When choosing radiolabeled compounds you have many options; tritium, deuterium, carbon 13, nitrogen 15 and carbon 14. For many reasons, carbon 14 is one of the most popular choices in radiolabeling. With an impressive half-life of >5000 years, as compared to tritium’s half life of 12.5 years, carbon 14 has a low energy and is easy to detect with beta emissions.
Carbon 14 Production
Need for c14 radiolabeling, it’s important to understand carbon 14 production. As opposed to carbon 12, which has a 6 to 6 ratio of protons and neutrons, carbon 14 contains six protons and eight neutrons. This imbalance is what gives carbon 14 it’s impressive half-life and makes it an emitter of beta particles.
In nature, carbon 14 production is in constant regeneration as cosmic rays interact with the atmosphere. This interaction rate has gone relatively unchanged for centuries and is dependent on the fluctuations of particles impacting the earth as the magnetic field deflects them. As these particles fluctuate, the quantity of natural carbon 14 production on earth fluctuates as well.
The Stages of Carbon 14 Production
As cosmic rays impact earth they create the atoms of carbon 14 by colliding with nuclei found in the upper atmosphere. The neutrons that are freed during this collision then interact with the nuclei of nitrogen in the surrounding air, replacing one of the 7 nitrogen protons. The result is now an atom containing six protons and eight neutrons, — carbon 14.
The Carbon gases that are formed alongside carbon 14 production are indistinguishable from other gases with carbon 12. The atoms are able to be absorbed into living matter the same as any other non-radioactive isotope, and out of every thousand billion atoms of carbon 12, at least one will be carbon 14.
Carbon-14
Carbon 14 is a naturally occurring part of nature, and it can also be used as a radioactive marker for custom radiolabeling processes. These processes are used mainly in drug manufacturing and are essential for monitoring how a drug metabolizes. Carbon 14 is one of the most popular isotopes used in radiolabeling, and as such is something to be familiar with if you are in the pharmaceutical industry today.