Determination of Zr and Hf in a Flux‐Free Fusion of Whole Rock Samples using Laser Ablation Inductively Coupled Plasma‐Mass Spectrometry (LA‐ICP‐MS) with Isotope Dilution Calibration

Abstract

Isotope dilution calibration has been applied to the determination of Zr and Hf in whole rocks by laser ablation (LA)‐ICP‐MS. Enriched isotopes were added during the preparation of flux‐free, synthetic whole rock glasses and homogenised through a combination of grinding and fusion. This method avoids problems, such as solution instability and the chemical resistance of minerals such as zircon, inherent in acid digestion sample preparation. The use of isotope dilution removes the need for external calibration using certified reference material glasses such as NIST SRM 612 for which certified Zr and Hf values are not available. The precision of Zr and Hf determinations were found to be < 1% and 3.5% respectively, limited by Poisson counting statistics which contributed to 50% of the final precision of analysis. Measured values correlate closely with compiled literature values.

Quantitation of Trace Metals in Liquid Samples by Dried-Droplet Laser Ablation Inductively Coupled Plasma Mass Spectrometry

“…Although solution introduction yields the highest accuracy and precision, 32 this approach has also been used for the determination of trace elements in various solid samples using LA-ICPMS. [15][16][17][18][19] Better than 10% precision and accuracy was reported in the above studies for most analytes, demonstrating the ability of ID to overcome the generally poor precision and accuracy associated with LA sampling while providing a simple quantitative calibration strategy. Thus, a third calibration strategy, isotope dilution, was also examined for quantitation of the three analytes in the drinking water and relied on the following equation:…”

“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19] leading to nonstoichiometric response, frequently occurs, although the sources of this problem are still open to debate. 7,8,21,22 This makes it difficult to achieve quantitative analytical results using this technique.…”

Applications of LA-ICP-MS in the elemental analyses of geological samples

“…Based on the sample preparation technique, LA-ICP-MS methods have been applied to the bulk analysis of various samples, including (1) the direct analysis of a rock slice [24,126], (2) the analysis of pressed-powder pellets both with binders [1, 26,127] and without binders [128], and (3) the analysis of fused glasses fused both with a flux agent [6, 129,130] and without a flux agent [22,23,25,61,[131][132][133][134].…”

“…The bulk content of volatile components (such as H 2 O and CO 2 ) in the sample should be accurately measured using other independent methods if the summed metal oxide normalization technique is used. With the isotopic dilution method, an isotopic spike can be added into the powdered sample during the preparation of the pressed pellet [29,50,140] or whole-rock glass [133]; trace elements can then be accurately measured without the use of any external standard.…”

“…B, Li and REE) [137]. A flux-free fusion technique involves the direct melting of the rock powders in an Ar environment into homogeneous glasses at 1300-1800°C using an iridium strip heater [22,25,133,134], a tungsten strip heater (Hf and Ta pollution may exist) [132] or a molybdenum strip heater [23,138], which avoids the above problems caused by the flux agent. For high-SiO 2 rocks, high-purity MgO needs to be added to reduce the melt viscosity and result in homogeneous glasses [134].…”