High-Speed Laser MS for Precise, Prep-Free Environmental Particle Tracking

Graphical representation of air quality index and monitoring © stokkete-chronicles-stock.adobe.com

Tracking airborne pollutants is a scientific and regulatory priority, given their impact on public health and the environment. Traditional techniques for analyzing particulate matter (PM) can be slow and require labor-intensive preparation. Now, a team of researchers from Oak Ridge National Laboratory (ORNL) has evaluated the effectiveness of a powerful new tool—laser ablation-inductively coupled plasma-time-of-flight mass spectrometry (LA-ICP-TOF-MS)—for the direct and rapid analysis of environmental air samples (1,2).

Their study, published in the Journal of Analytical Atomic Spectrometry, involved the deliberate release of ruthenium (Ru)-bearing particles and the collection of airborne samples using aerosol contaminant extractors (ACE) positioned at varying distances from the particle release source. The results show that LA-ICP-TOF-MS enables accurate, spatially-resolved detection of target and background particles in less than 30 minutes per sample, offering a major analytical advance for environmental monitoring (1).

Direct Analysis of Particles Without Digestion
Unlike conventional methods such as standard inductively coupled plasma-mass spectrometry (ICP-MS), which require extensive chemical digestion and preparation, LA-ICP-TOF-MS uses a focused pulsed laser to vaporize a sample surface. This ablated material is carried into the plasma and analyzed immediately, preserving the elemental and isotopic fingerprint of each particle. The Oak Ridge researchers utilized gunshot residue (GSR) tabs to "lift off" particles from the ACE collector surfaces, enabling the analysis of more than 10 samples per session in a completely automated fashion (1).

The technique proved particularly useful for detecting ruthenium isotopes (¹⁰¹Ru and ¹⁰²Ru), which were released intentionally during the field experiment at Idaho National Laboratory. Elemental maps showed higher Ru concentrations closer to the source, while background particles like iron (Fe) and strontium (Sr) remained consistent across all distances—demonstrating the specificity and sensitivity of the technique (1).

Comparison of TOF and Quadrupole Mass Analyzers
Two mass spectrometry platforms were compared in the study: a triple quadrupole ICP-MS (TQ-MS) and a time-of-flight ICP-MS (TOF-ICP-MS). The TOF-ICP-MS platform stood out for its ability to simultaneously detect all nuclides from ⁷Li to ²⁴²Pu with higher precision in isotopic ratio determination. The researchers noted that TOF-MS improved the relative standard deviation (RSD) by a factor of three compared to the quadrupole system when measuring Ru isotope ratios (1,2).

Additionally, TOF-MS enables non-targeted elemental analysis, crucial for identifying unknown or unexpected pollutants in complex environmental samples. Although TOF-based systems showed a small bias in isotopic ratios (−5.7% RD), the researchers noted that this can be corrected with proper standards (1,2).

Multi-Modal Validation with SEM-EDS
To validate the LA-ICP-TOF-MS results, the team used scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) to analyze the same regions of each sample. This multi-modal approach confirmed a 100% match between particles detected by SEM-EDS and LA-ICP-TOF-MS, underscoring the reliability of the laser-based method. Importantly, both methods showed excellent agreement on the identity and spatial distribution of Ru particles, highlighting the precision and versatility of the new spectroscopic technique (1).

Implications for Environmental and Public Health Monitoring
This research, led by Benjamin T. Manard and co-authored by Sarah E. Szakas, Jordan S. Stanberry, Brian W. Ticknor, Leslie O'Brien, Mark Boris, Joshua T. Hewitt, Paula Cable-Dunlap, and Hunter B. Andrews, all from Oak Ridge National Laboratory, represents a significant advancement in environmental atomic spectroscopy analytics. The LA-ICP-TOF-MS method allows for rapid, high-resolution, and high-throughput analysis of airborne contaminants—without the need for chemical digestion or pre-treatment.

Such capability is essential for monitoring pollutants that pose risks to human health and ecosystems. From industrial emissions to accidental releases of toxic metals, the ability to detect and quantify trace particles in near-real time could reshape how we respond to air quality challenges (1).

By combining speed, accuracy, and non-destructive analysis, LA-ICP-TOF-MS offers a powerful new pathway for understanding environmental exposure to harmful particles. As this technology matures, it could become an essential tool for environmental scientists, regulatory agencies, and public health officials alike.

References

(1) Manard, B. T.; Szakas, S.; Stanberry, J.; Ticknor, B. W.; O'Brien, L.; Boris, M.; Hewitt, J.; Cable-Dunlap, P.; Andrews, H. B. Evaluating the Feasibility of LA-ICP-TOF-MS for the Analysis of Environmental Particle Collections. J. Anal. At. Spectrom.2025, Advance articlein press. DOI: 10.1039/D5JA00009B

(2) Tanner, M.; Bussweiler, Y. Laser Ablation and Inductively Coupled Plasma–Time-of-Flight Mass Spectrometry—A Powerful Combination for High-Speed Multielemental Imaging on the Micrometer Scale. Spectroscopy2017, 32 (5), 14–20. https://www.spectroscopyonline.com/view/laser-ablation-and-inductively-coupled-plasma-time-flight-mass-spectrometry-powerful-combination-hig (accessed 2025-04-16).