1.7 Organische Spuren- und Lebensmittelanalytik
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Organisationseinheit der BAM
- 1 Analytische Chemie; Referenzmaterialien (31)
- 1.7 Organische Spuren- und Lebensmittelanalytik (31)
- 1.8 Umweltanalytik (4)
- 1.1 Anorganische Spurenanalytik (2)
- 4 Material und Umwelt (2)
- 6 Materialchemie (2)
- 1.4 Prozessanalytik (1)
- 4.1 Biologische Materialschädigung und Referenzorganismen (1)
- 4.2 Material-Mikrobiom Wechselwirkungen (1)
- 6.3 Strukturanalytik (1)
Oxidative degradation processes of tetrabromobisphenol A (TBBPA), a brominated flame retardant (BFR) in wood, plastics and electronics, were investigated by electrochemistry (EC) coupled online to electrospray ionization mass spectrometry (ESI/MS). Oxidative phase I and II metabolites production was achieved using an electrochemical flow-through cell equipped with a boron doped diamond electrode. Structural elucidation and prediction of oxidative metabolism pathways of TBBPA according to type II ipso-substitution were based on retention time, m/z ratio in negative mode and fragmentation pattern. Using the data obtained through high resolution MS analysis and the identification of single electron transfer (SET) as the initial step of a two-electron oxidation provided the necessary information to propose a mechanism for the electrochemical oxidation of TBBPA. Oxidation reactions involving aromatic hydroxylation and β-scission were the main degradation observed when studying the electrochemical behavior of TBBPA. Computational chemistry experiments using density functional theory (DFT) allowed to identify mono-hydroxylated reaction intermediate and dismissed the mechanism involving two concurrent hydroxylation. TBBPA oxidation products were compared to known metabolites of its biological and environmental degradation confirming the ability of electrochemistry to simulate β-scission reactions.
Ergot alkaloids form a toxicologically relevant group of mould toxins (mycotoxins) that are among the most common contaminants of foodstuff and animal feed worldwide. Reliable controls are essential to minimise health risks and economic damage. Due to their toxicological relevance, EU limit values for 12 priority ergot alkaloids have been introduced for the first time in 2022 and range from 500 μg/kg in rye milling products down to 20 ug/kg Processed cereal-based foods for infants and young children[1]. High-performance liquid chromatography - mass spectrometry is used to quantify low concentrations of ergots in food, however the European standard analytical procedure cannot be applied due to the lack of isotopically labelled reference standards.
The complex structure of the ergot alkaloids makes a total synthesis extremely challenging, expensive and time-consuming. Therefore, we are focusing on different semi-preparative methods (electrochemistry, organic synthesis, heterogeneous catalysis) to specifically N-demethylate the C8 carbon atom of the lysergic acid moiety. The norergot alkaloid formed is then isotopically labelled using an electrophilic methyl source, i.e. iodomethane or dimethyl sulphate to obtain the specific isotopic labelled ergot alkaloid. Initial experiments have shown that N-demethylation of the ergot alkaloid ergotamine is possible by both electrochemical and wet-chemical organic synthesis. The next step is to improve the previously determined reaction conditions to enable the synthesis of norergotamine on a mg scale for further reactions.
Ergot alkaloids form a toxicologically relevant group of mould toxins (mycotoxins) that are among the most common contaminants of food and animal feed worldwide. Reliable controls are essential to minimise health risks and economic damage. Due to their toxicological relevance, EU limit values for 12 priority ergot alkaloids have been introduced for the first time in 2022 and range from 500 µg/kg in rye milling products down to 20 ug/kg Processed cereal-based foods for infants and young children[1]. High-performance liquid chromatography - mass spectrometry is used to quantify low concentrations of ergots in food, however the European standard analytical procedure cannot be applied due to the lack of isotopically labelled reference standards.
The complex structure of the ergot alkaloids makes a total synthesis extremely challenging, expensive and time-consuming. Therefore, we are focusing on different semi-preparative methods (electrochemistry, organic synthesis, heterogeneous catalysis) to specifically N-demethylate the C8 carbon atom of the lysergic acid moiety. The norergot alkaloid formed is then isotopically labelled using an electrophilic methyl source, i.e. iodomethane or dimethyl sulphate to obtain the specific isotopic labelled ergot alkaloid. Initial experiments have shown that N-demethylation of the ergot alkaloid ergotamine is possible by both electrochemical and wet-chemical organic synthesis. The next step is to adapt the previously determined reaction conditions to enable the synthesis of norergotamine on a mg scale.
Lithium-based batteries (LiBs) have become increasingly important in modern society, as cutting-edge portable energy storage systems and as a crucial component in the energy revolution. However, they still face challenges such as safety concerns, capacity degradation, and the ever-growing demand for higher energy density. To address these issues, researchers have turned their attention to fluorinated organic compounds (FOCs) as part of LiBs electrolytes. These substances, closely related to per- and polyfluorinated alkyl substances (PFAS), have shown great potential in optimizing LiBs. Specifically, their strong fluorine-carbon bond offers enhanced oxidative and chemical resistance. Nevertheless, their environmental impact is a cause for concern. Fluorinated organics can persist in the environment or can lead to the formation of persistent end-products, which accumulate and contribute to global health problems.
To study the fate of fluorinated organic electrolytes in different environmental and application scenarios, a range of simulation methods are employed, including the TOP (Total Oxidizable Precursor) Assay, electrochemistry, photo-induced degradation, and cycling of self-assembled coin cells prepared with FOCs. Transformation products (TP) are identified using gas chromatography and liquid chromatography coupled with high resolution mass spectrometry (GC/LC-HRMS).
Lithium-ion battery (LiB) operation remains challenging, particularly in terms of safety, cycling stability, capacity rates and high-voltage applications. Although the electrolytes of LiBs account for 10-15% of the total battery weight, they are still an underestimated part. Data suggest that the composition of electrolytes offers great potential to deal with all these issues. In particular, fluorinated electrolyte solvents or even fluorinated additives offer several advantages due to the strength of the C-F bond, providing chemical and oxidative stability and increased electronegativity, exhibiting flame retardant properties and facilitating anode-mediated degradation, resulting in a LiF-rich and more stable solid electrolyte interphase (SEI), enabling more efficient surface passivation. Therefore, studies suggest that fluorinated equivalents, as well as entirely new compounds, are promising for solving battery-related problems.
But what happens to fluorinated organic compounds (FOCs) during usage? And what are the new potential risks associated with their release into the environment? The environmental and application-specific fate of FOCs is investigated by a selection of different fluorinated electrolytes, the application of various simulation methods, including the TOP (Total Oxidizable Precursor) Assay, electrochemistry, photo-induced degradation, and cycling of FOC-prepared self-assembled coin cells.
Gas chromatography and liquid chromatography coupled with high resolution mass spectrometry (GC/LC-HRMS) are used to identify transformation products (TP).
Non-target (NT) mass spectrometry techniques play a crucial role in metabolomics applications, particularly in areas such as environmental safety. Soft ionization methods, such as electrospray ionization (ESI), are commonly employed due to their ability to generate spectra containing molecular ions, aiding in the identification of unknown peaks. However, ESI may fail to ionize certain compounds effectively, resulting in their absence in NT approaches. In contrast, hard ionization methods like electron impact (EI) can ionize a wide range of compounds but often lack information about the molecular ion. Although extensive databases of EI spectra exist, their nominal mass resolution (NR) limits their utility for modern high-resolution (HR) EI mass spectrometers. Here, the often-applied conversion of HR spectra to nominal mass leads to the loss of unique characteristics, i.e. by grouping distinct masses into more ambiguous nominal masses.
Our study aims to (i) quantify the negative impact of such a binning approach and (ii) develop a machine learning (ML) tool capable of enhancing existing nominal mass spectral libraries. In the initial phase, we employed the RECETOX Exposome HR-[EI+]-MS library to assess the influence of HR spectra on identification. We compared the dot product of each spectrum against all others, utilizing bin sizes of 0.001 and 1 Da. The difference in dot product between the second-best candidate and the query spectrum (the best candidate, with a score of 1) was calculated for both HR and nominal mass spectra. Subsequently, we explored the application of ML techniques to predict HR spectra from nominal mass spectra using the before mentioned dataset.
Preliminary findings demonstrate the potential of high-resolution spectral libraries. As anticipated, HR spectra consistently exhibited lower similarity scores for the second candidate. This observation likely stems from the high redundancy and resulting ambiguity associated with nominal masses. Even after eliminating spectra containing multiple HR masses mapped to the same nominal mass, the aforementioned trend persisted. Furthermore, initial investigations into ML have revealed its ability to predict up to 40% of HR masses within a 10 mDa precision window.
The use of per- and polyfluorinated alkyl substances (PFAS), which are very persistent and cannot be completely degraded in the environment, is a well-known problem worldwide. In contrast, fluorinated organic compounds used as electrolytes in lithium-based batteries (LiBs) have been less studied. Despite their increasing use in LiBs due to beneficial properties, such as improving safety, cycling performance, or even enabling high-voltage applications, there is little data on their distribution, transformation, and fate in the environment.
To fill this gap, fluorine-containing electrolyte components are studied in oxidative and reductive transformation processes. The identified transformation products (TP) will be determined in relevant environmental matrices and LiBs.
Gas Chromatography coupled with Electron Ionisation Mass Spectrometry (GC-EI-MS) is a well-established technique which, in combination with spectral libraries, has the potential to identify compounds in a sample. Nevertheless, most libraries are dominated by spectra with nominal mass resolution which does not allow to make full use of the data generated by modern high-resolution instruments. The production of high-resolution spectral library is time consuming and expensive, while in silico fragmentation tools that are capable of generating HR mass spectra are still too computationally intensive. We explored the alternative of using ML models to upscale existing spectral libraries. The models were trained with spectra from the RECETOX metabolome (DOI: 10.5281/zenodo.5483564), RECETOX Exposome (DOI: 10.5281/zenodo.4471216), and MassBank (10.5281/zenodo.7436394) HR-GC-MS libraries. The model was used to generate a synthetic library which was compared with a synthetic library simulated with CFM-ID (DOI: 10.1021/acs.analchem.6b01622).
Mycotoxins (toxic compounds formed by fungi) in food and feed have caused problems for mankind since the beginning of time. The group of ergot alkaloids plays a special role in human history. Several tens of thousands of deaths during the middle ages caused by to ergotism (the disease caused by continuous intake of ergot alkaloid contaminated food) underscore the importance of reliable analytical methods to ensure food safety.
More than 50 compounds belong to the group of ergot alkaloids. The 12 most found structures – the major ergot alkaloids – are typically measured, when it comes to ergot alkaloid quantification. High performance liquid chromatography (HPLC) with a fluorescence detector (FLD) is typically used to quantify the ergot alkaloid content. The main disadvantage of this method are the high costs for calibration standards (12 different calibration substances are required). But also, the time and effort required for the analysis of 12 peaks and overlapping signals that occur in complex food samples such as bread. As all ergot alkaloids share the ergoline structure and just differ in the substituents attached to this backbone, measurement of all ergot alkaloids in one sum parameter presents a time and cost saving alternative. The most important step for the development of such a sum parameter method is the reaction used to transfer all ergot alkaloids to one uniform structure. Two promising reactions, the acidic esterification to lysergic acid methyl ester and hydrazinolysis to lysergic acid hydrazide, were examined for possible use in a routine analysis method. In addition to yield and reaction rate, factors such as handling of the reaction and the possibility of parallel sample workup play a role.
Aroma Sensing of Truffles
(2022)
The aim of this project is to develop a mobile technical device to search for truffles. This way, truffles can be harvested faster, cheaper and more efficiently compared to the current method using dogs.
For this purpose, suitable marker substances in the aroma of ripe truffles were identified using analytical-chemical methods. The collected data was used to create aroma profiles of different truffle species.
The specificity of possible marker substances was confirmed with a truffle dog study. The hypothesis “If trained truffle dogs recognize the substances as supposed truffles in the context of an experiment, they can be regarded as specific” was made. The results show that the truffle aroma is mainly characterized and perceived by dogs by dimethyl sulfide and dimethyl disulfide.
For the concentration measurement of these markers in the ambient air, we are currently building our own detector. The Challenge is to get a fast measurement with a very low limit of detection at the same time. The device will resemble a metal detector in terms of shape and handling and be particularly suitable for mobile use.
The R&D cooperation project between the Federal Institute for Materials Research and Testing (BAM) and sglux GmbH thus enables truffles to be harvested professionally and systematically. This brings the technical advances that have revolutionized agriculture over the last hundred years to truffle cultivation for the first time.