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Eingeladener Vortrag
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The occurrence and fate of brominated flame retardants (BFRs) in the environment are topics of increasing concern. In recent years, numerous studies about their global transport, UV degradation, bioaccumulation and toxicity were performed to assess their environmental fate. Thus, most of the first generation BFRs are banned or restricted, and replaced by new ones. However, based on similar properties these new compounds may also pose a serious risk by causing adverse effects to human health and the environment. According to the European Food Safety Authority (EFSA) the class of the “emerging” BFRs are defined as compounds that have been identified in any environmental compartments, but the potential for degradation or bioaccumulation of these emerging BFRs is partially unknown.
A representative of this class of compounds is the heterocyclic hexabrominated TDBP-TAZTO which was first detected in mollusks from Chinese bohai sea and in environmental matrices near a manufacturing plant in southern china. Furthermore, Wang et al. describe that the growth of the alga Nannochloropsis sp. is inhibited by TDBP-TAZTO in a concentration dependent manner but the photo-chemical behavior as well as the formation of possible photo-transformation products (PTPs) are still unknown. In order to clarify this complex issue photo-degradation experiments were by determining the rate constants and degradation half-life times of TDBP-TAZTO in different solvent compositions. In this study, the photodegradation of TDBP-TAZTO was performed for the first time to identify its photolysis products and to get a first understanding about the main degradation pathway in environmental matrices.
The formation of transformation products (TPs) from contaminants and residues is becoming an increasing focus of scientific community. All organic compounds can form different TPs, thus demonstrating the complexity and interdisciplinarity of this topic. The properties of TPs could stand in relation to the unchanged substance or be more harmful and persistent. To get important information about the generated TPs, methods are needed to simulate natural and manmade transformation processes. Current tools are based on metabolism studies, photochemical methods, electrochemical methods, and Fenton's reagent. Finally, most transformation processes are based on redox reactions. This review aims to compare these methods for structurally different compounds. The groups of pesticides, pharmaceuticals, brominated flame retardants, and mycotoxins were selected as important residues/contaminants relating to their worldwide occurrence and impact to health, food, and environmental safety issues. Thus, there is an increasing need for investigation of transformation processes and identification of TPs by fast and reliable methods.
1,3,5-Tris-(2,3-dibromopropyl)-1,3,5-triazine-2,4,6-trione (TDBP-TAZTO) is an emerging brominated flame retardant which is widely used in several plastic materials (electric and electronic equipment, musical instruments, automotive components).
However, until today, no photochemical studies as well as the identification of possible phototransformation products (PTPs) were described in literature. Therefore, in this study, UV-(C) and simulated sunlight irradiation experiments were performed to investigate the photolytic degradation of TDBP-TAZTO and to identify relevant PTPs for the first time. The UV-(C) Irradiation experiments show that the photolysis reaction follows a first-order kinetic model. Based on this, the photolysis rate constant k as well as the half-life time t1/2 were calculated to be k = (41 ± 5 ×10−3) min−1 and t1/2=(17±2) min. In comparison, a minor degradation of TDBP-TAZTO and no formed phototransformation products were obtained under simulated sunlight. In order to clarify the photochemical behavior, different chemicals were added to investigate the influence on indirect photolysis: (i) H2O2 for generation of hydroxyl radicals and (ii) two quenchers (2-propanol, sodium azide) for scavenging oxygen species which were formed during the irradiation experiments. Herein, nine previously unknown PTPs of TDBP-TAZTO were detected under UV-(C) irradiation and identified by HPLC-(HR)MS. As a result, debromination, hydroxylation, and dehydrobromination reactions could be presumed as the main degradation pathways by high-resolution mass spectrometry. The direct as well as the OH radical-induced indirect photolysis were observed.
In this study the direct and indirect photolysis of the novel brominated flame retardant 2,4,6-Tris-(2,4,6-tribromophenoxy)-1,3,5-triazine (TTBP-TAZ) in an organic solvent mixture (60:30:10, ACN:MeOH:THF) under UV-(C) and simulated sunlight irradiation was investigated, and the formed photo-transformation products were identified for the first time. TTBP-TAZ was almost completely degraded within 10 min under UV-(C) irradiation. Due to the fast degradation no specific kinetic order could be observed. In comparison, the reaction under simulated sunlight irradiation was much slower and thus, the kinetic first-order could be determined. The observed photolysis rate constant k as well as the half-life time t1/2 were estimated to be k = (0.0163 ± 0.0002) h-1 and t1/2 = 42.3 h, respectively. The addition of 2-propanol and hydrogen peroxide to investigate the influence of indirect photolysis under UV-(C) irradiation causes no influence on the degradation of TTBP-TAZ. Nevertheless, the removal of TTBP-TAZ under UV-(C) and simulated sunlight without additional chemicals (except solvent) indicates that the direct photolysis plays a significant role in the degradation mechanism of TTBP-TAZ. In both irradiation experiments, TTBP-TAZ was quantitatively degraded that involve the formation of previously unknown PTPs. Overall, two main PTPs were determined when irradiated with UV-(C) and eight sequential debromination products were observed when irradiated by simulated sunlight. These were determined by HPLC-DAD and - MS/(MS), respectively. Based on the chosen experimental conditions the consecutive debromination as well as photo-Fries rearrangement was confirmed as the main degradation pathway by high resolution mass spectrometry and X-ray diffraction.
Development of analytical method and certified reference material for zearalenone in edible oils
(2017)
Quality and safety of food products require their reliable analysis. Contaminants, in particular mycotoxins, are key-components for food safety. About 25 % of the world's food crops are contaminated with mycotoxins posing a severe health risk to humans. In order to strengthen food safety and consumer protection the European Commission (EC) set maximum levels for priority mycotoxins in certain foods for human consumption. In 2013, the EC and CEN (European Committee for Standardization) started an initiative to standardize analytical methods for mycotoxins in food which gained increasing relevance, e.g. zearalenone (ZEN).[1] ZEN, an estrogenic mycotoxin produced by several Fusarium species, contaminates cereal crops worldwide. Due to its lipophilic nature ZEN is often found in edible oils (particularly in maize germ oils) derived from contaminated plants. Therefore, an European maximum level of 400 µg/kg is currently in force.[2] To perform reliable food analysis a sustainable metrological infrastructure is of major importance enabling the quantification of priority mycotoxins (here: ZEN). To achieve this goal an integrated approach is needed targeted at the development of validated analytical methods and certified reference materials (CRM).
A highly selective method for ZEN in edible oils will be presented, based on solid phase extraction (SPE) using hydrazine-functionalized particles. This method was developed for manual application using commercial SPE cartridges as well as for automated SPE-HPLC online coupling. While ZEN is covalently coupled to the solid phase by means of a hydrazone bond, undesired matrix components can be removed very efficiently. Finally, ZEN is decoupled from the solid phase, leading to highly purified extracts which are measured by HPLC-FLD.
The development of the first European Reference Material (ERM®) for ZEN in maize germ oil (ERM®-BC715) will be presented and discussed. This ERM®-project underpins the urgent need for mycotoxin-CRMs to support food safety and public health.
[1] European Commission (EC) Mandate M/520 (2013) for standardisation addressed to CEN for methods of analysis for mycotoxins in food. [2] Commission Regulation (EC) No 1126/2007 amending Regulation (EC) No 1881/2006 setting maximum levels for certain contaminants in foodstuffs as regards Fusarium toxins in maize and maize products.
Die Gruppe der polybromierten Flammschutzmittel (PBFSM) umfasst strukturell verschiedene Verbindungen, die zur Reduzierung der Entflammbarkeit von Polymeren eingesetzt werden. Aufgrund ihrer globalen Verteilung, möglichen Persistenz, Bioakkumulation und Toxizität ist die Nutzung der meisten Vertreter der ersten PBFSM-Generation u.a. in der Europäischen Union verboten oder nur noch eingeschränkt zugelassen. Daher wurden diese z.T. durch neue PBFSM ersetzt. Bedingt durch ähnliche Eigenschaften kann von diesen neuen Verbindungen aber ebenfalls ein ernstes Risiko für die menschliche Gesundheit und Umwelt ausgehen. Vertreter dieser neuen Verbindungen, die bereits in Umweltkompartimenten nachgewiesen werden konnten, werden hierbei als „emerging“ PBFSM bezeichnet.
Das Umweltverhalten dieser alternativen PBFSM ist bislang weitgehend unerforscht. Ein Untersuchungsschwerpunkt lag in den letzten Jahren u.a. auf dem Gebiet möglicher photochemischer Abbaureaktionen ausgewählter Vertreter dieser PBFSM in Umwelt¬matrices. Dabei wurden potentielle Photo-Transformationsprodukte (PTPs) in Simulationsstudien bzw. Umweltproben nachgewiesen, wobei als Hauptabbauweg die UV-induzierte photolytische Debromierung identifiziert wurde.
Um eine Einschätzung über das Umweltverhalten bzw. die Bildung von PTPs für das heterozyklische „emerging“ PBFSM 1,3,5-Tris-(2,3-dibromopropyl)-1,3,5-triazin-2,4,6-trion (Abb. 1) vornehmen zu können, wurden u.a. Abbaukinetiken sowie die Quantenausbeute des UV-(C) Experiments ermittelt. Weiterhin sollte der Einfluss von OH-Radikalen und des Singulett-Sauerstoffs 1O2 auf den Abbau-mechanismus durch die Zugabe verschiedener Inhibitoren/Scavenger mit anschließender HPLC-MS und zur Identifizierung der gebildeten PTPs mit HRMS Detektion geklärt werden. Ziel der präsentierten Arbeit ist es, ein erstes Verständnis des Umweltverhaltens zu entwickeln, um so eine Bewertung zur toxikologischen Relevanz dieser Verbindung bzw. deren Photo-Transformations-produkte geben zu können.
Polybromierte Flammschutzmittel (PBFSM) umfassen eine Gruppe strukturell unter-schiedlicher Verbindungen, die zur Herabsetzung der Entflammbarkeit in Kunststoffen eingesetzt werden. Aufgrund der mitunter persistenten, bioakkumulierenden sowie toxischen Eigenschaften stellt die Migration und ubiquitäre Verbreitung von PBFSM der ersten Generation ein potenzielles Risiko dar. Daher sind diese Verbindungen mittlerweile in der Europäischen Union verboten bzw. nur noch eingeschränkt zugelassen. Die Industrie hat daher neue PBFSM auf den Markt gebracht, die auf Grundlage ähnlicher Eigenschaften jedoch ebenfalls ein ernstes Risiko für Mensch und Umwelt darstellen können. Diese alternativen PBFSM werden in zwei Klassen eingeteilt: "emerging" und "novel" PBFSM. Emerging PBFSM sind definiert als Verbindungen, die in allen Umweltkompartimenten identifiziert wurden, während novel PBFSM nur in Materialien und/oder Waren oberhalb von 0,1 Gew.-% nachgewiesen wurden. Aufgrund der begrenzten Datenlage bezüglich Vorkommen, physikalisch-chemischen Eigenschaften und Umweltverhalten wurden zwei Vertreter ausgewählt, um das Abbau- und Transformationsverhalten näher zu untersuchen.
Um ein erstes Verständnis über den Verbleib in der Umwelt und den Stoffwechsel dieser PBFSM zu erhalten, wurden oxidative Abbauprozesse durch Kopplung einer elektrochemischen Zelle mit massenspektrometrischer Detektion (EC/MS) simuliert. Zusätzlich wurden in vitro Studien auf der Basis von mikrosomalen Ansätzen (Ratten/Fisch Lebermikrosomen) durchgeführt. Ziel der präsentierten Arbeit ist es, diese verschiedenen Arten von Stoffwechselstudien zu vergleichen, um Daten über den Abbau und/oder Bio-Transformationswege dieser neuen Kontaminanten zu erhalten.
Phototransformation of the “emerging” BFR 1,3,5-Tris-(2,3-dibromopropyl)-1,3,5-triazine-2,4,6-trione
(2017)
The occurrence and fate of brominated flame retardants (BFRs) in the environment are topics of increasing concern. In recent years, numerous studies about their global transport, UV degradation, bioaccumulation and toxicity were performed to assess their environmental fate. As a result, most of the first generation BFRs are banned or restricted, and replaced by new ones. However, based on similar properties these new compounds may also pose a serious risk by causing adverse effects to human health and the environment. According to the European Food Safety Authority (EFSA) the class of the “emerging” BFRs are defined as compounds that have been identified in any environmental compartments, but the potential for degradation or bioaccumulation of these emerging BFRs is partially unknown.
A representative of this class of compounds is the heterocyclic TDBP-TAZTO which was first detected in mollusks from Chinese bohai sea and in environmental matrices near a manufacturing plant in southern china. Furthermore, Wang et al. describe that the growth of the alga Nannochloropsis sp. is inhibited by TDBP-TAZTO in a concentration dependent manner but the photo-chemical behavior as well as the formation of possible photo-transformation products (PTPs) are still unknown. In order to clarify this complex issue photo-degradation experiments were by determining the rate constants and degradation half-life times of TDBP-TAZTO in different solvent compositions. In this study, the photodegradation of TDBP-TAZTO was performed for the first time to identify its photolysis products and to get a first understanding about the main degradation pathway in environmental matrices.
Photodegradation of the „novel“ brominated flame retardant Tris-(2,4,6-tribromophenoxy)-s-triazine
(2016)
Brominated flame retardants (BFRs) comprise a class of structurally diverse compounds that are functionally related and used in materials to reduce the flammability of polymers. Due to their global distribution, potential persistence, bioaccumulation and toxicity most of the BFRs of the first generation are banned or restricted, and replaced by new ones. However, based on similar properties these new compounds may also pose a serious risk by causing adverse effects to human health and the environment. These alternative BFRs were grouped into two classes: „novel” and „emerging” BFRs. Emerging BFRs are defined as compounds that have been identified in any environmental compartments whereas novel BFRs are only detected in materials and/or goods above 0.1 wt.-%.
The environmental fate of these alternative BFRs is partially unknown. Over the past years a multitude of studies on the photodegradation of BFRs in environmental matrices have been conducted to assess the photochemical behavior and fate in the environment. The photolytic debromination reaction is particularly induced among BFRs by UV exposure. The novel brominated triazine-based flame retardant tris-(2,4,6-tribromophenoxy)-s-triazine (TTBP-TAZ) is a BFR that is mainly used in acrylonitrile butadiene styrene and high impact polystyrene.
Ballesteros-Gómez et al. detected TTBP-TAZ in 8 of 13 plastic parts of consumer products and in 9 of 17 indoor dust samples but the photochemical behavior and fate is not known until now. The results of the present study, focused on photodegradation processes were performed for the first time for TTBP-TAZ to identify the photolysis intermediates and products to assess the environmental fate.