We present a method to determine
88Sr/
86Sr and
87Sr/
86Sr simultaneously. The former variation reflects the mass-dependent isotopic fractionation through the physico-chemical processes, and the latter originates from
β--decay of the parent nuclide
87Rb as well as the mass-dependent isotopic fractionation. In order to determine the mass-dependent isotopic fractionation, the mass-discrimination effect on
88Sr/
86Sr was externally corrected by an exponential law using Zr. For the radiogenic growth of
87Sr/
86Sr, the mass-dependent isotopic fractionation effect on
87Sr/
86Sr was corrected by a conventional correction technique using the
88Sr/
86Sr ratio. The reproducibility of the
88Sr/
86Sr and
87Sr/
86Sr measurements for a high-purity Sr chemical reagent was 0.06‰ (2SD,
n = 20) and 0.07‰ (2SD,
n = 20), respectively. Strontium isotopic ratios (
88Sr/
86Sr and
87Sr/
86Sr) were measured on six geochemical reference materials (igneous rock: JB-1a and JA-2; carbonate mineral: JLs-1, JDo-1, JCp-1 and JCt-1) and one seawater sample. The resulting
87Sr/
86Sr ratios obtained here were consistent with previously published data within the analytical uncertainties. The resulting
88Sr/
86Sr ratios for igneous rock samples did not vary significantly within the samples, whereas the carbonate samples showed enrichments of the lighter Sr isotopes over the seawater sample. The
88Sr/
86Sr ratio of geochemical samples could reflect the physico-chemical processes for the sample formation. Also, a combined discussion of
88Sr/
86Sr and
87Sr/
86Sr of samples will render multi-dimensional information on geochemical processes.
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