Rapid radiochemical neutron activation analysis - status and future

The development of multielement radiochemical separations for neutron activation analysis (NAA) peaked in the mid-1970s with the >100 methods listed in the review of Girardi and Pietra. Since then, however, the number of new published methods has diminished markedly. Ion-exchange chromatography methods dominated the early period, closely followed by solvent extraction, with precipitation and distillation procedures accounting for most of the remainder. This contrasts with the authors review of the literature from 1980 to the present. Solvent extraction, precipitation, and adsorption techniques were evenly divided among the methods listed. The slower ion-exchange technique was reserved for the more difficult separations or where high precision and accuracy were required. Radiochemical NAA developments and applications have diminished as more and more fast instrumental techniques including short time activation analysis have been adopted. Because NAA has no blank problems after irradiation of the sample, however, in contrast to nonnuclear analytical techniques including ICP-MS, it becomes the obvious choice where high sensitivity and low limit of detection are required for trace elements in solid samples. Future developments of NAA will rely mainly on rapid and simple separation techniques whose detection limits are economically competitive. More sophisticated and complex procedures must be restricted to those elements whose presence in materials cannot be detected by conventional techniques