Reference value of the JNdi-1 isotopic material without normalization

• Published in: Journal of analytical atomic spectrometry 2024-08, Vol.39 (9), p.2165-2172
• Main Authors: Quemet, Alexandre, Lasnier, Guillaume, Mialle, Sébastien, Isnard, Hélène, Boyet, Maud, Garçon, Marion, Auclair, Delphine
• Format: Article
• Language: English
• Subjects: Evaporation; Fractionation; Ionization; Isotope ratios; Laboratories; Mass spectrometry; Neodymium isotopes; Ratios; Reference materials; Sciences of the Universe; Spectrometers
• ISSN: 0267-9477; 1364-5544
• DOI: 10.1039/d4ja00140k

The most used international reference material for neodymium isotope ratios is the JNdi-1 standard. The literature reference values were determined using Thermal Ionization Mass Spectrometry (TIMS) with a conventional internal normalization. In nuclear studies, such normalization is not possible for samples after irradiation, as there is no known isotope ratio that can be considered as a reference ratio. Nd isotopic analysis is essential for calculating the burnup of a reactor. To offer reference values without normalization, 61 measurements of the JNdi-1 material were obtained in three different laboratories on four thermal ionization mass spectrometers using the total evaporation method. Acquired measurements were compared to the exponential mass fractionation law demonstrating that the dominant bias comes from isotope fractionation which can be minimized using the total evaporation method. The suggested reference values and associated uncertainties with a coverage factor of 2, which indicates approximate 95% confidence, were calculated using the DerSimonian-Laird procedure ( n = 3): 142 Nd/ 144 Nd = 1.13966(23), 143 Nd/ 144 Nd = 0.511613(50), 145 Nd/ 144 Nd = 0.348729(33), 146 Nd/ 144 Nd = 0.72329(15), 148 Nd/ 144 Nd = 0.242505(95) and 150 Nd/ 144 Nd = 0.23780(14). All these ratios are significantly different from those obtained after normalization using 146 Nd/ 144 Nd = 0.7219. The new values obtained for the JNdi-1 can be used in nuclear laboratories where the Nd isotope ratios differ from the natural isotopic compositions or when the total evaporation method is used without internal normalization. JNdi-1 reference values were obtained without normalization using TIMS and total evaporation method.