Absolute Isotopic Composition and Atomic Weight of Commercial Zinc Using Inductively Coupled Plasma Mass Spectrometry

Abstract

Inductively coupled plasma mass spectrometry is introduced as a method for determining the absolute isotopic composition of zinc. The high ionization efficiency and time-independent characteristics of the mass spectrometry permit the absolute isotopic composition of high ionization potential elements. The mass discrimination of the instrument is calibrated by synthetic isotope mixtures prepared from highly enriched isotopes of zinc. The resulting isotope ratios yield atomic percents of 64Zn, 49.188 +/- 0.030; 66Zn, 27.792 +/- 0.041; 67Zn, 4.041 +/- 0.009; 68Zn, 18.378 +/- 0.050; and 70Zn, 0.600 +/- 0.003. This isotopic composition is different from those of conventional mass spectrometric measurements. Their differences depend on the mass differences about 0.8-1.2%/amu with enhancement of heavier isotopes. The atomic weight calculated from our isotopic composition is 65.3756 +/- 0.0040. The obtained atomic weight is fully consistent with that of a precise coulometric measurement in contrast to the previous mass spectrometric measurements. An isotopic variation of commercial zinc reagents has been investigated. A mass-dependent fractionation of 0.12%/amu is observed in a high-purity metal zinc, NIST-SRM 682, among five reagents. This mass dependence is probably inherited through their purification process.

Atomic weights of the elements 2007 (IUPAC Technical Report)

“…The authors calibrated their instrument using synthetic mixtures of highly enriched Zn isotopes. Their value for A r (Zn) measured from the isotope reference material IRMM-3702 is 65.377 77 (22), which is significantly different from the previous IUPAC value of 65.409(4) [1,2]. The latter is based on a calibrated measurement by Chang et al using TIMS [21].…”

“…The latter is based on a calibrated measurement by Chang et al using TIMS [21]. A calibrated MC-ICP-MS measurement by Tanimizu et al [22] found an atomic weight of Zn of 65.3756 (40), also significantly different from the earlier value [21]. It is important to note that the atomic weight of Zn of 65.377(3) determined much earlier using coulometric techniques [23] is in good agreement with the measurement by Ponzevera et al [20] and Tanimizu et al [22].…”

“…A calibrated MC-ICP-MS measurement by Tanimizu et al [22] found an atomic weight of Zn of 65.3756 (40), also significantly different from the earlier value [21]. It is important to note that the atomic weight of Zn of 65.377(3) determined much earlier using coulometric techniques [23] is in good agreement with the measurement by Ponzevera et al [20] and Tanimizu et al [22]. Both [20,22] proposed that the atomic weight reported in Chang et al [21] was affected by a systematic measurement bias.…”

Development of rapid and precise Pb isotope analytical techniques using MC-ICP-MS and new results for GSJ rock reference samples

“…However, in the routine analysis of natural samples, the Pb isotope ratios to be measured are different one by one, and inevitably the Pb isotope composition of the remaining Pb signal memory after 5 minute washout should vary significantly. If an analyzed sample has an extreme Pb isotopic composition, the memory may affect the measured value of the next sample like the case of zinc in double-spike analysis (Tanimizu et al, 2002), although we had shown that the level of the Pb memory is less than 0.01% of the sample signal in usual analysis (Fig. 1) Zindler and Hart, 1986).…”

A simple combined sample–standard bracketing and inter-element correction procedure for accurate mass bias correction and precise Zn and Cu isotope ratio measurements

“…The mass bias factor of the dopant in each sample and standard was calculated using the measured ratio (R measured ) and its natural abundance ratio (R true ) taken from literature. 19,20 In the case of Cu acting as dopant:…”