Open Access

Ziel dieses Forschungsprojekts war es, eine leistungsfähige Gesamtstrategie zur Bestimmung von leicht flüchtigen organischen Verbindungen (VVOC) auf Grundlage der Prüfmethode aus ISO 16000-6 in Verbindung mit EN 16516 vorzuschlagen. Es soll bei Emissionsmessungen sowohl aus Bauprodukten als auch in der Innenraumluft angewendet werden können und ein großes Emissionsspektrum abdecken, um möglichst wenige Einzelprüfungen durchführen zu müssen. Als Gegenstand für sämtliche Untersuchungen diente ein 60-komponentiger Testgasstandard. Mit dessen Hilfe erfolgten dann schließlich systematische Eignungsuntersuchungen für Chromatographiesäulen und Adsorbenzien für die Probenahme, die Untersuchung der Einflüsse von Luftfeuchtigkeit, Probenahmevolumen und -volumenstrom auf die Analyse, Untersuchungen zum Umgang mit Feuchtigkeit in der Probenluft, die Bestimmung von Wiederfindungsraten, Nachweis- und Bestimmungsgrenzen sowie der Robustheit des Verfahrens und der Messunsicherheit im Rahmen der Verfahrensvalidierung. Die entwickelte Messmethode wurde im Rahmen einer Emissionsmessung an einem Polyurethanschaum erprobt. Im Ergebnis entstand eine robuste Methode, die es erlaubt, komplexe VVOC-Gemische mit sehr guter Auflösung und niedrigen Nachweis- und Bestimmungsgrenzen zu analysieren. Ferner wurde ein Vorschlag zur Erweiterung des zu erfassenden Flüchtigkeitsspektrums bis C22 erarbeitet, der zwar nicht vollständig validiert werden konnte, jedoch die prinzipielle Machbarkeit zeigt.

In this investigation, we present a direct method employing UV-light radiation to induce point defects, specifically Ti3+ and VO, onto the surface of TiO2 nanosheets (TiO2-NSs) and efficiently decorate them with Pt particles. The addition of the Pt precursor is carried out during rest periods following UV-light cessation (light-induced samples, LI) and during UV-light exposure (photo-deposited samples, PD). The size and distribution of Pt particles on both LI and PD TiO2-NSs are systematically correlated with varying resting times, enabling precise control over Pt loading. The characterization of various TiO2-NSs is extensively conducted using microscopy techniques (FESEM, TEM, and HAADF-STEM) and spectroscopy (XPS). Gas chromatography is also employed for the evaluation of the H2 photocatalytic performance of various samples. Our findings reveal that Pt particles deposit on the TiO2-NSs surfaces as nanoparticles under illumination. After a 5 minutes resting time, a combination of Pt single atoms (SAs) and clusters, with a maximum loading of 0.37 at%, is formed. Extending the resting time to 60 minutes results in a gradual reduction in Pt SAs and clusters, leading to the deposition of Pt nanoparticles with lower loadings. Notably, Pt SAs and clusters exhibit superior performance in hydrogen evolution, showcasing a remarkable 4000-fold increase over pristine TiO2-NSs. Additionally, sustained UV radiation during Pt addition in the photo-deposited samples results in the formation of Pt nanoparticles with lower loading compared to LI samples, consequently diminishing photocatalytic hydrogen production. This study not only provides insights into the controlled manipulation of Pt SAs on TiO2-NSs but also highlights their exceptional efficacy in hydrogen evolution, offering valuable contributions to the design of efficient photocatalytic systems for sustainable hydrogen generation.

The low-temperature plasma (LTP) probe is a common plasma-based source used for ambient desorption–ionization mass spectrometry (MS). While the LTP probe has been characterized in detail with MS, relatively few studies have used optical spectroscopy. In this paper, two-dimensional (2D) imaging at selected wavelengths is used to visualize important species in the LTP plasma jet. First, 2D steady-state images of the LTP plume for N2+ (391.2 nm), He I (706.5 nm), and N2 (337.1 nm) emissions were recorded under selected plasma conditions. Second, time-resolved 2D emission maps of radiative species in the LTP plasma jet were recorded through the use of a 200 ns detection gate and varying gate delays with respect to the LTP trigger pulse. Emission from He I, N2+, and N2 in the plasma jet region was found to show a transient behavior (often referred to as plasma bullets) lasting only a few microseconds. The N2+ and He I maps were highly correlated in spatial and temporal structure. Further, emission from N2 showed two maxima in time, one before and one after the maximum emission for N2+ and He I, due to an initial electronic excitation wave and ion–electron recombination, respectively. Third, the interaction of the LTP probe with a sample substrate and an electrically grounded metallic needle was studied. Emission from a fluorophore on the sample substrate showed an initial photon-induced excitation from plasma-generated photons followed by electronic excitation by other plasma species. The presence of a grounded needle near the plasma jet significantly extended the plasma jet lifetime and also generated a long-lived corona discharge on the needle. The effect of LTP operating parameters on emission spectra was correlated with mass-spectral results including reagent-ion signals. Lastly, five movies provide a side-by-side comparison of the temporal behavior of emitting species and insights into the interactions of the emission clouds with a sample surface as well as an external needle. Temporally and spatially resolved imaging provided insights into important processes in the LTP plasma jet, which will help improve analyte ion sampling in LTP–MS.

The recovery and reprocessing of technology-critical elements (TCE) present in printed circuit boards (PCB) from electrical and electronic waste is essential both for recycling valuable materials subject to supply risk and for reducing the environmental impact. Although the quantitative knowledge of TCE amounts in endof- life PCB plays a key role, there are neither matrix certified reference materials nor harmonized analytical methods available to establish the traceability of the results to the International System of Units. To fill these gaps, we developed and applied five reference analytical methods based on ICP-MS standard addition calibrations and INAA k0- and relative calibrations suitable to certify reference materials. In addition, we developed and tested six analytical methods based on more commonly used ICP-MS external standard calibrations to provide industry with routine analysis methods. Twenty TCE (Ag, Au, Co, Cu, Dy, Ga, Gd, Ge, In, La, Li, Nd, Ni, Pd, Pr, Pt, Rh, Sm, Ta and Ti) were selected as target analytes and a batch of powdered PCB was used as measurement material. An overall mutual agreement was observed among data collected by reference methods at a few percent relative uncertainty levels. Moreover, all but one of the methods developed for routine analysis demonstrated their suitability in industrial applications by producing data within ± 20% of the values established with reference methods.

This study introduces an improved spectrometric method with enhanced precision to determine isotope ratios in geological samples without chromatographic separation. Firstly, the improvement is achieved by increasing the spectral resolution of the spectrometer applied in well-known high-resolution continuum source atomic absorption spectrometry (HR-CS-AAS). The resulting resolving power and linear dispersion of the upgraded setup, which is denoted in the following as HR+CS-AAS, is well adapted to the line widths of the Li isotope components we investigated. Secondly, our proposed method combines optical absorption spectrometry with machine learning data analysis using an extreme gradient boosting algorithm (XGBoost). This method was applied to analyze certified geological reference materials with δLSVEC(7Li/6Li) (hereafter δ7Li) values ranging from −0.5 ‰ to 4.5 ‰. With a pixel related optical resolving power of λ/∆λ ≈ 780 000, we obtain precisions in δ7Li measurements from 1.0 ‰ to 2.5 ‰. The method is validated by comparing the results with multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), confirming its metrological compatibility. This work presents a fast, robust, and reliable method for δ7Li measurement in geological samples.