  The abundance and fractionation of the stable strontium (Sr) isotope system
are being increasingly utilized to move forward our understanding in geological
and cosmological processes. Two analytical techniques are commonly used to
measure stable Sr isotopes: 1) double-spike thermal ionization mass
spectrometry (DS-TIMS) and 2) Zr-doped sample-standard bracketing
multi-collector inductively coupled plasma mass spectrometry (Zr-doped SSB via
MC-ICP-MS). Relative to DS-TIMS, Zr-doped SSB via MC-ICP-MS allows simultaneous
determinations of both 87Sr/86Sr and 88Sr/86Sr ratios, increasing measurement
efficiency and sample throughput. However, this technique is currently
associated with greater uncertainties in measurement precision and accuracy. In
this study, we evaluated potential factors that can affect the quality of Sr
isotope measurements during Zr-doped SSB. Our tests show that incomplete Sr
recovery during chromatographic separation, mismatches of Sr and Zr
concentrations and acid molarity between sample and bracketing standard, and
cation contamination could all affect the precision and accuracy of Sr isotope
measurements. We present evidence that, with updated preparation procedures and
diligent concentration checks, a long-term reproducibility (2{\sigma}SD:
87Sr/86Sr = +/-0.000015 and {\delta}88/86Sr = +/-0.03 permil) comparable to
that of DS-TIMS is achievable when using the Zr-doped SSB method via MC-ICP-MC.
