Tin is determined at the low nanogram level in biological samples by neutron activation using the pure β−emitter121Sn of half-life 27 hours. The method is based on the concept of extracting tin selectively into an organic phase, which, after
addition of a scintillant (PPO), can be directly counted by liquid scintillation counting with near 100% efficiency. Tin is
first selectively extracted as its iodide into toluene, stripped and then re-extracted selectively into a toluene solution
of N-benzoyl N-phenylhydroxylamine for scintillation counting. Results are given for various biological reference materials.