by the pattern of decay emissions (e In this technique, radioactive isotopes are used. The radiation emitted by compounds containing the radioactive isotopes darkens a piece of photographic film, recording the position of these compounds relative to one another in the gel. This article is mainly concerned with Still photography film For Motion picture film please see Film stock.
Isotopic (isotope) tracers are some of the most important tools in geology, because they can be used to understand complex mixing process in earth systems. Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit Isotope tracers are almost always used in the form of isotope ratios. By studying the ratio between two isotopes of the same element, we avoid effects involving the overall abundance of the element, which would usually swamp the much smaller variations in isotopic abundances. Further discussion of the application of isotopic tracers in geology is covered under the heading of isotope geochemistry. Isotope geochemistry is an aspect of Geology based upon study of the relative and absolute concentrations of the elements and their Isotopes in the
Isotopic tracers are usually subdivided into two categories: radiogenic isotope tracers and stable isotope tracers. A radiogenic Nuclide is one that is produced by a process of Radioactive decay. Stable isotopes are chemical isotopes that are not Radioactive (to current knowledge A radiogenic isotope tracer  involves an isotope produced by radioactive decay, which is usually ratioed against a non-radiogenic isotope (whose abundance in the earth does not vary due to radioactive decay). Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation.
A stable isotope tracer involves only non-radiogenic isotopes. In this case, relative variations in abundance between the two isotopes is most often caused by mass-dependant fractionation. In theory, any element with two stable isotopes can be used as an isotopic tracer. However, the most commonly used stable isotope tracers involve relatively light isotopes which readily undergo fractionation in natural systems. See also isotopic signature. An isotopic signature (also isotopic fingerprint) is a ratio of stable or unstable Isotopes of particular elements found in an investigated material