Michael Spiteller

Primary photoproducts and half-lives

The photolytically induced decomposition of fluoroquinolone carboxylic acids (enrofloxacin, danofloxacin, ciprofloxacin and norfloxacin) at concentrations of 10 mg/l in pure water and an irradiation intensity of 200 W/m2 (xenon lamp) led to half-lives from 20.6 min (danofloxacin) to 105.9 min (norfloxacin). The environmental half-life of enrofloxacin was calculated by the GCSOLAR program and resulted in 1.8 to 55.4 hours, depending on the season and degree of latitude. During the irradiation procedure, products were built up which primarily demonstrated alterations involving the piperazine ring as compared with the parent compounds. The amount of14CO2 evolved by the photomineralization of14C-labeled enrofloxacin reached 26.4 % of the applied radioactivity. The main photoproducts were isolated by HPLC and their structural elucidation was carried out by different spectroscopic methods (MS, GC/MS and1H-NMR).

Photolytic degradation of fluoroquinolone carboxylic acids in aqueous solution

Subsequent to irradiation with a xenon lamp simulating sunlight, fluoroquinolone carboxylic acids in aqueous solution form polar pyridone dicarboxylic and tricarboxylic acids. After liquid/liquid partition with chloroform/water these substances can be isolated by ion exchange chromatography of the aqueous phase. They can be regarded as intermediate compounds on the route to a complete photomineralization. The structural elucidation is performed by such mass spectroscopic methods as MS, GC/MS and HPLC/MS, whereby HPLC/MS shows the highest reliability. Additionally1H- and13C-NMR measurements confirm the structure of the main polar degradation product.Subsequent to irradiation with a xenon lamp simulating sunlight, fluoroquinolone carboxylic acids in aqueous solution form polar pyridone dicarboxylic and tricarboxylic acids. After liquid/liquid partition with chloroform/water these substances can be isolated by ion exchange chromatography of the aqueous phase. They can be regarded as intermediate compounds on the route to a complete photomineralization. The structural elucidation is performed by such mass spectroscopic methods as MS, GC/MS and HPLC/MS, whereby HPLC/MS shows the highest reliability. Additionally(1)H- and(13)C-NMR measurements confirm the structure of the main polar degradation product.

Polar photodegradation products of quinolones determined by HPLC/MS/MS

The photochemical degradation of quinolones in aqueous solution proceeds in two main steps. The first step is the degradation of the piperazine substitution forming 7-amino compounds which are more stable against photolysis than the corresponding parent compound. Further photochemical degradation down to CO2 formed intermediate polar substances. By liquid/liquid partition with chloroform/water, ion exchange chromatography and semipreparative HPLC the polar compounds could be isolated. The structures of the photolytically formed pyridone tri- and dicarboxylic acids were elucidated on the basis of HPLC/MS/MS measurement. Additionally the half-life of the main polar compound, 1-cyclopropyl-pyridone-2,3,5-tricarboxylic acid was analysed by HPLC.

Environmental fate of amitrole: influence of dissolved organic matter

In this study the environmental fate of amitrole in terrestrial and aquatic model ecosystems was investigated. Under aerobic conditions mineralization of amitrole is the main degradation pathway. The experiments revealed that the leaching behaviour is low in the presence or the absence of dissolved organic matter (DOM) despite the high water solubility due to a strong binding of amitrole to soil constituents. Under anaerobic conditions the addition of DOM increases the transport of amitrole in soil columns. The tests with water/sediment model ecosystems showed that the mineralization of amitrole is lower in comparison to aerobic soil experiments. Up to 80.6% of the applied 14C-labelled amitrole transfer into the sediment and about 1/3 of this amount formed bound residues, which are not extractable.

Interaction of aquatic substances with anilazine and its derivatives: The nature of the bound residues

Abstract This study is focused on the binding behaviour of the triazine fungicide anilazine and its main metabolites such as dihydroxyanilazine in aquatic ecosystems. For this purpose anilazine and its derivatives were incubated with ultrafiltrated dissolved organic matter (DOM) and isolated fulvic and humic acids, respectively and the adsorption isotherms according to Freundlich were determined. More than 90% bound residues were formed and up to 60% of anilazine metabolites were released with a recently developed silylation method. The study of the reactivity of metabolites and model compounds as well as our NMR investigations showing ether bondings led to a suggested binding scheme of anilazine to humic substances. To have more realistic conditions the behaviour of anilazine and dihydroxyanilazine in aquatic model ecosystems with water and sediment from a river was also part of this study. Furthermore the release of active ingredients or derivatives from sediment by different extraction methods was examined.