Laser Ablation for ICP-MS – what is it and should I use it?

Importance of the Topic

Direct solid sampling by laser ablation combined with inductively coupled plasma mass spectrometry (LA-ICP-MS) eliminates lengthy and hazardous digestion procedures, reduces contamination risk and labor costs, and expands the range of analysable materials from metals and minerals to plastics and biological tissues. This capability is critical for geosciences, environmental monitoring, clinical research and forensic investigations where in situ elemental and isotopic information is required.

Objectives and Study Overview

This overview introduces the principles of laser ablation sampling, compares laser types and wavelengths, describes integration with different ICP-MS platforms, and outlines key operational parameters. Practical guidance on system configuration, tuning routines and application examples—including bulk analysis, depth profiling, elemental imaging and isotope ratio measurements—is provided to support method selection and optimization.

Methodology and Instrumentation

• Principle of Ablation: Pulsed UV lasers (266 nm, 213 nm, 193 nm) focus energy on the sample surface to generate an aerosol carried by helium into the plasma.
• Laser Types and Pulse Duration:
  – Q-switched Nd:YAG and excimer lasers (ns pulses) for general analyses.
  – Femtosecond lasers (150–350 fs) for thermally sensitive or conductive materials, achieving minimal melt effects.
• Key Ablation Parameters:
  – Spot size (2–200 µm) balances spatial resolution and signal intensity.
  – Fluence (J·cm⁻²) must exceed the ablation threshold without causing excessive melting.
  – Repetition rate (Hz) controls material throughput and data acquisition speed.
• Data Acquisition: Time-resolved acquisition enables quantitative depth profiling and imaging. Elemental maps are generated by rastering the sample stage under constant laser scanning.

Used Instrumentation

• ICP-MS Systems: Thermo Scientific iCAP RQ and TQ quadrupole systems; ELEMENT HR sector field platform; NEPTUNE Plus multicollector MC-ICP-MS.
• Laser Sources: Teledyne CETAC (Excite, LSX, Pharos), Elemental Scientific Lasers (NWR193, NWR213, NWR266), Australian Scientific Instruments (RESOlution), Applied Spectra (J200 LA and LIBS).
• Software and Accessories: Qtegra ISDS with laser control plug-ins and trQuant for dedicated LA-ICP-MS data evaluation; QCell collision/reaction cell for interference removal.

Main Results and Discussion

Detection limits in the ng·g⁻¹ range are achievable, often outperforming solution-based MDLs once preparation losses and dilutions are considered. Spatial resolution down to 2–5 µm is possible but depends on cell washout times; fast-washout ablation cells minimize signal carry-over and blurring. A case study of Sc distribution in garnet demonstrated the capability for high-resolution elemental imaging using a 5 µm spot on an iCAP TQ with mass-shift mode.

Benefits and Practical Applications

• Rapid bulk analysis without acid digestion.
• Elemental and isotopic imaging in geological and biological samples.
• Geochronology, environmental forensics and material fingerprinting.
• Reduced sample handling and contamination risk.

Future Trends and Opportunities

Advances in femtosecond laser technology and faster washout cells will push spatial resolution and minimize thermal artifacts. Automated mapping routines and improved software integration will enhance throughput for large-scale studies. Integration with complementary imaging modalities (e.g., micro-CT, Raman) and expansion into industrial QA/QC and additive manufacturing offer new avenues for LA-ICP-MS applications.

Conclusion

Laser ablation ICP-MS provides a versatile, contamination-free route for in situ elemental and isotopic analysis across diverse sample types. Optimal performance relies on careful selection of laser wavelength, pulse parameters, carrier gas settings and ICP-MS platform. As technology evolves, LA-ICP-MS will continue to open new frontiers in high-resolution mapping and rapid material characterization.