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RESEARCH PRODUCT

Direct determination of halogens in powdered geological and environmental samples using isotope dilution laser ablation ICP-MS

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Abstract Laser ablation inductively coupled plasma isotope dilution mass spectrometry (LA-ICP-IDMS) with a special laser ablation system for bulk analyses (LINA-Spark™-Atomiser) was applied for direct determinations of chlorine, bromine, and iodine in rock and sediment samples. Special attention was focused on possible inter-halogen fractionations and analyte/spike isotope fractionations by using LA-ICP-MS and LA-ICP-IDMS, respectively. A variation of Br/Cl and I/Cl element intensity ratios by a factor of 1.3–3 was observed when changing the nebulizer gas flow rate in the range of 0.84–1.0 L min−1 and the laser power density in the range of 2–10 GW cm−2, respectively. When using an internal standard for halogen quantification in LA-ICP-MS, this inter-element fractionation can cause systematic errors, which can be avoided by applying the isotope dilution technique. However, at high laser power densities (>5.7 GW cm−2 for iodine and >4.0 GW cm−2 for bromine and chlorine) the corresponding measured isotope ratio of the isotope-diluted sample deviates significantly from the target value. Under optimised conditions concentrations in the range of 30 μg g−1–16 × 103 μg g−1 for chlorine,