ICP-MS Techniques

Laser ablation trace element analysis (concentration measurements in solid samples)

Variety of trace elements in silicate, sulphide and carbonate materials can be analysed in solid samples using laser ablation ICP-MS. The list of elements that can be determined and their respective detection limits will depend on the type of sample (matrix), required spatial resolution and availability of suitable standards - please contact us for details. Normally, ppm (ppb) to % concentration levels can be detected and the precision on individual analyses usually varies between 5-10%. All analyses are verified using international reference materials and/or secondary standards. Samples should be prepared as polished 1 inch in diameter mounts in epoxy resin or conventional polished electron microprobe/SEM sections, preferably at least 100 microns thick (no coating is required). In order to speed up the analysis, it is advisable that the users prepare a detailed map of each sample in advance. The analytical protocol follows the procedure outlined in

Longerich HP, Jackson SE and Günther D (1996): Laser ablation-inductively coupled plasma mass spectrometric transient signal data acquisition and analyte concentration calculation. J. Anal. At. Spectrom. 11, 899–904.

One elemental analysis by laser ablation usually takes 2-3 minutes and the results are processed off-line using the Glitter software.

U-Th-Pb dating of accessory minerals (in-situ isotopic analysis)

Laser ablation ICP-MS can now be routinely used for in-situ U-Th-Pb dating of zircons and monazites, although dating of other phases that require a common lead correction such as is allanite or titanite is under development (please enquire for details). Laser ablation zircon dating is especially useful for sediment provenance studies where 60-120 detrital zircon grains should be dated per sample. Precise and accurate Th-Pb and U-Pb ages can also be determined for metamorphic monazites analysed in-situ from a polished thin section. The precision on individual ages usually varies between 1-5 %, subject to the mineral age, U content and the grain size. All analyses are verified using a secondary zircon or monazite standard. Zircon samples for detrital studies should be prepared as polished 1 inch in diameter mounts in epoxy resin, monazite grains can also be analysed from conventional polished electron microprobe sections (no coating is required). Please contact us for advice with sample preparation. In order to ease the data interpretation and to speed up the analysis, we urge the users to image the grains using BSE and/or CL techniques and to prepare a detailed map of each sample prior the analysis by laser ablation. The technique follows the analytical procedures outlined in

Košler J, Fonneland H, Sylvester P, Tubrett M, Pedersen RB (2002): U-Pb dating of detrital zircons for sediment provenance studies – a comparison of laser ablation ICPMS and SIMS techniques. - Chemical Geology, 182, 605-618.

and

Košler J, Sylvester PJ (2003): Present trends and the future of zircon in geochronology: laser ablation ICPMS. In: Hanchar JM and Hoskin PWO (eds), Zircon. Reviews in Mineralogy & Geochemistry, vol 53, 243-275.

One analysis takes ca. 4 minutes and the results are processed off-line using an Excel spreadsheet based program (LAMDATE) and Kenneth Ludwig's IsoplotEx. Additional information on laser ablation ICP-MS dating of accessory minerals can be found in the ST-19 short course material from 2004 Plasma Spectrochemistry Winter Conference.

Laser ablation ICP-MS analysis of isotopic ratios (in-situ isotopic analysis)

Variety of isotopic ratio measurements can be obtained in-situ from solid samples using laser ablation coupled either to our single-collector (Element 2) or to multi-collector (Neptune) ICP-MS instrument. As some of these techniques are still under development, please contact us for more information on isotopes and types of samples that can be analysed.

Trace element analysis of solutions by ICP-MS (bulk sample solution analysis)

Concentration of trace elements (down to sub ppb level) can be determined using our single-collector ICP-MS (Element 2). Sample matrices that we routinely deal with include variety of geological (rocks and minerals), archaelogical (artefacts, building material) and biological (tissues, blood serum, proteins) materials and water. It is important that all samples are digested and then dissolved in weak mineral acids (normally 2% HNO3) prior to the analysis by ICP-MS. Contact us for advice with sample preparation.

Isotopic ratio analysis of solutions by ICP-MS (bulk sample solution analysis)

Variety of isotopic ratio measurements can be obtained by analysis of solutions using our multi-collector (NU Plasma II) ICP-MS instrument. Elements that are to be analysed for isotopic composition have to be chemically separated from the sample matrix prior to the analysis by MC ICP-MS. Contact us for advise with sample preparation. Commonly analysed elements include Nd, Hf, Sr, Pb and Li. Techniques for isotopic analysis of Fe, B and U-Th series are currently being developed.

Inductively coupled plasma mass spectrometry (ICP-MS)

ICPMS is analytical instrumental technique that is capable of measuring isotopic composition and concentration of elements present in the samples. The samples are introduced either as solutions in the form of a fine aerosol in Ar or Ar-He gas mixture (solution ICP-MS) or, alternatively, solid materials can be sampled directly (in situ) using laser ablation. The laser ablation sampling utilizes highly energetic photons generated in a laser (light amplification by stimulated emission of radiation) to liberate fine particles (aerosol) from the solid sample. The aerosol is then analyzed in the ICP mass spectrometer. Laser ablation results in damage of the sample surface and in the formation of a laser pit that is up to few hundred microns in diameter and ca. 20 - 200 microns deep. The ablated material is carried away in a stream of inert gas (argon or helium) to the ICP source of the mass spectrometer. The fine aerosol from the solution, or the ablated material from the laser sampling, enter the RF-generated argon plasma (temperatures up to 10 000 K) where almost all atoms and molecules are converted to ions before they enter the vacuum stage of the mass spectrometer through a small entrance hole in the interface. The ions are accelerated and focused into an ion beam by a series of electrostatic lenses. The ion beam is then analyzed in magnetic sector (mass filter) and ions are separated on the basis of their mass/charge ratio so that only specific isotopes are allowed through the filter and can enter the detector. Single collector instruments detect the ions sequentially, usually using an electron multiplier detector. Multiple collector instruments use a number of detectors (electron multipliers, faraday cups or a combination of the two) for simultaneous detection of several ion beams and are capable of achieving precise (down to 5-10 ppm) isotopic ratio measurements. 

Further comprehensive information on the technique can be found in "Inductively Coupled Plasma Mass Spectrometry" edited by Akbar Montaser (Wiley-VCH, 1998), "Laser Ablation ICPMS in the Earth Sciences" edited by Paul Sylvester (MAC Short course 29, 2001) and "Laser Ablation ICP–MS in the Earth Sciences: Current Practices and Outstanding Issues" edited by Paul Sylvester (MAC Short course 40, 2008).

Inductively coupled plasma optical emission spectrometry (ICP-OES)

ICP-OES utilizes the high temperature in the ICP to atomize and ionize elements present in the sample (solution or aerosol generated by laser ablation). The atomic emission spectrum is then analyzed in echelle spectrometer and captured by a CCD camera. The processed CCD images are converted to signal intensities for individual chemical elements, and subsequently to their concentrations in the analyzed samples. The technique is suitable for major (wt%) and trace (ppm) element analysis of geological, environmental and biological samples.