Chemische Charakterisierung und Spurenanalytik
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Analytical Sciences has developed from Ostwald’s “unentbehrlichen Dienstmagd” to a chemical discipline at the core of many of today’s fundamental and applied scientific problems and innovations. An atomic or molecular understanding of basic processes in chemistry, soft matter physics, materials and life science is enabled only through new analytical methods and instrumentation. Similar observations can be found for pressing sociopolitical conflicts of the future: A rational discussion of global climate change or new energy sources is only possible with reliable analytical results. Progress in Analytical Sciences is only possible if the underlying interdisciplinary character is acknowledged and valued. The talk will illustrate the scope of modern Analytical Science through examples from process analysis relevant to modern process intensification and industry 4.0 to bioanalysis and the use of synchrotron radiation to elucidate fundamental reactions materials.
An improved algorithm for calibration-free laser induced breakdown spectroscopy (CF LIBS) will be presented which includes several novel features in comparison with previously proposed similar algorithms. In particular, it allows using spectral lines with arbitrary optical thickness for the construction of Saha-Boltzmann plots, retrieves the absorption path length (plasma diameter) directly from a spectrum, replaces the Lorentzian line profile function by the Voigt function, and allows for self-absorption correction using pre-calculated and tabulated data rather than approximating functions. The tabulated data embody the solutions of the radiative transfer equation for numerous combinations of optical thicknesses and line widths. The algorithm is thoroughly verified using synthetic spectra.
Neurodegenerative diseases are one of the major problems for our ageing society. Alzheimer’s disease (AD) as the most common neurodegenerative disorder affects over 46.8 million people worldwide and the number will increase as the population ages. The diagnosis of AD is challenging and only half of the patients are identified yet and often only in late stages. One reason is that existing assays for identification and quantification of AD biomarkers lack accuracy and are poorly comparable.
This study is part of the EU project “ReMiND” aiming to develop accurate, reliable and traceable methods for the detection and quantification of known and suspected AD biomarkers. Our target is the tau protein, as brain load and distribution of tau is highly correlated with the clinical progression of AD. We intend to develop a measurement method for the accurate quantification of tau by means of inductively coupled plasma mass spectrometry (ICP-MS).
ICP-MS is a powerful method for the matrix independent quantitative analysis of target elements. Developed for the use in inorganic trace analysis, ICP-MS is nowadays emerging as a valuable tool for bioanalytical questions. Especially the use of ICP-MS for quantitative proteomics by measuring heteroatoms is highly promising, considering that established quantification methods like organic mass spectrometry depend on the existence of matched protein and peptide standards or labelling of the target protein. In this work, we applied isotope dilution analysis (IDA) using ICP-MS to quantify proteins of known stoichiometry via their sulphur content. Sulphur is present in two amino acids, cysteine and methionine, and hence is omnipresent in nearly all proteins. A NIST standard bovine serum albumin (BSA) was quantified using sulfur IDA to optimize sample preparation and method parameters. Our goal is to employ the developed method in a proof of concept study for the quantification of the AD biomarker tau extracted from brains of a mouse model for AD.
Many current nanomaterials can serve as contrast agents in cellular or tissue imaging, drug delivery vehicles or therapeutics, whereas others can cause toxic effects. In order to evaluate nano-bio interactions, the number of nanoparticles (NPs) inside cells as well as their localisation within cellular substructures is of particular interest. The cellular uptake depends on the primary characteristics of the NPs (e.g. size, shape, surface coating) and on the cell type.
Laser ablation inductively coupled plasma mass spectrometry (LA‑ICP‑MS) is more and more used to study the NP pathway from uptake, via intracellular processing up to cell division. High-spatial resolution laser ablation at single cell level is achieved using novel low-dispersion LA chambers and by careful optimisation of laser energy, ablation frequency and scan speed at small laser spot sizes down to 1 µm. Different examples from BAM, Division 1.1 and cooperation partners using LA-ICP-MS to localize and quantify metal-containing nanoparticles are shown. The results demonstrate the potential of LA-ICP-MS providing insight into NP uptake, intracellular distribution and cell-to-cell variation.
qNMR provides the most universally applicable form of direct concentration or purity determination without need for reference materials of impurities or the calculation of response factors but only exhibiting suitable NMR properties. The workshop presents basic terms of statistics and uncertainty analysis, which are the basis for qNMR spectroscopy and data analysis such as, e.g., standard deviations, linear regression, significance tests, etc. and gives typical examples of applications in qNMR spectroscopy.
To establish the SI traceability of the element content w(Hg) of a gravimetrically prepared 1 g/kg mercury solution, the latter was compared to a primary reference solution by means of high accuracy inductively coupled plasma optical emission spectrometry (ICP OES) measurements. For this purpose, the ICP OES bracketing method previously described [1] was improved to yield a relative expanded uncertainty of the mercury element content of Urel(w(Hg)) = 0.5 % (with k = 2) associated with the comparison of two monoelemental solutions. In case of mercury, such a small uncertainty was achieved for the first time. Before, in general, such small uncertainties were only reported applying isotope dilution methods performed with MC-ICP-MS. However, for mercury solutions at this concentration range, several dilution steps are necessary to prepare the samples for ID-MC-ICP-MS. The sum of the uncertainty contributions stemming from the dilution steps, as well as the intrinsic difficulties of measuring mercury at low concentrations, result in an overall uncertainty of the ICP-MS measurements, which is comparable to or even larger than those, achieved with the ICP OES method applied. We will present details of the sample preparation as well as of the dedicated ICP OES measurement approach, which were crucial to achieve such a small measurement uncertainty.
The newly developed method was successfully applied in the context of the development and production of elemental solution chemical reference standards (CRS), which are distributed by the EDQM. The CRS are intended to support measurements required by the European Pharmacopoeia, which has recently incorporated a new international guideline for the control of elemental impurities in medicinal products.
Analytical glow discharges with optical (GD-OES) and mass spectrometric (GD-MS) detection are able to obtain depth resolved information about the light elements hydrogen, carbon, nitrogen and oxygen in solid samples, where most of the other analytical techniques fail. However, the interpretation or even quantification of the measured signals is still very challenging. Problems arise due to physical effects (plasma processes such as the ‘Hydrogen effect’, the Doppler effect, self absorption or diffusion of hydrogen in the sample during sputtering) chemical effects(e.g. formation of compounds with argon or the matrix, poisoning of the sample or gettering) as well as instrumental difficulties (e.g. of the sensitivity, calibration and vacuum quality)..
The GD techniques are direct solid sampling methods and require reference materials for calibration. Unfortunately the list of available certified reference materials (CRM) suited for calibration of light elements in different matrix is relatively short Therefore, sintered materials doped with the analytes H2, O2 and N2 were produced at IFW Dresden and applied as calibration standards for hydrogen, oxygen and nitrogen. Due to the high analyte concentration added, it is very likely that the real concentration agree well with the added amount of light elements in the corresponding phases. The validation of the determination of the light element concentration in the sintered samples was possible in some cases only due to the lack of suitable techniques. This fact proves the need for the development of a reliable quantification of light elements by GDS.
A systematic dependence of the sputtering rate on the composition was found and can be explained by basic principles.
Using mixtures of TiH2 and ZrH2 with Cu the ratio of hydrogen and Cu lines has a good correlation with the corresponding concentration ratio. The hydrogen emission yield however decreases over 0.3 m% hydrogen and finally the hydrogen intensity may even decrease. This behaviour can be explained by a very similar quenching of the hydrogen and copper intensity caused by the hydrogen effect. First experiments with GD-MS show no saturation of the hydrogen ion current and thus confirm the quenching of the emission yield in GD-OES.
Sintered material for the oxygen calibration (Al2O3, CuO, Cu2O and MgO mixed with Cu, Al and Mg) confirmed the blue line shift effect at O I 130.22 nm, first time reported by Köster 2009 [1]. The effect is more pronounced at Mg than in Al and Cu, which due to line interference leads to a matrix dependent EY. This effect is negligible at O I 777.19 nm and the EY is matrix independent. Using GD-MS first promising results for the calibration of oxygen with these sintered samples could be obtained, when the sputtering rate was included in the evaluation.
More recently also sintered material for nitrogen calibration (AlN mixed with Al and Si3N4 mixed with Cu) was produced and points to a matrix independent emission yield of nitrogen
Reference materials are essential, when the accuracy and reliability of measurement results need to be guaranteed in order to generate confidence in the analysis.
These materials are frequently used for determining measurement uncertainty, for validation of methods, suitability testing and quality assurance. Especially direct solid sampling methods require reference materials for calibration.
They guarantee that measurement results can be compared to recognized reference values.
This presentation gives an overview about the use of GDMS in various certification procedures. Because it represents a fast, sensitive, multielement analyses technique without extensive sample preparation it plays a special role for the purity determination of high purity standards. Various calibration strategies and the preparation of traceable matrix matched calibration standards will be discussed.
For the certification of analyte content in matrix materials mainly techniques with solvent sample preparation are used. Here GD-MS is used to identify possible loss or contamination with analytes during the sample preparation step. Typically used acids to dissolve matrices lead to interferences in the ICP- mass spectrometric detection of various analytes and their quantification. Here GD-MS as direct method can also add an important contribution in the certification process.
Laser induced plasma (LIP) is a highly dynamic, short living event which presents significant difficulty for both diagnostics and modeling. The former requires precise spatially- and time-resolved measurements on a micron-nanosecond scale while the latter needs numerous descriptive parameters; many of them can only be obtained from experiment. Diagnostics and modeling should always complement each other for obtaining a truthful picture of LIP.
In this presentation, a newly developed collisional-dominated model will be presented. The model is based on the coupled Navier-Stokes, state, radiative transfer, material transport, and chemical equations. The model incorporates plasma chemistry through the equilibrium approach that relies on atomic and molecular partition functions. Several chemical systems are modeled including Si-C-Cl-N and B-H-Cl systems.
The model is used to study the equilibrium states of the systems as functions of the concentrations of plasma species and plasma temperature. The model also predicts the evolution of number densities of atomic and molecular species in the expanding plasma plume.
This course will provide an introduction to plasma diagnostic techniques. The major focus of the course will be on the discussions of the practical procedures as well as the underlying physical principles for the measurements of plasma fundamental characteristics (e.g., temperatures, thermodynamic properties, and electron number density). Particular emphasis will be placed on inductively coupled plasma–atomic emission spectrometry, but other analytical plasmas will also be used as examples when appropriate. Selected examples on how one can manipulate the operating conditions of the plasma source, based on the results of plasma diagnostic measurements, to improve its performance used for spectrochemical analysis will also be covered. Topics to be covered include thermal equilibrium, line profiles, temperatures, electron densities, excitation processes, microreactions, pump and probe diagnostics, tomography, temporal and spatial resolution. Basics of plasma computer modeling will be presented.
Generell ist es Ziel der Prozessführung, Reaktions- und Trennprozesse wirtschaftlich optimal zu betreiben. Hierzu werden in großen Anlagen modellbasiere Echtzeitoptimierungsverfahren (Real-time Optimization, RTO) eingesetzt. Die Qualität der Ergebnisse der Optimierung hängt dabei entscheidend von der Güte des verwendeten Modells ab. Die Entwicklung hochgenauer Modelle ist allerdings aufwändig, was für kleine Produktionsvolumina ein wesentliches Hindernis zur Nutzung solcher Methoden darstellt. Mit Hilfe der sogenannten Modifier-Adaptation ist eine iterative Betriebspunktoptimierung auch mit ungenauen Modellen möglich, wenn Messungen der für die Bewertung relevanten Größen (beispielsweise Produktkonzentrationen im Ausgangsstrom) verfügbar sein. Für eine Lithiierungsreaktion in einem bei INVITE kontinuierlich betriebenen Reaktor wurde im Rahmen des EU-Projekts CONSENS eine solche iterative Optimierung auf der Grundlage einer Messung der Zusammensetzung des Ausgangsstroms des Reaktors mit einem Online-NMR-Spektrometer realisiert. Das Spektrometer wurde an den Betrieb in einer explosionsgefährdeten Umgebung angepasst. Es konnte gezeigt werden, dass die Messdaten genau genug sind, um darauf eine Optimierung der Produktausbeute aufzubauen. Die iterative Optimierung führt den Prozess ausgehend vom mit dem Modell berechneten Betriebspunkt schrittweise zum wirtschaftlichen Optimum für die reale Anlage. Dabei reagiert die Optimierung auch auf unbekannte Abweichungen im Prozess (wie die Zusammensetzung des Feeds) und fährt iterativ den jeweils optimalen Betriebspunkt an.
Die Arbeiten wurden im Rahmen des EU-SPIRE-Projekts CONSENS, Förderkennzeichen 636942, durchgeführt.
Produzieren Sie schon oder kalibrieren Sie noch? – Online-NMR-Spektrometer als Smarte Feldgeräte
(2018)
Der Übergang von der aktuellen Automatisierungslandschaft zur nächsten Generation von Automatisierungskonzepten für die Prozessindustrie hat bereits begonnen. Intelligente Funktionen der Sensoren vereinfachen ihre Anwendung und ermöglichen eine Plug-and-Play-Integration, auch wenn sie auf den ersten Blick komplexer erscheinen mögen. Dies ist die Basis für die Digitalisierung der Prozessindustrie und hilft uns, komplexere Prozesse schneller umzusetzen.
Der Vortrag fasst die derzeit diskutierten allgemeinen Anforderungen an „Smarte Feldgeräte“ zusammen und diskutiert dieses am Beispiel eines smarten Online-NMR-Sensors. NMR-Spektroskopie bietet sich durch den Vorteil der direkten Vergleichsmethode (ohne Kalibrierung) für die Prozess-Steuerung an und verringert somit die Rüstzeiten. Zudem basiert der Sensor auf physikalisch motivierten Modellen (Indirect Hard Modeling, IHM), die sich modular kombinieren lassen. Die Methoden wurden anhand eines vorgegebenen pharmazeutischen Reaktionsschrittes im Rahmen des „Horizon 2020“-Projekts CONSENS der Europäischen Union demonstriert und validiert.
Zuletzt werden Anforderungen an die Weiterentwicklung der Datenauswertemethoden diskutiert, um letztlich die semantische Information aus den Messdaten herauszulesen oder das in der Industrie 4.0 geforderte „durchgehende Engineering“ für die Automatisierungskomponenten zu ermöglichen.
Atherosklerotische Läsionen können durch Magnetresonanztomographie (MRT) unter Verwendung von sehr kleinen Eisenoxidnanopartikeln (VSOP) sichtbar gemacht werden. VSOP akkumulieren in atherosklerotischen Plaques und dienen somit als Atherosklerosesonde.
Das Ziel dieses Projektes war die Abbildung der Verteilung von Europium-dotierten VSOP (Eu-VSOP) durch Laserablation ICP-MS in histologischen Dünnschnitten der Aortenwurzelregion des ApoE-Knockout-Mausmodells, das reich an atherosklerotischen Plaques ist. Darüber hinaus wurde untersucht, ob die VSOP-Akkumulation in den Plaques mit anderen Biomarkern der Entzündung wie Makrophagen und verändertem Endothel korreliert. Somit wäre eine Beurteilung, ob es sich hierbei um instabile bzw. vulnerable Plaque-Regionen handelt möglich. Zu diesem Zweck wurden Antikörper mit verschiedenen Lanthaniden markiert und mit der Eu-VSOP-Verteilung unter Verwendung von LA-ICP-MS in einem Multiplex-Messmodus korreliert.
Eine mögliche Korrelation von reaktiven Stickstoffspezies (RNS) mit endogenem Eisen oder Eu-VSOP kann ebenfalls durch LA-ICP-MS nachgewiesen werden. Zu diesem Zweck wurden RNS-spezifische Antikörper auch mit Lanthaniden markiert.
Analysis of single cells via LA-ICP-MS is a technique with great potential, however manual targeting of single cells is laborious and therefore microarraying of cells looks promising. In this work, we investigate the potential of a commercial non-contact piezo dispenser arraying system (S3, Scienion AG, Berlin), equipped with a novel technology for single-cell isolation called CellenONE™ (Cellenion, Lyon). Usually if one aims to create a microarray of single cells via spotting a suitably diluted cell suspension, one will observe a Poisson-distributed cell number per spot. CellenONE™ overcomes this problem by controlling the number of cells optically in the piezo dispense capillary (PDC) via image recognition to obtain true single cell arrays. The figures of merit of the customized and optimized setup will be presented. In a proof of concept experiment we investigated the trace elemental fingerprint of THP-1 cells by LA-ICP-TOF-MS (Analyte G2, Teledyne Cetac; icpTOF, TOFWERK) and quantified two metal cell dyes, mDOTA-Ho (CheMatech, Dijon), and Ir-DNA intercalator (Fluidigm, San Francisco). For that, matrix matched calibration standards after Wang et al. were successfully prepared using the same arraying system. We believe that this novel approach opens new ways for automated quantitative single cell LA-ICP-MS.
In chemical elements with three or more stable isotopes, mass-dependent stable isotope fractionation yields correlated isotope ratios, m2/m1 and m3/m1. In three-isotope space, i.e. in a δ’m2/δ’m1 vs. δ’m3/δ’m1 plot, data align along a slope θ, the so called ‘triple isotope fractionation exponent’ that scales the two isotope ratios. Theoretical calculations predict small differences in θ for kinetic- and equilibrium isotope fractionation (Young et al. 2002) and thus the precise measurement of θ allows constraining the reaction mechanism. However, due to an apparent lack of precision of stable isotope analysis by MC-ICP-MS, θ is merely used as analytical quality control, i.e. for demonstration that samples and standards plot within their analytical precision in the range of theoretical θ-values originating in δ-zero.
We show how θ can be determined precisely enough by MC-ICP-MS to distinguish kinetic- and equilibrium isotope fractionation, even when isotopic differences between samples are low. For low magnitudes of isotope fractionation, we exploit new, isotopically fractionated isotope standard materials (Vogl et al. 2016). We determine quality norms regarding interferences and measurement conditions to warrant trueness and to maximize precision. We exemplary explore the measurement of the three-isotope composition of Mg stable isotopes, budget the uncertainty of θ-values, and report the first θ-values of carbonate-water pairs and bioapatite. Our measurement approach adds a new dimension to isotope data beyond the δ-scale that has a high potential to reveal different modes of (bio)mineral precipitation in the sedimentary and biological record and thus to contribute solving conundrums in the Earth and Life Sciences.