A novel approach to obtain a fractionation free 11B/ 10B isotope ratio based on oxygen isotopes determined in situ from the same filament loading by N-TIMS is described. The method uses only a few nanograms of B to produce BO2- ions. First, the oxygen isotopes are determined at a lower filament temperature using ReO 4- ions and employing 187Re/185Re for internal normalization. Subsequently, the filament temperature is increased to get sufficient BO2- ions and predetermined 18O/16O isotopes from the same filament loading is used to correct for boron mass fractionation. The validity of the method has been demonstrated by analyzing a NIST-SRM-951 boron isotopic certified standard, two synthetic B mixtures, and two coral reference materials. An average analytical precision of 0.6‰ (n = 6) has been demonstrated. This is an important and crucial step forward in making the application of BO2- ions by N-TIMS routine in coral, foraminifera, and other samples where only limited amounts of boron are available. This new method does not require any additional effort in loading or in carrying out the mass spectrometric analysis but eliminates the need of assuming a fixed 18O/16O ratio and thus provides higher accuracy for applications in paleo-oceanography, geochemistry, and cosmochemistry.
All Science Journal Classification (ASJC) codes
- Analytical Chemistry