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

Aluminum Oxide-18O3 Antimony 121 Metal Isotope Antimony 123 Metal Isotope
Barium Carbonate-13C Barium-135 Carbonate Isotope Barium-136 Carbonate Isotope
Barium-137 Carbonate Isotope Barium-138 Carbonate Isotope Boric 11 Acid Isotope
Boric Acid 10-B Boron-10 Carbide Isotope Boron-10 Isotope
Boron-10 Oxide Isotope Boron-10 Trifluoride Isotope Boron-10B Trifluoride Diethyl Etherate
Boron-11 Carbide Isotope Boron-11 Isotope Boron-11 Oxide Isotope
Boron-11 Trifluoride Isotope Cadmium-106 Metal Isotope Cadmium-106 Oxide Isotope
Cadmium-108 Metal Isotope Cadmium-108 Oxide Isotope Cadmium-110 Oxide Isotope
Cadmium-111 Chloride Isotope Cadmium-111 Oxide Isotope Cadmium-112 Metal Isotope
Cadmium-112 Oxide Isotope Cadmium-113 Chloride Isotope Cadmium-113 Metal Isotope
Cadmium-113 Oxide Isotope Cadmium-114 Oxide Isotope Cadmium-116 Oxide Isotope
Calcium-40 Carbonate Isotope Calcium-42 Carbonate Isotope Calcium-43 Carbonate Isotope
Calcium-44 Carbonate Isotope Calcium-44 Chloride Isotope Calcium-44 Metal Isotope
Calcium-46 Carbonate Isotope Chromium-50 Oxide Isotope Chromium-52 Oxide Isotope
Chromium-53 Metal Isotope Chromium-53 Oxide Isotope Chromium-54 Oxide Isotope
Copper-63 Metal Isotope Copper-63 Oxide Isotope Copper-65 Metal Isotope
Copper-65 Oxide Isotope Dysprosium-160 Oxide Isotope Dysprosium-161 Oxide Isotope
Dysprosium-162 Oxide Isotope Dysprosium-164 Oxide Isotope Erbium-162 Oxide Isotope
Erbium-166 Oxide Isotope Erbium-168 Oxide Isotope Erbium-170 Oxide Isotope
Europium-151 Oxide Gadolinium-155 Oxide Isotope Gadolinium-156 Oxide Isotope
Gadolinium-158 Oxide Isotope Gadolinium-160 Oxide Isotope Gallium-69 Metal Isotope
Gallium-71 Sesquioxide Isotope Hafnium-180 Oxide Isotope Indium-113 Metal Isotope
Indium-113 Oxide Isotope Iridium-191 Metal Isotope Iridium-193 Metal Isotope
Iron-54 Metal Isotope Iron-54 Oxide Isotope Iron-56 Metal Isotope
Iron-57 Chloride Iron-57 Metal Isotope Iron-57 Oxide Isotope
Iron-58 Metal Isotope Iron-58 Oxide Isotope Lead 204 Carbonate Isotope
Lead 204 Metal Isotope Lead 206 Carbonate Isotope Lead 206 Metal Isotope
Lead 206 Oxide Isotope Lead 207 Carbonate Isotope Lead 207 Metal Isotope
Lead 207 Nitrate Isotope Lead 207 Oxide Isotope Lead 207 Sulfate Isotope
Lead 208 Carbonate Isotope Lead 208 Metal Isotope Lithium-6 Carbonate Isotope
Lithium-6 Chloride Lithium-6 Deuteroxide Deuterate Lithium-6 Fluoride
Lithium-6 Hydroxide Monohydrate Lithium-6 Metal Isotope Lithium-6 Oxide
Lithium-6 Sulfate Lithium-7 Carbonate Lithium-7 Fluoride
Lithium-7 Hydroxide Monohydrate Lithium-7 Metal Isotope Lithium-7 Oxide
Lutetium-176 Oxide Isotope Magnesium-24 Metal Isotope Magnesium-24 Oxide Isotope
Magnesium-25 Metal Isotope Magnesium-25 Oxide Isotope Magnesium-26 Metal Isotope
Magnesium-26 Oxide Isotope Mercury-202 Metal Isotope Molybdenum-100 Metal Isotope
Molybdenum-94 Trioxide Isotope Molybdenum-95 Metal Isotope Molybdenum-95 Trioxide Isotope
Molybdenum-96 Trioxide Isotope Molybdenum-97 Metal Isotope Molybdenum-97 Trioxide Isotope
Molybdenum-98 Trioxide Isotope Neodymium 145 Oxide Isotope Neodymium 150 Oxide Isotope
Nickel 58 Metal Isotope Nickel 60 Metal Isotope Nickel 61 Metal Isotope
Nickel 62 Metal Isotope Nickel 64 Metal Isotope Osmium 187 Metal Isotope
Osmium 188 Metal Isotope Palladium 102 Metal Isotope Palladium 104 Metal Isotope
Palladium 105 Metal Isotope Palladium 108 Metal Isotope Platinum 194 Metal Isotope
Platinum 196 Metal Isotope Platinum 198 Metal Isotope Potassium 40 Chloride Isotope
Potassium 41 Chloride Isotope Potassium Cyanoborodeuteride Potassium Dideuterium Phosphate
Rhenium 185 Metal Isotope Rubidium-85 Chloride Isotope Rubidium-87 Chloride Isotope
Ruthenium 100 Metal Isotope Ruthenium 101 Metal Isotope Ruthenium 104 Metal Isotope
Ruthenium 99 Metal Isotope Samarium 144 Oxide Isotope Samarium 152 Oxide Isotope
Samarium 154 Oxide Isotope Selenium 74 Isotope Selenium 76 Isotope
Selenium 77 Isotope Selenium 78 Isotope Selenium 82 Isotope
Silicon 28 Dioxide Isotope Silicon 29 Dioxide Isotope Silicon 29 Isotope
Silicon 30 Dioxide Isotope Silver 107 Metal Isotope Silver 109 Metal Isotope
Silver Cyanide- 13C,15N Sodium Chloride-35Cl Isotope Sodium Cyanoborodeuteride
Sodium Deuteroxide Solution Sodium Dideuterium Phosphate Sodium-79 Bromide Isotope
Sodium-81 Bromide Isotope Strontium 86 Carbonate Isotope Strontium 87 Carbonate Isotope
Strontium 88 Carbonate Isotope Sulfur-33 Isotope Sulfur-34 Isotope
Tellurium 122 Isotope Tellurium 123 Isotope Tellurium 124 Isotope
Tellurium 125 Isotope Tellurium 126 Isotope Thallic 203 Oxide Isotope
Tin 112 Metal Isotope Tin 116 Metal Isotope Tin 117 Metal Isotope
Tin 118 Metal Isotope Tin 119 Metal Isotope Tin 119 Oxide Isotope
Titanium 49 Oxide Isotope Tungsten 182 Metal Isotope Tungsten 182 Trioxide Isotope
Tungsten 183 Metal Isotope Tungsten 184 Trioxide Isotope Tungsten 186 Trioxide Isotope
Ytterbium 171 Oxide Isotope Ytterbium 172 Oxide Isotope Ytterbium 174 Oxide Isotope
Ytterbium 176 Oxide Isotope Zinc 64 Oxide Isotope Zinc 66 Metal Isotope
Zinc 66 Oxide Isotope Zinc 67 Metal Isotope Zinc 67 Oxide Isotope
Zinc 68 Metal Isotope Zinc 68 Oxide Isotope Zinc 70 Metal Isotope
Zinc 70 Oxide Isotope Zirconium 90 Metal Isotope Zirconium 91 Oxide Isotope

Recent Research & Development for Isotopes

Determination of Osmium Concentration and Isotope Composition at Ultra-low Level in Polar Ice and Snow., Seo, Ji-Hye, Sharma Mukul, Osterberg Erich C., and Jackson Brian P. , Anal Chem, 2018 May 01, Volume 90, Issue 9, p.5781-5787, (2018)

Mesoproterozoic juvenile crust in microcontinents of the Central Asian Orogenic Belt: evidence from oxygen and hafnium isotopes in zircon., He, Zhen-Yu, Klemd Reiner, Yan Li-Li, Lu Tian-Yu, and Zhang Ze-Ming , Sci Rep, 2018 Mar 22, Volume 8, Issue 1, p.5054, (2018)

Metallome evolution in ageing C. elegans and a copper stable isotope perspective., Sauzéat, Lucie, Laurençon Anne, and Balter Vincent , Metallomics, 2018 Mar 14, (2018)

Selective internal radiation therapy (SIRT) with yttrium-90 microspheres for unresectable intrahepatic cholangiocarcinoma., Abeysinghe, Vindya, Sundararajan Siva, Delriviere Luc, and Tibballs Jonathan , BMJ Case Rep, 2018 Mar 09, Volume 2018, (2018)

Precision Mass Measurements of Neutron-Rich Neodymium and Samarium Isotopes and Their Role in Understanding Rare-Earth Peak Formation., Orford, R, Vassh N, Clark J A., McLaughlin G C., Mumpower M R., Savard G, Surman R, Aprahamian A, Buchinger F, Burkey M T., et al. , Phys Rev Lett, 2018 Jun 29, Volume 120, Issue 26, p.262702, (2018)

Thallium isotopes reveal protracted anoxia during the Toarcian (Early Jurassic) associated with volcanism, carbon burial, and mass extinction., Them, Theodore R., Gill Benjamin C., Caruthers Andrew H., Gerhardt Angela M., Gröcke Darren R., Lyons Timothy W., Marroquín Selva M., Nielsen Sune G., Alexandre João P. Trabucho, and Owens Jeremy D. , Proc Natl Acad Sci U S A, 2018 Jun 11, (2018)

Radioactive and stable cesium isotope distributions and dynamics in Japanese cedar forests., Yoschenko, Vasyl, Takase Tsugiko, Hinton Thomas G., Nanba Kenji, Onda Yuichi, Konoplev Alexei, Goto Azusa, Yokoyama Aya, and Keitoku Koji , J Environ Radioact, 2018 Jun, Volume 186, p.34-44, (2018)

Minimal starting time of data reconstruction for qualitative myocardial perfusion rubidium-82 positron emission tomography imaging., van Dijk, Joris D., Huizing Eline D., van Dalen Jorn A., Timmer Jorik R., and Jager Pieter L. , Nucl Med Commun, 2018 Jun, Volume 39, Issue 6, p.533-538, (2018)

Strontium carbonate precipitation as a sample preparation technique for isotope ratio analysis of Sr in mineral water and wine by quadrupole-based inductively coupled plasma mass spectrometry., Dronov, Michail, Koza Tim, Schwiers Alexander, Schmidt Torsten C., and Schram Jürgen , Rapid Commun Mass Spectrom, 2018 Jan 30, Volume 32, Issue 2, p.149-158, (2018)

Application of 1013 ohm Faraday cup current amplifiers for boron isotopic analyses by solution mode and laser ablation multicollector inductively coupled plasma mass spectrometry., Lloyd, Nicholas S., Sadekov Aleksey Yu, and Misra Sambuddha , Rapid Commun Mass Spectrom, 2018 Jan 15, Volume 32, Issue 1, p.9-18, (2018)

Stable isotope fractionation of strontium in coccolithophore calcite: Influence of temperature and carbonate chemistry., Müller, M N., Krabbenhöft A, Vollstaedt H, Brandini F P., and Eisenhauer A , Geobiology, 2018 Feb 12, (2018)

Barium isotope fractionation during the experimental transformation of aragonite to witherite and of gypsum to barite, and the effect of ion (de)solvation., Böttcher, Michael E., Neubert Nadja, von Allmen Katja, Samankassou Elias, and Nägler Thomas F. , Isotopes Environ Health Stud, 2018 Feb 05, p.1-12, (2018)

Determination of the Heart-to-Mediastinum Ratio of 123I-MIBG Uptake Using Dual-Isotope (123I-MIBG/99mTc-Tetrofosmin) Multipinhole Cadmium-Zinc-Telluride SPECT in Patients with Heart Failure., Blaire, Tanguy, Bailliez Alban, Ben Bouallegue Fayçal, Bellevre Dimitri, Agostini Denis, and Manrique Alain , J Nucl Med, 2018 Feb, Volume 59, Issue 2, p.251-258, (2018)

Iodine isotopes (I and I) in the hydrosphere of Qinghai-Tibet region and South China Sea., Yi, Peng, Chen Xuegao, Wang Zixia, Aldahan Ala, Hou Xiaolin, and Yu Zhongbo , J Environ Radioact, 2018 Dec, Volume 192, p.86-94, (2018)