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Laser Ablation ICP-MS


LA-ICP-MS (laser ablation in combination with inductively coupled plasma mass spectrometry) combines laser ablation with mass spectrometry, thus enabling analyses of very small samples in the range of a few micrograms (μg) combined with high spatial resolution. The LA-ICP-MS is therefore essentially non-invasive – an invaluable asset for particularly valuable objects.


The LA-ICP-MS is a method that has been established and continuously developed in recent decades not only in archaeometry, geo- and materials science, but also in many other fields. The combination of laser ablation and mass spectrometry with inductively coupled plasma enables a quantitative, spatially resolved analysis of the major, minor and trace elements on the basis of very small sample quantities in the order of a few µg. Due to the small sample mass required for analysis, the method can be characterized as non-invasive, which is of utmost importance for valuable objects.

Trace element analysis can be applied in order to answer various questions in archaeometry, e.g. regarding provenance, authenticity, fineness and purity, workshop identification or, for example, to distinguish different metal batches of the objects examined.

Two different setups are available:

–          A stationary LA-ICP-MS is routinely used at CEZA for trace element analysis in metals (gold, silver, copper and iron alloys). Ablation is performed either on a tiny sample or in situ on smaller objects (see below). Wet chemical digestion, which is problematic with many materials, can be avoided by analysis with a stationary LA setup.

–          The portable LA-Setup (pLA) is currently used for major, minor and trace element analysis of gold objects, as well as for nearly non-invasive sampling for the determination of lead isotope ratios of silver objects. Further developments of this method for the sampling of other materials is in progress. Generally, transportable LA systems allow samples to be taken independently of a laboratory environment. The mobile setup can be applied worldwide, for example in museums, making transport of the objects to be examined unnecessary. In addition, this method offers the possibility to analyze much larger objects than with the laboratory-based LA-ICP-MS (see below).

In addition to metals, a large number of other materials can also be analyzed with regard to different questions. We are currently developing further applications from various fields for both LA systems. You are welcome to contact us for any questions or suggestions.


Laser ablation is a special sampling technique that is mostly used on solids. A laser beam is focused to a diameter of only a few µm (2-100 µm [stationary setup] or 55-120 µm [portable setup]) on the sample surface. This creates a physical plasma, i.e. an electrically charged gas, at this position. The material heats up very strongly – yet limited to the diameter of the laser focus – so that some part of the material is detached. This process is defined as an ablation process.

In the case of the stationary UV laser device (Resonetics 50-E with an ATL SI-300 laser, λ = 193 nm ArF), this is coupled with the analytical instrument, an ICP mass spectrometer (Thermo Fisher ICAPQ with CCT [collision cell technology]); the ablated material is transported to the mass spectrometer by a carrier gas. In the portable laser setup (Bright Solutions Wedge HB 532, λ = 532 nm in combination with a custom ablation unit from the ETH Zurich), however, the ablated material is first collected on membrane filters on site, for example in a museum, and then transported to the laboratories. There, the material is dissolved from the filter with various acids depending on the material under investigation and the filter used. In a further step, the chemical and/or isotopic composition is subsequently determined by means of ICP mass-spectrometry.

The stationary LA-ICP-MS offers various advantages over conventional analysis in solution, inter alia the processing of very small samples, in-situ measurements with high sensitivity (e.g. of solder joints) and a spatially resolved analysis (e.g. of inclusions, “coatings”, gold plating), as well as the possibility of relatively fast serial analyses with high sensitivity. With the stationary system, a wet-chemical digestion is not required, rendering the method particularly suitable for materials that are not easily dissolved. Since this is not necessary, the sample material is usually almost completely preserved and is therefore available for further analyses (e.g. isotope analyses).

In case of the stationary system, the maximum dimensions of the object to be analyzed are limited by the size of the ablation chamber. With the portable LA setup, the quasi-non-invasive sampling for chemical and/or isotopic analysis can also take place outside the laboratory. In addition, the sampling of large objects is possible. Other mobile methods, such as X-ray fluorescence analysis, are completely non-invasive but are much less sensitive. Among other things, such analyses are usually not sufficient to answer questions regarding the origin and authenticity of objects. In addition, laser ablation can examine much deeper layers of the material (approx. 100-200 µm). The commercial offer of the mobile LA method currently represents a unique feature of CEZA.

Figure 1 – The mobile laser ablation setup (schematics). Draft: Moritz Numrich (CEZA); Photograph of the Lockenring: W. P. Tolstikow – M. J. Trejster, Der Schatz aus Troja. Stuttgart, Zürich 1996/97, 60, Kat.-Nr. 35.
Figure 2 – The mobile laser ablation setup. Photograph: Elka Duberow (CEZA).

Quantitative chemical analyses may generally be accomplished for most elements in the mass range from 7Li to 238U. In general, the elements to be analyzed depend on the sample material and the research question. Most often the lack of reference material is the limiting factor. In the case of the stationary LA-ICP-MS, gold, silver, copper alloys and iron are routinely analyzed with detection limits in the ppb and ppm range. But also other materials such as glass are examined in our laboratory, while the portable LA system, as mentioned above, is currently primarily used for the analyses of gold and silver objects.

While the described chemical steps are carried out in a clean room, the samples are taken with the described laser ablation systems in a special laser laboratory. However, the mobile laser system can be used outside of these laboratories without limitations.


The LA-ICP-MS method is characterized by minimally-invasive sampling with significantly increased sensitivity compared with other portable methods.

If the objects to be examined can be transported to the CEZA laboratories and their dimensions do not exceed those of the sample chamber (dimensions: see below), stationary analysis in the laboratory is recommended. Ablation parameters can be adapted to the sample material or object to be examined. Moreover, when using the stationary LA-ICP-MS, a depth profile analysis of the examined object or sample is also possible which enables the direct analyses of the unaltered surfaces.

Non-transportable and/or larger objects can be examined worldwide with the mobile laser ablation system. However, travel costs have to be taken into account in addition to the analyses themselves.

Sample properties

Stationary LA setup:

The maximum sample size is determined by the size of the sample chamber. Its interior measures approx. 65 x 75 x 25 mm. However, the actual volume that can be used is slightly smaller, about 45 x 45 x 25 mm. Ideally, the objects to be analyzed are prepared specimens, such as polished sections. But also fragments, chips or small objects with a height of up to approx. 25 mm can usually be mounted in the sample chamber without problems. Chips or shavings can theoretically also be very small, almost powdery. For larger series of analyses, however, the samples should be at least 1-2 mm long and 1 mm wide.

Portable LA setup:

With the portable method, objects of any size can be examined. Both planar and convex surfaces of the objects to be examined can usually be sampled without any restrictions. If the inside of concave objects is to be sampled, the mobile setup is currently limited to objects with a larger diameter in the range of several centimeters.

Please do not hesitate to contact us regarding an assessment of the sampling possibilities.