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Determination of lead in atmospheric air and in aluminum by helium-3-induced nuclear reactions.

Helium-3 activation analysis has been applied to develop a very sensitive means of trace lead analysis. The procedure involves the bombardrment of samples with 3He particles to induce a Pb + 3He yields 207Po reaction on lead isotopes. The 992keV gamma -ray of 5.84-hr 207Po is used as the signal'' for lead determination. Only milligram amounts of srmpls are required, The excitation function for the production of 207Po from the reaction of 3He with lead of natural isotopic composition is presented. If necessary, destructive analysis may be carried out, and a radiochemical separation procedure to plate polonium onto a silver foil is discussed. The accuracy of the measurement is about 3 to 5% for comparative analyses. For absolute determinations, the error is estimated to be 9-12%. Under reasonable irradiation and counting conditions, the detection limit is approximately 50 pg/ cm2, corresponding to 0.5 ppb in a matrix 100 mg/cm2 thick.