Use of Non‐Matrix Matched Reference Materials for the Accurate Analysis of Calcium Carbonate by LA‐ICP‐MS

Abstract

Advances in laser ablation inductively coupled plasma‐mass spectrometry have improved analytical precision for mineral analysis, expanding geological interpretations from LA‐ICP‐MS results. However, with improvements in analytical precision, systematic errors from calibration can become more obvious and affect data quality. To improve the accuracy of the LA‐ICP‐MS technique, a fully quantified method is presented for the analysis of minerals with a CaCO3 matrix. An in‐house calcite sample (P‐Cal) was developed with an independently constrained composition and compared with measurement results from LA‐ICP‐MS analysis, generated using multiple spot sizes, laser fluences and calibration methods. For many elements, calibration against NIST SRM 612 as a calibration reference material and USGS GSD‐1G and USGS BCR‐2G as secondary reference materials (calibration B) provided the best accuracy for CaCO3 analysis. Ablation rates and element yield (ICP‐MS signal intensity in counts per second for a given isotope relative to the mass fraction of the respective element) in calcium carbonate closely resembles NIST SRM 612; however, the down‐hole fractionation curves of USGS BCR‐2G (basaltic glass matrix) are a better fit for carbonate. Variations in accuracy for measurements at different spot sizes are negligible compared with the other effects discussed. Additionally, ablation characteristics for powdered crystals versus large fragments produce a negligible effect on the accuracy of the results for calcium carbonate.

New CGSP Carbonate Matrix Reference Materials for LA‐ICP‐MS Analysis

“…More importantly, carbonate samples would be thermally decomposed and cannot be prepared as glass by the fusion method. There may be certain problems with powder samples, for example they are subject to element partitioning into the mineral phases within the powder, and the excess particles removed during ablation of the pressed powders cannot be transported to the ICP due to their larger size (Thompson et al 2021). The element contents regarded as an important factor affecting RSD in CGSPs are not as high as those in NIST SRM 610 (most above 500 μg g -1 ).…”

“…The element compositions of NIST series glasses, which are the most used references materials in LA-ICP-MS, are different from any natural rock and mineral samples (Liu et al 2013). Although non-matrixmatched reference materials have been developed for the analysis of calcium carbonate by LA-ICP-MS, certain analytical errors will inevitably be introduced during the measurement process (Thompson et al, 2021). Some carbonate matrix-matched reference materials have been prepared by melting the carbonate matrix powder to form a glass disc (Sinclair et al 1998) or by pressing carbonate matrix powder to form a pellet (Perkins et al 1991, Bellotto et al 2000.…”

“…2013). Although non‐matrix‐matched reference materials have been developed for the analysis of calcium carbonate by LA‐ICP‐MS, certain analytical errors will inevitably be introduced during the measurement process (Thompson et al ., 2021). Some carbonate matrix‐matched reference materials have been prepared by melting the carbonate matrix powder to form a glass disc (Sinclair et al .…”

Measuring Pb, Th, and U inter-element ratios in geological materials using extreme ultraviolet laser ablation and ionization mass spectrometry

“…For example, laser parameters such as wavelength, pulse length, spot size, uence, irradiance, repetition rate, ablation mode (i.e., raster vs. single spot), and the gas environment all play a role in correctly measuring the isotope ratio. [12][13][14][15] Additionally, the ICP parameters (RF-power, plasma potential, gas ows, etc.) also play a role alongside the sample properties (absorbance, morphology, homogeneity, etc.).…”

“…, raster vs. single spot), and the gas environment all play a role in correctly measuring the isotope ratio. 12–15 Additionally, the ICP parameters (RF-power, plasma potential, gas flows, etc. ) also play a role alongside the sample properties (absorbance, morphology, homogeneity, etc.…”