ll see what i can do to help downstream the natural abundance background is important to the diagnostic power of many isotopic labeling and low blank trace element detection techniques as well for example a colleague of mine irradated a nanogram sized particle with so many neutrons that every u atom in it was fissioned and then counted the number of fission tracks that resulted he found one which in turn allowed him to infer u abundance assuming solar system abundance ratios and hence total u abundance in the particle as well