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About Isotopes

Isotopes are variants of chemical elements: while all isotopes of a given element contain the same number of protons, they vary in the number of neutrons they contain. Variation in neutron number produces chemically identical atoms with different masses, which can be exploited to allow tracing of specific individual atoms through a system.

Stable isotopes

Stable isotopes are generally defined as non-radioactive isotopic elements that do not decay over time. Radioactive isotopes may also be classified as stable isotopes when their half-lives are too long to be measured. These elements can often be found to occur in nature and include isotopes of carbon, nitrogen, hydrogen, oxygen, noble gases and metals. For example, three naturally occurring isotopes of hydrogen include protium (H) having one neutron, deuterium (2H) having two neutrons, and tritium having three neutrons.

Isotopically labeled compounds

Isotopically labelled compounds are compounds that incorporate isotopic elements within their molecular structure and are thus ‘labelled’ by the isotope. These compounds are used to study chemical and biochemical reactions, metabolic pathways or cellular transport. Specifically, isotope-labelled compounds are routinely used for a variety of applications including magnetic resonance imaging (MRI), spectroscopy, nuclear magnetic resonance (NMR), and geochemical analyses. An example of using an isotopic label includes replacing the most common isotope of hydrogen, protium, with deuterium to observe hydrogen exchange reactions in water.

Isotope separation methods

Distillation and Diffusion Processes

Distillation or diffusion are processes which are for enrichment used when there are relatively large mass differences between different isotopes of an element.

Centrifuge enrichment

Centrifuge processes for enrichment includes gas centrifugation and improvements upon the gas centrifuge techniques. This process involves rotating cylinders in order to move the heavier gas molecules containing a given isotope to the outer radius of the cylinder while collecting the lighter gas molecules containing the given isotope in the center of the cylinder.

Electromagnetic enrichment

Electromagnetic isotope separation processes involves first vaporizing the isotope containing molecules followed by ionizing the vapor with positively charged ions. A mass spectrometer, known as the Calutron, is then used to redirect a stream of cations onto a target for collection.

Other methods: laser enrichment, photochemical enrichment and plasma separation

Laser enrichment processes provide for lower energy inputs and thus more economical enrichment. One method currently under investigation is known as the Separation of Isotopes by Laser Excitiation (SILEX). Another laser method that is used to enrich uranium containing the 235U atom is known as molecular laser isotope separation (MLIS) which involves using infrared laser at UF6 molecules and a second laser to free a fluorine atom resulting in precipitation of the remaining UF5 compound out of the gas.

Plasma separation involves the principle of ion cyclotron resonance and uses superconducting magnets to energize a given isotope in plasma consisting of an ionic mixture.



Metabolic studies

Biochemical markers and probes are used to research the uptake of compounds by the body. For example, nutritional studies are commonly performed using isotopic labeled compounds.

Brain and kidney function

Studies of brain and kidney function are performed by tracing isotopes throughout these organs for both diagnostics and treatment applications.


Precursors for therapeutic radioisotopes or radiation therapy are used for a variety of therapies. For example, neuroendocrine tumors are treated by radiotherapy using hormone bound lutetium-177 and yttrium-90.

Clinical pharmacology

Tracing drug metabolism requires the use of isotopes bound to drug in order to understand the processing of the given pharmaceutical by the body.



A wide range of biochemical processes can be studied using stable isotopes. For example, a technique known as stable isotope labeling by amino acids in cell culture (SILAC) is used in proteomics research to help identify disease biomarkers.


The use of isotope labeling allows chemists to study the mechanisms of chemical reactions, as individual atoms can be followed through a system.

Environmental science

Isotopes are valuable for studying release and spread of pollutants in the environment.


The tracing of isotope movement, either within a local system such as an estuary or on a global scale, can allow study of circulation patterns.


Various compounds labeled with nitrogen-15 are used in the study of processes such as plant metabolism and fertilizer uptake.

Isotope Products

Isotopic metals and compounds are available in a variety of forms and enrichment levels. Compounds include stable isotopes containing carbon, nitrogen, deuterium, noble gases, and metals such as oxides, sulfates, carbonates and more. Additionally, we can produce custom syntheses according to customer needs and specifications for research and development.

Recent Research & Development for Isotopes

  • Stable isotopes and iron oxide mineral products as markers of chemodenitrification. L Camille Jones, Brian Peters, Juan S. Lezama Pacheco, Karen Casciotti, and Scott Fendorf. Environ. Sci. Technol.: February 16, 2015
  • Muonium Addition Reactions and Kinetic Isotope Effects in the Gas Phase: k Rate Constants for Mu+C2H2. Donald J. Arseneau, David M. Garner, Ivan D. Reid, and Donald George Fleming. J. Phys. Chem. A: February 9, 2015
  • H2O-Involved Two-Electron Pathway for Photooxidation of Aldehydes on TiO2: An Isotope Labeling Study. Tao Shi, Wei Chang, Hongna Zhang, Hongwei Ji, Wanhong Ma, Chuncheng Chen, and Jincai Zhao. Environ. Sci. Technol.: February 3, 2015
  • Development and Validation of an Universal Interface for Compound-Specific Stable Isotope Analysis of Chlorine (37Cl/35Cl) by GC-High-Temperature Conversion (HTC)-MS/IRMS. Julian Renpenning, Kristina L. Hitzfeld, Tetyana Gilevska, Ivonne Nijenhuis, Matthias Gehre, and Hans-Hermann Richnow. Anal. Chem.: February 3, 2015
  • Metal Stable Isotope Signatures as Tracers in Environmental Geochemistry. Jan G. Wiederhold. Environ. Sci. Technol.: February 2, 2015
  • A Stable Isotope Approach to Assessing Water Loss in Fruits and Vegetables during Storage. Markus Greule, Andreas Rossmann, Hanns-Ludwig Schmidt, Armin Mosandl, and Frank Keppler. J. Agric. Food Chem.: January 31, 2015
  • Hydrogen Isotope Effects in Ti–V–Cr Alloy Hydrides. Yongbin Yang, Deli Luo, Wensheng Guo, and Xiaoqiu Ye. J. Phys. Chem. C: January 30, 2015
  • Compound-Specific Carbon, Nitrogen, and Hydrogen Isotope Analysis of N-Nitrosodimethylamine in Aqueous Solutions. Stephanie Spahr, Jakov Bolotin, Jürgen Schleucher, Ina Ehlers, Urs von Gunten, and Thomas B. Hofstetter. Anal. Chem.: January 26, 2015
  • Nitrogen Stable Isotope Composition (?15N) of Vehicle-Emitted NOx. Wendell W. Walters, Stanford R. Goodwin, and Greg Michalski. Environ. Sci. Technol.: January 26, 2015
  • Simplified Method for Quantifying Sulfur Mustard Adducts to Blood Proteins by Ultrahigh Pressure Liquid Chromatography–Isotope Dilution Tandem Mass Spectrometry. Brooke G. Pantazides, Brian S. Crow, Joshua W. Garton, Jennifer A. Quiñones-González, Thomas A. Blake, Jerry D. Thomas, and Rudolph C. Johnson. Chem. Res. Toxicol.: January 15, 2015
  • The Challenge of Studying TiO2 Nanoparticle Bioaccumulation at Environmental Concentrations: Crucial Use of a Stable Isotope Tracer. Adeline Bourgeault, Cécile Cousin, Valérie Geertsen, Corinne Cassier-Chauvat, Franck Chauvat, Olivier Durupthy, Corinne Chanéac, and Olivier Spalla. Environ. Sci. Technol.: January 14, 2015