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Crustal Geophysics and Geochemistry Science Center

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Laser Ablation ICP-MS Laboratory

Photo of New Wave UP 213 Laser Ablation System
New Wave UP 213 Laser Ablation System
The Laser Ablation (LA) ICP-MS facility operates operates two quadrupole ICP-MS systems dedicated to Laser Ablation work to perform direct analyses of virtually any material. The LA-ICP-MS technique is particularly useful for in-situ analyses of trace elements for applications requiring understanding of the spatial variation of elemental content within the sample.

The laboratory currently operates an ELAN 6000 quadrupole ICP-MS and an ELAN DRC. Several Laser Ablation systems are available covering a wide range of specific applications, including a solid-state 193 nm system, a 213 nm system, a 266 nm system and a large spot capable 266 nm system (see picture). The high energy UV laser ablation (LA) system produces craters in the sample ranging in size from 2 microns to 1200 microns. The ablated material is then swept from the sample cell directly into the plasma of the ICP-MS. The ablated material is then ionized similarly to any liquid sample aerosol (for more information on ICP-MS). The LA system is fully computer controlled with a real-time video imaging system capable of reflected and transmitted light (polarized light available) viewing. The system can be programmed to ablate continuous lines, spots or a variety of more complex ablation patterns.

Samples intended for LA-ICP-MS can be prepared in a variety of routine ways. The LA systems employed by the lab routinely accept standard thin sections, thick sections, thin section sized chips up to 1 cm thick, microprobe round mounts or any sample less than 1.5 cm thick and less than 45 mm in diameter.

Quantitative LA-ICP-MS analyses are possible if the following criteria are met:

  1. the sample must be of somewhat known matrix (i.e., is it a pyrite or chalcopyrite?) and must be known or assumed to be of known major element composition (i.e., is it stoichiometric pyrite or does it contain 5% arsenic?)
  2. the sample must be of matrix of which a calibration standard reference material (SRM) of close matrix match is available.

The technique is capable of determining many trace elements down to low ppm or even ppb levels, although absolute detection levels are highly element, sample matrix and spot size dependant. New developments with both smaller and larger craters now allow new directions in understanding geological processes.

Photo of laser ablation laboratory.The USGS LA-ICP-MS facility has been involved in a wide variety of studies involving geological, biological, environmental and material science related samples. Examples of materials studied by LA-ICP-MS include trace element studies of coral, sheep horns, bird feathers, shells, bones, tree rings, whiskers, teeth, sulfides, silicates, phosphates and phosphatic materials, pipe scale, steel, bitumen, coal, glasses and pressed powders. Current areas of development include new routines for automated trace element mapping of minerals, trace element analyses of fluid inclusions, improved methods for analyses of biological materials, improvements of accuracy and precision for all analyses and improved methods for data processing. The lab works closely with the USGS Geochemical Reference Materials Program, developing and characterizing new microanalytical reference materials.

The application of laser ablation for in-situ isotopic measurements using the multi-collector ICP-MS is also under development.

A few examples of materials studied by LA-ICP-MS:

Photo of garnet ablated by the laser. Photo of coal and pyrite ablated by the laser.
The photomicrographs above show the detail of craters ablated by the laser in the solid materials. The spot sizes range from 100 microns in the garnet (above left) and the coal (above right) and 10 microns in the pyrite (above right).
Photo of LA-ICP-MS line scan through moose tooth and graph of raw data.
Analysis of moose teeth: LA-ICP-MS line scan through glue, dark material, enamel and dentine. The graph is raw ICP-MS signal (cps). Note the enrichment of Mn, Zn and Pb in this dark material. The Pb signal in this analysis is higher than most others of the dark material.
Photo of bitumin ablated by the laser.
The photomicrograph above shows LA line scans ablated in bitumen (50 micron diameter lines).

The use of firm, trade, and brand names is for identification purposes only and does not constitute endorsement by the U.S. government.

For further information contact Alan Koenig (akoenig@usgs.gov).

Mineral Resources Program
Eastern Central GMEG Alaska Minerals Information Crustal Geophysics and Geochemistry Spatial Data

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