MC‐ICP‐MS Isotope Measurements with Direct Injection Nebulisation (d‐DIHEN): Optimisation and Application to Boron in Seawater and Carbonate Samples

Abstract

We report here an optimisation of the demountable direct injection high efficiency nebuliser (d‐DIHEN) for isotopic measurements with a Neptune (ThermoFisher Scientific, Bremen, Germany) multi‐collector inductively coupled plasma‐mass spectrometer (MC‐ICP‐MS) and describe a method for boron isotopic ratio determination. With direct injection nebulisation 100% of the analyte was introduced into the ICP‐MS plasma and wash times were drastically reduced for elements such as boron and thorium. Compared to the classical stable introduction system (SIS: double Scott/cyclonic spray chamber), sensitivity for boron was 2–5 times higher with d‐DIHEN and wash times up to ten times shorter. Repeatability of 11B/10B sample‐calibrator bracketing measurements reached 0.25‰ (2s) for seawater and coral samples. Method accuracy and reproducibility were tested on mixed reference solutions having δ11B values in the ranges −90 to +40‰ and −2 to +2.5‰, demonstrating our ability to distinguish δ11B values with differences of only 0.25‰. The international seawater reference material NRCC NASS‐5 (National Research Council, Ottawa, Canada), analysed in different sessions over a 10‐month period, yielded an average δ11B value of +39.89 ± 0.25‰, in the upper range of previously published seawater values. A comparison between δ11B determined by d‐DIHEN MC‐ICP‐MS and positive‐TIMS (P‐TIMS) for four modern corals showed an excellent agreement (with bias of less than 0.4‰).

Abrupt sea surface pH change at the end of the Younger Dryas in the central sub-equatorial Pacific inferred from boron isotope abundance in corals (<i>Porites</i>)

“…The reproducibility and accuracy of the 11 B/ 10 B ratios were calculated from repeated analyses of the boric acid standard NBS-951 and the North Atlantic Seawater Standard NASS-II. The measured external reproducibility of 0.25‰ (2 σ ) is similar to the reproducibility that was recently published for MC-ICPMS analyses by Neptune (Foster, 2008;Louvat et al, 2010). A mean δ 11 B of 39.9‰ (n=20, 2 σ ) was measured for NASS-II.…”

“…A mean δ 11 B of 39.9‰ (n=20, 2 σ ) was measured for NASS-II. This value is also within the external precision range of 39.7-40.2‰ previously published for thermal ionization mass spectrometry (TIMS) or MC-ICPMS measurements (Gaillardet and Allègre, 1995;Hemming and Hanson, 1992;Hönisch et al, 2004;Louvat et al, 2010). The external reproducibility of 0.25‰ (2 σ ) represents our analytical precision for Table 1.…”

“…Most of the δ 11 B values presented here were determined using the direct injection technique, which allows a strong reduction of the analytical blank contributions. These contributions were lower than 0.5‰ for each isotope with a rinse time of 3 min or less (Louvat et al, 2010). Using direct injection (d-DIHEN) and conventional introduction, comparison of repeated analyses for four different samples (DW1281c 78a1; DW1261 68a1; DW1281 75a2; MOO 3A-1-02) yields excellent agreement within the analytical uncertainty of 0.25‰ given here (Fig.…”

Light and temperature effects on δ<sup>11</sup>B and B / Ca ratios of the zooxanthellate coral <i>Acropora</i> sp.: results from culturing experiments

“…In turn, this may result in internal boron isotope redistribution, which would allow both BO 3 and BO 4 to be incorporated while preserving the internal (site of calcification) δ 11 B isotopic composition. In addition, because the incorporation of seawater boric acid would shift the boron isotopic composition of coral skeletons to considerably higher values (McCulloch et al, 2012), it appears unlikely that the trigonal B(OH) − 3 species detected in calcite and aragonite is directly derived from seawater.…”

Combination of nitrate (N, O) and boron isotopic ratios with microbiological indicators for the determination of nitrate sources in karstic groundwater

“…[18] Boron was first extracted from the samples using ion exchange chromatography. A volume of 5-30 mL of the samples at pH 9 was introduced into a column filled with 50 mL of resin (Amberlite IRA-743).…”