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 Mo-92 and Mo-98 isotope spikes. The absolute isotopic composition of the NIST SRM 3134 molybdenum reference material with 2 s.d. uncertainty was determined to be Mo-92 = 14.65(4), Mo-94 = 9.187(12), Mo-95 = 15.873(10), Mo-96 = 16.673(3), Mo-97 = 9.582(6), Mo-98 = 24.29(3), and Mo-100 = 9.74(2). The atomic weight of molybdenum in SRM 3134 was calculated as A(r) = 95.949(3). Delta values (reported as delta Mo-98/95 relative to SRM 3134) were determined for SCP Science - PlasmaCal molybdenum as -0.42(10)parts per thousand and for Johnson-Matthey pure molybdenum rod as -0.45(12)parts per thousand. The total natural variation of molybdenum of -1.5 parts per thousand to +3 parts per thousand results in a calculated atomic weight interval of A(r) = [95.944, 95.956].