Analytische Chemie
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Multidrug solids have a potential use to efficiently treat and control a superfluity of medical conditions.
To address the current drawbacks of drug development in R&D, it was targeted to achieve new pharmaceutical solid forms of fenamic acids having improved solubility and thermal stability. Subsequently, five new multicomponent solids consisting of three salt hydrates of trimethoprim (TMP) with mefenamic acid (TMP-MFA-H2O), tolfenamic acid (TMP-TFA-H2O) and flufenamic acid (TMP-FFA-H2O), and two cocrystals of sulfamethazine (SFZ) with flufenamic acid (SFZ-FFA) and niflumic acid (SFZ-NFA) were prepared by liquid assisted grinding. Looking at the structures of active pharmaceutical ingredient (API) molecules, it was quite expected that a wide range of supramolecular synthons would lead to cocrystallization.
New forms were characterized thoroughly by various solid-state techniques, including single crystal X-ray diffraction (SCXRD), which provided details of hydrogen bonding, molecular packing and interactions between drug and coformer. Kinetic solubility at pH 7.4 buffer study has been carried out and a comparison is made with respect to the parent drugs. A significant enhancement of NSAIDs solubility was observed in all salt hydrate systems of TMP. Thus with increasing physicochemical properties such as improved solubility further leads to the enhancement of bioavailability, which has implications to overcoming the formulation related problems of active pharmaceutical ingredients (APIs).
Our aim is to develop a new simple and inexpensive method for full field X-ray fluorescence imaging . We combine an energy dispersive array detector with a coded aperture to obtain high resolution images . To obtain the information from the recorded image a reconstruction step is necessary . The reconstruction methods we have developed , were tested on simulated data and then applied to experimental data . The first tests were carried out at the BAM line @ BESSY II. This method enables the simultaneous detection of multiple elements , which is important e.g. in the field of catalysis.
Mechanochemistry paves the way to simple, fast, and green syntheses. Despite considerable effort, there is a lack in understanding of the underlying mechanisms. In situ investigations help to understand these mechanisms, which occur during a mechanochemical reaction. Here we present a universal strategy for simultaneous real-time in situ analysis, combining X-ray diffraction, Raman spectroscopy, and thermography. The potential of of our approach is shown for diffrent model reactions.
We present the optical sensing of phthalate Esters (PAEs), a group of endocrine-disrupting chemicals. The sensing takes place as changes in the fluorescence emission intensity of aminopyrene covalently bound to the organic ligands of the metal−organic framework compound ZIF-8. In the presence of PAEs, a quenching of the fluorescence emission is observed. We evaluated strategies to engineer colloidal size distribution of the sensing particles to optimize the sensory response to PAEs. A thorough characterization of the modified ZIF-8 nanoparticles included powder X-ray diffractometry, transmission electron microscopy, high-performance liquid chromatography, and photophysical characterization. The presented capability of the fluorophore-functionalized ZIF-8 to sense PAEs complements established methods such as chromatography-based procedures, which cannot be used on-site and paves the way for future developments such as hand-held quick sensing devices.
Mechanochemically synthesized metal–organic Framework material HKUST-1 in combination with acrylonitrile butadiene styrene polymer was used to form a polymer metal–organic framework composite material by a simple extruder.
This composite filament was used for 3D printing. Xray diffraction measurements were used to prove the homogeneous distribution of the metal–organic framework in the polymer on a centimeter scale, whereas X-ray Absorption Edge Tomography using a synchrotron radiation source was able to evaluate the 3D distribution of the metal–organic framework material both in the filament and the resultant printed sample with a resolution of a few lm. Our very first data indicate that, apart from a few clusters having significantly higher Cu concentration, HKUST-1 is distributed homogeneously down to the 100 lm length scale in both polymer bulk materials in the form of clusters with a size of a few lm. Absorption Edge Tomography in combination with data fusion also allows for the calculation of the metal–organic framework amount located on the external polymer surface.
Our aim is to develop a new method for full field X ray fluorescence imaging at the BAM line @ BESSY II. We will combine an energydispersive array detector for X rays with a coded aperture to get high resolution images . In coded aperture imaging , an object is projected through a mask , producing many overlapping images on the detector . The first part of the project is to perform raytracing simulations to get realistic data and to develop a reconstruction method that allows to get the Information about the investigated object out of the projected image .
A series of phenolic-acid-based 2-oxazoline monomers with methoxysubstituted phenyl and cinnamyl side chains is synthesized and polymerized in a microwave reactor at 140 °C using methyl tosylate as the initiator. The obtained poly(2-oxazoline)s are characterized by NMR spectroscopy, MALDITOF mass spectrometry, and size-exclusion chromatography (SEC). Kinetic studies reveal that the microwave-assisted polymerization is fast and completed within less than ≈10 min for low monomer-to-initiator ratios of ≤25.
Polymers with number-average molar masses of up to 6500 g mol−1 and low dispersity (1.2–1.3) are produced. The aryl methyl ethers are successfully cleaved with aluminum triiodide/N,N′ diisopropylcarbodiimide to give a poly(2-oxazoline) with pendent catechol groups.
Besides conventional scanning X-ray fluorescence imaging at synchrotron sources, full-field X-ray fluorescence (FF-XRF) imaging techniques that do not implicitly require spatial scanning of the sample have become available. FF-XRF has become achievable thanks to the development of a new type of energy dispersive CCD-based 2D detector, also referred to as a 'color X-ray camera (CXC)' or 'SLcam'. We report on different imaging schemes for biological samples using FF-XRF imaging: (a) 2D 'zoom' imaging with pinhole optics using the 'camera obscura' principle; (b) 2D 'fixed magnification' imaging using magnifying polycapillary optics; and (c) 3D-FF-XRF imaging using an X-ray sheet beam or computed tomography (CT). The different FF-XRF imaging modes are illustrated using the crustacean Daphnia magna, a model organism for investigating the effects of metals on organism/ecosystem health, and foraminifera, a class of amoeboid protist. Detailed analytical characterization of the set-up is performed through analyzing various reference materials in order to determine limits of detection (LODs) and sensitivities. Experiments were performed using the BAMline at the BESSY synchrotron (Berlin, Germany) and using the P06 Hard X-ray Microprobe at the PETRAIII synchrotron (Hamburg, Germany).
The elemental analysis of seawater is often critical to the understanding of marine chemistry, marine geochemistry, and the deep-sea ecosystems. Laser-induced breakdown spectroscopy (LIBS) with the advantage of rapid multi-elements detection, has a great potential for in-situ elemental analysis of seawater. In practice, it is crucial to create a compact, low cost and power saving instrument for the long-term deep-sea observation. A recently appeared diode-pumped solid-state (DPSS) laser seems to be a promising candidate as it is both compact and robust. Additionally, its high repetition rate up to hundreds of kHz can provide a considerable throughput for LIBS analysis. However, the DPSS lasers operate at moderate pulse energies, usually less than one mJ, which cannot sustain stable breakdowns in bulk water. To ensure stable laser-induced plasmas underwater with such a μJ-DPSS laser, we introduced an ultrasound source to assist the breakdown process. The phase interface and mass flow generated by the near-field ultrasound can greatly reduce the breakdown threshold and enhance element-specific emissions. Meanwhile, the high repetition-rate pulses can also improve the breakdown probability and generate unique emission lines originated from the water molecule. We further demonstrate that the high repetition-rate DPSS laser combined with the Echelle spectrometer can provide effective quantitative analysis for metal elements in bulk water.
Matrix‐assisted ionization (MAI) mass spectrometry does not require voltages, a laser beam, or added heat to initiate ionization, but it is strongly dependent on the choice of matrix and the vacuum conditions. High charge state distributions of nonvolatile analyte ions produced by MAI suggest that the ionization mechanism may be similar to that of electrospray ionization (ESI), but different from matrix‐assisted laser desorption/ionization (MALDI). While significant information is available for MAI using mass spectrometers operating at atmospheric and intermediate pressure, little is known about the mechanism at high vacuum.
Eleven MAI matrices were studied on a high‐vacuum time‐of‐flight (TOF) mass spectrometer using a 266 nm pulsed laser beam under otherwise typical MALDI conditions. Detailed comparisons with the commonly used MALDI matrices and theoretical prediction were made for 3‐nitrobenzonitrile (3‐NBN), which is the only MAI matrix that works well in high vacuum when irradiated with a laser.
Screening of MAI matrices with good absorption at 266 nm but with various degrees of volatility and laser energies suggests that volatility and absorption at the laser wavelength may be necessary, but not sufficient, criteria to explain the formation of multiply charged analyte ions. 3‐NBN produces intact, highly charged ions of nonvolatile analytes in high‐vacuum TOF with the use of a laser, demonstrating that ESI‐like ions can be produced in high vacuum. Theoretical calculations and mass spectra suggest that thermally induced proton transfer, which is the major ionization mechanism in MALDI, is not important with the 3‐NBN matrix at 266 nm laser wavelength. 3‐NBN:analyte crystal morphology is, however, important in ion generation in high vacuum.
The 3‐NBN MAI matrix produces intact, highly charged ions of nonvolatile compounds in high‐vacuum TOF mass spectrometers with the aid of ablation and/or heating by laser irradiation, and shows a different ionization mechanism from that of typical MALDI matrices.
We developed a setup for time- and lateral-resolved X-ray absorption fine structure (XAFS) spectroscopy. A dispersive element is placed behind the sample to investigate. The broadband incoming beam transmits the sample, is then dispersed and finally collected by a position sensitive detector. This allows the recording of a whole X-ray absorption near edge structure (XANES) or extended X-ray absorption fine structure (EXAFS) spectrum in a single shot. The dispersive element is a Si(111) crystal, bent by means of a so called wafer bender, developed in house. Our setup is very flexible, easy to adjust and allows a time resolution down to one second which can be used to follow chemical reactions with dynamics on this time scale.
A two-component core-shell UiO-68 type metal-organic framework (MOF) with a nonfunctionalized interior for efficient guest uptake and storage and a thin light-responsive outer shell was prepared by initial solvothermal MOF synthesis followed by solvent-assisted linker exchange. The bulky shell linker features two tetra-ortho-fluorinated azobenzene moieties to exploit their advantageous photoisomerization properties. The obtained perfect octahedral MOF single crystals can be switched repeatedly and with an unprecedented efficiency between E- and Z-rich states using visible light only. Due to the high photoswitch density per pore of the shell layer, its steric demand and thus molecular uptake (and release) can be conveniently modulated upon green and blue light irradiation. Therefore, the "smart" shell acts as a light-controlled kinetic barrier or "gate" for the diffusion of cargo molecules in and out of the MOF crystals.
Mechanochemistry offers an environmentally benign and facile synthesis method for a variety of cement paste constituents. In addition, these methods can be used to selectively tune the properties of cement components. The mineral ettringite is an important component of cementitious materials and has additional technological potential due to its ion exchange properties.
Synthesis of ettringite via mechanochemistry is an environmentally friendly alternative to conventional wet-chemical synthesis established in industry. This contribution explores the mechanism of a two-step mechanochemical synthesis of ettringite, which was previously found to greatly improve the reaction conversion as compared with one-pot synthesis. The crystallinity of Al(OH)3 was found to decrease during the first stage of this mechanochemical synthesis. This was correlated to a significant decrease in the particle size of Al(OH)3 in this stage. No other significant changes were found for the other components, suggesting that mechanochemical activation of Al(OH)3 is responsible for the enhanced formation of ettringite by the two-step approach. The environmentally friendly approach developed for ettringite synthesis offers a versatile synthetic strategy, which can be applied to synthesise further cementitious materials.
In X-ray fluorescence (XRF), a sample is excited with X-rays, and the resulting characteristic radiation is detected to detect elements quantitatively and qualitatively. Quantification is traditionally done in several steps:
1. Normalization of the data
2. Determination of the existing elements
3. Fit of the measured spectrum
4. Calculation of concentrations with fundamental parameters / MC simulations / standard based
The problem with standard based procedures is the availability of corresponding standards. The problem with the calculations is that the measured intensities for XRF measurements are matrix-dependent. Calculations must, therefore, be performed iteratively (= time consuming) in order to determine the chemical composition.
First experiments with gold samples have shown the feasibility of machine learning based quantification in principle. A large number of compositions were simulated (> 10000) and analyzed with a deep learning network. For first experiments, an ANN (Artificial Neural Network) with 3 hidden layers and 33x33x33 neurons was used. This network learned the mapping of spectra to concentrations using supervised learning by multidimensional regression. The input layer was formed by the normalized spectrum, and the output layer directly yielded the searched values. The applicability for real samples was shown by measurements on certified reference materials.
Bundling analytical capacities to understand phase formation in recycling of functional materials
(2019)
Transitioning from combustion engine-driven transportation to e-mobility demands a paradigm shift – from a system geared to maximize energy efficiency (i.e. fuel consumption) to a system that may be constrained by the availability of high technology (critical) metals required for electrical energy storage systems and drives. In the wake of these developments efforts in securing new resources of these metals from recycling of end-of-life products are increasing steadily.
Recycling of Li-Ion batteries has recently been evaluated. The results pinpoint to a critical need for understanding slag Formation and its dependence on metal components like Mn under extreme conditions. This will allow researchers to predict optimal Operation setting and to react quickly to changing market demands (which may be Li or Co at one point but may also shift to Ni or rare earth elements (REE)). The long-term goal is to control the formation of specific phases in slags allowing for a Maximum yield of elements of interest and optimal recovery in the separation processes that follows. The combination of data on the physical micro structure and local chemistry of the multi-Phase products during and after processing will help to understand and derive thermodynamic and kinetic data on its formation.
In this paper we are giving an overview on the analytical challenges and approaches to provide robust data on local element concentration and species (especially Mn which is a common component of next generation Li-ion batteries cathodes), spanning the dimensions from the nanometer scale to the bulk material. The complementary interactions of X-rays and electrons make them ideal probes to collect Interface and “in-depth” information. Before- and -after studies as well as in situ structural changes and Phase (trans)formation, changes in elemental and elemental species (e.g. oxidation state) distribution may be tracked by X-ray diffraction (XRD), X-ray fluorescence microscopy and X-ray Absorption spectroscopy. The application of such advanced analytical tools will not only provide essential clues during early lab-based experiments towards the development of new recycling technologies, but may also be deployed for on-line and in-line monitoring of industrial processes.
Synchrotron radiation sources with their unique properties in terms of intensity, polarization and adjustability offer a wide range of possibilities in materials research. A basic introduction about the creation and special properties of synchrotron radiation will be given. Examples of current work at BAMline, the high-energy measuring facility of the Federal Institute for Materials Research and Testing at the synchrotron BESSY, are used to illustrate the possibilities and limitations of existing measuring methods. It will be shown how the formation of corrosion layers can be tracked, how the abrasion of implants leads to the introduction of heavy metals into the surrounding bone matrix and how the detection of smallest impurities in gold is possible by optimizing the measuring conditions. Finally, an outlook at the hardware and software developments to be expected in the coming years is given.
CsCoO2, featuring a two-dimensional layered architecture of edge- and vertex-linked CoO4tetrahedra, is subjected to a temperature-driven reversible second-order phase transformation at 100 K, which corresponds to a structuralrelaxation with concurrent tilting and breathing modes of edge-sharing CoO4tetrahedra. In the present investigation, it was found that pressure induces a phase transition, which encompasses a dramatic change in the connectivity ofthe tetrahedra. At 923 K and 2 GPa, beta-CsCoO2 undergoes a first-order phasetransition to a new quenchable high-pressure polymorph,alpha-CsCoO2. It is built up of a three-dimensional cristobalite-type network of vertex-sharing CoO4 tetrahedra. According to a Rietveld refinement of high-resolution powderdiffraction data, the new high-pressure polymorph gamma-CsCoO2 crystallizes in the tetragonal space groupI41/amd:2 (Z= 4) with the lattice constants a= 5.8711 (1) and c= 8.3214 (2) A, corresponding to a shrinkage in volume by 5.7% compared with the ambient-temperature and atmospheric pressure-CsCoO2polymorph.The pressure-induced transition (beta>gamma) is reversible;-CsCoO2 stays metastable under ambient conditions, but transforms back to the-CsCoO2structure upon heating to 573 K. The transformation pathway revealed isremarkable in that it is topotactic, as is demonstrated through a clean displacive transformation track between the two phases that employs the symmetry oftheir common subgroupPb21a(alternative setting of space group No. 29 that matches the conventional-phase cell).
The mechanochemical formation of the ionic cocrystals of glucose (Glc) and sodium salts Glc2NaCl·H2O (1) and Glc2NaX (X = Br (2), I (3)) is presented. Products are formed by co-milling Glc with three sodium salts (NaCl, NaBr, NaI). The ionic cocrystals were obtained under both neat grinding and liquid-assisted grinding conditions, the later found to accelerate the reaction kinetics. The crystal structures of the ionic cocrystals (2) and (3) were solved from powder X-ray diffraction data. The structure solution contrasts with the structure of Glc2NaCl·H2O (1) where the electron density at three halide crystallographic sites is modeled as of being the intermediate between water molecule and a chloride ion. The reaction pathways of the three ionic cocrystals were investigated in real time using our tandem approach comprising a combination of in situ synchrotron powder X-ray diffraction and Raman spectroscopy. The results indicate the rapid formation of each cocrystal directly from their respective starting materials without any intermediate moiety formation. The products were further characterized by DTA-TG and elemental analysis.
Zeolitic imidazolate frameworks (ZIFs) have been widely investigated for their use in separation, gas adsorption, catalysis, and biotechnology. Their practical applications, however, can be hampered by their structural instability in humid acidic conditions. Here, guided by density functional theory calculations, we demonstrate that the acidic stability of two polymorphic ZIFs (i.e., ZIF-8 and ZIF-L) can be enhanced by the incorporation of functional groups on polypeptides or DNA. A range of complementary synchrotron investigations into the local chemical structure and bonding environment suggest that the enhanced acidic stability arises from the newly established coordinative interactions between the Zn centers and the inserted carboxylate (for polypeptides) or phosphate (for DNA) groups, both of which have lower pKas than the imidazolate ligand. With functional biomolecular homologs (i.e., enzymes), we demonstrate a symbiotic stability reinforcement effect, i.e., the encapsulated biomolecules stabilize the ZIF matrix while the ZIF exoskeleton protects the enzyme from denaturation.