Precise measurements of trace neodymium isotopes as Nd+ ions by thermal ionization mass spectrometry using film porous ion emitters

Neodymium isotope analysis as Nd+ ions is more favored than as NdO+ ions due to less potential isobaric interferences and no need for complicated oxygen isotope corrections. However, the poor sensitivity and inadequate reproducibility seriously hinder its application. In this study, a new analytical method by thermal ionization mass spectrometry (TIMS) is initially presented for the precise measurement of Nd-143/Nd-144 ratio as Nd+ ions with film porous ion emitter (FPIE), combined with a simplified Nd chemical separation procedure. The Nd+ ion yields were one order of magnitude higher than those of traditional Nd+ ion analysis method. Repeated measurements of reference material JNdi-1 (1 ng) yielded a Nd-143/Nd-144 value of 0.512113 +/- 33 (2SD, n = 9). The achieved external precisions fulfilled the requirements for applications in nuclear forensics. Rock powder reference materials and uranium ore samples were analyzed to further test the accuracy and reproducibility of our method. We believe that this method is not only a particular value for nuclear forensic purposes, but also can expand the applications of Nd isotope ratio analysis in geochemistry, geochronology and environmental sciences.