Environment & Energy

Over the years, I've sourced a lot of heavy isotope labeled compounds, never ¹⁴C. Generally in our lab we're looking for deuterium labeled, but it does happen sometimes we need to appeal to ¹³C. Up around a MW of 500, one starts to get interferences from the 1% natural ¹³C.

If I were looking to get ¹⁴C, I think it would be wise to avoid irradiated graphite in favor of neutron irradiated ¹⁴N, which would produce it pure out of the box.

I'm not sure though how it's done, but the use of ¹⁴C was pretty common at one point, and may still be practiced in places, thus the separation, if required in lieu of the ¹⁴N(n,p)¹⁴C reaction must be well known and widely practiced. The neutron method would offer the advantage of depleting ¹⁴N and thus enriching the low levels of ¹⁵N in natural nitrogen.

¹³C is easier to handle though and again, mass spec can follow it pretty well, as can NMR. There are means to recover enough labeled compound by extraction for NMR with solid phase extraction, particularly if one is willing to invest a lot of accumulation time on the instrument.

Mass spec is faster and cheaper though, assuming one has paid for the mass spec.

Both mass spec and NMR of course, offer structural information in DMPK settings, where as ¹⁴C only offers organ distribution.