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

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 Ar = 95.949(3). Delta values (reported as δ98/95Mo 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 Ar = [95.944, 95.956].