Laser ablation – ICPMS is a multielement, microanalytical technique that has developed rapidly since its inception by Gray in 1985. Its multidisciplinary character follows from applications in various fields such as biology, medicine, geology, archaeology, forensics, materials science, etc. Initially a tool for probing the bulk element concentrations of multifarious solid samples (biological tissues, alloys, plastics, glasses, etc.) via drilling or line scanning actions, it has become a very powerful technique to assess the surface (2-dimensional) and volume (3-dimensional) element distribution. During the last five years, instrumental improvements to the laser ablation cell and its interface with the ICPMS have led to 25-100 times faster surface and volume mapping times, making high resolution scans in reasonable mapping times (hours) possible. With the latest generation of laser ablation – ICPMS instruments one can obtain better than 5x5 µm2 pixel resolution with a detection limit on the µg kg-1 level for most elements of the periodic table. This presentation focused on the fundamentals of the laser ablation – ICPMS technique, the development of the technique, its latest incarnation, and examples of multidisciplinary applications.
B.04 Guest lecture
COBISS.SI-ID: 6550042Plants are world's primary producers representing the basis for animal and human diet. Therefore, it is of extreme importance that they contain sucient amounts of mineral nutrients and essential organic compounds, and low amounts of antinutrients and noxious elements. In addition, plants synthesise a plethora of secondary metabolites that are benecial for human health, or can be used to treat dierent diseases. To maintain homeostasis with optimal cell functioning and integrity and/or to avoid toxicity, proper allocation of elements and biomolecules at organ, tissue, cellular and sub-cellular levels is necessary, with proper element/metal speciation and ligand environment presenting a key to bioavailability and homeostasis in organisms. Studies of element and biomolecular spatial distribution, as well as element speciation and ligand environment, are therefore crucial to reveal the mechanisms of element homeostasis, transport and also tolerance and toxicity. Moreover, element and biomolecular localization studies in grains of staple food crops, are of high applicative value, allowing to determine element/biomolecular concentrations in particular tissues and dierent milling fractions without potential contamination due to mechanical mixing of tissues. In the last two decades, a remarkable progress has been made in the development and the application of dierent 2D imaging techniques in complex biological systems, especially with regard to improved lateral resolution and sensitivity as well as sample preparation. The latest development and applications of focused beam techniques like PIXE, XRF, LA-ICPMS and SIMS in imaging the distributions of elements and biomolecules in plants was presented in this work.
B.04 Guest lecture
COBISS.SI-ID: 5082703Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is one of the up and coming techniques for high resolution (multi)elemental mapping of various matrices at low concentrations. Generally, data are generated in line scanning mode by pulsed laser ablation of the surface and ICP-MS sampling (signal integration) of one or more pulses. Especially with the recent advent of "fast" LA cells, the playing field for elemental mapping has taken a leap forward with regard to mapping time. Only a couple of years ago we were happy with mapping rates of 10k pixels/h, whereas now we can go up to 100k pixels/h without breaking a sweat, and 1000k pixels/h are looming with the latest instrumental improvements. However, one needs to realize that fast mapping may introduce all kinds of imaging artifacts such as blur, aliasing and noise that may deteriorate the image quality when non-optimal operating conditions are used. This presentation offers insights into the selection of optimal conditions for fast and high-quality LA-ICP-MS (multi)elemental mapping to circumvent or minimize these artifacts based on a modeling approach.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 6573850LA-ICP-MS is a well-established microanalytical technique for 2D elemental imaging of samples from biomedical, geological, archaeological, etc. origin. For proper elemental quantification and visualization of features in LA-ICP-MS maps one needs to be aware of image degradation via blur, in the form of “halo effects” (due to the physical size of the laser beam) and “smearing effects” (evoked by poor cell washout and transfer of LA generated particles), and noise (for real-world situations mostly related to flicker noise). To quantify image degradation, ablation targets with periodic gratings are required for the construction of a modulation transfer function (MTF) and subsequent determination of the lateral resolution as a function of image noise and contrast. Since ablation targets with suitable matrix composition are not readily available, computer-generated periodic gratings were virtually ablated via a computational process based on a two-step convolution procedure using empirical/experimental input data. This experimental-modeling procedure simulates LA-ICP-MS imaging based on two consecutive processes, viz. LA sampling (via ablation crater profiles [ACPs]) and aerosol washout / transfer (via single pulse responses [SPRs]). We will demonstrate that by random selection of experimental SPRs from a large database for each individual pulse during the simulation, the convolution procedure simulates an accurate elemental image map of the periodic gratings with realistic noise. In this way indirect retrieval of the experimental lateral resolution is facilitated without performing actual line scanning on periodic gratings. Although lateral resolution is normally used as a quality-criterion for imaging, we will show that linear artifacts with an angular aspect to the line scan direction may have a different spatial resolution, depending on the blur introduced as a result of “smearing effects” by the LA cell/ICP-MS interface. Via the computational approach described above, using a radial resolution target (Siemens star), we were able to visualize this angular resolution dependency. The latest generation of “ultrafast” LA cells, with FW0.01M values lower than 10 ms, minimizes “smearing effects” and as a result, the resolution becomes practically independent of the angular aspect between line scan and artifact, even for very fast scanning.
B.04 Guest lecture
COBISS.SI-ID: 6107162A focus of the research involves Laser Ablation - Inductively Coupled Plasma - Mass Spectrometry (LA-ICP-MS) and hand-held X-ray fluorescence (p-XRF) for the analysis of glaze composition of Dutch tin-glazed earthenware. By means of these analytical techniques, the influence of raw materials on the colour and morphology of Delft tin-glaze objects has been investigated. These techniques are applied to gain greater insight into the provenance of a range of Dutch Delftware.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 6326810