The absolute isotopic composition and atomic weight of molybdenum in SRM 3134 using an isotopic double-spike

Abstract

Analytical techniques have been developed to perform a fully calibrated measurement of the isotopic composition of molybdenum reference materials using multiple collector inductively coupled plasma mass spectrometry. A correction for instrumental mass bias was performed using a molybdenum double-spike prepared from gravimetric mixtures of ⁹²Mo and ⁹⁸Mo isotope spikes. The absolute isotopic composition of the NIST SRM 3134 molybdenum reference material with 2 s.d. uncertainty was determined to be ⁹²Mo = 14.65(4), ⁹⁴Mo = 9.187(12), ⁹⁵Mo = 15.873(10), ⁹⁶Mo = 16.673(3), ⁹⁷Mo = 9.582(6), ⁹⁸Mo = 24.29(3), and ¹⁰⁰Mo = 9.74(2). The atomic weight of molybdenum in SRM 3134 was calculated as A_r = 95.949(3). Delta values (reported as δ^98/95Mo relative to SRM 3134) were determined for SCP Science – PlasmaCal molybdenum as −0.42(10)‰ and for Johnson-Matthey pure molybdenum rod as −0.45(12)‰. The total natural variation of molybdenum of −1.5‰ to +3‰ results in a calculated atomic weight interval of A_r = [95.944, 95.956].