Obtaining Accurate Isotopic Compositions with the Double Spike Technique: Practical Considerations

Abstract

8 Ever-increasing precision in isotope ratio measurements requires a concomitant small bias and minimisation of 9 inter-laboratory bias. The double spike technique is the most suitable method to obtain reliable isotope 10 composition data that are accurately corrected for instrumental mass fractionation. Compared with other 11 methods, such as sample-standard bracketing, only the double spike technique can correct for all sources of 12 fractionation after equilibration of the sample with the double spike, such as that incurred during chemical 13 separation and measurement. In addition, it is not dependent on a priori assumptions of perfect matrix 14 matching of samples to reference materials or quantitative recovery of the sample through the chemical 15 separation procedure to yield accurate results. In this review article, we present a detailed discussion of the 16 merits of the double spike technique, how to design and calibrate a suitable double spike and analytical 17 strategies. Our objective is to offer a step-by-step introduction to the use of the double spike technique in 18 order to lower potential barriers that researchers new to the subject might face, such that double spiking will 19 replace sample-standard bracketing as the measurement method of choice. 20