Unsealed tracers

Feasibility review

Carbon-14 for research

The label that sits in a molecule's carbon backbone, for following carbon through cells, animals, plants and soil.

Half-life
5,700 years
Beta max
156.5 keV
Decay
Beta minus to N-14
Exempt quantity
100 µCi
Request a C-14 feasibility review

Request a feasibility review for C-14

No license file needed to ask. A scientist reads every request and replies with the next step.

How ordering works
C-14 at a glanceIAEA evaluated data
aSIMULATED BETA SPECTRUM050100150200Energy (keV)Electrons per keVEndpoint 156.5 keVMean 49.47 keVb05,00010,000050100Time (years)Activity (%)T½ 5,700 y
a Energy of the emitted beta particles, calculated from the IAEA endpoint energy; dashed line: mean energy. b Activity left after the reference date. Data: IAEA [1]

Research applications

Where C-14 does the work.

Figures are simulated examples of each measurement.

  • aSIMULATED0481216Exposure to ¹⁴CO₂ (s)050100Share of fixed ¹⁴C (%)phosphoglyceratesugar phosphates

    Plant biology

    The path of carbon in photosynthesis2, 3

    Seconds-long exposures to ¹⁴CO₂ showed which compound carbon enters first.

    More: The path of carbon in photosynthesis

    Algae and leaves were given ¹⁴CO₂ for 0.4 to 15 seconds. At the shortest times most of the fixed label was in 3-phosphoglyceric acid; it then moved into sugar phosphates, which mapped the Calvin-Benson cycle.

  • bSIMULATED0200400600Light (µmol photons m⁻² s⁻¹)024mg C (mg Chl a)⁻¹ h⁻¹EkPmax

    Oceanography and limnology

    Primary production4, 5, 6

    A trace of ¹⁴C measures how fast the algae in a water sample fix carbon.

    More: Primary production

    Samples incubate for 1.5 to 4 hours across a range of light, and the fixed ¹⁴C is counted.

    Rate against light gives the photosynthesis-irradiance curve, fit with a hyperbolic tangent. Across 5,711 marine experiments, the mean light-saturated rate was 3.11 mg of carbon per mg of chlorophyll a per hour.

  • cSIMULATED0306090120Days050100% of applied ¹⁴Cmass balanceparent¹⁴CO₂boundmetabolites

    Environmental science

    Fate of chemicals in soil7

    A ¹⁴C-labeled test chemical shows how fast it breaks down in soil and where its carbon ends up.

    More: Fate of chemicals in soil

    Under OECD Test Guideline 307, traps catch the ¹⁴CO₂ released as the chemical mineralizes, and combustion measures the residue bound to soil. Studies run for up to 120 days.

    At every sampling, 90 to 110 percent of the applied radioactivity must be accounted for.

  • dSIMULATED024487296120144168Hours after dosing050100Recovered (% of dose)90% of doseurine + fecesurine

    Drug metabolism

    Mass balance and distribution in rats8, 9, 10, 11

    A ¹⁴C-labeled drug candidate accounts for all drug-related material in excreta and tissues.

    More: Mass balance and distribution in rats

    Urine and feces are collected for up to 7 days, or until at least 90 percent of the dose is recovered. In one rat study, 91.6 percent was recovered within 48 hours.

    Quantitative whole-body autoradiography images where the radioactivity goes throughout the body.

    The label sits at a metabolically stable carbon. Each labeled carbon gives at most about 62 mCi/mmol.

  • eSIMULATED060120180Minutes¹⁴CO₂ released[1-¹⁴C]palmitate+ glucose

    Cell metabolism

    Substrate oxidation12, 13

    Cells given [¹⁴C]palmitate or [¹⁴C]glucose release ¹⁴CO₂, a direct measure of how fast they burn each fuel.

    More: Substrate oxidation

    Acid stops the reaction, and a paper soaked in base traps the ¹⁴CO₂ for counting.

    In cultured heart cells, palmitate oxidation rose linearly with time, and adding glucose cut it by half.

  • fSIMULATED123Figure of merit (keV/photoelectron)050100Efficiency (%)H-3C-14more quench →

    Radioactivity counting

    Liquid scintillation counting14, 15

    Unquenched carbon-14 counts at about 94 percent efficiency in scintillation cocktail.

    More: Liquid scintillation counting

    Quench lowers the efficiency and shifts counts to lower energy, so labs correct each sample with a quench curve. Tritium, at about 65 percent unquenched, is far more sensitive to quench.

    Ethanolamine traps collect ¹⁴CO₂ for counting.

Forms

C-14 forms researchers ask for

Every form is confirmed with its manufacturer before you order.

  • Labeled compound

    A sugar, fatty acid, amino acid or drug candidate labeled with carbon-14, in solution

    Tracing, metabolism and fate studies

    Feasibility review

  • Labeled bicarbonate

    Sodium [¹⁴C]bicarbonate in aqueous solution

    Photosynthesis and primary production

    Feasibility review

  • Custom labeling

    Carbon-14 labeling of a compound you supply or specify, at a stable position

    Mass balance, metabolism and soil fate studies

    Feasibility review

  • Counting standard

    Sealed carbon-14 standard in a scintillation vial

    Counter efficiency and quench checks

    Feasibility review

Activity, certificate and lead time are set with the manufacturer at quote.

Before you order

Plan for decay and licensing.

Plan around decay

C-14 has a half-life of 5,700 years. Ask for the activity you need on the day you start using it.

Activity remaining after
  1. 1 year100%
  2. 5 years99.9%
  3. 10 years99.9%
  4. 20 years99.8%

Licensing

Exempt quantityNeeds a license100 µCi
Activity of one vial, log scale

A single quantity of C-14 at or below 100 µCi is an exempt quantity under 10 CFR 30.71, Schedule B. Above that, your institution needs a license that covers it.

  • Combining exempt quantities to exceed the limit is not covered.
  • Carbon-14 betas travel about 24 cm in air and 0.3 mm in water, so millicurie amounts need no shielding. The hazard is intake, and many carbon-14 compounds pass through gloves and skin.
  • Liquid scintillation counting is the best readily available way to count carbon-14 wipe tests.
  • Agreement States apply equivalent rules. Your RSO reviews the exact material before you order.

Sources: 16, 17, 18

Start a request

Request a feasibility review for C-14.

No license file needed to ask. A scientist reads every request and replies with the next step.

  1. Name the labeled carbonSay which position carries the label, and the specific activity you need.
  2. Plan the countingConfirm the cocktail, counter and any CO₂ traps for your samples.
  3. Agree the waste routeCarbon-14 waste is long-lived, so settle disposal with your RSO first.
  1. 01Need
  2. 02Details
  3. 03Contact
Where are you starting?

You get Feasibility reply and a candidate supplier path

Decay data

C-14 decay data

Decay schemeC-14 to N-14
14C5,700 yQ 156.476 keV14N0β− 100%
Energies in keV, with emission probability per decay. Levels not to scale. Data: IAEA [1]
Half-life
5,700 years ± 30
Decay mode
Beta minus (100%)
Daughter
N-14
Decay energy (Q)
156.476 keV
C-14 emissions
RadiationEnergy (keV)Per 100 decays
Beta156.5 max, 49.5 mean100

Source: IAEA LiveChart of Nuclides, ENSDF evaluation by F. AJZENBERG-SELOVE (literature cutoff 1 July 1990), retrieved 25 September 2026 [1]. Reference values; a manufacturer's certificate states the activity of a specific lot.

Questions, answered

C-14 questions

How long does carbon-14 last?

Its half-life is 5,700 years, so its activity is effectively constant during any experiment. The same half-life keeps its waste radioactive for thousands of years.

Can we buy carbon-14 without a radioactive materials license?

For small amounts, possibly. A single quantity of C-14 at or below 100 microcuries is an exempt quantity under 10 CFR 30.71, and a distributor licensed under 10 CFR 32.18 can supply exempt quantities to users without a license. Larger amounts need a license that covers them. Your RSO decides how your institution handles each case.

What specific activity can carbon-14 give?

At most about 62 mCi/mmol (2.31 GBq/mmol) for each labeled carbon. Animal mass balance, whole-body autoradiography and agrochemical studies usually use material above 1.9 GBq/mmol.

Why do metabolism and soil studies use carbon-14?

A label on a stable carbon stays with the compound and its metabolites, so every product can be counted. Test guidelines ask for carbon-14 in mass balance and soil transformation studies.

Does carbon-14 need shielding?

Not for millicurie amounts: its betas travel about 24 cm in air and 0.3 mm in water. The hazard is intake, so avoid skin contact, ingestion and inhalation.

What should we tell you about the compound?

The molecule, which carbon carries the label, the specific activity and the amount. We confirm a matching product and certificate with the manufacturer before you order.

More isotopes

  • Phosphorus-32 for research

    P-32 · Half-life 14.27 days

    An energetic beta label for DNA and RNA probes, kinase assays and gel shift experiments.

  • Tritium (H-3) for research

    H-3 · Half-life 12.32 years

    A low-energy beta label that leaves a molecule almost unchanged, for binding, cell and metabolism studies.

  • Iodine-125 for research

    I-125 · Half-life 59.41 days

    A high specific activity label for proteins, peptides and receptor ligands, counted in a gamma counter.

  • Sulfur-35 for research

    S-35 · Half-life 87.37 days

    The label for newly made proteins, G protein activation and sharp autoradiographs.

  • Americium-241 for research

    Am-241 · Half-life 432.6 years

    Alpha particles near 5.49 MeV and a 59.5 keV gamma ray, from one long-lived source.

  • Barium-133 for research

    Ba-133 · Half-life 10.55 years

    Gamma lines from 81 to 384 keV and cesium X-rays near 31 keV: a standard for low- and mid-energy calibration.

Sources

References

  1. IAEA Nuclear Data Section. LiveChart of Nuclides, C-14 decay data (ENSDF evaluation). Retrieved 25 September 2026. www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html
  2. Bassham JA, Benson AA, Kay LD, Harris AZ, Wilson AT, Calvin M. The path of carbon in photosynthesis. XXI. The cyclic regeneration of carbon dioxide acceptor. Report UCRL-2369. Berkeley: University of California Radiation Laboratory; 1953. Published in J Am Chem Soc. 1954;76(7):1760-1770. doi.org/10.2172/915417
  3. Calvin M. The path of carbon in photosynthesis. Nobel Lecture, 11 December 1961. www.nobelprize.org/uploads/2017/03/calvin-lecture.pdf
  4. Steemann Nielsen E. The use of radio-active carbon (C14) for measuring organic production in the sea. J Cons Int Explor Mer. 1952;18(2):117-140. doi.org/10.1093/icesjms/18.2.117
  5. Jassby AD, Platt T. Mathematical formulation of the relationship between photosynthesis and light for phytoplankton. Limnol Oceanogr. 1976;21(4):540-547. doi.org/10.4319/lo.1976.21.4.0540
  6. Bouman HA, Platt T, Doblin M, et al. Photosynthesis-irradiance parameters of marine phytoplankton: synthesis of a global data set. Earth Syst Sci Data. 2018;10(1):251-266. doi.org/10.5194/essd-10-251-2018
  7. OECD. Test No. 307: Aerobic and anaerobic transformation in soil. OECD Guidelines for the Testing of Chemicals, Section 3. Paris: OECD Publishing; 2002, corrected 2025. doi.org/10.1787/9789264070509-en
  8. OECD. Test No. 417: Toxicokinetics. OECD Guidelines for the Testing of Chemicals, Section 4. Paris: OECD Publishing; 2010. doi.org/10.1787/9789264070882-en
  9. Yang C, Xue M, He Y, et al. Absorption, distribution, metabolism, and excretion of [14C]BS1801, a selenium-containing drug candidate, in rats. Molecules. 2023;28(24):8102. doi.org/10.3390/molecules28248102
  10. Solon EG. Autoradiography techniques and quantification of drug distribution. Cell Tissue Res. 2015;360(1):87-107. doi.org/10.1007/s00441-014-2093-4
  11. Babin V, Taran F, Audisio D. Late-stage carbon-14 labeling and isotope exchange: emerging opportunities and future challenges. JACS Au. 2022;2(6):1234-1251. doi.org/10.1021/jacsau.2c00030
  12. Huynh FK, Green MF, Koves TR, Hirschey MD. Measurement of fatty acid oxidation rates in animal tissues and cell lines. Methods Enzymol. 2014;542:391-405. doi.org/10.1016/B978-0-12-416618-9.00020-0
  13. Rosenthal MD, Warshaw JB. Interaction of fatty acid and glucose oxidation by cultured heart cells. J Cell Biol. 1973;58(2):332-339. doi.org/10.1083/jcb.58.2.332
  14. US Environmental Protection Agency, Nuclear Regulatory Commission and other federal agencies. Multi-Agency Radiological Laboratory Analytical Protocols Manual (MARLAP), Volume II, Chapter 15: Quantification of radionuclides. NUREG-1576, EPA 402-B-04-001B; 2004. www.epa.gov/sites/default/files/2015-05/documents/402-b-04-001b-15-final.pdf
  15. Zimmerman BE, Collé R. Standardization of 63Ni by 4πβ liquid scintillation spectrometry with 3H-standard efficiency tracing. J Res Natl Inst Stand Technol. 1997;102(4):455-477. doi.org/10.6028/jres.102.031
  16. U.S. Nuclear Regulatory Commission. 10 CFR 30.71, Schedule B (exempt quantities). eCFR, current as of 23 September 2026. www.ecfr.gov/current/title-10/section-30.71
  17. U.S. Nuclear Regulatory Commission. 10 CFR 30.18, Exempt quantities. eCFR, current as of 23 September 2026. www.ecfr.gov/current/title-10/section-30.18
  18. Emory University Environmental Health and Safety Office. Nuclide safety data sheet: carbon-14. ehso.emory.edu/sso/documents/content-guidelines/nuclide-data-safety-sheets.pdf

Technical review by ConductScience, 25 September 2026. Next review 25 September 2027.

Need C-14 for a specific instrument or measurement?

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