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Two new approaches towards an emission reference material for use in quality assurance measures for materials emissions testing were developed and intensively tested. The overall goal was to obtain solid materials with homogenous and reproducible (S)VOC release. Since the application in inter-laboratory comparisons is aimed at, it should furthermore be long-term stable to ensure safe shipment to the customer without sustaining compound losses. In the first approach, thermoplastic polyurethane (TPU) was impregnated with the VOC texanol under high-pressure with liquid CO2 as solvent. In the second, styrene (VOC) and the SVOC 2,6-diisopropylnaphthalene (DIPN) were spiked into vacuum grease (VG) and a mixture of paraf-fin/squalane (P/S). For the prediction of the emission rates a finite element model (FEM) was developed for the VG and P/S type materials. All requirements for reference materials were fulfilled, whereas the TPU samples need to be aged for about 10 days until repeatable and re-producible emission rates were obtained.
Two new approaches towards an emission reference material for use in quality assurance measures for materials emissions testing were developed and intensively tested. The overall goal was to obtain solid materials with homogenous and reproducible (S)VOC release. Since the application in inter-laboratory comparisons is aimed at, it should furthermore be long-term stable to ensure safe shipment to the customer without sustaining compound losses. In the first approach, thermoplastic polyurethane (TPU) was impregnated with the VOC texanol under high-pressure with liquid CO2 as solvent. In the second, styrene (VOC) and the SVOC 2,6-diisopropylnaphthalene (DIPN) were spiked into vacuum grease (VG) and a mixture of paraf-fin/squalane (P/S). For the prediction of the emission rates a finite element model (FEM) was developed for the VG and P/S type materials. All requirements for reference materials were fulfilled, whereas the TPU samples need to be aged for about 10 days until repeatable and reproducible emission rates were obtained.
In this work, we use a gas sensor system consisting of a commercially available gas sensor in temperature cycled operation. It is trained with an extensive gas profile for detection and quantification of hazardous volatile organic compounds (VOC) in the ppb range independent of a varying background of other, less harmful VOCs and inorganic interfering gases like humidity or hydrogen. This training was then validated using a different gas mixture generation apparatus at an independent lab providing analytical methods as reference. While the varying background impedes selective detection of benzene and naphthalene at the low concentrations supplied, both formaldehyde and total VOC can well be quantified, after calibration transfer, by models trained with data from one system and evaluated with data from the other system. The lowest achievable root mean squared errors of prediction were 49 ppb for formaldehyde (in a concentration range of 20–200 ppb) and 150 μg/m³ (in a concentration range of 25–450 μg/m³) for total VOC. The latter uncertainty improves to 13 μg/m³ with a more confined model range of 220–320 μg/m³. The data from the second lab indicate an interfering gas which cannot be detected analytically but strongly influences the sensor signal. This demonstrates the need to take into account all sensor relevant gases, like, e.g., hydrogen and carbon monoxide, in analytical reference measurements.
Sintered bioactive glass scaffolds of defined shape and porosity, e.g. made via additive manufacturing, must provide sufficient bioactivity and sinterability. As higher bioactivity is often linked to high corrosion and crystallization tendency, a certain compromise between sintering ability and bioactivity is therefore required. Groh et al. developed a fluoride-containing bioactive glass (F3), which allows fiber drawing and shows a bioactivity well comparable to that of Bioglass®45S5.
To study whether and to what extent the sinterability of F3 glass powder is controlled by particle size, coarse and fine F3 glass powders (300-310µm and 0-32µm) were prepared by crushing, sieving and milling. Sintering, degassing and phase transformation during heating were studied with heating microscopy, vacuum hot extraction (VHE), DTA, XRD, and SEM.
For the coarse glass powder, sintering proceeds slowly and is limited by surface crystallization of primary Na2CaSi2O6 crystals. Although the crystallization onset of Na2CaSi2O6 is shifted to lower temperature, full densification is attained for the fine powder. This finding indicate that certain porosity might be tuned via particle size variation. Above 900°C, intensive foaming is evident for the fine powder. VHE studies revealed that carbon species are the main foaming source.
The OECD test guidelines (TGs) for testing chemicals have been widely used for regulatory purposes all over the world since the establishment of the Mutual Acceptance of Data (MAD) principle in 1984. This MAD principle ensures that, if a chemical is tested under the Good Laboratory Practice (GLP) conditions accordingly to an OECD TG, the data should be accepted in all OECD countries. The TGs have been developed, harmonized, internationally validated (round robin tests) and adopted by OECD countries to be used for the physical-chemical characterisation, fate estimation, and hazard identification for risk assessment of various chemicals. In addition to the TGs, OECD Guidance Documents (GDs) usually provide guidance on how to use TGs and how to interpret the results. These GDs do not have to be fully experimentally validated, and hence they are not under MAD, but they are based on relevant published scientific research.
But are the existing TGs and the related GDs applicable and adequate for the regulatory testing of nanomaterials? In general, it is accepted that most of the "endpoints" or more precisely measurement variables are applicable also for nanomaterials. However, for some endpoints new or amended TGs are needed. In addition, several GDs are needed to give more precise advice on the test performance in order to gain regulatory relevant data on nanomaterials.
The poster will present the status quo on recent TGs and GDs development for nanomaterials at OECD level with relevance for physical-chemical characterisation. Emphasis will be given to the proposed OECD TG on particle size and size distribution for manufactured nanomaterials. The development of such a TG is of special importance as particle size and size distribution is considered as major information for nanomaterial identification and characterization. A reliable and reproducible characterisation of particle size and size distribution is also needed for chemicals risk assessment of nanomaterials, for instance to interpret and compare test results and - in future – to forecast interaction and effects of nanomaterials. The presented poster will illustrate the way from the idea for a new TG and new GD to an accepted OECD TG/GD.
The new OECD test guideline will address the following four main steps in the determination of the length and width distributions of fibers: sample preparation, image acquisition, data evaluation and uncertainty analysis. As the sample preparation has to be optimized for each material, general quality criteria will be given in the protocol. For full visibility of a fiber the appropriate resolution has to be chosen. In the data evaluation the length and diameter of each fiber will be determined concurrently to allow for application of different regulatory definitions. The quality of the results critically depends on the sample preparation as well as the data evaluation. In this step the classification rules have to be formulated and followed accurately in order to optimize reproducibility of the method. The SOP will be validated in an international round robin test, which is planned for 2018/2019.
The properties of nanomaterials are influenced not only by their chemical composition but also by physical properties (such as size, geometry and crystal structure). For the reliable determination and assessment of behaviour and effects of nanomaterials as well as for the determination of the exposure of humans and environment a comprehensive physical-chemical characterization of nanomaterials is essential. This is an important prerequisite to identify them as nanomaterials and to interpret and compare test results and - in future – to forecast interaction and effects of nanomaterials.
In 2006, the OECD launched a sponsorship program for the testing of nanomaterials in which 11 nanomaterials were thoroughly investigated using a variety of methods. The aim of the project was, among other things, to find out where problems occur and where there are gaps in the measurement and test procedures and where are changes required. An important outcome of the sponsorship program was the finding that the OECD Test Guidelines should in several cases be extended to the specific needs in testing of nanomaterials. The existing standardized test methods of the OECD for physical-chemical characterization have not been developed for nanomaterials in particular. A high demand for an extension of the test guidelines was identified. Germany complied with the OECD's request in 2017 and has agreed to extend the “Test Guideline on Particle Size Distribution / Fiber Length and Diameter Distributions Test Guideline” for Manufactured Nanomaterials (MN). UBA commissioned BAM and BAuA with the preparation of the Test Guideline. The aim of the project is the development of a harmonized test protocol for a valid and reproducible determination of particle size and size distribution which is one of the most relevant physical-chemical properties for MNs.
Different measuring methods provide different results for the size distribution of the particles. This is caused by the different measuring principles of the methods. Each method measures a specific parameter that ultimately determines particle size. First, the measured quantity differs for each method (Scattered light intensity, 2D image / projection, electric mobility, etc.). Second, the calculated diameters of the MN may differ (Feret Diameter, Area Projection, Mobility Diameter, Aerodynamic Diameter, Hydrodynamic Diameter). Third, a measuring method provides a size distribution which is measured either mass-based, surface-based or number-based. A conversion between the results requires additional parameters and thus possibly increases the measurement error.
In addition to the technical differences, the individual parameters are strongly influenced by the structure and material of the nanoparticles. For example, a surface functionalization can lead to very different results in the size distribution. The suitability of measurement methods differs with the material of the MN. As a result, two very different results can be measured for the particle size distribution using two different methods, which are nevertheless both correct. Several large projects in recent years therefore concluded that nanomaterials should be characterized by at least two complementary method. Imaging techniques are regarded as one of these methods for the characterization, the complementary methods are supposed to be statistical methods.
The different results for the size distribution of nanomaterials become problematic for the registration of new MN. A comparable and reproducible size distribution is a prerequisite for a standardized registration. In the future, the particle size distribution in the EU will also decide on the classification of a substance as a nanomaterial or as a non-nanomaterial. Especially in borderline cases, a standardized and comparable measurement methodology is therefore essential.
Nach 1850 wurde zur weiteren Herabsetzung der Einbrenntemperatur von Glasmalfarben Borax (Na2B4O7 · 10 H2O) zugesetzt. Das Verhältnis war nun 1 Teil SiO2, 3 Teile PbO und 0,5 Teile Borax. Der analytische Nachweis von Bor in eingebrannten Malschichten war bisher jedoch nicht möglich.
In Laborversuchen wurden Glasmalfarben mit unterschiedlichem Gehalt an Borax auf Modellgläser aufgetragen, eingebrannt und anschließend unter simulierten Umweltbedingungen zeitraffend im Klimaschrank bewittert. Mit Hilfe von elektronenmikroskopischen Untersuchungen können Malschichten charakterisiert werden und somit Hinweise auf mögliche Schadensursachen liefern. Der Nachweis von Bor erfolgte mit Hilfe von LIBS-Messungen (Laser Induced Breakdown Spectroscopy) an im Labor hergestellten Glasmalfarben mit unterschiedlichem Boraxgehalt.