Dataset Information

Evaluation strategies and uncertainty calculation of isotope amount ratios measured by MC ICP-MS on the example of Sr.

ABSTRACT: This paper critically reviews the state-of-the-art of isotope amount ratio measurements by solution-based multi-collector inductively coupled plasma mass spectrometry (MC ICP-MS) and presents guidelines for corresponding data reduction strategies and uncertainty assessments based on the example of n((87)Sr)/n((86)Sr) isotope ratios. This ratio shows variation attributable to natural radiogenic processes and mass-dependent fractionation. The applied calibration strategies can display these differences. In addition, a proper statement of uncertainty of measurement, including all relevant influence quantities, is a metrological prerequisite. A detailed instructive procedure for the calculation of combined uncertainties is presented for Sr isotope amount ratios using three different strategies of correction for instrumental isotopic fractionation (IIF): traditional internal correction, standard-sample bracketing, and a combination of both, using Zr as internal standard. Uncertainties are quantified by means of a Kragten spreadsheet approach, including the consideration of correlations between individual input parameters to the model equation. The resulting uncertainties are compared with uncertainties obtained from the partial derivatives approach and Monte Carlo propagation of distributions. We obtain relative expanded uncertainties (U rel; k?=?2) of n((87)Sr)/n((86)Sr) of

SUBMITTER: Horsky M

PROVIDER: S-EPMC4709391 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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Evaluation strategies and uncertainty calculation of isotope amount ratios measured by MC ICP-MS on the example of Sr.

Horsky Monika M Irrgeher Johanna J Prohaska Thomas T

Analytical and bioanalytical chemistry 20160101 2

This paper critically reviews the state-of-the-art of isotope amount ratio measurements by solution-based multi-collector inductively coupled plasma mass spectrometry (MC ICP-MS) and presents guidelines for corresponding data reduction strategies and uncertainty assessments based on the example of n((87)Sr)/n((86)Sr) isotope ratios. This ratio shows variation attributable to natural radiogenic processes and mass-dependent fractionation. The applied calibration strategies can display these differ ...[more]

PMID: 26472320

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Project description:At Norje Sunnansund, an Early Holocene settlement in southern Sweden, the world's earliest evidence of fermentation has been interpreted as a method of managing long-term and large-scale food surplus. While an advanced fishery is suggested by the number of recovered fish bones, until now it has not been possible to identify the origin of the fish, or whether and how their seasonal migration was exploited. We analysed strontium isotope ratios (87Sr/86Sr) in 16 cyprinid and 8 pike teeth, which were recovered at the site, both from within the fermentation pit and from different areas outside of it, by using laser ablation multi-collector inductively coupled plasma mass spectrometry. Our investigation indicates three different regions of origin for the fish at the site. We find that the most commonly fermented fish, cyprinids (roach), were caught in the autumn during their seasonal migration from the Baltic Sea to the sheltered stream and lake next to the site. This is in contrast to the cyprinids from other areas of the site, which were caught when migrating from nearby estuaries and the Baltic Sea coast during late spring. The pikes from the fermentation pit were caught in the autumn as by-catch to the mainly targeted roach while moving from the nearby Baltic Sea coast. Lastly, the pikes from outside the fermentation pit were likely caught as they migrated from nearby waters in sedimentary bedrock areas to the south of the site, to spawn in early spring. Combined, these data suggest an advanced fishery with the ability to combine optimal use of seasonal fish abundance at different times of the year. Our results offer insights into the practice of delayed-return consumption patterns, provide a more complete view of the storage system used, and increase our understanding of Early Holocene sedentism among northern hunter-fisher-gatherers. By applying advanced strontium isotope analyses to archaeological material integrated into an ecological setting, we present a methodology that can be used elsewhere to enhance our understanding of the otherwise elusive indications of storage practices and fish exploitation patterns among ancient foraging societies.

Project description:In situ Sr isotopes analysis of apatite by LA-(MC)-ICP-MS is challenged by the difficulty to monitor and correct isobaric interferences from atomic and polyatomic ions. We present a new routine procedure for analysing rock-forming apatites with a Thermo Scientific Neptune XT MC-ICP-MS coupled with a Teledyne Cetac Analyte Excite+ 193 nm laser ablation system. Five apatite standards that cover a large range of REE/Sr ratios were selected, and their 87Sr/86Sr ratios were measured in solution after dissolution and purification of Sr [Durango: 0.706321(5); Madagascar: 0.711814(5); Slyudyanka; 0.707705(4); Sumé: 0.707247(4); and Ipirá: 0.710487(4)]. The optimisation of both instrument setup and data reduction schemes was achieved through repeated measurements of calibration solutions and of apatite standards at four different rectangular-shaped laser ablation beam sizes (50 × 50, 25 × 25, 13 × 13 and 10 × 10 μm). Two complementary methods were developed for data reduction: Method 1, which corrects measured intensities for gas blank and instrumental mass bias only; and Method 2, which additionally corrects for isobaric interferences of 87Rb+, 166, 168 and 170Er++, 170, 172, 174 and 176Yb++, 40Ca44Ca+, 40Ca46Ca+, 44Ca43Ca+ and 40Ca48Ca+. A precision of ca. 100 ppm (2 s.e.) can be achieved on the 87Sr/86Sr ratio with a 50 μm laser ablation beam when using Method 2, and it remains better than 3000 ppm at 10 μm with Method 1. Method 1 gives precise and accurate 87Sr/86Sr ratios when 173Yb++ is below the global limit of detection (with LODglobal = 3 s.d. of the means of all gas blanks measurements). When 173Yb++ is above the LODglobal, Method 2 should be preferred as it provides more accurate 87Sr/86Sr ratios. Overall, this study offers a robust and reliable approach for LA-MC-ICP-MS analysis of Sr isotopes in rock-forming apatite at a high spatial resolution (i.e. down to 10 μm), overcoming previous limitations associated with instrumental set up and data reduction.

Dataset Information

Evaluation strategies and uncertainty calculation of isotope amount ratios measured by MC ICP-MS on the example of Sr.

Publications

Evaluation strategies and uncertainty calculation of isotope amount ratios measured by MC ICP-MS on the example of Sr.

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