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Flow cytometry-based immunoassays are valuable in biomedical research and clinical applications due to their high throughput and multianalyte capability, but their adoption in areas such as food safety and environmental monitoring is limited by long assay times and complex workflows. Rapid, simplified bead-based cytometric immunoassays are needed to make these methods viable for point-of-need applications, especially with the increasing accessibility of miniaturized cytometers. This work introduces superparamagnetic hybrid polystyrene-silica core−shell microparticles as promising alternatives to conventional polymer beads in competitive cytometric immunoassays. These beads, featuring high specificity, sensitivity, and excellent handling capabilities via magnetic separation, were evaluated with three different antibodies and binding methods, showing variations in signal intensity based on the antibody and its attachment method. The optimal performance was achieved through a secondary antibody binding approach, providing strong and consistent signals with minimal uncertainty. The optimized protocol made it possible to achieve a detection limit of 0.025 nM in a total assay time of only 15 min and was successfully used to detect ochratoxin A (OTA) in raw flour samples. This work highlights the potential of these beads as versatile tools for flow cytometry-based immunoassays, with significant implications for food safety, animal health,
environmental monitoring, and clinical diagnostics.
Single-particle inductively coupled plasma-mass spectrometry (sp-ICP-MS) is one of the most powerful tools in the thriving field of nanomaterial analysis. Along the same lines, single-cell ICP-MS (sc-ICP-MS) has become an invaluable tool in the study of the variances of cell populations down to a per-cell basis. Their importance and application fields have been listed numerous times, across various reports and reviews. However, not enough attention has been paid to the immense and ongoing development of the tools that are currently available to the analytical community for the acquisition, and more importantly, the treatment of single-particle and single-cell-related data. Due to the ever-increasing demands of modern research, the efficient and dependable treatment of the data has become more important than ever. In addition, the field of single-particle and single-cell analysis suffers due to a large number of approaches for the generated data—with varying levels of specificity and applicability. As a result, finding the appropriate tool or approach, or even comparing results, can be challenging. This article will attempt to bridge these gaps, by covering the evolution and current state of the tools at the disposal of sp-ICP-MS users.
Graphical Abstract
The analysis of per- and polyfluoroalkyl substances (PFAS) via sum parameters like extractable organic fluorine (EOF) in combination with high resolution-continuum source-graphite furnace molecular absorption spectrometry (HR–CS–GFMAS) is highly promising regarding fluorine sensitivity and selectivity. However, the HR–CS–GFMAS method includes several drying and heating steps which can lead to losses of volatile PFAS before the molecular formation step using e.g., GaF formation. Hence, the method leads to a strong discrimination of PFAS within the EOF depending on their physical/chemical properties and is therefore associated with reduced accuracy. To reduce this discrepancy and to indicate realistic PFAS pollution values, an optimization of the HR–CS–GFMAS method for PFAS analysis is needed. Hence, we determined fluorine response factors of several PFAS with different physical/chemical properties upon application of systematic optimization steps. We could therefore improve the method's sensitivity for PFAS analysis using a modifier drying pre-treatment step followed by a sequential injection of sample solutions. The highest improvement in sensitivity of volatile PFAS was shown upon addition of a Mg modifier during drying pre-treatment. Thereby, during optimization the relative standard deviation of fluorine response factors could be reduced from 55 % (initial method) to 27 % (optimized method) leading to a more accurate determination of organofluorine sum parameters. The method provides an instrumental LOD and LOQ of β(F) 1.71 μg/L and 5.13 μg/L, respectively. Further validation aimed to investigate several matrix effects with respect to water matrices. Here, substance-specific behavior was observed. For example, perfluorooctanoic acid (PFOA) which was used as calibrator, showed signal suppressions upon high chloride concentrations (>50 mg/L). Hence, a thorough separation of Cl from analytes during sample preparation is needed for accurate sum parameter analysis.
Ytterbium-doped LiYF4 (Yb:YLF) is a promising material for all-solid-state optical cryocoolers, but the impact of foreign rare-earth impurities on the laser-cooling performance is not completely understood. In particular, Tm3+ has been reported to reduce the background absorption. This study quantitatively assesses the impact of Ho3+, Tm3+, and Er3+ impurities on laser-cooling of Yb:YLF by anti-Stokes fluorescence. We grew five Yb(5%):YLF crystals intentionally doped with tens of ppm levels of these impurities. Laser-induced thermal modulation spectroscopy tests confirmed that these rare-earth impurities reduce the external quantum efficiency of Yb:YLF without affecting the background absorption coefficient. Although Er3+ is a well-known quencher for Yb3+, Er3+ co-doping only slightly decreases the laser-cooling efficiency at low pump intensities but becomes detrimental at high pump intensities (>5 kW cm−2). However, this detrimental effect diminishes at lower temperatures, as evidenced by cooling an Er3+ co-doped crystal to the same minimum temperature of 144K as a solely Yb3+-doped crystal. Contrary to previous reports, Tm3+ proved to be the most detrimental among the three impurities.
An accurate measurement of the amount fraction of hydrogen in gas mixtures is mandatory for practical applications, requiring methods that are fast, continuous, robust, and cost-effective. This study compares the performance of Raman and benchtop NMR process spectroscopy for determining the hydrogen amount fraction in gas mixtures. A setup was designed to integrate both techniques, enabling measurements of the same sample.
Tests were conducted with gravimetrically prepared gas mixtures of reference quality ranging from 1.20 cmol/mol to 85.83 cmol/mol of hydrogen. The results demonstrate that Raman spectroscopy provides superior performance, with a minimal root mean square error (RMSE) of 0.22 cmol/mol and excellent linearity. In contrast, benchtop NMR spectroscopy faced challenges, such as overlapping peaks and longer measurement times, resulting in a higher RMSE of 0.71 cmol/mol. Raman spectroscopy proves to be particularly well-suited for
practical applications due to its high accuracy and linearity. Meanwhile, benchtop NMR spectroscopy holds potential for future enhancements through ongoing technological advances, such as higher magnetic field strengths. In summary, the results from our study indicate that Raman spectroscopy is already a serviceable method for precise hydrogen quantification, whereas benchtop NMR spectroscopy can be attributed potential for future applications.
In den deutschen Zulassungen für Gefahrgutverpackungen muss der minimale Schüttwinkel angegeben werden, für den die Verpackung verwendet werden darf. Dieser fungiert als Maß für die Fließeigenschaften pulverförmiger oder körniger Stoffe und ist wichtig für die Sicherheit beim Gefahrguttransport. In den Prüfstellen existiert jedoch eine Reihe von Messmethoden für diese Kenngröße. In der Vergangenheit war hierbei unklar, welche dieser Methoden für welche Prüffüllgüter prinzipiell geeignet sind. Die BAM nahm dies zum Anlass, die gebräuchlichen Messmethoden systematisch zu untersuchen. Dieser Artikel gibt einen Gesamtüberblick über die Ergebnisse und stellt die Schlussfolgerungen für die Prüfpraxis in den anerkannten Prüfstellen für Gefahrgutverpackungen dar.
Die Fließeigenschaften fester Gefahrgüter spielen für die Sicherheit beim Gefahrguttransport eine wichtige Rolle. Diese haben einen Einfluss sowohl auf die mechanische Sicherheit der verwendeten Verpackung als auch auf die Freisetzung fester Substanzen unter normalen Beförderungsbedingungen aufgrund ungenügender Staubdichtheit. Bei festen Gefahrgütern kann es sich entweder um pulverförmige oder um körnige Stoffe handeln. Um der sicherheitsrelevanten Bedeutung der Fließeigenschaften fester Füllgüter Rechnung zu tragen, muss in den deutschen Zulassungen für Gefahrgutverpackungen der minimale Schüttwinkel angegeben werden, für welche die Verpackung verwendet werden darf. In der Praxis der Prüfstellen existiert jedoch eine Reihe von Messmethoden für diese Kenngröße. In der Vergangenheit war hierbei unklar, welche dieser Methoden für welche Prüffüllgüter prinzipiell geeignet sind. Es ist jedoch essenziell, die Vor- und Nachteile sowie die Grenzen der einzelnen Verfahren zu kennen. Dieser Artikel gibt eine Einführung in die Thematik und in experimentelle Untersuchungen, die in der BAM durchgeführt wurden, um eine Klärung herbeizuführen. Die Ergebnisse dieser Versuche werden in einem Folgeartikel vorgestellt.
Im November 2019 wurde der Entwurf der VDI-Richtlinie 3783 Blatt 1 „Ausbreitung von störungsbedingten Freisetzungen“ als Gründruck veröffentlicht.
Neben den Einsprüchen zur Richtlinie in Bezug auf unklare Formulierungen, wurde oft das Fehlen eines Referenzprogramms, als auch die Abkehr vom etablierten Gauß-Wolken-Modell bemängelt.
Im Rahmen der darauffolgenden Überarbeitung des Richtlinienentwurfs wurde ein Gauß-Wolken-Modell entwickelt, das mit einem geringen Rechenaufwand in einem begrenzten Anwendungsbereich mit dem Lagrange’schen Partikelmodell vergleichbare Berechnungsergebnisse liefert.
Darüber hinaus wurden Empfehlungen zur praktischen Umsetzung von Szenarien in den neuen Richtlinienentwurf, der voraussichtlich im Oktober 2024 als Gründruck vorliegt, aufgenommen.
Quantum dots (QDs) possess unique optoelectronic properties, which make them very attractive to be used as optical probes in biosensing and bioimaging applications. The strong absorbance and light scattering of biological compounds like tissue and blood in the visible range pose a problem. However, if optical probes emitting in the near-infrared (NIR) range are used, scattering, absorption, and autofluorescence of biological components are strongly reduced. This allows for an increased light penetration depth and higher spatial and temporal resolution for the investigation of biological processes. The synthesis and application of NIR emitting QDs is a fast-growing research field and the benefits of using QDs were demonstrated for a variety of applications, such as photoelectrochemical biosensor, in vivo vascular imaging, and fluorescence-guided surgery. This article reviews the state-of-the-art developments in the preparation of NIR/IR QDs and highlights the latest research about their utilization in biosensing and bioimaging applications.
The analysis of the presence and content of substances that are toxic to aquatic life in waste is essential for classification of waste with regard to hazard property (HP) 14 ‘ecotoxic’. For the determination of HP14 classified copper (Cu) and zinc (Zn) compounds in various municipal solid waste incineration bottom ashes (IBA) and one fly ash (FA) from Germany we applied X-ray absorption near-edge structure (XANES) spectroscopy in combination with linear combination fitting. The analysis showed that approx. 50–70% of Cu in the IBA are Cu(I) compounds and elemental Cu(0), but these compounds were not equally distributed in the different IBA. In contrast, the majority (approx. 50–70%) of Zn in all IBA is elemental zinc, which originates from brass or other alloys and galvanized metals with a large content of zinc in the waste. The FA contain higher mass fraction on Zn and other toxic elements, but similar Cu and Zn species. Additional performed selective extraction at a pH of 4 with an organic acid of some IBA showed that the ecotoxic Zn fraction is mainly elemental zinc and zinc oxide. In contrast, for the ecotoxic Cu fraction within the IBA no specific compound could be identified. Furthermore, the XANES analysis showed that the HP14 properties of especially Cu in IBA is overestimated with current best-practice guidelines for sample processing for the current substance-related approach with the 0.1% cut-off rule for each substance. However, it should be considered whether it would not be better from an environmental point of view to take the ecotoxicologically leachable copper and zinc as a reference value.