Biomedical subjects

Stefan Hahn

Publications and source records attributed to Stefan Hahn.

3 recordsLinked to original sources

PubMed2003

Comparative studies on algal toxicity testing using fluorometric microplate and Erlenmeyer flask growth-inhibition assays.

Two fluorometric microplate algae growth-inhibition assays with a liquid volume of 2 mL and 200 microL per well are presented, and comparative studies on the toxicity of chemicals are carried out with Erlenmeyer flask assays. The test procedures are in accordance with the standards ISO 8692 (DIN 38412 L9 and EN 28692), OECD 201 and DIN 38412 L33. By testing four toxicants several times laboratory internal repeatability is proven. Statistical evaluation demonstrates that the results obtained with both the 24-well and the 96-well microplates are nearly identical with the results of the Erlenmeyer flask assay. Therefore, the microplate growth-inhibition assays can be applied for the testing of a wide range of chemicals and environmental samples if some methodical aspects are taken into account. Apart from that, there is a strong need for harmonization if the dependency of the EC values on the toxicological endpoint is considered.

Eukaryota↗

PubMed2002

Biodegradability testing of synthetic ester lubricants--effects of additives and usage.

The optimised biodegradability test system "O2/CO2 Headspace Test with GC-TCD" is used for the assessment of synthetic ester lubricants. The effects of both additives and usage on biodegradability are examined and discussed. Ester based cutting fluids and hydraulic fluids with and without additives are used under defined conditions at machine tools and hydraulic and plain bearing test benches. The lubricants are characterised additionally with respect to kinematic viscosity, acidity and elemental composition. Furthermore, a formulated mineral oil is characterised before and after usage at an hydraulic test bench. The results clearly show that the mineral oil is far less biodegradable than the ester oils and that their biodegradability is not affected by usage. Biodegradability of the ester oils is mainly depending on the characteristics of the base fluids and not affected by the additives. Antioxidants are influencing stability respectively biodegradability indirectly, since they prevent oxopolymerisation effects. Other effects of usage on biodegradation are not detected. In this context, the antioxidants ensure ready biodegradability and have a positive effect on the environmental fate of synthetic ester lubricants.

Antioxidants↗

PubMed2002

Assessment of the influence of use on ecotoxicological characteristics of synthetic ester lubricants.

Synthetic ester lubricants need optimisation about their technical and their ecotoxicological characteristics. To determine the ecotoxicological potential the required examinations can be based on the procedure for a risk assessment of chemicals. At present risk classification of lubricant oils is carried out with new oil fluids that are normally prepared before application in aqueous bioassays. In order to improve the ecotoxicological characteristics of some lubricant oils, the quality of the preparation method has been optimised. The resulting preparation protocol leads to aqueous extracts of the oil fluids that can be tested using biological assays. The extent of the changes of the chemical composition caused by the use as well as the ecotoxicological effects caused by additives have to be taken into consideration. For this reason various used lubricants are tested in addition to new oil fluids. In this work various lubricant samples were examined with standardised bacterial growth assays with Vibrio fischeri and Pseudomonas putida, luminescence inhibition assay with V. fischeri, survival assay with Daphnia magna and algal growth inhibition assay with Scenedesmus subspicatus. The chemical characterisation of the aqueous extracts included the determination of pH, conductivity, heavy metals, the content of dissolved organic carbon, inorganic anions and the content of phosphorus. The results emphasize the thesis that environmentally acceptable lubricants can undergo a change of their ecotoxicological potential during the use. Some of the substances that are normally added to base fluids in order to enhance the applicability of the oils may possess a high toxicological potential.

Animals↗