WPC: Hyphenation of a high-speed laser ablation system to Quadrupole Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for imaging applications

Significance of the Topic

Laser ablation coupled with inductively coupled plasma mass spectrometry (LA-ICP-MS) enables spatially resolved elemental mapping directly from solid samples without complex digestion steps.
High-speed laser ablation systems combined with quadrupole ICP-MS significantly reduce analysis time while maintaining high spatial resolution and sensitivity, supporting applications in biomaterials research, geosciences, and quality control.

Objectives and Study Overview

This study evaluates the coupling of a dedicated high-speed laser ablation system (Elemental Scientific Lasers imageGEO193 with TwoVol3 cell) to a Thermo Scientific iCAP TQ triple quadrupole ICP-MS.
Key aims include demonstrating ease of integration, optimizing dwell times for signal-to-background ratio and image contrast, and achieving rapid multi-elemental imaging on a human tooth section.

Instrumentation

• Elemental Scientific Lasers imageGEO193 Laser Ablation System with TwoVol3 ablation chamber
• Thermo Scientific iCAP TQ triple quadrupole ICP-MS equipped with Dual Concentric Injector (2.0 mm quartz injector, Ni cones with high-sensitivity skimmer)
• Qtegra Intelligent Scientific Data Solution (ISDS) Software for data acquisition
• Iolite Laser Ablation Data Reduction Software with Precognition™ plugin for dwell time optimization
• ActiveView™ software for laser control and imaging lasso scans

Methodology

A human molar tooth was embedded in epoxy, sectioned, polished, and cleaned before analysis.
Laser settings: 25 µm square spot, ~3.0 J·cm⁻² energy, 250 Hz repetition rate, 20 µm overlap, scan rate 1,250 µm·s⁻¹.
ICP-MS settings: RF power 1,300 W, make-up gas 0.66 L·min⁻¹, CRC flow 0.320 mL·min⁻¹ O₂, total cell gas 0.800 L·min⁻¹ (analytical cup), Intelligent Mass Selection (iMS) in Q1, reactive gas in Q2, product ions in Q3.
Washout optimization was performed by ablating a low-repetition line and measuring 44Ca.16O at 1 ms dwell; observed peak width of 27 ms set the upper limit for dwell times.
Data were acquired in triple quadrupole mode using Reaction Finder for optimal collision/reaction settings, then processed in Iolite with Precognition to finalize dwell times and generate images.

Key Results and Discussion

Optimized washout and dwell settings enabled scanning of multiple m/z channels without signal blurring at 1,250 µm·s⁻¹.
A 12.87 × 15.50 mm map of the tooth was acquired in just over two hours, revealing distinct elemental distributions between enamel and dentine.
Triple quadrupole operation with reactive O₂ gas effectively reduced interferences (e.g., oxide formation), enhancing sensitivity and specificity.
Limitation: sequential scanning restricts the number of analytes per run, though sensitivity gains in triple quadrupole mode largely offset this constraint.

Benefits and Practical Applications

High-speed multi-elemental imaging with 25 µm spatial resolution completes large-area maps in hours rather than days.
Minimal sample prep reduces contamination risk and accelerates throughput.
Applicable to dental studies, metallomics, geological thin sections, and industrial QA/QC scenarios requiring spatially resolved elemental data.

Future Trends and Opportunities

Further enhancements in low-dispersion ablation cells and aerosol transfer could push scan rates higher while preserving resolution.
Integration with advanced detectors or parallel acquisition systems may overcome sequential scanning limits and allow more simultaneous channels.
Real-time data processing and machine learning–based peak deconvolution could streamline workflows for complex matrices.

Conclusion

The successful integration of a high-speed laser ablation system with triple quadrupole ICP-MS enables rapid, sensitive, and interference-free elemental imaging.
Optimized parameters deliver high-quality multi‐element maps in significantly reduced time, demonstrating the potential for broad applications across analytical chemistry fields.

References

• S. J. M. Van Malderen et al., Spectrochimica Acta Part B, 2018, 140, 29–34.