Structural annotation of electro- and photochemically generated transformation products of moxidectin using high-resolution mass spectrometry

Moxidectin (MOX) is a widely used anthelmintic drug for the treatment of internal and external parasites in food-producing and companion animals. Transformation products (TPs) of MOX, formed through metabolic degradation or acid hydrolysis, may pose a potential environmental risk, but only few were identified so far. In this study, we therefore systematically characterized electro- and photochemically generated MOX TPs using high-resolution mass spectrometry (HRMS). Oxidative electrochemical (EC) TPs were generated in an electrochemical reactor and photochemical (PC) TPs by irradiation with UV-C light. Subsequent HRMS measurements were performed to identify accurate masses and deduce occurring modification reactions of derived TPs in a suspected target analysis. In total, 26 EC TPs and 59 PC TPs were found. The main modification reactions were hydroxylation, (de-)hydration, and derivative formation with methanol for EC experiments and isomeric changes, (de-)hydration, and changes at the methoxime moiety for PC experiments. In addition, several combinations of different modification reactions were identified. For 17 TPs, we could predict chemical structures through interpretation of acquired MS/MS data. Most modifications could be linked to two specific regions of MOX. Some previously described metabolic reactions like hydroxylation or O-demethylation were confirmed in our EC and PC experiments as reaction type, but the corresponding TPs were not identical to known metabolites or degradation products. The obtained knowledge regarding novel TPs and reactions will aid to elucidate the degradation pathway of MOX which is currently unknown

Middle to Late Holocene Variations in Salinity and Primary Productivity in the Central Baltic Sea: A Multiproxy Study From the Landsort Deep

Anthropogenic forcing has led to an increased extent of hypoxic bottom areas in the Baltic Sea during recent decades. The Baltic Sea ecosystem is naturally prone to the development of hypoxic conditions due to its geographical, hydrographical, geological, and climate features. Besides the current spreading of hypoxia, the Baltic Sea has experienced two extensive periods of hypoxic conditions during the Holocene, caused by changing climate conditions during the Holocene Thermal Maximum (HTM; 8–4.8 cal ka BP) and the Medieval Climate Anomaly (MCA; 1–0.7 cal ka BP). We studied the variations in surface and bottom water salinity and primary productivity and their relative importance for the development and termination of hypoxia by using microfossil and geochemical data from a sediment core retrieved from the Landsort Deep during IODP Expedition 347 (Site M0063). Our findings demonstrate that increased salinity was of major importance for the development of hypoxic conditions during the HTM. In contrast, we could not clearly relate the termination of this hypoxic period to salinity changes. The reconstructed high primary productivity associated with the hypoxic period during the MCA is not accompanied by considerable increases in salinity. Our proxies for salinity show a decreasing trend before, during and after the MCA. Therefore, we suggest that this period of hypoxia is primarily driven by increasing temperatures due to the warmer climate. These results highlight the importance of natural climate driven changes in salinity and primary productivity for the development of hypoxia during a warming climate

Four Chemical Trends Will Shape the Next Decade's Directions in Perfluoroalkyl and Polyfluoroalkyl Substances Research

Per- and polyfluoroalkyl substances (PFAS) represent a versatile group of ubiquitously occurring chemicals of increasing regulatory concern. The past years lead to an ever expanding portfolio of detected anthropogenic PFAS in numerous products encountered in daily life. Yet no clear picture of the full range of individual substance that comprise PFAS is available and this challenges analytical and engineering sciences. Authorities struggle to cope with uncertainties in managing risk of harm posed by PFAS. This is a result of an incomplete understanding of the range of compounds that they comprise in differing products. There are analytical uncertainties identifying PFAS and estimating the concentrations of the total PFAS load individual molecules remain unknown. There are four major trends from the chemical perspective that will shape PFAS research for the next decade. Mobility: A wide and dynamic distribution of short chain PFAS due to their high polarity, persistency and volatility.Substitution of regulated substances: The ban or restrictions of individual molecules will lead to a replacement with substitutes of similar concern.Increase in structural diversity of existing PFAS molecules: Introduction of e.g., hydrogens and chlorine atoms instead of fluorine, as well as branching and cross-linking lead to a high versatility of unknown target molecules.Unknown “Dark Matter”: The amount, identity, formation pathways, and transformation dynamics of polymers and PFAS precursors are largely unknown.These directions require optimized analytical setups, especially multi-methods, and semi-specific tools to determine PFAS-sum parameters in any relevant matrix

Geruch und Ernährung. Tl.3: Lebensmittelaromen und ihre Analytik

Identifying those odorants in a food that actually contribute to the perceivable aroma requires a very elaborate and multi-step analytical procedure. As part of this analytical task, human sensory as well as instrumental analytical techniques are combined. Due to the large inhomogeneity of the possible odorants in the foods of interest, a specific strategy needs to be developed for each analysis. Usually, key food odorants are identified by first carefully processing the food samples and extracting the volatile fraction. These extracts are used in aroma extract dilution analyses to identify the most potent candidate substances. After quantification of the odor-ants, their odor thresholds are correlated to their actual concentration. In a matrix similar to the tested food, the identified odorants are recombined to model the aroma and to check whether they are sufficient. The odorants can only be proven to be required and thus be considered a key food odorant by omitting single odorants from this optimized combined mix. This elaborate process clearly shows which hurdles automatised high speed analytical tools on a microelectronic or biological basis will have to overcome

On-line monitoring tools for food processing

For routine analysis, wet chemical methods are often used to determine food quality. In addition, instrumental methods and human sensory analyses have been utilized for the determination of shelf life, food quality and origin. Unfortunately, apart from the time-consuming aspect of these methods, they are sensitive to misinterpretation. In the last decade, new devices, so-called electronic noses, have been described as both a cost-effective and time-saving substitute. However, most of these chemical sensors showed deficiencies in selectivity, sensitivity and reproducibility, and only a few applications are classified to partly replace the classical methods

Detection of tetrabromobisphenol A and its mono- and dimethyl derivatives in fish, sediment and suspended particulate matter from European freshwaters and estuaries

An analytical method was developed for the determination of tetrabromobisphenol A (TBBPA), 3,3′,5,5′-tetrabromobisphenol-A-monomethyl ether (MM-TBBPA) and 3,3′,5,5′-tetrabromobisphenol-A-dimethyl ether (DM-TBBPA), and its valid application on fish muscle matrix (bream and sole), suspended particulate matter (SPM) and surface sediment layer samples, using only 0.5 g sample material, is demonstrated. Here, for the first time, DM-TBBPA could be determined by an LC-MS/MS-based method applying atmospheric pressure photoionization (APPI), using the same sample extracts for all three analytes. Samplings covered freshwater fish (bream; annually, period 2007–2013) and SPM or sediment (every second year in the period 2008–2014) at selected European sites (rivers: Tees/UK, Mersey/UK, Western Scheldt/NL, Götaälv/SE, Rhône/FR; Lake Belau/DE). TBBPA could be quantified in 13 of 36 bream samples (range about 0.5–1.2 μg kg−1 ww) and 7 of 7 sole muscle samples (range about 0.5–0.7 μg kg−1 ww). Further, it could be quantified in 11 of the 14 SPM samples (range about 0.5–9.4 μg kg−1 dw) and in both of the surface sediment layer samples (2.3–2.6 μg kg−1 dw). MM-TBBPA could be quantified in 12 of 36 bream and 4 of 7 sole muscle samples (range about 0.8–1.8 μg kg−1 ww). Further, it could be quantified in 10 of the 14 river SPM samples (range about 2.3–4.5 μg kg−1 dw) and in both lake surface sediment layer samples (5.2–5.5 μg kg−1 dw). DM-TBBPA was rarely detectable and could not be quantified above the limit of quantification in any sample

Transformation Products of Organic Contaminants and Residues—Overview of Current Simulation Methods

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.Peer Reviewe

Processing Induced Degradation Routes of Prochloraz in Rapeseed Oil

Analyzing the fate of substances in complex matrices, such as processed food, is a major challenge in modern analytical chemistry. However, current regulatory procedures for pesticides only include high temperature hydrolysis of the active substance in water (OECD 507) to simulate food processing. This study shows that heating radiolabeled [imidazolyl-2-14C]prochloraz in virgin rapeseed oil at temperatures up to 240 °C leads to an extensive degradation of the active substance. In total, 11 degradation products were identified. Several of these products were formed by reactions of the active substance with ingredients from the oil. 2-[(1-H-Imidazole-1-carbonyl)(propyl)amino]ethyl oleate (icpame-oleate), a reaction product of an oleic acid moiety and the prochloraz backbone, was identified for the first time. The quantification of prochloraz, icpame-oleate, imidazole, and 2,4,6-trichlorophenol demonstrated the dependency of the degradation process on temperature, heating duration, and type of oil. The obtained results in this study show the enormous impact of high temperature food processing on the fate of pesticides. The necessity to consider matrix related reactions in pesticide regulation is emphasized, and the suitability of the OECD 507 guideline is questioned. Concerning possible toxicological risks of novel degradation products, future studies will have to assess potential hazards or opportunities of food processing, ultimately yielding in safer food