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Laser Ablation - ICP-MS

ESI NWR193UC Laser Ablation SystemWe have an ESI NWR193uc Laser Ablation instrument that can be interfaced to the Nexion ICP-MS for direct solid sampling. This is mainly a microanalysis technique but may also be used for bulk sample analysis.

We use this system for the in-situ analysis of trace and rare earth elements in minerals such as garnets, cpx, olivine, opx, and other silicate as well as carbonate samples.

Major element composition is used as internal standard for concentration determinations, so samples are usually analysed first by the electron probe though this can be done after LA-ICP-MS.

Whenever possible, sections of samples should be prepared 100 micron thick compared to normal thin sections which may only be 30 micron. The size of the glass slide should be 46-48mm long x 25-30 mm width and also conveniently fits the sample holder for the electron probe. Separated grains may be mounted and polished in an epoxy resin block 25 mm in diameter.

LA-ICP-MS craters in garnet and Cr-diopside in a garnet lherzolite from the Kaapvaal craton. Each crater has a diameter of ~80 microns.

Any graphite coating (for probe analysis) should be removed prior to ICP-MS analysis by gentle polishing with a fine diamond paste, rinsed clean and dried.

Finding specific spots to analyse on the LA-ICP-MS can be time-consuming: users are strongly encouraged to bring along printouts of sample 'maps'. Small marks can also be made on the edges of the slide to help locate some features. The microscope on the laser is not equivalent to dedicated petrological microscopes.

We use Glitter software (GEMOC, Australia) for data reduction of LA-ICP-MS data. See the screenshot below for an illustration of Glitter, which makes data processing very efficient and powerful.of the smaller features. 

Software used for Laser Ablation Data Reduction

Earth Sciences at Cambridge