A Laser Ablation ICP-MS Protocol for High-Resolution Iodine-to-Calcium Ratio (I/Ca) Analysis on Corals

IF 1.8 3区化学 Q4 BIOCHEMICAL RESEARCH METHODS Rapid Communications in Mass Spectrometry Pub Date : 2025-02-09 DOI:10.1002/rcm.10002

Ashley N. Prow-Fleischer, Zunli Lu

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Abstract

Rationale

Corals are continuous, time-resolved archives of ambient seawater geochemistry and can extend climate records beyond direct monitoring. The iodine-to-calcium (I/Ca) ratio may be a proxy for local oxygen depletion in corals, but the current solution-based ICP-MS protocol limits sampling resolution. A protocol was developed for rapid analysis of coral I/Ca using laser ablation ICP-MS.

Methods

Two reference materials, a powdered coral (JCp-1) and a synthetic carbonate (MACS-3), were compared for precision in measuring Sr, Mg, I, Ba, and U. Then, the influence of laser parameters (spot size, fluence, repetition rate, and scan speed) on iodine sensitivity from the reference material was evaluated to optimize laser settings for accurate and reproducible I/Ca calibration. Then, I/Ca was measured in line scans along and across the ambulacrum in a Diploria labyrinthiformis coral.

Results

We find that JCp-1 has greater precision in measuring iodine, as well as other traces, compared to MACS-3. At a 10 Hz repetition rate, spot sizes from 150 to 85 μm obtained concentrations in agreement with certified values, but higher repetition rates overestimated iodine concentrations from JCp-1. Certain scan speeds and fluence can introduce noise, likely due to matrix effects, but the signal-to-noise ratio can be improved by adjacent-average filtering. Using this simple data filtering routine and optimized laser settings, the highest resolution for accurate I/Ca analysis is < 100 μm. While the fine-scale (< 250 μm) I/Ca variabilities in parallel transects in a coral sample likely resulted from biomineralization processes, large -scale features (> 500 μm) along the ambulacrum tend to correlate.

Conclusions

LA-ICP-MS has great potential for accurate, high-resolution I/Ca profiling in corals using JCp-1 as a calibration standard. Because of compositional variability near centers of calcification, it is important to pay attention to how the laser transect is aligned relative to skeletal elements, which may incorporate iodine differently.

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来源期刊

Rapid Communications in Mass Spectrometry 化学-分析化学

CiteScore

4.10

自引率

5.00%

发文量

219

审稿时长

2.6 months

期刊介绍： Rapid Communications in Mass Spectrometry is a journal whose aim is the rapid publication of original research results and ideas on all aspects of the science of gas-phase ions; it covers all the associated scientific disciplines. There is no formal limit on paper length ("rapid" is not synonymous with "brief"), but papers should be of a length that is commensurate with the importance and complexity of the results being reported. Contributions may be theoretical or practical in nature; they may deal with methods, techniques and applications, or with the interpretation of results; they may cover any area in science that depends directly on measurements made upon gaseous ions or that is associated with such measurements.