Research and Thesis Projects
Characterization and Evaluation of a Nitrogen based Microwave Inductively Coupled Atmospheric-Pressure Plasma as Ion Source for Inorganic Mass Spectrometry
Keywords: nitrogen plasma, microwave-induced plasma, mass spectrometry, characterization
Nitrogen based plasmas gained a lot of attention as alternative ion source for ICPMS due to the environmental-friendly nitrogen gas and its lower operating cost to sustain the plasma. However, initial plasma generation approaches were limited by their low operating power. In this project a recently developed high-power microwave inductively coupled atmospheric-pressure plasma (MICAP) is investigated as ion source for mass spectrometry (MS). The studies focus on fundamental properties of the MICAP ion source and its performance in element and isotope analyses. The combination of the new source with different sample introduction systems such as pneumatic nebulization and laser ablation is evaluated with respect to analyte sensitivity, molecular ion formation as well as attenuation of plasma background ions using a dynamic reaction cell. Additionally, the influence of the plasma solvent load and the matrix tolerance of the ion source are investigated. Furthermore, the abundances and impact of nitrogen based spectral interferences in the N2 MICAP are analysed.
Doctoral Student: Monique Kuonen
Funding: SNSF project number 200021_197224
Coupling laser ablation to a nitrogen microwave inductively coupled atmospheric-pressure plasma mass spectrometer (MICAP-MS) for elemental analysis
Keywords: Laser ablation, nitrogen plasma, mass spectrometry
Laser ablation (LA) as a solid sampling technique has been established over the years for direct analysis while remaining micro-invasive. This enabled a broad range of applications in material sciences, forensics, geology, medicine and among others. More recently, a high-power microwave inductively coupled atmospheric-pressure plasma (MICAP) using nitrogen proved to be competitive with the traditional argon plasma source for elemental mass spectrometry. Unlike the argon ICP, the MICAP has proven to be stable towards introduction of direct air. Furthermore, nitrogen remains an unexplored ablation environment and the ablation behavior as well as the aerosol transport under nitrogen will be studied as a cheaper alternative to helium and argon. Combining LA with such a versatile plasma source as the N2-MICAP opens new possibilities in terms of analytical procedures or hardware compatibility. Ultimately, the reduction of the measurement costs by replacing argon with nitrogen will increase the accessibility of elemental analysis for all types of proven applications.
Doctoral Student: Dylan Käser
Funding: Radom™ Corporation, USA
Rare Earth Elements in Wastewater
Keywords: Nanoparticles, Single-particle ICP MS, Rare earth elements, Environmental samples
Rare earth elements are increasingly critical to modern technology. Defined by IUPAC as scandium, yttrium and the lanthanides, they have a wide range of applications, from magnets to optical technology, and are intensively mined. Due to their now widespread use, they are considered to be emerging micropollutants, but the knowledge about their impact on the environment is still limited.
In the course of this project, their behavior in wastewater treatment plants is investigated, as they regulate the amount of anthropogenic REE that will enter surface waters. Samples from effluent, influent and sewage sludge are analyzed by ICP-MS, and the removal efficiency of the REE is determined. Furthermore, sp-ICP-MS is used to gain information on the elemental composition of REE particles present in wastewater, and establish under which form REE are most commonly present. The impact of REEs on the bioaccumulator freshwater mussel Dreissena bugensis and REE concentration in tissue and shell sample will be studied in order to evaluate if they can be used as a biomonitor to track REE emissions.
Doctoral Student: Chiara Fabbretti
Funding: ETH Zurich, Grant: ETH-30 21-2
Collaboration: Ralf Kägi, Eawag
High resolution Imaging of Dawsonite using LA-ICP-TOFMS
Keywords: LA-ICPMS, imaging, geological samples
Over the past decades Carbon Capture Storage (CCS) has been widely investigated as a possibility for the safe storage of anthropogenically emitted CO2. A mineral, which shows promising characteristics for CCS, is Dawsonite, NaAl(CO3)(OH)2, which is formed in saline aquifers through a process known as mineral trapping, wherein CO2 becomes immobilized. Initially discovered in Quebec, Canada, in 1874, Dawsonite has since been found in numerous locations worldwide, like the Green River Formation (USA) and the Hailaer Basin (China). Variations in the composition of the host-rock minerals have been identified as significant factors influencing the quantity of storable CO2 and the formation of Dawsonite in general. However, a comprehensive examination of the precise composition, including trace elements, of both Dawsonite itself and the host-rock mineral remains incomplete.
Elemental imaging offers a promising approach to determine a geological material’s composition. By using the method proposed by Neff et al. in 2020, employing LA-ICPTOF-MS (Laser Ablation-Inductively Coupled Plasma-Time of Flight-Mass Spectrometry), a 2D quantitative elemental distribution over the sample’s surface with a remarkable resolution as fine as 5 μm can be achieved. Notably, major, minor and trace elements can be detected due to the high sensitivity of ICP-MS. In this study, we carry out the analytical characterization of a dawsonite sample occurring within rocks of the geothermal system of Mt. Amiata (Italy) to constrain the conditions at which this mineral formed in its geological environment.
Doctoral Student: Barbara Umfahrer
Funding: ETH Zurich
Collaboration: Paolo S. Garofalo, Università degli Studi di Bologna
Development of novel sample preparation and quantification approaches in LA-ICP-MS
Keywords: Mass Spectrometry Imaging, Sample Preparation, LA-ICP-TOFMS
LA-ICP-MS, especially when combined with TOF technology, enables rapid elemental analysis across diverse sample types, including minerals, polymers, metals and biological specimen. While count-rate based distribution maps already provide valuable insights into the spatial distribution of major, minor and trace components, converting these signals into concentrations would enhance data comparability and interpretation. However, quantitative analysis is often limited by the lack of suitable reference materials, particularly for biological tissues. To address this, two strategies are being investigated: non-matrix-matched quantification of various materials using microdroplets and in-vitro fossilization of soft tissues such as skin, liver or kidney. Microdroplets allow us to introduce discrete nm to µm sized salt particles that behave similarly to the laser-induced aerosols when being vaporized, atomized and ionized in the plasma. On the other hand, in-vitro fossilization introduces SiOx networks into biological tissue, assimilating a glass matrix comparable to common microanalytical reference materials used in LA-ICP-MS. Overall, this approach could enable quantitative analysis while correcting for instrumental drift as well as variations in ablation rates, advancing elemental bioimaging beyond current capabilities.
Doctoral Student: Tobias Schöberl
Funding: SNSF 200021-231340