Elemental characterization of impurities at trace and ultra-trace levels in metallurgical lead samples by INAA

The purity of several economically important metals is routinely verified by a reference material. Further, it is essential to provide a means of maintaining the consistency between laboratories and on disseminating the accurate value.This work, developed within an activity of certification promoted by EURATOM, reports the results on impurity determination (Ag, As, Cd, Ni, Sb, Sn, Te and Zn) at trace (µg g^{− 1}) and ultra-trace (ng g^{− 1}) levels in three metallurgical lead samples (99.99% of purity). Among the different analytical techniques available for the characterization, the use of a nuclear technique, i.e. Instrumental Nuclear Activation Analysis, has allowed to reach high sensitivity and to obtain accurate values for these elements.The irradiations were performed in the rotating rack (Lazy Susan) and in the central channel of the Triga Mark II reactor reaching a total integrated flux of 9.36 × 10¹⁷ n cm^{− 2} and 2 × 10¹⁹ n cm^{− 2}, respectively.The results about the determination of elements such as Ni, Sn, Te and Zn present at ultra-trace levels (ng/g), are showed and discussed. This task is very interesting for the radio-analytical and methodological implications: in fact, for analyzing them a radiochemical separation is involved and an anti-Compton gamma spectrometer is necessary due to their very low levels.