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Paper des Monats
- ja (1)
The X-ray crystallographic study of the macrocyclic tetrakis-N[N-2-hydroxyethyl-piperazino]calix[4]resorcinarene·3CH3CH2OH·H2O (3) reveals a self-assembled dimeric capsule-like complex held together by an array of intermolecular hydrogen bonds. Pairs of concave molecules associate directly in bowl-to-bowl fashion and enclose an accessible supramolecular cavity of Å3 hosting one water and three ethanol molecules. The supramolecular arrangement displays alternating layers of facing bowls and interlocking lower rim aliphatic moieties. The helical conformation of the 2-hydroxyethyl piperazinomethyl moieties displays chirality of a bimolecular capsule frozen in the solid state. 3 crystallises in the triclinic space group P-1 with two symmetry independent molecules in the asymmetric unit. Two enantiomeric capsules form a racemic pair in the unit cell.
Delta-Hexabromocyclododecane
(2007)
The ecotoxicological characterization of waste is part of its assessment as hazardous or non-hazardous according to the European Waste List. For this classification 15 hazard criteria are derived from the Council Directive 91/689/EEC on hazardous waste. Some of the hazard criteria are based on the content of dangerous substances. The criterion H14 'ecotoxic' lacks of an assessment and testing strategy and no specific threshold values have been defined so far. Based on the recommendations of CEN guideline 14735 (2005), an international round robin test (ring test) was organized by the German Federal Environment Agency in order to define suitable test methods for the biological assessment of waste and waste eluates. A basic test battery, consisting of three aquatic and three terrestrial tests, was compiled. In addition, data were submitted for ten additional tests (five aquatic (including a genotoxicity test) and five terrestrial ones). The tests were performed with three representative waste types: an ash from an incineration plant, a soil containing high concentrations of organic contaminants (polycyclic aromatic hydrocarbons) and a preserved wood waste. The results of this ring test confirm that a combination of a battery of biological tests and chemical residual analysis is needed for an ecotoxicological characterization of wastes. With small modifications the basic test battery is considered to be well suitable for the hazard and risk assessment of wastes and waste eluates. All results and documents are accessible via a web-based data bank application.
Phosphorus recycling from sewage sludge will be obligatory in Germany from 2029. Phosphorus content determination in sewage sludge is crucial to assess the prescribed recycling rates. Currently, German law regards sample preparation using aqua regia digestion in a microwave or under reflux conditions as well as instrumental phosphorus determination by ICP-OES, ICP-MS, or photometric determination with ammonium molybdate as equivalent. However, it is questionable whether these methods are indeed equivalent regarding phosphorus quantification in sludges near the limit of 20 g/kg for mandatory recycling. To answer this question, 15 sewage sludges of 11 different wastewater treatment plants were investigated with all permitted method (digestion and measurement) combinations. Moreover, one sewage sludge was also examined in an interlaboratory comparison (ILC) with 28 participants. This study shows that the above-mentioned methods differ in some cases significantly but across all method combinations and sludges, phosphorus recovery was between 80 and 121% after normalization to the grand mean (average of 15 sludges between 85 and 111%). The ILC and the examination of 15 sludges produced largely similar results. There is a tendency to higher phosphorus recovery after microwave digestion compared to reflux digestion and ICP-OES measurements determine higher phosphorus contents than ICP-MS and photometric phosphorus determination. As a result, the authors recommend ICP-OES determination of phosphorus in sewage sludge after microwave digestion.
The statistical tool eCerto was developed for the evaluation of measurement data to assign property values and associated uncertainties of reference materials. The analysis is based on collaborative studies of expert laboratories and was implemented using the R software environment. Emphasis was put on comparability of eCerto with SoftCRM, a statistical tool based on the certification strategy of the former Community Bureau of Reference. Additionally, special attention was directed towards easy usability from data collection through processing, archiving, and reporting. While the effects of outlier removal can be flexibly explored, eCerto always retains the original data set and any manipulation such as outlier removal is (graphically and tabularly) documented adequately in the report. As a major reference materials producer, the Bundesanstalt für Materialforschung und -prüfung (BAM) developed and will maintain a tool to meet the needs of modern data processing, documentation requirements, and emerging fields of RM activity. The main features of eCerto are discussed using previously certified reference materials.
Microplastics can affect biophysical properties of the soil. However, little is known about the cascade of events in fundamental levels of terrestrial ecosystems, i.e., starting with the changes in soil abiotic properties and propagating across the various components of soil−plant interactions, including soil microbial communities and plant traits. We investigated here the effects of six different microplastics (polyester fibers, polyamide beads, and four fragment types: polyethylene, polyester terephthalate, polypropylene, and polystyrene) on a broad suite of proxies for soil health and performance of spring onion (Allium fistulosum). Significant changes were observed in plant biomass, tissue elemental composition, root traits, and soil microbial activities. These plant and soil responses to microplastic exposure were used to propose a causal model for the mechanism of the effects. Impacts were dependent on particle type, i.e., microplastics with a shape similar to other natural soil particles elicited smaller differences from control. Changes in soil structure and water dynamics may explain the observed results in which polyester fibers and polyamide beads triggered the most pronounced impacts on plant traits and function. The findings reported here imply that the pervasive microplastic contamination in soil may have consequences for plant performance and thus for agroecosystems and terrestrial biodiversity.
Three chromatographic procedures were investigated regarding their potential for the quantification of aniline and 19 of its methylated and chlorinated derivatives in groundwater. These methods were based on liquid-liquid-extraction in combination with gas chromatography and single quadrupole mass spectrometry (GC/MS) according to German standard DIN 38407-16:1999 and its extension using tandem mass spectrometry (GC/MS-MS), both following liquid-liquid extraction, and as third alternative the direct injection of the water sample into a liquid chromatograph coupled to tandem mass spectrometry (LC/MS-MS). Results were compared using fortified water and real-world contaminated groundwater used in an interlaboratory comparison. It could be shown that GC/MS and GC/MS-MS yielded results deviating less than 10% from each other while all three procedure displayed quantification results deviating less than 15% from the intercomparison reference values in case of each analyte in the concentration range between 1 and 45 µg L-1. Though GC/MS-MS displays a ten-fold higher sensitivity than single quadrupole GC/MS, the precision of both methods in the concentration range was similar. LC/MS-MS has the advantage of no further sample preparation due to the direct injection and leads for methylanilines and meta-, para- substituted chloroanilines to results sufficiently equivalent to the standardised GC/MS method. However, LC/MS-MS is not suitable for ortho-chloroaniline derivates due to significantly lower ion yields than meta- and para-substituted chloroanilines.
Stir bar sorptive extraction (SBSE) was compared with standardized pump sampling regarding the prospects to assess airborne levels of polycyclic aromatic hydrocarbons (PAHs) in indoor environments. A historic railway water tower, which will be preserved as a technical monument for museum purposes, was sampled with both approaches because the built-in insulationmaterial was suspected to release PAHs to the indoor air. The 16 PAHs on the US EPA list were quantified using gas chromatography with mass spectrometric detection in filters from pump sampling after solvent extraction and on SBSE devices after thermal desorption. SBSEwas seen to sample detectable PAHmasseswith excellent repeatability and a congener pattern largely similar to that observed with pump sampling. Congener patterns were however significantly different from that in the PAH source because release from the insulation material is largely triggered by the respective congener vapor pressures. Absolute masses in the ng range sampled by SBSE corresponded to airborne concentrations in the ng L−1 range determined by pump sampling. Principle differences between SBSE and pump sampling as well as prospects of SBSE as cost-effective and versatile complement of pump sampling are discussed.
Evidence for the formation of difluoroacetic acid in chlorofluorocarbon-contaminated ground water
(2019)
The concentrations of difluoroacetic acid (DFA) and trifluoroacetic acid (TFA) in rainwater and surface water from Berlin, Germany resembled those reported for similar urban areas, and the TFA/DFA ratio in rainwater of 10:1 was in accordance with the literature. In contrast, nearby ground water historically contaminated with 1,1,2-trichloro-1,2,2-trifluoroethane (R113) displayed a TFA/DFA ratio of 1:3. This observation is discussed versus the inventory of microbial Degradation products present in this ground water along with the parent R113 itself. A microbial Transformation of chlorotrifluoroethylene (R1113) to DFA so far has not been reported for environmental media, and is suggested based on well-established mammalian metabolic pathways.
Odor Perception by Dogs: Evaluating Two Training Approaches for Odor Learning of Sniffer Dogs
(2017)
In this study, a standardized experimental set-up with various combinations of herbs as odor sources was designed. Two training approaches for sniffer dogs were compared; first, Training with a pure reference odor, and second, training with a variety of odor mixtures with the target odor as a common denominator. The ability of the dogs to identify the target odor in a new context was tested. Six different herbs (basil, St. John’s wort, dandelion, marjoram, parsley, ribwort) were chosen to produce reference materials in various mixtures with (positive) and without (negative)chamomile as the target odor source. The dogs were trained to show 1 of 2 different behaviors, 1 for the positive, and 1 for the negative sample as a yes/no task. Tests were double blind with one sample presented at a time. In both training approaches, dogs were able to detect chamomile as the target odor in any presented mixture with an average sensitivity of 72% and a specificity of 84%. Dogs trained with odor mixture containing the target odor had more correct indications in the transfer task.
The concentration of contaminants in groundwater samples can be decreased by degradation in the time course between field sampling and quantification in the laboratory, especially in samples from sites where degradation activity is enhanced by remediation measures. The sampling sites covered a variety of priority organic pollutants such as volatile aromatic and chlorinated compounds, phenols and petroleum hydrocarbons and different remediation strategies such as anaerobic and aerobic microbial in situ degradation, in situ chemical oxidation, and on-site purification with biological treatment. The stability of the contaminants' concentration was investigated over a time range of several hours without cooling in the autosampler of the analytical equipment (short term) and over several days of storage until analysis (long term). A number of stabilisation techniques suggested in international standards ISO 5667-3:2013 and ASTM D6517:2000 were compared both with regard to short term and long term stabilisation of the contaminants and their practicability for field sampling campaigns. Long term storage turned out to be problematic for most compound groups even under cooling. Short term stability was problematic also for volatiles such as benzenic aromates, naphthalene and volatile organic halogenated compounds to be analysed by headspace gas chromatography. Acidification (pH <2) was sufficient to prevent degradation of benzenic aromates, naphthalene, phenols and petrol hydrocarbons for up to seven days. The use of acids was not applicable to stabilise volatiles in waters rich in carbonates and sulphides due to stripping of the volatiles with the liberated gases. The addition of sodium azide was successfully used for stabilisation of volatile organic halogenated compounds.
The nature and concentrations of volatile organic compounds (VOCs) in chars generated by hydrothermal carbonization (HTC) is of concern considering their application as soil amendment. Therefore, the presence of VOCs in solid HTC products obtained from wheat straw, biogas digestate and four woody materials was investigated using headspace gas chromatography. A variety of potentially harmful benzenic, phenolic and furanic volatiles along with various aldehydes and ketones were identified in feedstock- and temperature-specific patterns. The total amount of VOCs observed after equilibration between headspace and char samples produced at 270 °C ranged between 2000 and 16,000 µg/g (0.2–1.6 wt.%). Depending on feedstock 50–9000 µg/g of benzenes and 300–1800 µg/g of phenols were observed. Substances potentially harmful to soil ecology such as benzofurans (200–800 µg/g) and p-cymene (up to 6000 µg/g in pine wood char) exhibited concentrations that suggest restrained application of fresh hydrochar as soil amendment or for water purification.
A number of currently recommended sampling techniques for the determination of hydrogen in contaminated groundwater were compared regarding the practical proficiency in field campaigns. Key characteristics of appropriate sampling procedures are reproducibility of results, robustness against varying field conditions such as hydrostatic pressure, aquifer flow, and biological activity. Laboratory set-ups were used to investigate the most promising techniques. Bubble stripping with gas sampling bulbs yielded reproducible recovery of hydrogen and methane which could be verified for groundwater sampled in two field campaigns. The methane content of the groundwater was confirmed by analysis of directly pumped samples thus supporting the trueness of the stripping results. Laboratory set-ups and field campaigns revealed that bubble stripping of hydrogen may be restricted to the type of used pump. Concentrations of dissolved hydrogen after bubble stripping with an electrically driven submersible pump were about one order of magnitude higher than those obtained from diffusion sampling. The gas chromatographic determination for hydrogen and methane requires manual injection of gas samples and detection by a pulsed discharge detector (PDD) and allows limits of quantification of 3 nM dissolved hydrogen and 1 µg L-1 dissolved methane in groundwater. The combined standard uncertainty of the bubble stripping and GC/PDD quantification of hydrogen in field samples was 7% at 7.8 nM and 18% for 78 nM.
A practical method for the quantification of
total purgeable organic sulfur (POS) in highly contaminated
groundwater is described. Volatile organic sulfur
compounds (VOSC) are purged from the water samples by
a stream of oxygen and combusted. The emerging sulfur
dioxide is absorbed in H2O2 and converted to sulfate which
is quantified by ion chromatography and reported as mass
sulfur equivalent. The overall limit of quantification is
0.03 mg l1. The content of POS is balanced with the total
VOSC determined by GC-AED after liquidliquid extraction.
Separate determination of the non-volatile organic
sulfur compounds by direct combustion of the water sample
and adsorption to charcoal yielded a mass balance of
the total sulfur content. Semi-quantitative GC-MS after
purge & trap accumulation revealed that the VOSC mixture
is composed of C1C4 alkyl sulfides. The implementation
of the developed methodology for the quantification of
VOSC as potential catalyst poison in a cleaning plant
for groundwater contaminated with volatile haloorganics
(VOX) is presented.
The reliability in measurement results obtained during environmental monitoring is crucial for the assessment and further planning of remediation efforts on the respective contaminated sites by the responsible authorities. A case study concerned with groundwater contaminated with perchloroethylene, trichloroethylene and 1,1,2-trichlorotrifluoroethane including their degradation products which involves private contract laboratories and an independent provider of quality assurance (QA) is presented. The experience gained with biannual monitoring campaigns over 14 years indicates that the selection of contractors on basis of accreditation status and successful performance in interlaboratory comparisons are not sufficient. Rather the auditing of the contractors by the QA provider prior to each campaign and the crosschecking of selected monitoring samples by the QA provider led to a lasting improvement of reliability in the contractors' measurement results. A mean deviation of 20% from the reference value determined by the QA provider for the crosschecked samples was reached.
High-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) was applied to sterospecifically quantify the content of α-, β-, and γ-hexabromocyclododecane (HBCD) in six fish species from the Norwegian Etnefjorden. A combination of a β-PM cyclodextrin and an achiral column enabled the paired chromatographic separation of the stereoisomers in the order (-)-α-, (+)-α-, (-)-β-, (+)-β-, (+)-γ- and, (-)-γ-HBCD. The limits of detection were in the range of 6–21 pg g-1 depending on the stereoisomer and the concentrations of α-, β-, and γ-HBCD in fillets ranged from <5.4 ng g-1 to 11.1 µg g-1 lipid weight. α-HBCD enantiomers were throughout dominating, and in most cases the accumulation of the respective first eluted enantiomers ((-)-α-, (-)-β- and (+)-γ-HBCD) was observed. Deviations from the racemic EF-value were considered to be significant if it was outside of the expanded uncertainty range for each of the racemic HBCD-ratios. The composition of HBCD isomers varied between the investigated fish species and the relative high values for the γ-HBCD concentrations for the bottom-dwellers flounder and thorny skate seems to echo the HBCD pattern of ocean sediments.
Two different hair reference materials, one produced from authentic hair displaying an ethyl glucuronide (EtG) content of about 25 pg/mg and one obtained by fortification of blank hair to an EtG level of 85 pg/mg were submitted to accelerated aging between 4 degrees C and 60 degrees C for periods between one and 24 months. Subsequently, the EtG content was determined in the aged samples and untreated reference samples stored at -22 degrees C under repeatability conditions following the so-called isochronous approach. The EtG content remained stable even at 40 degrees C for 24 months and at 60 degrees C over six months. This is in contrast to many organic analytes contained in trace concentrations in diverse matrices. A slight but significant increase of the recovered EtG in case of authentic hair samples having been exposed for 24 months between 4 degrees C and 60 degrees C may be due to a temperature-driven process that allows increased recoveries of the physiologically embedded EtG.
A procedure for the quantification of the PCB marker congeners 28, 52, 101, 138, 153, 180 in plastic waste form the recycling of cables in the range of content between 0.1 mg kg-1 and 20 mg kg-1 was validated. Representative reference materials for laboratory analyses were produced using granulates from different recycling processes. The method development included aspects of grinding, sieving, homogenising as well as the comparison of extraction methods and chromatographic conditions. The validated procedure foresees grinding of the technical sample to an upper particle size limit of 0.50 mm followed by extraction with an unpolar solvent such as n-hexane and gas chromatographic determination. LOD and LOQ for individual congeners ranged between 0.01 mg kg-1 and 0.08 mg kg-1. Electron capture detection (ECD) and mass selective detection (MS) were equivalent if chromatographic conditions were appropriately selected. The application of MS was advantageous in presence of significant amounts of interfering components which have been found in some cables.
Three reference materials containing the marker congeners in the range of 0.1 mg kg-15 mg kg-1 were submitted to a final validation intercomparison with 23 selected field laboratories using the developed method. Relative reproducibility standard deviations varied between 15% and 33%.
Towards the standardization of biochar analysis: the COST action TD1107 interlaboratory comparison
(2016)
Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and many other applications. However, analytical methods for its physical and chemical characterization are yet far from being specifically adapted, optimized, and standardized. Therefore, COST Action TD1107 conducted an interlaboratory comparison in which 22 laboratories from 12 countries analyzed three different types of biochar for 38 physical–chemical parameters (macro- and microelements, heavy metals, polycyclic aromatic hydrocarbons, pH, electrical conductivity, and specific surface area) with their preferential methods. The data were evaluated in detail using professional interlaboratory testing software. Whereas intralaboratory repeatability was generally good or at least acceptable, interlaboratory reproducibility was mostly not (20% < mean reproducibility standard deviation < 460%). This paper contributes to better comparability of biochar data published already and provides recommendations to improve and harmonize specific methods for biochar analysis in the future.
The interconversion of the stereoisomers contained in technical 1,2,5,6,9,10-hexabromocyclododecane, a major brominated flame retardant increasingly found in the environment and in biota, was investigated at elevated temperatures. The application of pure enantiomers of the three constituents α-, β-, and γ-HBCD enabled the unambiguous elucidation of the individual isomerisation reactions as well as the quantification of all respective rate constants. At 160 °C the rate constants range over two orders of magnitude from 1.50 × 10-3 to 1.88 × 10-5 mol(%) s-1. A preliminary mechanistic explanation for the differences of the rate constants which govern the composition of HBCD diastereomers at equilibrium is given.
In recent years numerous reports have highlighted the options of chemical breath analysis with regard to noninvasive cancer detection. Certain volatile organic compounds (VOC) supposedly present in higher amounts or in characteristic patterns have been suggested as potential biomarkers. However, so far no clinical application based on a specific set of compounds appears to exist. Numerous reports on the capability of sniffer dogs and sensor arrays or electronic noses to distinguish breath of cancer patients and healthy controls supports the concept of genuine cancer-related volatile profiles. However, the actual compounds responsible for the scent are completely unknown and there is no correlation with the potential biomarkers suggested on basis of chemical trace analysis.
It is outlined that specific features connected with the VOC analysis in breath – namely small concentrations of volatiles, interfering background concentrations, considerable sampling effort and sample instability, impracticability regarding routine application - stand in the way of substantial progress. The underlying chemicalanalytical challenge can only be met considering the severe susceptibility of VOC determination to these adverse conditions.
Therefore, the attention is drawn to the needs for appropriate quality assurance/quality control as the most important feature for the reliable quantification of volatiles present in trace concentration. Consequently, the advantages of urine as an alternative matrix for volatile biomarker search in the context of diagnosing lung and other cancers are outlined with specific focus on quality assurance and practicability in clinical chemistry. The headspace over urine samples as the VOC source allows adapting gas chromatographical procedures well-established in water analysis. Foremost, the selection of urine over breath as non-invasive matrix should provide considerably more resilience to adverse effects during sampling and analysis. The most important advantage of urine over breath is seen in the option to partition, dispense, mix, spike, store, and thus to dispatch taylor-made urine samples on demand for quality control measures. Although it is still open at this point if cancer diagnosis supported by non-invasively sampled VOC profiles will ultimately reach clinical application the advantages of urine over breath should significantly facilitate urgently required steps beyond the current proof-of-concept stage and towards standardisation.
In recent years, an increasing trend towards investigating and monitoring the contamination of the environment by microplastics (MP) (plastic pieces < 5 mm) has been observed worldwide. Nonetheless, a reliable methodology that would facilitate and automate the monitoring of MP is still lacking. With the goal of selecting practical and standardized methods, and considering the challenges in microplastics detection, we present here a critical evaluation of two vibrational spectroscopies, Raman and Fourier transform infrared (FTIR) spectroscopy, and two extraction methods: thermal extraction desorption gas chromatography mass spectrometry (TED-GC-MS) and liquid extraction with subsequent size exclusion chromatography (SEC) using a soil with known contents of PE, PP, PS and PET as reference material. The obtained results were compared in terms of measurement time, technique handling, detection limits and requirements for sample preparation. The results showed that in designing and selecting the right methodology, the scientific question that determines what needs to be understood is significant, and should be considered carefully prior to analysis. Depending on whether the object of interest is quantification of the MP particles in the sample, or merely a quick estimate of sample contamination with plastics, the appropriate method must be selected. To obtain overall information about MP in environmental samples, the combination of several parallel approaches should be considered.