RESUMO
A new approach is presented for experimental determination of the potassium traces in foodstuffs, soil, sediment and plants, by use of natural [40]K radiation. Potassium maintains the salt balance in plant and animal cells and is important for healthy metabolis. Its role is often likened to that of the oil in an engine. There are actually three potassium isotopes'. [39]K, a stable isotope, is the most abundant, at 93.26% of the total; [41]K is next in abundance at 6.73% and is also a stable isotope. The potassium isotope of interest is a radioactive isotope, [40]K. It is present in all potassium at a very low concentration, 0.0118%. It has a very long half-life, 1,260,000,000 years. When it decays 89% of the events give rise to the emission of a beta ray with maximum energy of 1.33 Mev. The other 11% of the decays produce a gamma ray with an energy of 1.46 Mev. The long half-life and low abundance might seem to imply that this radioisotope, [40]K, is of little or no consequence, so it is usually ignored. In fact the knowledge that all potassium contains this radioactive isotope does not seem to be widely known. Very few of the discussions about potassium mention its radioactivity, which seems to imply that either it is not known or that this trivial level can be safely ignored. This radioactive element is vital for our good health. It is an element that is essential for the body's growth and maintenance. Potassium is also necessary in order to maintain normal water transport between the cells and body fluids. It also plays an essential role in the response of nerves to stimulation and in the contraction of muscles