Assessing Matrix and Nonmatrix, Single, and Multipoint Calibration of Trace Elements Using LA-ICP-MS on a Tropical...

Area of Science:

• Paleoclimatology
• Geochemistry
• Analytical Chemistry

Background:

• Trace elements in speleothems serve as crucial proxies for reconstructing past climate change.
• Laser ablation techniques, specifically Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS), are vital for high-resolution elemental analysis in paleoclimate archives.
• Limited research exists on optimizing LA-ICP-MS protocols for speleothem analysis, particularly concerning reference material selection and calibration strategies.

Purpose of the Study:

• To investigate the impact of using matrix-matched (carbonate) versus non-matrix-matched (silicate) reference materials in LA-ICP-MS speleothem analysis.
• To evaluate the effectiveness of 1-point versus multiple-point calibration curves for accurate trace element quantification.
• To provide insights into best practices for LA-ICP-MS protocols in paleoclimatology.

Main Methods:

• Performed two experimental runs on a speleothem section using both silicate and carbonate reference materials.
• Utilized a 193-nm wavelength laser ablation system coupled to an ICP-MS instrument.
• Calculated trace element concentrations using 1-point, 2-point, and 3-point calibration curves.

Main Results:

• Trace element to calcium ratios showed minimal deviation regardless of whether matrix-matched or non-matrix-matched standards were used.
• Multi-point calibration curves (2- and 3-point) effectively bracketed sample concentration ranges, unlike single-point curves.
• Calculated paleotemperatures derived from Mg/Ca ratios remained consistent across different calibration methods.

Conclusions:

• A minimum of a 2-point calibration curve, incorporating both silicate and carbonate standards, is recommended for accurate speleothem LA-ICP-MS analysis.
• Calibration curves must adequately bracket the range of sample concentrations for reliable quantification.
• These findings have significant implications for improving the accuracy of LA-ICP-MS techniques in speleothem and other carbonate archive studies.