Detlef Günther

Colloidal quantum dots (QDs) have become firmly established in the display market, yet many relevant QD compositions contain heavy metals whose concentrations are regulated in consumer products. Accurate characterization of hazardous metal content in QD displays is therefore essential but challenging due to their complex multilayer structure. Here, a commercially available QD display film is analyzed using complementary techniques, with laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) as the central tool. The film contains CdSe‐based core‐shell QDs as the green component and, for the first time in a commercial product, lead halide perovskite (LHP) QDs as the red component. Principal component analysis combined with k‐means clustering enabled the extraction of bead‐like pixel populations corresponding to CdSe and LHP QDs, with classification accuracies of 84% and 95%, respectively. This approach establishes a pathway toward advanced analytical strategies for assessing the regulatory compliance of commercial QD displays.

Material deposition during laser ablation in nitrogen was assessed and compared with the laser-induced fractionation in helium. In addition, the ICP-induced fractionation of a N ₂ -ICPMS was also compared to a conventional Ar-ICPMS.

Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS), particularly in its time-of-flight (TOF) configuration, enables rapid, high-resolution elemental imaging across complex geological materials, offering spatial and chemical insights at the micrometer scale. However, quantitative accuracy is often limited in fine-grained or mineralogically heterogeneous matrices due to the failure of global normalization strategies, such as 100 wt % oxide assumptions, to account for mixed-phase compositions. Here, we present a workflow that leverages Uniform Manifold Approximation and Projection (UMAP) for unsupervised dimensionality reduction and k-means clustering to segment mineralogical phases directly from per-pixel elemental concentration maps. Cluster compositions are matched to known minerals based on stoichiometric similarity, enabling pixel-wise, phase-specific normalization (e.g., oxides vs carbonates). Validated with dawsonite-bearing sandstones from Mt. Amiata, Italy, this approach significantly reduces quantification errors, correcting systematic over- or underestimations of up to 60%. The method also enables a consistent, phase-resolved geochemical comparison across depth profiles. This study establishes UMAP not only as an exploratory tool but also as a practical guideline for accurate and interpretable quantification in multielemental imaging.

In 2016, five fragments from a copy of “The Great Holy Family of Francis I” were brought to the Cologne Institute of Conservation Sciences (CICS) for research and conserva-tion/restoration. A comprehensive technical and material analysis was carried out to as-sist provenance studies. From the analysis of pigments, binder, additives, and canvas fi-bres alongside radiocarbon dating of the lead white pigment, oil binder, and canvas sup-port, as well as the lead stable isotope study, it could be determined that, with high proba-bility, the copy was created in Northern Europe between the late 16th century and the mid-17th century. During this period the original painting was initially displayed in Fon-tainebleau in the “Chapelle Haute” before being transferred in the early 17th century to the newly built “Cabinet des Peintures”, also in Fontainebleau, where it would probably have been more accessible for copying. Interestingly, the written sources describe a copy made during this period to replace the original in the “Chapelle Haute”, the location of which is currently not known. However, the different overall dimensions of the present copy speak against it, having been created to replace the original.

Dual sample introduction of laser-induced aerosols and monodisperse microdroplets into an ICP-TOFMS enabled accurate quantification across inorganic and proteinaceous matrices.

Quantitative assessment of the sensitivity difference of gaseous and particulate carbon in LA-ICP-MS.

The composition of laser generated aerosols produced during single spot ablation was analyzed by inductively coupled plasma time of flight mass spectrometry (LA-ICP-TOFMS) and compared to that if the corresponding material deposited on the sample surface. Differences between the signals recorded during single spot ablation and by analysis of the deposits allowed to study and describe non-stoichiometric processes at the ablation site. These measurements allowed for the determination of transport efficiencies for the elements measured in NIST SRM 610, which were element specific and always higher than 85 %. A mass balance of, e.g., ²³⁸U⁺/²³²Th⁺ signal intensity ratios allowed differentiation of laser-induced and ICP-induced elemental fractionation based on LA-ICP-TOFMS data only, i.e., without the need for off-line analysis of collected material. All phenomena reported here were studied using a range of laser fluences (7.4 – 25 J/cm²) and for single spot ablation (100 – 600 pulses per spot). The method presented here provided direct access to important parameters, which influence the accuracy of quantitative analysis in LA-ICPMS, such as the amount and composition of deposited material around the crater and information about the aforementioned transport efficiencies for individual elements. In addition, the proposed analysis and calculation procedure allowed distinguishing laser- and ICP-induced elemental fractionation for different LA and ICPMS operating conditions. Knowledge about these parameters will allow to study the ablation behavior of different matrices and may therefore improve non-matrix matched quantification in LA-ICPMS.

Benzene vapor was introduced into the reaction cell of an inductively coupled plasma tandem mass spectrometer. By evaporating benzene into the helium supply of the octopole reaction cell, product ion spectra for plasma-based atomic and molecular ions were recorded. Based on these spectra, product ions for the separation of the atomic ions from spectral overlaps from isobaric or molecular ion interferents were selected. Background equivalent concentrations (BECs) or sensitivity ratios for analytes and interferents were compared to on-mass analyses without benzene addition. Depending on the analyte, up to 4 orders of magnitude improvement could be achieved. Specifically, the detection of S and Se could be improved substantially, and their BECs were reduced to the μg/L and ng/L ranges, respectively. The separation of isobaric Rb and Sr isotopes or of CeO⁺ from Gd⁺ was less effective with the use of benzene adducts alone. The separation could be substantially improved by using benzene and oxo or water adducts, and analyte/interferent sensitivity ratios greater than 10⁴ were obtained. Finally, the attenuation of ¹⁴N₂⁺, interfering with ²⁸Si⁺, was evaluated under dry plasma conditions. In this case, benzene could be used to lower the BEC for Si in both on-mass and mass-shift measurements by nearly 3 orders of magnitude.

An calibration methodology for laser ablation-single-particle inductively coupled plasma mass spectrometry (LA-sp-ICP-MS) of nanoparticles without the need for particulate reference material is presented.