An IRMM 87Rb isotopic reference material IRMM-618

Abstract

An 87Rb isotopic reference material (spike) IRMM-618 has been prepared in the form of RbCl in HNO 3. The rubidium concentration, (0.11443 ± 0.000 17) × 10 −3 mol Rb kg −1 was determined by isotope dilution mass spectrometry against NIST SRM 984 RbCl. IRMM-618 is certified for its 87Rb concentration of (6.753 ± 0.010) × 10 19 atoms 87Rb kg −1 of solution, i.e. (0.112 13 × 0.000 17) × 10 −3 mol 87Rb kg −1 of solution, and for its isotopic composition, 97.9913 ± 0.0023 mol% 87Rb and 2.0087 ± 0.0023 mol% 85Rb. Uncertainties are 2 s or the equivalent estimate thereof. The isotopic reference material is available in quartz ampoules containing approximately 5 g of solution. Using this isotopic reference material, 85Rb or total Rb concentrations in unknown samples can be determined by isotope dilution mass spectrometry through a measurement of the molar isotope dilution ratio R B = n( 85 Rb)/n( 87 Rb) in the blend.