WHAT IT IS
A laser ablation (LA) system is an accessory for analytical instruments such as inductively coupled plasma mass spectrometry (ICP-MS) that enables direct analysis of solid samples. Instead of dissolving or digesting material, the system uses a focused pulsed laser to remove tiny amounts of sample from the surface. The ablated material is converted into an aerosol, carried by a transport gas, and introduced into the plasma for ionization and mass spectrometric detection. LA systems are widely used for elemental and isotopic analysis in geology, materials science, environmental studies, and life sciences.
HOW IT WORKS
The laser ablation process consists of several stages:
Laser Beam Generation
A pulsed laser (commonly excimer at 193 nm, Nd:YAG at 213 nm, or femtosecond sources) produces a beam with defined wavelength, energy, and pulse width.
Shorter wavelengths (UV) and ultrashort pulses (fs) provide more efficient ablation with less thermal damage.
Beam Delivery and Focusing
The laser beam is guided by mirrors and lenses into an ablation cell.
Spot size, shape, and scanning pattern can be adjusted for line scans, spots, or rastering.
Ablation of the Sample
When the laser pulse hits the sample, material is removed as vapor, plasma, and fine particles.
Nanosecond lasers often generate some melting, while femtosecond lasers eject material almost stoichiometrically with minimal heat transfer.
Aerosol Transport
The ablation cell is flushed with carrier gas (typically He, sometimes mixed with Ar).
The gas stream carries aerosol particles to the ICP torch. Fast-washout cell designs minimize memory effects and improve time resolution.
Ionization and Detection
Inside the ICP, the aerosol is atomized and ionized.
The resulting ions are analyzed by the mass spectrometer, yielding quantitative and isotopic data.
KEY FEATURES
Laser Types: Excimer (193 nm), Nd:YAG (213/266 nm), and femtosecond sources are most common.
Ablation Cell Design: Determines washout speed, transport efficiency, and spatial resolution.
Spot Size and Resolution: Typically 1–100 µm, enabling micro-analysis and mapping.
Control Software: Synchronizes laser firing, stage movement, and data acquisition.
Direct Solid Sampling: Eliminates need for chemical digestion or solution preparation.
IMPACT ON PERFORMANCE
Elemental Fractionation: Shorter wavelengths and femtosecond lasers reduce thermal effects and improve accuracy.
Spatial Resolution: Adjustable spot sizes allow micron-scale analysis and elemental mapping.
Sample Versatility: Suitable for geological, biological, metallic, ceramic, and synthetic materials.
Throughput: Direct solid analysis reduces preparation time compared with solution-based ICP-MS.
Data Quality: Provides in-situ measurements, preserving spatial context in heterogeneous samples.
CHALLENGES AND LIMITATIONS
Fractionation and Matrix Effects: Differences in volatility and particle transport can cause bias, especially with longer-wavelength lasers.
Transport Efficiency: Aerosol size distribution and washout times affect sensitivity and resolution.
System Complexity: Requires alignment, calibration, and regular maintenance of optics and gas flows.
Cost: High purchase and operating costs compared with solution introduction.
Sample Constraints: Best suited for solid, flat surfaces; porous or uneven samples are more difficult to analyze.