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Due to the fast growth of industry and the use of metal-containing compounds such as sewage sludge in agricultural fields, soil pollution associated with heavy metals presents a terrifying threat to the environment. Throughout the world, there are already 5 million sites of soil contaminated by heavy metals1. Some heavy metals pollutants can influence food chain safety and food quality, which in turn affects human health. According to the German Federal Soil Protection and Contaminated Site Ordinance (BBodSchV) 13 heavy metals such as arsenic (As), lead (Pb) and cadmium (Cd) are classified as heavily toxic to human health2. Therefore, elemental analysis and precise quantification of the heavy metals in soil are of great importance.
Inductively coupled plasma mass spectrometry (ICP-MS) emerged as a powerful technique for trace analysis of soil due to its multi-element capability, high sensitivity and low sample consumption. However, despite its success and widespread use, ICP-MS has several persistent drawbacks, such as high argon gas consumption, argon-based polyatomic interferences and the need for complicated RF-power generators. Unlike argon-based ICP, the nitrogen microwave inductively coupled atmospheric pressure mass spectrometry (MICAP-MS) uses nitrogen as plasma gas, which eliminates high operating costs associated with argon-gas consumption as well as the argon-based interferences3. For the first time, the applicability of MICAP-MS for elemental analysis of environmental soils is investigated in this work. For this purpose, 7 reference- and 3 random soil samples containing vanadium (V), cobalt (Co), zink (Zn), copper (Cu), chrome (Cr), mercury (Hg), As, Pb and Cd are digested with aqua regia and used for analysis. Concentrations of selected elements are determined using MICAP-MS and validated using ICP-MS. Sensitivities, limits of detection and gas consumption for both methods are compared and discussed in detail. Moreover, the performance of MICAP-MS under different nitrogen plasma gas concentrations is investigated and compared
The use of renewable energy sources, electromobility, and portable
electronics relies on lithium-ion batteries (LIBs). However, one
detrimental effect, which can result in significant performance loss,
is the corrosion of the current collectors caused by the aging
mechanisms, especially in high-energy-density batteries
Glow discharge optical emission spectroscopy (GD-OES) provides
depth profile analysis through sputtering using argon plasma, which
enables the analysis of the corrosion behavior at different depths of
the cathodes.
Due to the fast growth of industry and the use of metal-containing compounds such as sewage sludge in agricultural fields, soil pollution associated with heavy metals presents a terrifying threat to the environment. Throughout the world, there are already 5 million sites of soil contaminated by heavy metals1. Some heavy metals pollutants can influence food chain safety and food quality, which in turn affects human health. According to the German Federal Soil Protection and Contaminated Site Ordinance (BBodSchV) 13 heavy metals such as arsenic (As), lead (Pb) and cadmium (Cd) are classified as heavily toxic to human health2. Therefore, elemental analysis and precise quantification of the heavy metals in soil are of great importance.
Inductively coupled plasma mass spectrometry (ICP-MS) emerged as a powerful technique for trace analysis of soil due to its multi-element capability, high sensitivity and low sample consumption. However, despite its success and widespread use, ICP-MS has several persistent drawbacks, such as high argon gas consumption, argon-based polyatomic interferences and the need for complicated RF-power generators. Unlike argon-based ICP, the nitrogen microwave inductively coupled atmospheric pressure mass spectrometry (MICAP-MS) uses nitrogen as plasma gas, which eliminates high operating costs associated with argon-gas consumption as well as the argon-based interferences3. For the first time, the applicability of MICAP-MS for elemental analysis of environmental soils is investigated in this work. For this purpose, 7 reference- and 3 random soil samples containing vanadium (V), cobalt (Co), zink (Zn), copper (Cu), chrome (Cr), mercury (Hg), As, Pb and Cd are digested with aqua regia and used for analysis. Concentrations of selected elements are determined using MICAP-MS and validated using ICP-MS. Sensitivities, limits of detection and gas consumption for both methods are compared and discussed in detail. Moreover, the performance of MICAP-MS under different nitrogen plasma gas concentrations is investigated and compared.
The optical properties of these materials strongly depend on the excitation power density, i.e., the number of photons absorbed per time interval. The upconversion quantum efficiencies (ΦUC) of these materials, the excitation power dependent population i.e. the emission characteristics, and the deactivation dynamics are influenced by nanoparticle architecture, doping concentration, and the microenvironment. We will discuss how time resolved measurements can help to understand the fundamental photophysical mechanisms and discuss differences to other nanocrystals like quantum dots.
The climate and energy crisis are extreme challenges. One possible solution could be hydrogen technology. Safety is a big concern. Steel used for pipelines and storage is under permanent stress from low temperatures and high pressures. The content of different alloyed metals determines the performance of the steel. Nitrogen microwave inductively coupled atmosphere pressure plasma mass spectrometry (N2-MICAP-MS) is a promising method for trace metal analysis in steel. Nitrogen is cheap and can be generated on site. It has fewer interferences than argon. Additionally, MICAP-MS is very matrix tolerant, proving the matrix-matched calibration expendable. Safety in technology and chemistry is the mission of BAM. Providing reference methods and materials can create trust in future technologies like hydrogen.
Lithium-ion batteries (LIBs) are one technology to overcome the challenges of climate and energy crisis. They are widely used in electric vehicles, consumer electronics, or as storage for renewable energy sources. However, despite innovations in batteries' components like cathode and anode materials, separators, and electrolytes, the aging mechanism related to metallic aluminum current collector degradation causes a significant drop in their performance and prevents the durable use of LIBs. Glow-discharge optical emission spectroscopy (GD-OES) is a powerful method for depth-profiling of batteries' electrode materials. This work investigates aging-induced aluminum deposition on commercial lithium cobalt oxide (LCO) batteries' cathodes. The results illustrate the depth-resolved elemental distribution from the cathode surface to the current collector. An accumulation of aluminum is found on the cathode surface by GD-OES, consistent with results from energy-dispersive X-ray spectroscopy (EDX) combined with focused ion beam (FIB) cutting. In comparison to FIB-EDX, GD-OES allows a fast and manageable depth-profiling. Results from different positions on an aged cathode indicate an inhomogeneous aluminum film growth on the surface. The conclusions from these experiments can lead to a better understanding of the degradation of the aluminum current collector, thus leading to higher lifetimes of LIBs.
Investigation of degradation of the aluminum current collector in lithium-ion batteries by GD-OES
(2022)
Lithium-ion batteries (LIBs) are one technology to overcome the challenges of climate and energy crisis. They are widely used in electric vehicles, consumer electronics, or as storage for renewable energy sources. However, despite innovations in batteries' components like cathode and anode materials, separators, and electrolytes, the aging mechanism related to metallic aluminum current collector degradation causes a significant drop in their performance and prevents the durable use of LIBs. Glow-discharge optical emission spectroscopy (GD-OES) is a powerful method for depth-profiling of batteries' electrode materials. This work investigates aging-induced aluminum deposition on commercial lithium cobalt oxide (LCO) batteries' cathodes. The results illustrate the depth-resolved elemental distribution from the cathode surface to the current collector. An accumulation of aluminum is found on the cathode surface by GD-OES, consistent with results from energy-dispersive X-ray spectroscopy (EDX) combined with focused ion beam (FIB) cutting. In comparison to FIB-EDX, GD-OES allows a fast and manageable depth-profiling. Results from different positions on an aged cathode indicate an inhomogeneous aluminum film growth on the surface. The conclusions from these experiments can lead to a better understanding of the degradation of the aluminum current collector, thus leading to higher lifetimes of LIBs.
Aging Mechanisms of Lithium Batteries: How can we make batteries more durable and more sustainable in the future?
Lithium batteries are particularly susceptible to ageing processes. During each charging and discharging process in an electric battery, lithium ions are deposited in the electrodes of the cell like in the pores of a sponge. Over time, however, fractures and cracks occur in the filigree structures. The result: more and more lithium ions no longer fit into the hollow spaces of the „sponge“, instead they accumulate in heaps around the electrodes and hinder the movement of other ions. The performance of the battery decreases.
We present our new project, in which we are developing a fast and cost-effective method with which companies that produce lithium batteries can already assess the ageing behaviour of their batteries in the laboratory.
The unique optoelectronic properties of semiconductor nanocrystals, also termed quantum dots (QDs), have led to many advances in optoelectronic devices, bioimaging, and biosensing. This strong potential in a wide range of applications sparked the interest for a better understanding of the QD formation mechanisms. Recent studies have shown that atomically defined, zero-dimensional magic-size clusters (MSCs) play a crucial role during the nucleation and growth of QDs. Thereby MSCs consist of discrete numbers of ions leading to narrow size distributions and thus narrow absorption peaks, which evolve in discrete steps from one stable size to the next. The formation of MSCs was found in the synthesis of II-VI and III-V QDs but only limited synthesis approaches are available for the synthesis of MSCs in single-ensemble form without coexistence of other-size QDs. These MSCs can further self-assemble into two- and three-dimensional hybrid structures using organic ligands like diamines, leading to enhanced photoluminescence properties and catalytic activities.
In this contribution, we present a synthesis strategy for the preparation of single-sized ZnSe MSCs. With a band gap of 2.7 eV and being an earth-abundant material, ZnSe QDs are interesting for light-emitting devices, blue-green lasers, photocatalysis, and fluorescence probes. In contrast to other studies, our approach is based on a one-pot heat-up synthesis and uses less toxic and dangerous zinc precursors (e.g. zinc stearate). Knowing that thiol-based ligands can alter the formation process of ZnSe QDs, we investigated the influence of 1-dodecanethiol on the ZnSe MSC formation using absorption spectroscopy, TEM, XPS, and XRD. By variation of the thiol ligand concentration and reaction temperature, we were able to synthesize two new ZnSe MSC sizes, the largest so far, by using easy-to-handle precursors.
Fluorescent semiconductor nanocrystals, also known as quantum dots (QDs), enabled many advancements in biotechnology, photovoltaics, photocatalysis, quantum computing and display devices. The high versatility of this nanomaterial is based on their unique size-tunable photoluminescence properties, which can be adjusted from the visible to the near-infrared range. In contrast to other nanomaterials, QDs made the transition from a laboratory curiosity to the utilization in commercial products, like the QLED television screen or in smartphone displays. The best investigated QDs are composed of heavy metals like cadmium or lead, which is not the best choice in terms of toxicity and environmental pollution. A more promising material is Indium Phosphide (InP), which is also currently used by Samsung, Sony and co. in the QLED displays.
In this contribution, I would like to give you a sneak peek behind the curtains of nanomaterial synthesis and show how this material is produced, how to stabilize their structural properties, and assess their toxicity in environmentally relevant conditions. Furthermore, I would like to present a synthesis method to accomplish the last open challenge in display technology of a blue luminescent LED based on QDs by introducing a new element to the InP QDs.
Near-infrared (NIR) spectroscopy is a promising candidate for low-cost, nondestructive, and highthroughput mass quantification of microplastics in environmental samples. Widespread application of the technique is currently hampered mainly by the low sensitivity of NIR spectroscopy compared to thermoanalytical approaches commonly used for this type of analysis. This study shows how the application of NIR spectroscopy for mass quantification of microplastics can be extended to smaller analyte levels by combining it with a simple and rapid microplastic enrichment protocol. For this purpose, the widely used flotation of microplastics in a NaCl solution, accelerated by centrifugation, was chosen which allowed to remove up to 99 % of the matrix at recovery rates of 83–104 %. The spectroscopic measurements took place directly on the stainless-steel filters used to collect the extracted particles to reduce sample handling to a minimum. Partial least squares regression (PLSR) models were used to identify and quantify the extracted microplastics in the mass range of 1–10 mg.
The simple and fast extraction procedure was systematically optimized to meet the requirements for the quantification of microplastics from common PE-, PP-, and PS-based packaging materials with a particle size < 1 mm found in compost or soils with high natural organic matter content (> 10 % determined by loss on ignition). Microplastics could be detected in model samples at a mass fraction of 1 mg g-1. The detectable microplastic mass fraction is about an order of magnitude lower compared to previous studies using NIR spectroscopy without additional enrichment. To emphasize the cost-effectiveness of the method, it was implemented using some of the cheapest and most
compact NIR spectrometers available.
Nonporous corundum powder, known as an abrasive material in the industry, was functionalized covalently with protein binders to isolate and enrich specific proteins from complex matrices. The materials based on corundum were characterized by TEM, ESEM, BET, DLS, and zeta potential measurements. The strong Al-O-P bonds between the corundum surface and amino phosphonic acids are used to introduce functional groups for further conjugations. The common cross-linker glutaraldehyde was compared with a hyperbranched polyglycerol (PG) of around 10 kDa. The latter is oxidized with periodate to generate aldehyde groups that can covalently react with the amines of the surface and the amino groups from the protein via a reductive amination process. The amount of bound protein was quantified via aromatic amino acid analysis (AAAA). This work shows that oxidized polyglycerol can be used as an alternative to glutaraldehyde. With polyglycerol, more of the model protein bovine serum albumin (BSA) could be attached to the surface under the same conditions, and lower nonspecific binding (NSB) was observed. As a proof of concept, IgG was extracted with protein A from crude human plasma. The purity of the product was examined by SDS-PAGE. A binding capacity of 1.8 mg IgG per g of corundum powder was achieved. The advantages of corundum are the very low price, extremely high physical and chemical stability, pressure resistance, favorable binding kinetics, and flexible application.
Nonporous corundum powder was functionalized covalently with protein binders to isolate and enrich specific proteins from complex matrices.The common crosslinker glutaraldehyde was compared with a hyperbranched polyglycerol (PG) of around 10 kDa. The latter was oxidized with periodate to generate aldehyde groups that can covalently react with the amines of the surface and the amino groups from the protein via a reductive amination process. The amount of bound protein was quantified via aromatic amino acid analysis (AAAA). As a proof of concept, IgG was extracted with protein A from crude human plasma. The advantages of corundum include the very low price, extremely high physical and chemical stability, pressure resistance, favorable binding kinetics, convenient handling, and flexible application.
Concrete structures often show severe damage during their lifetime. One such damage is pitting corrosion of the steel reinforcement caused by chloride ingress into the porous concrete structure. Laser-induced breakdown spectroscopy (LIBS) is a promising method in civil engineering, which is used for detection of chlorine in concrete structures in addition to conventional methods of wet chemistry. To assess LIBS as a trustful analytical technique, its accuracy and robustness is carefully tested. The presentation will outline the results of the interlaboratory comparison of chlorine quantification in cement paste samples, which was carried out by 12 laboratories in 10 countries. Two sets of samples with chloride content ranging from 0.06-1.95 wt.% in the training set and 0.23-1.51 wt.% in the test sample set (“unknowns”), with additional variations in the type of cement and chlorine source (salt type) were sent to the laboratories. The overall result demonstrates that LIBS is suitable for the quantification of the investigated sample compositions: average relative bias was mostly below 15 %. Considering that the laboratories did not receive instructions on how to perform the analysis or how to process the data, the results can be evaluated as a true status quo of the LIBS technique for this type of analysis.
In the interest of exploring their potential in the field of single particle analysis, a Microdroplet Generator (MDG) was coupled to an ICP-ToF-MS.
Isotopic Dilution Analysis was also incorporated for the size determination of three different Platinum Nanoparticles samples (50, 63 and 70 nm). The performance of the technique was validated by comparison to traditional size characterization techniques (sp-ICP-ToF-MS, TEM), while the robustness of the technique was proven by incorporating NaCl in the samples’ matrix, up to 100 mg/L.
Isotope reference materials
(2022)
The variation of isotope ratios is increasingly used to unravel natural and technical questions. In the past, the investigation and interpretation of such variations was the field of a limited number of experts. With new upcoming techniques and research topics in the last decades, such as provenance or food authenticity studies, the number of published isotope data strongly increased. Instrumental developments such as the enhancement of inductively coupled plasma mass spectrometers (ICP-MS) from an instrument for simple quantitative analysis to highly sophisticated isotope ratio machines influenced this process significantly. While in former times only experts in mass spectrometry were able to produce reliable isotope data, nowadays many laboratories, never been in touch with mass spectrometry before, produce isotope data with an ICP-MS. Isotope reference materials (iCRM) are indispensable to enable a reliable method validation or in rare cases even SI-traceability. The fast development and the broad availability of ICP-MS also lead to an expansion of the classical research areas and new elements are under investigation. Irrespective of the investigated element or the knowledge of the user all isotope ratio applications require reference materials either for correction of instrumental isotope fractionation, for method validation or to provide a common accepted basis as needed for delta measurements. This presentation will outline the basic principles and illustrate the urgent need for new iCRMs. Consequently, the production and certification of iCRMs will be discussed and illustrated by examples of already completed certification projects. Finally, plans for future iCRMs to be produced at BAM will be presented.
IRWG strategy update
(2022)
MALDI-TOF-MS-based identification of monoclonal murine anti-SARS-CoV-2 antibodies within one hour
(2022)
During the SARS-CoV-2 pandemic, many virus-binding monoclonal antibodies have been developed for clinical and diagnostic purposes. This underlines the importance of antibodies as universal bioanalytical reagents. However, little attention is given to the reproducibility crisis that scientific studies are still facing to date. In a recent study, not even half of all research antibodies mentioned in publications could be identified at all. This should spark more efforts in the search for practical solutions for the traceability of antibodies. For this purpose, we used thirty-five monoclonal antibodies against SARS-CoV-2 to demonstrate how sequence-independent antibody identification can be achieved by simple means applied onto the protein. First, we examined the intact and light chain masses of the antibodies relative to the reference material NIST-mAb 8671. Already half of the antibodies could be identified based solely on these two parameters. In addition, we developed two complementary peptide mass fingerprinting methods with MALDI-TOF-MS that can be performed in 45 minutes and had a combined sequence coverage of over 80%. One method is based on the partial acidic hydrolysis of the protein by 5 mM of sulfuric acid at 99 °C. Furthermore, we established a fast way for a tryptic digest without an alkylation step. We were able to show that the distinction of clones is possible simply by a brief visual comparison of the mass spectra. In this work, two clones originating from the same immunization gave the same fingerprints. Later, a hybridoma sequencing confirmed the sequence identity of these sister clones. In order to automate the spectral comparison for larger libraries of antibodies, we developed the online software ABID 2.0 (https://gets.shinyapps.io/ABID/). This open-source software determines the number of matching peptides in the fingerprint spectra. We propose that publications and other documents critically relying on monoclonal antibodies with unknown amino acid sequences should include at least one antibody fingerprint. By fingerprinting an antibody in question, its identity can be confirmed by comparison with a library spectrum at any time and context.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is increasingly used to study the distribution of metal-containing drugs, imaging probes and nanomaterials in connection with disease related changes and therapy progress. Additionally, biomolecules can be detected indirectly by using metal-tagged antibodies.
The extracellular matrix (ECM) is, besides the cells, an important component of all body tissues. The macromolecular network of the ECM consists of structural proteins (e.g., collagen, elastin) and proteoglycans composed of highly negatively charged carbohydrates, the glycosaminoglycans (GAGs), which are covalently linked to a protein core. Many diseases, including inflammatory processes and tumors, are associated with characteristic ECM changes at an early stage. Recent studies have shown that contrast agents for magnetic resonance imaging (MRI), which are based on gadolinium containing chelate complexes or iron oxide nanoparticles, can bind themselves to ECM components.
To elucidate the role of GAGs like keratan sulfate (KS) and its modification state in disease, highly specific tools are necessary. As a complement to conventional immunohistochemistry LA-ICP-MS was applied to investigate the distribution of KS in tissue thin sections using a well characterized anti-KS antibody labelled with metal ions. Furthermore, LA-ICP-MS was used for the detection of MRI contrast agents and the identification of their target cells and molecules in tissue samples from animal models, e.g. for cardiovascular diseases. The results show the possibilities of LA-ICP-MS for the elucidation of pathological tissue changes.
The simultaneous detection of different analytes has gained increasing importance in recent years, especially in the fields of medical diagnostics and environmental analysis. Multiplex assays allow for a range of biomarkers or pollutants to be rapidly and simultaneously measured. Particularly suitable formats for multiplexing are bead-based assays. The beads employed need to fulfil size and density requirements, important for instance for flow cytometry, and shall exhibit a high modularity to be facilely adapted to various kinds of analytes and detection systems. Core/shell particles are ideally suited in this sense because of their modularity in design and adaptability for various (bio)analytical assays. Here, polystyrene particles coated with different kinds of shells are presented, possessing features that are useful for a multitude of assay formats.
The particles in focus were coated with mesoporous and non-porous silica shells, with the possibility to introduce magnetic features to facilitate easier handling dependent on the assay format (e.g., in microfluidics). With high throughput analyses in mind, cytometric model assays were developed. Different factors such as pH or mediator salt used during shell preparation were evaluated with shell inspection by electron microscopy (SEM/TEM/EDX) being key to architectural control of the monodisperse particles. The optimized core/shell particles can be functionalized with capture biomolecules for toxins, viruses, or drugs to demonstrate particle performance. Showing how tailoring of the shell’s surface area controls sensitivity and dynamic range of the assay, an antibody-based assay for the detection of mycotoxins and a multiplex assay for the determination of DNA from different human papilloma virus (HPV) lines were developed.
Inductively coupled plasma-mass spectrometry (ICP-MS) is a well-established analytical method offering high sensitivity and multi-element analysis. ICP-MS has found acceptance in various application areas ranging from material analysis to applications in the life sciences. Within the last 15 years new strategies for the sensitive detection and accurate quantification of biomolecules in complex biomedical samples have been developed. Recent instrumental improvements have contributed to this progress.
As most of the biomolecules do not contain endogenous metals etectable with ICP-MS, bioconjugation with artificial metal-containing tags based on metal-loaded chelate complexes or nanoparticles is increasingly applied to determine biomolecules indirectly. Especially, the combination of immunohistochemical workflows using lanthanoid-tagged antibodies and ICP-MS detection provides new insights in the complexity and interdependency of cellular processes. Single-cell ICP-MS, also termed as mass cytometry, allows high-dimensional analysis of biomarkers in cell populations at single-cell resolution. For that purpose, lanthanoid isotope labelled antibodies are used to detect their corresponding target molecules. The visualisation of the elemental distribution is possible with laser ablation ICP-MS (LA-ICPMS) at high spatial resolution. Especially, the combination of LA with ICP time-of-flight mass spectrometry, also referred to as imaging mass cytometry (IMC), opens new possibilities for multiparametric tissue imaging at the single-cell level and even below. The lanthanoid localisation and concentration can be linked to their conjugated antibody target providing valuable information about surface markers, intracellular signalling molecules to measure biological function, and the network state of an individual cell in a tissue.
This book chapter focuses on new applications, where the multi-element capabilities of ICP-MS are used for the detection of lanthanoids applied as artificial elemental stains or tags for biomolecules and in particular antibodies.
Protein immobilization for the functionalization of particles is used in various applications, including biosensors, lateral-flow immunoassays (LFIA), bead-based assays, and others. Common methods for the quantification of bound protein are measuring protein in the supernatant before and after coating and calculating the difference. This popular approach has the potential for a significant overestimation of the amount of immobilized protein since layers not directly bound to the surface (soft protein corona) are usually lost during washing and handling. Only the layer directly bound to the surface (hard corona) can be used in subsequent assays. A simplified amino acid analysis method based on acidic hydrolysis and RP-HPLC-FLD of tyrosine and phenylalanine (aromatic amino acid analysis, AAAA) is proposed to directly quantify protein bound to the surface of gold nano- and latex microparticles. The results are compared with indirect methods such as colorimetric protein assays, such as Bradford, bicinchoninic acid (BCA), as well as AAAA of the supernatant. For both particle types, these indirect quantification techniques show a protein overestimation of up to 1700% compared to the direct AAAA measurements. In addition, protein coating on latex particles was performed both passively through adsorption and covalently through EDC/sulfo-NHS chemistry. Our results showed no difference between the immobilization methodologies. This finding suggests that usual protein determination methods are no unambiguous proof of a covalent conjugation on particles or beads.
Quantitative 1H Nuclear Magnetic Resonance (qNMR) of Aromatic Amino Acids for Protein Quantification
(2022)
qNMR is a valuable technique for metrological studies due to the uniformity of its signal response for all chemical species of an isotope of interest, which enables compound-independent calibration. However, protein quantification remained challenging as large molecules produce wide, low-intensity signals that reduce the already low sensitivity. Combining qNMR with the hydrolysis of protein samples into amino acids circumvents many of these issues and facilitates the use of NMR spectroscopy for absolute protein and peptide quantification.In this work, different conditions have been tested for quantifying aromatic amino acids and proteins. First, we examined the pH-based signal shifts in the aromatic region. The preferable pH depends on the selection of the amino acids for quantification and which internal standard substance should be used to avoid peak overlap. Several aromatic compounds, such as terephthalic acid, sulfoisophthalic acid, and benzene tricarboxylic acid, have been applied as internal standards. The quantification of amino acids from an amino acid standard, as well as from a certified reference material (bovine serum albumin), was performed. Using the first two suggested internal standards, recovery was ~ 97 % for histidine, phenylalanine, and tyrosine at a concentration of approximately 1 mM in solution. Acidic hydrolysis of a certified reference material (CRM) of bovine serum albumin (BSA) and subsequent quantification of Phe and Tyr yielded recoveries of 98 ± 2 and 88 ± 4 %, respectively, at a protein concentration of 16 g/L or 250 µM.
Quantification of the Total and Accessible Number of Functional Groups and Ligands on Nanomaterials
(2022)
Surface-functionalized organic and inorganic nanoparticles (NP) are of great interest in the life and material sciences, as they can be used e.g. as drug carriers, fluorescent sensors, and multimodal labels in bioanalytical assays and imaging applications. NP performance in such applications depends not only on particle size, size distribution, and morphology, but also on surface chemistry, i.e. the total number of surface functional groups (FG) and the number of FG accessible for subsequent functionalization with ligands or biomolecules, which in turn determines surface charge, colloidal stability, biocompatibility, and toxicity. Methods for FG quantification should be simple, robust, reliable, fast, and inexpensive, and allow for the characteriza-tion of a broad variety of nanomaterials differing in size, chemical composition, and optical properties.
Aiming at the development of simple, versatile, and multimodal tools for the quantification of many bioanalytically relevant FG such as amine, carboxy, thiol and aldehyde functionalities, we investigated and compared various analytical methods commonly used for functional group quantification. This includes electrochemical titration methods, dye-based optical assays, and other instrumental analytical techniques such as nuclear magnetic resonance, mass spectrometry, and thermal analysis methods.
Functionalized nanomaterials (NM) with their unique size-dependent properties are of increasing relevance for current and future developments in various fields such as medical and pharmaceutical industry, computing, electronics or food and consumer products. The performance and safety of NM are determined by the sum of their intrinsic physicochemical properties.1 Besides other key parameters, the particle surface chemistry, which is largely controlled by the chemical nature and density of functional groups and ligands, must be considered for a better performance, stability, and processibility of NM, as well as their interaction with the environment. Thus, particle standards with well-designed surfaces and methods for functional group quantification can foster the sustainable development of functional and safe(r) NM.2 Here we provide a brief overview of the ongoing research in division Biophotonics to design tailored amorphous silica reference particles with bioanalytically relevant functional groups and ligands, for the development of standardized and validated surface functional group quantification methods.
Estrogens are endocrine disrupting chemicals and of high concerns due to demonstrated harmful effects on the environment and low effect levels. For monitoring and risk assessment, several estrogens were included in the "watch list" of the EU Water Framework Directive which sets very low environmental quality standard (EQS) levels for Estrone (E1) and 17β-Estradiol (E2) of 0.4 ng L−1 and for 17α-Ethinylestradiol (EE2) of 0.035 ng L−1 requiring sensitive detection methods, as well as extensive sample preparation. A sensitive, derivatization-free, isotope dilution calibration HPLC-MS/MS method for a panel of 5 selected estrogens (including the 3 estrogens of the EU WFD watchlist), and a procedure for the reproducible preparation of a representative whole water matrix including mineral water, humic acids and solid particulate matter are presented. These are used in a diligent comparison of classical solid phase extraction (SPE) on hydrophilic-lipophilic balanced (HLB) phase to SPE on an estrogen-specific molecularly imprinted polymer phase (MISPE) for ultra-trace levels of the analytes (1–10 ng L−1). Additionally, a two-step procedure combining HLB SPE disks followed by MISPE is evaluated. The tow-step procedure provides superior enrichment, matrix removal and sample throughput while maintaining comparable recovery rates to simple cartridge SPE. Estimated method quantification limits (MQLs) range from 0.109–0.184 ng L−1 and thus meet EQS-levels for E1 and E2, but not EE2. The representative whole water matrix provides a reproducible comparison of sample preparation methods and lays the foundation for a certified reference material for estrogen analysis. The presented method will serve as the basis for an extended validation study to assess its use for estrogen monitoring in the environment.
pH presents one of the most important analytes in the life and material sciences, indicating, e.g., diseases and corrosion processes. This includes the optical monitoring of pH in living cells for studying cellular internalization pathways, such as phagocytosis, endocytosis, and receptor mediated internalization with the aid of molecular and nanoscale fluorescent sensors. Nanoparticle (NP)-based sensors, that are labelled or stained with a multitude of sensor dyes, have several advantages as compared to conventional molecular probes like enhanced brightness, i.e., amplified signals, ease of designing ratiometric systems by combining analyte-sensitive and inert reference dyes, and increased photostability. Moreover, this can enable the use of hydrophobic dyes in aqueous environments. Versatile templates and carriers for the fabrication of nanosensors by staining and/or labelling with different fluorophores and sensor molecules are surface-functionalized particles like silica (SiO2) and polystyrene (PS) particles. Here we present a platform of blue-red-green fluorescent pH nanosensors for the measurement of acidic, neutral, and basic pH utilizing both types of matrices and two spectrally distinguishable sensor dyes with an integrated reference dye and demonstrate its applicability for cellular studies.
Im Rahmen von der BAM und anderen Partnern ins Leben gerufene Initiative „Digitale Qualitätsinfrastruktur“ ist der Fokus auf die Entwicklung von neuen Regelwerken und Zertifizierungsworkflows ausgerichtet. Dabei ist eine besondere Bedeutung dem Zusammenführen von Operational Technology (OT) und Informationstechnik (IT) beizumessen, wenn aktuelle Prozess- und Parameterdaten
zuverlässig zur Verfügung gestellt werden sollen. In dem Use Case Wasserstofftankstelle werden digitale Abbilder erprobt, die u.a. der Kalibrierung von Sensoren, dem Nachweis über die Wasserstoffreinheit und der vorausschauenden Wartung dienen sollen.
Großenteils der verfahrenstechnischen Bestandsanlagen, die sogenannten Brownfield-Anlagen, sind nach einem konservativen und hierarchischen Automatisierungskonzept ausgelegt. Hierbei können sämtliche Prozessdaten,
besonders aus der Feldebene, einer oberen informationstechnische Ebene
unzugänglich bleiben. Eine Brückentechnologie nach der NAMUR Open Architecture (NOA) soll möglichst viele Informationen und Daten aus der vorgegebenen Brownfield-Automatisierung sicher und rückwirkungsfrei zur
Verfügung stellen. Zusätzliche Sensorik soll ebenso zu der Datenerweiterung beitragen und letztendlich den digitalen Zwilling, bzw. das digitale Abbild des verfahrenstechnischen Prozesses, ergänzen.
Die Herausforderungen einer solchen Infrastruktur gelten vor allem einer universellen
Kommunikationsschnittstelle und der Sicherheit. Darüber hinaus werden vorgeschlagene Normen und Empfehlungen untersucht und erprobt.
MXenes are a new family of two-dimensional (2D) transition metal carbides, carbonitrides, and nitrides discovered in 2011. Among many reported family members, titanium carbide is the most widely studied and explored due to the optimized synthesis conditions and promising characteristics like good mechanical strength, solution processability, and excellent conductivity. Here, we report the development of an electrochemical biosensor involving the amine-functionalized Few-Layered-Titanium Carbide Nanosheets and monoclonal antibodies against the SARS-CoV-2 nucleocapsid protein (anti-SARS-CoV-2 mAb) to design a point-of-care device for detection of the SARS-CoV-2 nucleocapsid protein (SARS-CoV-2 NP) antigen.
Per- and polyfluorinated alkyl substances (PFASs) are a substance class of over 4730 individual compounds. Several PFASs are extremely persistent, bioaccumulative and toxic. The analysis of PFASs is challenging because of their different chemical and physical properties as well as the high number of target substances. Target-based approaches (e.g., LC-MS/MS) are limited to the availability of analytical grade standards and are not suitable for the analysis of new/unknown PFASs and transformation products. Therefore, PFAS sum parameter methods become increasingly important to indicate a realistic PFAS pollution level.
PFAS sum parameters compromise the proportion of organically bound fluorine that can either be extracted (EOF) or adsorbed to activated carbon (AOF). For the instrumental analysis of such sum parameters, a fluorine selective detector is needed. High resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) is a sensitive and highly selective tool for indirect fluorine determination. The method is based on the in situ formation of diatomic gallium-mono fluoride (GaF) in a graphite furnace at a temperature of 1550°C. The molecular absorption of GaF can be detected at its most sensitive wavelength at 211.248 nm providing limits of quantification of c(F) 2.7 µg/L.
Here, we describe a fast and simple extraction method for the determination of the EOF using HR-CS-GFMAS in soil samples. Common approaches for the EOF determination use solid phase extraction (SPE). To omit the bias of this time consuming and expensive step we optimized a fast and simple SPE-free extraction method. The developed extraction method consists of a liquid-solid extraction using acidified methanol. Comparison of the method with and without an SPE clean-up step revealed a drastic underestimation of EOF concentrations using SPE. In the next step, the applicability of our method was tested for other solid matrices. In view of steadily increasing numbers of PFASs, our method will make an important contribution in assessing the pollution situation as well as support policy makers in deriving exposure limits for PFASs in the future.
Per- and polyfluorinated alkyl substances (PFASs) are a group of several thousand individual compounds. Many PFASs are extremely persistent, bioaccumulative and toxic. The analysis of PFASs is challenging because of their various chemical and physical properties as well as the high number of compounds. Target-based approaches (e.g., LC-MS/MS) are limited to the availability of analytical grade standards and are not suitable for the analysis of new/unknown PFASs and transformation products. Therefore, PFAS sum parameter methods become increasingly important to indicate realistic PFAS pollution levels.
PFAS sum parameters display the proportion of organically bound fluorine that can either be extracted (EOF) or adsorbed to activated carbon (AOF). For the instrumental analysis of such sum parameters, a fluorine selective detector is needed. High resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) is a sensitive and highly selective tool for fluorine determination. The method is based on the in situ formation of diatomic gallium-mono fluoride (GaF) in a graphite furnace at a temperature of 1550°C. The molecular absorption of GaF can be detected at its most sensitive wavelength at 211.248 nm providing limits of quantification of c(F) 2.7 µg/L.
In the present work a HR-CS-GFMAS method for EOF analysis was utilized for suspended particulate matter (SPM) analysis in German rivers in time lines from 2005–2020. Therefore, time and spatial resolved trends were investigated. In addition, SPM samples were analyzed for the Σ41PFAS using target analysis based on UHPLC-HRMS. Overall, target analysis drastically underestimated the total PFAS burden in SPM of German rivers compared to the EOF HR-CS-GFMAS analysis. Using a fluorine mass balance approach, only 0.2% to 38.6% of the EOF was explainable using the Σ41PFAS determined with target analysis. Our study highlights the need to integrate PFAS sum parameters (e.g., EOF with HR-CS-GFMAS) in PFAS risk assessment strategies.
Per- and polyfluorinated alkyl substances (PFASs) are a group of over 4730 individual compounds. Several PFASs are extremely persistent, bioaccumulative and toxic. The analysis of PFASs is challenging because of their various chemical and physical properties as well as the high number of compounds. Target-based approaches (e.g., LC-MS/MS) are limited to the availability of analytical grade standards and are not suitable for the analysis of new/unknown PFASs and transformation products. Therefore, PFAS sum parameter methods become increasingly important to indicate realistic PFAS pollution levels.
PFAS sum parameters display the proportion of organically bound fluorine that can either be extracted (EOF) or adsorbed to activated carbon (AOF). For the instrumental analysis of such sum parameters, a fluorine selective detector is needed. High resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) is a sensitive and highly selective tool for fluorine determination. The method is based on the in situ formation of diatomic gallium-mono fluoride (GaF) in a graphite furnace at a temperature of 1550°C. The molecular absorption of GaF can be detected at its most sensitive wavelength at 211.248 nm providing limits of quantification of c(F) 2.7 µg/L.
Here, we present an improved method for the determination of PFASs using HR-CS-GFMAS via GaF detection. The optimized method includes a Ga pretreatment as described by Gawor et al. resulting in overall lower detection limits. Furthermore, during optimization the influence of species-specific responses during HR-CS-GFMAS analysis was reduced resulting in a more accurate determination of PFAS sum parameters. To test the applicability of the improved method, we analyzed soil samples from a former fire-fighting training area combining the improved method for detection with our previously optimized extraction method for EOF determination in soils.
Per- and polyfluorinated alkyl substances (PFASs) are a group of over 4730 individual compounds. Several PFASs are extremely persistent, bioaccumulative and toxic. The analysis of PFASs is challenging because of their various chemical and physical properties as well as the high number of compounds. Target-based approaches (e.g., LC-MS/MS) are limited to the availability of analytical grade standards and are not suitable for the analysis of new/unknown PFASs and transformation products. Therefore, PFAS sum parameter methods become increasingly important to indicate realistic PFAS pollution levels.
PFAS sum parameters display the proportion of organically bound fluorine that can either be extracted (EOF) or adsorbed to activated carbon (AOF). For the instrumental analysis of such sum parameters, a fluorine selective detector is needed. High resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) is a sensitive and highly selective tool for fluorine determination. The method is based on the in situ formation of diatomic gallium-mono fluoride (GaF) in a graphite furnace at a temperature of 1550°C. The molecular absorption of GaF can be detected at its most sensitive wavelength at 211.248 nm providing limits of quantification of c(F) 2.7 µg/L.
Here, we present an improved method for the determination of PFASs using HR-CS-GFMAS via GaF detection. The optimized method includes a Ga pretreatment as described by Gawor et al. resulting in overall lower detection limits. Furthermore, during optimization the influence of species-specific responses during HR-CS-GFMAS analysis was reduced resulting in a more accurate determination of PFAS sum parameters. To test the applicability of the improved method, we analyzed soil samples from a former fire-fighting training area combining the improved method for detection with our previously optimized extraction method for EOF determination in soils.
2. Projekttreffen mit dem Umweltbundesamt zum Projekt MARKERIA (VH1802).
Ziel des Projektes ist es, die Eignung der Bestimmung eines oder mehrerer der genannten anthropogenen Marker im Abwasser zur Volumenkorrektur („Kalibration“) im SARS-CoV-2-Monitoring von Abwässern auf der Basis eines von der BAM zu erhebenden Messdatensatzes zu evaluieren.
Vortrag zum Kick-off des Projektes.
Ziel des Projektes ist es, die Eignung der Bestimmung eines oder mehrerer der genannten anthropogenen Marker im Abwasser zur Volumenkorrektur („Kalibration“) im SARS-CoV-2-Monitoring von Abwässern auf der Basis eines von der BAM zu erhebenden Messdatensatzes zu evaluieren.
A vast number of emerging pollutants is being detected in the environment. Another lingering problem are health-threatening contaminants, such as mycotoxins, that deteriorate food and feed, and the pathogens themselves. Analytical methods, suitable for trace analysis, are needed that are desirably also fast, inexpensive and, if possible, robust and portable. It is set out, how immunoana-lytical, i.e., antibody-based methods, which are elaborated in a broad range of formats, can be profitably used to gain insights on the distribution and concentration trends of the target analytes at the point-of-need.
In urban waters, a multitude of organic micropollutants, often termed emerging pollutants, has been found over the last decades. Analytical methods suitable for trace analysis are needed that are desirably also fast, inexpensive and, if possible, robust and portable. Immunoanalytical, i.e., antibody-based, methods which are available in a broad range of formats, can be profitably used here to screen for the distribution and to monitor the trends of concentration levels of contaminants of emerging concern in the environment. Some of these formats are single-analyte but high-throughput methods. To use them wisely, indicator substances, sometimes called anthropogenic markers, should be selected and used in screening approaches, i.e., as indicators for contamination and the pre-selection of samples at which to have a closer look by multiplex methods like LC-MS/MS. Other methods are suitable to be performed on portable instrumentation in the field (on-site) or in facilities such as wastewater treatment plants for on-line monitoring of the treatment and elimination process. Furthermore, array technologies have been established that allow for parallel (multiplex) analysis of several analytes of interest.
The microtiter-plate based ELISA (Enzyme-linked Immunosorbent Assay) is the method of choice for the analysis of a large number of samples [1]. ELISAs are available to monitor for anthropogenic markers such as the antiepileptic carbamazepine, the analgesic diclofenac, the antihistaminic cetirizine, the steroid hormone estrone, the antimicrobial sulfamethoxazole, psychoactive caffeine and cocaine, the priority pollutant bisphenol A, and the bile acid isolithocholic acid. For on-site screening and monitoring, simpler formats, like mix-and-read assays, e.g., the Fluorescence Polarization Immunoassay (FPIA) [2] or Lateral-flow Immunoassays (LFIA) [3] are more suitable tools, the latter based on dipsticks or little cassettes, with which users have become very familiar during the COVID-19 pandemic via rapid antigen tests. The suitability of multi-analyte formats such as immunomicroarrays depends on the choice of a signal-producing system that provides small uncertainties and good reproducibility of the measurements. Bead-based (“suspension”) arrays, read out in flow cytometers, are a powerful platform for multiplex assays [4]. Electrochemical formats, run on portable devices, provide additional advantages as no light source is required. They are most promising for stand-alone analysers and biosensors [5].
The speed, low cost and on-site capabilities of these methods allow to gather a lot more data on anthropogenic compounds which enables to quantify inputs, differences in degradation power of elimination processes, dilution phenomena and a more precise image of individual water cycles which is demonstrated by several examples.
Analytical methods based on the selectivity of antibodies, often called immunoassays, are a back-bone of clinical laboratory diagnostics. To bring them to the field, i.e., to make immunoanalytical methods portable, hopefully even faster, more sensitive, and robust, advanced materials are re-quired. Materials can be novel labels, e.g., chemical or particle labels, such as fluorophores or na-noparticles. Carrier particles, such as magnetic or polymer beads, make it possible to adopt the as-says to meso- or microfluidic set-ups and encoding them opens the path to multiplex analysis. Spe-cialty electrodes can enable for higher sensitivity in electrochemical detection. Without research into better materials, efforts to bring analysis to the point-of-need will not bear fruit.
Immunoanalytical Techniques, i.e., antibody-based analytical methods, have been used for decades in clinical diagnostics. What makes them attractive for other fields of application is their short time-to-result and high sensitivity. Microplate-based assays such as ELISA have been adopted early in environmental and food analysis. Yet, to make immunoassays even faster, more sensitive, robust, and, most desirable, portable, advanced materials, sometimes developed for other purposes, can be profitably used to achieve these goals. Materials can be novel labels, e.g., chemical or particle labels, such as fluorophores or nanoparticles. Carrier particles, such as magnetic or polymer beads, make it possible to adopt the assays to meso- or microfluidic set-ups and encoding them opens the path to multiplex analysis. Specialty electrodes can enable for higher sensitivity in electrochemical detection. All this broadens the scope of application and lowers effort and cost for analysis at the point-of-need.
ESI-CorA ist ein nationales Verbundprojekt mit dem Ziel des Nachweises von SARS-CoV-2 im Abwasser.
Das UBA hat als Teilprojekt das Projekt MARKERIA (VH1802) an die BAM vergeben.
Ziel des Projektes ist es, die Eignung der Bestimmung eines oder mehrerer der genannten anthropogenen Marker im Abwasser zur Volumenkorrektur („Kalibration“) im SARS-CoV-2-Monitoring von Abwässern auf der Basis eines von der BAM zu erhebenden Messdatensatzes zu evaluieren.
1. Projektreffen mit dem Umweltbundesamt für das Projekt MARKERIA (VH1802).
Ziel des Projektes ist es, die Eignung der Bestimmung eines oder mehrerer der genannten anthropogenen Marker im Abwasser zur Volumenkorrektur („Kalibration“) im SARS-CoV-2-Monitoring von Abwässern auf der Basis eines von der BAM zu erhebenden Messdatensatzes zu evaluieren.
In the present talk the basics of the Raman spectroscopy and particularly of Raman microscopy are explained. Advantages and disadvantages of the method are highlighted through selected case studies. In the second part of the lecture examples of correlative imaging with electron, X-ray, ion and optical microscopies from micro- to the nanoscale are highlighted.