Quantitative extraction and high precision isotope measurements of nickel by MC-ICPMS

Abstract

This paper presents a new technique for the precise and accurate determination of Ni isotopic composition in geological samples, involving a two-stage ion-exchange procedure for nickel extraction and the use of a large-geometry high-resolution MC-ICPMS instrument. The key step of the chemical separation is an ion-exchange procedure based on the complexation of Ni with dimethylglyoxime which replaces the previous liquid–liquid extraction technique. The new method allows for quantitative recovery of Ni even for silicate samples as opposed to the previous technique. Measurements of an Ni standard doped with Fe or Zn show that isobaric interferences of these elements can be accurately corrected as long as Fe/Ni < 0.1 and Zn/Ni < 0.0006. Replicate measurements of a standard solution yield long-term external reproducibilities (2σ) of ±50 ppm for ⁶⁰Ni/⁵⁸Ni and ±120 ppm for ⁶¹Ni/⁵⁸Ni, when ratios are normalized to ⁶²Ni/⁵⁸Ni.