Elemental Imaging by Laser Ablation ICP-MS
Elemental imaging by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) is a powerful analytical technique used to visualize and quantify the spatial distribution of elements within a solid sample. The process begins with a focused laser beam that ablates (removes) a minute portion of the sample’s surface. The ablated material is carried by an inert gas (typically argon or helium) into an inductively coupled plasma, where it is ionized. The resulting ions are then directed into a mass spectrometer, which separates them based on their mass-to-charge ratio, providing elemental and isotopic information.
What makes LA-ICP-MS particularly valuable is its ability to provide both qualitative and quantitative multi-elemental analysis at very high spatial resolutions—down to a few microns. This capability allows scientists to construct high-resolution, two- or three-dimensional elemental maps of the sample, revealing heterogeneities that are not detectable by bulk analysis. Because the technique does not require chemical digestion or matrix dissolution, it minimizes sample preparation and preserves spatial integrity.
Applications and Use Cases
LA-ICP-MS has a wide range of applications across disciplines such as geology, environmental science, materials science, forensics, biology, and medicine. In geosciences, it is used for mapping trace elements in minerals, determining provenance of archaeological artifacts, and dating zircon grains. In biological research, the technique enables spatially resolved trace metal analysis in tissues, such as mapping iron, zinc, and copper distributions in brain or liver tissue, which can offer insights into disease mechanisms or toxicological effects. Similarly, in forensic science, it is employed to analyze gunshot residues or trace evidence.
One of its key strengths in biomedical and life sciences is its ability to perform multi-elemental imaging without the need for labeling or staining, unlike fluorescence-based methods. This allows researchers to detect endogenous metals and exogenous metal-tagged pharmaceuticals in situ with minimal interference. Advances in laser technology and ICP-MS instrumentation have significantly enhanced detection limits, allowing the visualization of elements at concentrations in the low parts-per-billion (ppb) to parts-per-trillion (ppt) range, even in complex matrices.
Advantages Over Other Imaging Techniques
Compared to other elemental or molecular imaging techniques like Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDS), Secondary Ion Mass Spectrometry (SIMS), or X-ray fluorescence (XRF), LA-ICP-MS offers a unique combination of high sensitivity, broad elemental coverage (including rare earth and heavy metals), and quantitative accuracy. SEM-EDS and XRF are typically limited to higher detection limits (ppm level) and a narrower range of detectable elements. SIMS can achieve higher spatial resolution, but at the cost of limited quantification capabilities and often lower throughput.
Moreover, LA-ICP-MS avoids the need for extensive calibration procedures required by techniques like SIMS and can be calibrated using matrix-matched standards for more accurate quantification. The technique is also non-destructive to surrounding areas (localized ablation), which is advantageous when working with rare or valuable specimens.
Brooks Applied Labs utilize an Iridia Laser ablation system coupled to an Agilent 8800/8900 ICPMS to provide high-resolution, sensitive, multi-elemental analysis of solids, especially when preserving the spatial context of those elements is important.