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

Abstract

The modified sample-standard bracketing method (m-SSB) combines a sample-standard bracketing and an inter-element correction procedure to account for instrumental mass fractionation during multi-collector ICP-MS measurements. Precisions for Cu and Zn isotopes in plant and experimental granite leachate samples are in line with those obtained using other mass bias correction techniques. In addition, the inherent temporal drift of mass bias during the analytical session and the empirical linear relationship between dopant and analyte are used to apply independent correction schemes that rigorously check the accuracy of data obtained by m-SSB. Consequently, a very robust isotope data set is obtained. We further suggest the use of a matrix-element spike in inter-element doped standards to increase the mass bias variability. This improves the quality of the empirical relationship between dopant and analyte and enables crosschecking of the m-SSB method when instrumental mass bias is stable.

Ion Exchange Chromatography and Mass Bias Correction for Accurate and Precise Zn Isotope Ratio Measurements in Environmental Reference Materials by MC-ICP-MS

“…14,15,29,31,37 The simplest technique used to correct mass bias is sample standard bracketing (SSB), consisting of analyzing an unknown sample bracketed by standards that are used to interpolate and correct the mass bias drift during data collection. 15,31 The SSB approach assumes that temporal drift in mass bias between bracketing standards is predictable and approximates to a simple mathematical expression (typically a linear interpolation), requiring a stable mass bias over the measurement session with no significant matrix-induced mass bias. Another technique widely applied is the external normalization which consists of doping samples and standard with an element with a known isotope composition and similar fractionation behavior to the element being analyzed (e.g., Zr doping to Mo isotope analysis, Mg doping for Si and Cu doping for Zn isotope analysis).…”

“…Another technique widely applied is the external normalization which consists of doping samples and standard with an element with a known isotope composition and similar fractionation behavior to the element being analyzed (e.g., Zr doping to Mo isotope analysis, Mg doping for Si and Cu doping for Zn isotope analysis). 15,31,38 The measured isotope ratio of the dopant can be compared to its known value to quantify instrumentinduced fractionation (or factor of fractionation (f)) and a correction can then be applied to the isotope ratio of the target element. 15…”

“…15,31,38 The measured isotope ratio of the dopant can be compared to its known value to quantify instrumentinduced fractionation (or factor of fractionation (f)) and a correction can then be applied to the isotope ratio of the target element. 15…”

“…[1][2][3]11 The natural variations in the Zn isotopic composition are small (< 1‰), requiring reliable analytical procedures including chromatographic separation of Zn from the matrix [12][13][14] and accurate correction of the instrumental mass bias. [14][15][16] To date, a number of ion exchange chromatographic protocols for specific sample types such as rocks, sediments, marine and fresh water, aerosols, plants and food has been published. [17][18][19][20][21][22][23][24][25][26] Moreover, our understanding about instrumental controls of mass bias including effect of acid strength, dopant/analyte ratios, wet and dry plasma and matrix has improved.…”

New Insights from Zinc and Copper Isotopic Compositions into the Sources of Atmospheric Particulate Matter from Two Major European Cities

“…Instrumental 216 mass bias effects were corrected using an in-house 64 Zn-67 Zn double-spike for Zn and 217 standard sample bracketing for Cu. 40 255 We find large enrichments of Cu, Fe and Sb, which reflect significant anthropogenic 256 contribution ( Figure S4). supports an important contribution from fuel or oil combustion.…”