The article discusses and provides theoretical verification of methods for determining the parameters of a spike solution (the content of the element under study and its isotopic composition) using strontium as an example. The study of its isotopic composition in rocks and minerals is widely used in geochemical and isotope-geochronological studies. The authors propose a new method for certifying a strontium spike — determining its parameters based on the results of isotopic analysis of two mixtures of the tracer with a reference solution. In this case, the ratios between three stable isotopes (Sr, Sr, Sr) are used and precise knowledge of the Sr concentration in the spike solution is not required. The isotopic composition of one of the mixtures is specified by the average geometric value of the isotopic compositions of the reference solution and the spike, and the isotopic composition of the other is the average arithmetic value of these indicators. The combined use of these mixtures makes it possible to obtain all the parameters of the spike — the Sr concentration and its isotopic composition. The authors believe that the most correct way to determine these parameters is to use all four stable isotopes of Sr. One of the promising ways to determine the parameters of the spike solution is to use a reference solution enriched with the isotope Sr, in which the natural ratios of the remaining isotopes are preserved. The proposed methods are given a detailed theoretical justification and a graphical representation.
Yu.V. Goltsman (2025) studied this question.