Using triple quadrupole interference removal to improve data quality in laser ablation ICP-MS for geochemical applications

Significance of the topic

Geological materials challenge conventional sample preparation due to complex matrices and resistance to chemical digestion. Laser ablation coupled to ICP-MS avoids elaborate acid treatments and enables spatially resolved analysis of trace elements and isotopes in minerals. However matrix induced isobaric interferences, notably mercury on lead, lutetium and ytterbium on hafnium, and polyatomic species in rare earth element determinations, must be addressed to ensure accurate data quality.

Goals and overview

This study illustrates how a triple quadrupole ICP-MS instrument, using selective reactive gases and quadrupole mass filters, can effectively remove isobaric interferences during laser ablation analysis of geological samples. We present applications to U-Pb zircon geochronology, Hf isotope petrogenesis, and rare earth element mapping in garnet using NH3 and O2 reaction modes.

Methodology

Standard zircon reference materials (91500 and Plešovice) and garnet-rich eclogite-blueschist thin sections were analyzed by laser ablation ICP-MS. Reactive ammonia gas in Triple Quadrupole mode eliminated mercury interferences on m/z 204 and enabled mass shift of Hf clusters to m/z 258 for interference-free 176Hf measurements. Oxygen reaction gas facilitated oxide mass shift for REE mapping, preserving sensitivity. Data reduction employed iolite for U-Pb ages, Microsoft Excel for Hf isotopes, and the CellSpace module for elemental imaging.

Used Instrumentation

• Thermo Scientific iCAP TQ ICP-MS
• Teledyne CETAC LSX-213 G2+ laser ablation system
• Teledyne CETAC Analyte G2 excimer laser ablation system
• Standard aerosol transfer systems and ARIS

Main results and discussion

U-Pb ages for Plešovice zircon matched reference values within analytical uncertainty (206Pb/238U age ~334 Ma). Mercury was fully removed by NH3 chemistry without biasing lead signals. Hafnium isotope ratios obtained via NH3 mass shift were accurate but limited to percent-level precision due to sequential SEM detection. Rare earth element maps revealed manganese zoning and partial melt features in garnet; O2 reaction mode enhanced sensitivity and contrast compared to KED.

Contributions and practical applications

The demonstrated TQ-ICP-MS approach enables robust, interference-free geochronological and geochemical analyses in complex matrices without extensive sample cleanup. It supports high accuracy U-Pb dating, reliable Hf isotope determination, and high-resolution elemental imaging, benefiting research in petrology, geochronology, and mineral characterization.

Future trends and potential applications

Expanding the mass shift strategy to lutetium-hafnium isochrons, integrating multicollector detection for enhanced Hf precision, applying TQ-ICP-MS to additional isotope systems, and adopting advanced algorithms or machine learning for optimized reaction conditions may further extend analytical capabilities.

Conclusion

Triple quadrupole interference removal in laser ablation ICP-MS significantly improves data quality by eliminating isobaric interferences, enabling accurate U-Pb ages, reliable Hf isotopes, and detailed element maps. This methodology advances spatially resolved geochemical investigations and streamlines sample handling.

References

• Steiger RH, Jäger E Convention on the use of decay constants in geo- and cosmochronology Earth Planet Sci Lett 36 359–362 1977
• Paton C et al Improved laser ablation U-Pb zircon geochronology through robust downhole fractionation correction Geochemistry Geophys Geosystems 11 2010
• Yang L, Sturgeon RE Comparison of mass bias correction models for the examination of isotopic composition of mercury using sector field ICP-MS J Anal At Spectrom 18 1452 2003
• Paul B et al CellSpace module for creating spatially registered laser ablation images within iolite J Anal At Spectrom 27 700 2012