Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)
Sample introduction to the ICP-MS system is setup for both liquid samples by nebulizer and solid material by laser ablation. For liquid samples contact Jürgen Kuhn (Jurgen.kuhn [at] biol.lu.se), for laser ablation contact Tomas Næraa (tomas.naeraa [at] geol.lu.se).
LA-ICP-MS is a powerful method for element analysis in a wide variety of solid materials (i.e. minerals, bone & teeth materials, wood, ceramics, etc.) at spatial resolutions from a few up to several hundred µm. Quantitative analyses can be obtained for most elements in the mass range 5-250 amu (practically 7Li to 238U).
At the laboratory we have a number of analytical procedures that are done routinely, which are listed below. We are always interested in developing new methods together with users of the laboratory, so please contact us to discuss your project. At the lab we use the software Iolite for data reduction.
Laser spot dimensions
The laser system has two different apertures for controlling beam size and shape. The mask aperture provides predefined circular and square spots with sizes that range from 1 to 155 µm; these spots can further be expanded through a lens which increases the size with 1.6 meaning the maximum spot size is 258 µm. The x-y aperture provides similar sized ablation spots either as squares or rectangles that can rotate 360 degrees.
Tubing between laser and ICP-MS
We are operating either with tygon tubing with an insert “squid” for signal smoothing or with ARIS (Aerosol Rapid Introduction System) by which it is possibly to resolve single pulses at sample rates up to 60 Hz.
Sample holders and preparation
We have three different sample holders, one that holds 9 one inch mounts (2.54 cm in diameter), one that holds two to four thin-sections and three one inch mounts and one for odd size samples (10*10 cm and max 1 cm high).
In order to avoid mistakes and to obtain the best results possible, please consult the laboratory prior to your sample preparation.
In the software that controls the laser, it is possibly to work on several image layers (e.g. images from SEM or light microscope) for easier navigation on samples. Also the software is setup for creating mosaics which can also be used for easier navigation on samples. Proper image preparation will greatly help your work and optimize your analytical time at the instrument, and we are happy to help with the image preparation.
U-Pb isotope age dating
We have methods set up for precise U-Pb ages for a number of uranium bearing accessory minerals such as zircon, monazite, baddeleyite, rutile, titanite and apatite among others.
Routine methods or methods under development at the lab
- Zircon U-Pb: We routinely use reference zircon GJ1 and 91500 as primary and secondary standards. Depending on zircon grain size and internal textures, spot size is routinely set between 20 and 35 µm. For such settings 206Pb/238U age precision on 91500 are around 1.5-2 % on single spot analyses.
- Monazite U-Pb: For this method we use monazite 44069 as primary standard and we are in the process of developing several in-house reference monazites. Spot sizes are in the range of ca. 5 to 15 µm.
- Titanite U-Pb: For this method we use MKED1, ONT2 and Khan as reference materials. Spot size range from 25 µm.
- Baddeleyite U-Pb: This method is under development. Our test results show that we can ablate with ca. 20 µm spot size and obtain sample average 207Pb/206Pb age precision around 0.3-0.5 %.
Reference materials at the lab
- GJ1 - natural zircon for U-Pb
- 91500 - natural zircon for U-Pb
- 44069 - natural monazite for U-Pb + several natural in-house materials
- MKED1 - natural titanite for U-Pb and trace elements
- Baddeleyite (several natural in-house reference samples)
Trace element analyses are possible for most solid materials; the main limiting factor is weather materials can be ablated with the laser beam. Another factor is the quantification of element concentrations; this can be done if matrix matched material of known concentration is available. However for many silicate materials, NIST standard glasses are sufficient for element quantification.
- Silicates, e.g. garnet, zircon and epidote, calibration using NIST 610-612-614 glass and USGS basaltic glasses (e.g. BCR2G/BHVO)
- Titanite, calibration using MKED1, ONT2 and Khan natural titanite
- Chromite, calibration using inhouse reference material together with NIST glass
Other possible materials
- Bone, teeth materials, wood, ceramics, etc.
Reference materials at the lab
- NIST glasses - 610, 612 and 614
- BCR - basalt glass
- BHVO - basalt glass
- MASS-1 - sulfide, pressed pellet
- MACS-3 – carbonate, pressed pellet
2D trace element maps can be done on various materials. Imaging is an area under fast development and a focus area for this laboratory. We are in the process of installing an ARIS (Aerosol Rapid Introduction System) which allows the user to resolve individual single pulses at sampling rates of up to 30 Hz for biological materials and up to 60 Hz for geological materials.
Below is shown an example with mapping a oolite grain. The figure shows a trace element map with U concentration shown in color scale and Mg and Ba concentrations shown on the z-axis. In the example, we used a 20x20 µm square spots, 8 Hz pulse rate, 2 J/cm2 and a scanning speed of 8 µm/sec. Trace element image setup is done with Iolite.