Elemental Analysis of Pure Metals and Alloys by Femtosecond Laser Ablation (LA-)ICP-MS

Significance of the Topic

Direct analysis of metals and alloys by femtosecond laser ablation ICP-MS (fs LA-ICP-MS) addresses key practical challenges in elemental analysis. By eliminating wet digestion steps, the method reduces contamination risk, preserves volatile components, and accelerates throughput. Femtosecond pulses minimize thermal effects and elemental fractionation, enabling high accuracy and spatial resolution in both bulk and imaging applications.

Objectives and Study Overview

This work evaluates a novel 100% normalization function in Agilent ICP-MS MassHunter software for quantifying pure metals and alloys without matrix-matched standards. Using a well-characterized glass reference (NIST 612), the study analyzes three certified reference materials (CRMs)—an Al/Mg alloy (BAM 310), a Ni alloy (NIST 1249), and pure Cu (ERM-EB385)—to assess accuracy, precision, and calibration flexibility.

Methodology

• Laser parameters: 290 fs pulse width, 257 nm wavelength, 10 µm spot, 20 kHz repetition, 1.5×1.5 mm raster at 8 µm line spacing.
• Sample preparation: Acid cleaning, pre-ablation step to remove surface contamination, gas-blank measurement.
• ICP-MS acquisition: Agilent 8900 Triple Quadrupole in helium collision mode (3 mL/min), Ar makeup gas, integration times of 0.6–1 s, triplicate measurements per site.
• Data processing: Raw element concentrations calibrated to NIST 612, then normalized so summed elemental content equals 100%—correcting for ablation yield differences. Compound-specific corrections (e.g., CaO) can be applied automatically.

Used Instrumentation

• Agilent 8900 Triple Quadrupole ICP-MS with ORS4 cell and KED He mode.
• Seishin RAIJINα femtosecond laser ablation system (290 fs, 257 nm) with galvanometer beam scanning.
• Gas setup: Argon carrier gas (1.0 L/min) due to He supply unavailability, with Ar–He mixing at the torch via Y-piece.

Main Results and Discussion

• Accuracy: Most element recoveries fell within 80–120% of certified values across trace (ppm) to major (% level) concentrations.
• Precision: Standard deviations below 2% for Al/Mg and Ni alloys; up to 5% for trace elements in pure Cu.
• Interference correction: Doubly charged 48Ti++ on 24Mg+ in NIST 1249 was resolved using half-mass correction in the software, yielding accurate Mg quantification.
• Femtosecond ablation improved particle yield consistency and minimized fractionation, supporting reliable use of non-matrix-matched calibration.

Benefits and Practical Applications

• Eliminates need for custom solid standards, simplifying routine analysis of alloys and metals.
• Reduces sample preparation time and chemical consumption.
• Enables high spatial resolution mapping and bulk quantification in QA/QC, metallurgy, and materials research.

Future Trends and Opportunities

• Integration with automated data workflows and machine-learning calibration validation.
• Extension to complex matrices such as ceramics, geological samples, and semiconductor materials.
• Advances in laser technologies (shorter wavelengths, higher repetition rates) to further improve sensitivity and spatial resolution.
• Development of open-source normalization algorithms for broader adoption across instrument platforms.

Conclusion

The 100% normalization approach, combined with femtosecond LA-ICP-MS, provides a simple, accurate, and flexible calibration strategy for direct elemental analysis of metals and alloys. By removing the dependence on matrix-matched standards and minimizing fractionation, the method is positioned to become a standard practice in analytical laboratories.

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