Determination of low concentrations of americium and curium by photon/electron rejecting alpha liquid scintillation

The determination of very low activities of americium and curium has been performed by a new analytical method based on alpha liquid scintillation (PERALS®). The detection limit has been determined for several americium and curium isotopes. For both actinides, the values calculated are lower than those of other methods like inductively coupled plasma mass spectrometry (ICPMS), time-resolved laser-induced spectrofluorimetry or α spectrometry. The conditions required to obtain optimal extraction yields during the liquid–liquid extraction step have been determined in several media. All the results obtained show that the PERALS system is a promising method for the determination of low α-emitter activities. Indeed, it is possible to detect activities as low as a few mBq l−1. The procedure has been applied with success to French granitic-mineral-doped water and to complex media (biological samples like urines, mineral samples,…). In this latter case, the extraction is not quantitative: it is then necessary to determine the recovery yields by labeling. Attempts to use 243Am as a spike of 241Am were unsuccessful because of the low difference in energy of α particles for both nuclides (ca. 210 keV) in comparison with the PERALS resolution. On the contrary, labeling with 246Cm or 248Cm for 244Cm and 148Gd for all americium and curium isotopes is possible and discussed in this paper.