The Langmuir Group

Laser Ablation (LA)-ICP-MS

Introduction

Laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS) has been widely used as a powerful analytical technique for solid micro sampling analyses in geological, biological, environmental, nuclear, and metallurgical applications. It is a rapid and moderate cost technique for analytical chemists. The technique combines the advantages of the high sensitivity multi-element capability by ICP-MS and in situ micro solid sampling by LA. It is particularly attractive to scientists who want to study dissolution-resistant solid materials or study spatial distributions of trace elements and isotopic composition in a micro scale area on sample surfaces.

Advantages

Direct analysis of solid materials, particularly for dissolution-resistant minerals.
Minimum sample preparation.
Reduced reagent and labor costs.
Providing spatial information by allowing analysis of small selected areas.
Avoiding solvent induced spectral interferences.
Avoiding volatile element loss (e.g. As and Se).
Avoiding dilution errors and sample transfer losses arising from sample handling steps.

Principles

In analytical atomic spectrometry, free atoms or ions are required for the interaction with light energy. The sampling-generation of such free atoms or ions by dissociation and ionization can be achieved either in one-step process (e.g., arcs or sparks) or two-step process (e.g., combination of an arc with ICP-MS). The potential use of laser light as vaporization, dissociation and excitation source for spectrometric analysis was known soon after the first report of laser action in ruby. A laser beam focused by the optics of a microscope on the surface of a solid can lead to the evaporation of a micro amount of sample. There are two distinctive categories for the role of lasers in atomic spectrometry: using laser for both ablating and ionizing the sample (one-step) or using laser only introducing material materials into an ionizing devices (two-step). In one-step techniques, the laser energy affects the sampling, atomization and excitations. The measured signal may not be a direct function of ablated mass since the ablated materials is not fully vaporized. Two-step procedures have two nearly independent processes. After laser ablation deals only with sampling, the micro amount of the laser-ablated materials is transported by a carrier gas to the second excitation process (e.g., ICP). In the second process, the ablated materials are evaporated, atomized, and excited by the second energy source. An advantage of this two-step operation is the potential of increased efficiencies during the evaporation, atomization, and excitation steps. In LA-ICP-MS, it uses two step procedures to combine a laser ablation sampling system with a high sensitivity multi-element ICP-MS.

Schematic of Laser Ablation System

Data Acquisition

LA-ICP-MSData Acquisition

Precision and Accuracy

Precision of BHVO-2 Silicate Glass Analysis by LA-ICP-MS

Precision

Accuracy of BHVO-2 Silicate Glass Analysis by LA-ICP-MS

Accuracy

Applications

Due to its rapid method, moderate cost and combination of the advantages of the high sensitivity multi-element capability by ICP-MS and in situ micro solid sampling by LA, LA-ICP-MS has been widely used as a powerful analytical technique for solid micro sampling analyses in geological, biological, environmental, nuclear, and metallurgical applications. It is particularly attractive to scientists who want to study dissolution-resistant solid materials or study spatial distributions of trace elements in a micro scale area on the sample surface. Some of applications using LA-ICP-MS are shown below.