Research topics
1. Environmental geochemical analysis of natural organic compounds by ion chromatography (IC) and IC - mass spectrometry (IC-MS)
Natural, low molecular mass organic substances (LMMOS) with high polarity, e. g. carboxylic acids, amino acids, and carbohydrates, are widespread distributed in the environment, e. g. soils, sediments and aerosols. Furthermore, they are constituents of wastewaters, solid wastes, and of the related technical treatment residues, e. g. sewage sludges and dump leachates. Many organisms, e. g. plants, soil bacteria, and fungi, exudate LMMOS into their habitats. These exudates are very important for chemical and biological processes in the root-containing zones of soils (the rhizosphere).
These LMMOS are well suited for ion chromatographic analysis. We improve established IC methods for LMMOS detection due to their chemical structure, their physical-chemical distribution properties and to their pH-dependent charge and we develop new methods with respect to current application needs. Most of the new methods make use of the IC-MS hyphenation.
- Indorf, C., Bode, S., Boeckx, P., Dyckmans, J., Meyer, A., Fischer, K., Joergensen, R. G. (2013): Comparison of HPLC methods for the determination of amino sugars in soil hydrolysates. Anal. Lett. 46(14), 2145-2164.
- Fischer, K., Höffler, S., Meyer, A. (2011): ESI single quadrupole mass spectrometric investigation of polyhydroxy acids. Anal. Lett. 44(7), 1173-1186.
- Fischer, H., Eckhardt, K.-U., Meyer, A., Neumann, G., Leinweber, P., Fischer, K., Kuzyakov, Y. (2010): Rhizodeposition of maize: Short-term carbon budget and composition. J. Plant Nutr. Soil Sci. 173, 67-79.
2. Development of HPLC and HPLC-MS methods for the detection of organic pollutants and of their transformation products
Aromatic diamines like p-phenylenediamine (PPD) and p-toluenediamine (PTD) are ingredients of many hair and body (tattoo) colorants.These compounds and some of their reaction products are toxic and have the potential to induce allergic skin deseases (contact dermatitis). Aryldiamines are highly susceptible to oxidative transformations and they are subject to autooxidation processes. Furthermore, they are photochemically degradable. They are metabolized by several enzymes, e. g. N-acetyl transferase, in the human skin and in other organs. We generate the prerequisites for the in-depth examination of aryldiamine transformation processes and products by developing adequate HPLC and HPCL-MS methods.
A further topic of our analytical research is the determination of organic phosphoric acid esters in wastewaters. Amongst other applications, these compounds are utilized as flame retardants and plasticizers. For this purpose we choose a combination of solid phase extraction (SPE) and MS.
- Meyer, A., Höffler, S., Fischer, K. (2016): Determination of trialkyl phosphates in wastewater by solid phase extraction–flow injection–atmospheric pressure chemical ionization–mass spectrometry. Anal. Lett. 49(6), 867-882. DOI: 10.1080/00032719.2015.1081918.
- Fischer, K., Höffler, S., Wacht, M., Meyer, A. (2013): HPLC separation of aryldiamine transformation products using a polar-modified RP-C18 column. Anal. Lett. 46(17), 2673-2689
- Meyer, A., Blömeke, B., Fischer, K. (2009): Determination of p-phenylenediamine and its metabolites MAPPD and DAPPD in biological samples using HPLC-DAD and amperometric detection. J. Chromatogr. B 877, 1627-1633.
3. Enzyme activities and their importance for the biological wastewater clarification
Biological treatment techniques, especially the activated sludge process, are of high importance for the removal of both organic components and phosphorus and nitrogen compounds from wastewaters. Enzymes are the most important tool for the water purifying microorganisms. Thus, a close relation between the diversity/activity of the activated sludge enzymes and the efficiency of the biological wastewater treatment is supposed to exist. With the aim to prove this hypothesis we analyse and compare the enzyme profiles ("enzymatic fingerprints") of various wastewater treatment plants, focussing on extracellular hydrolases. Enzyme activities and kinetics are determined by photometric and fluorimetric assays.
- Kreutz, A., Böckenhüser, I., Wacht, M., Fischer, K. (2016): A 1-year study of the activities of seven hydrolases in a communal wastewater treatment plant: trends and correlations. Appl. Microbiol. Biotechnol. 100(15), 6903-6915, DOI: 10.1007/s00253-016-7540-6.
4. Determination of factors ruling the biological pollutant degradation in wastewater treatment plants
Since a few years, polar organic compounds, i .e. various pharmaceuticals, have attracted high interest at the examination of the clarification efficiency of wastewater treatment plants. A multitude of studies revealed highly different degradation degrees for identical micropollutants in different sewage treatment plants. For this, the reasons are not sufficiently known. In this context we conducted several investigations to identify potential correlations between activated sludge properties, operation parameters of sewage treatment plants, and removal rates for various pharmaceuticals, i .e. carbamazepine, diclofenac, sulfamethoxoazole, and paracetamol. It was found that the proportion of the active heterotrophic biomass on the activated sludge and the sludge age (solid retention time) are of high importance for the degradation of the tested pharmaceuticals.
- Fischer, K. and Majewsky, M. (2014): Cometabolic degradation of organic wastewater micropollutants by activated sludge and sludge-inherent microorganisms. Appl. Microbiol. & Biotechnol. 98(15), 6583-6597.
- Majewsky, M., Gallé, T., Yargeau, V., Fischer, K. (2011): Active heterotrophic biomass and sludge retention time (SRT) as determining factors for biodegradation kinetics of pharmaceuticals in activated sludge. Biores. Technol. 102, 7415-7421.
