Analysenmethoden für Antibiotika und perfluorierte Tenside in wässrigen Matrizes mittels LC-MS/MS nach SPE-Anreicherung - Methodenentwicklung, Methodenvalidierung, Datenerhebung

Die vorliegende Arbeit beschäftigt sich mit der Analytik zweier Stoffgruppen anthropogenen Ursprungs in der aquatischen Umwelt, einerseits mit einer Auswahl antibiotisch wirkender Substanzen als Rückstände aus Arzneimittelanwendungen (Umweltproblem: bakterielle Resistenzen), andererseits mit der Stoffgruppe der perfluorierten Tenside (PFT) als Rückstände industrieller Verarbeitungs- und Veredelungsprozesse (Umweltproblem: Persistenz und Bioakkumulation). Der erste Schwerpunkt der Untersuchungen lag dabei auf der Entwicklung und Optimierung der Extraktions- und Anreicherungsmethoden in erster Linie aus wässrigen Matrizes sowie der Identifizierung und Quantifizierung dieser Substanzen mittels Kopplung von hochleistungsflüssig-chromatographischen Trenn- und massenspektrometrischen Detektionsverfahren. Das Untersuchungsspektrum ergab sich für die Antibiotika aus Datenerhebungen zum Antibiotikaeinsatz im Universitätsklinikum Bonn und aus der dokumentierten Verordnungspraxis innerhalb der gesetzlichen Krankenversicherung in Deutschland, für die perfluorierten Tenside (perfluorierte Alkylcarbonsäuren und perfluorierte Sulfonsäuren) anhand ihrer Leitsubstanzen PFOA (Perfluoroctansäure) und PFOS (Perfluoroctansulfonsäure) und deren kürzer- bzw. längerkettigen Homologen. Mit den jeweiligen Multikomponenten-Methoden (29 Antibiotika und 12 Perfluortenside) konnten Nachweis- und Bestimmungsgrenzen im ein- bis niedrigen zweistelligen ng/L-Bereich erreicht werden. Die Methoden wurden im Rahmen mehrerer, zum Teil bundesweiter Laborvergleichsuntersuchungen erfolgreich validiert. Den zweiten Schwerpunkt der Arbeit bildete die Anwendung der neuen Methoden bei der Untersuchung von Realproben: Im Bereich der Antibiotika wurde das Abwasser des Universitätsklinikums Bonn vom Ort seiner Entstehung über die Kläranlage bis in den Rhein untersucht. Zusätzliche Datenerhebungen erfolgten für weitere Kläranlagen und Oberflächengewässer in Nordrhein-Westfalen, ebenso wurden ein Talsperrenwasser (zur Trinkwassergewinnung) und einige oberflächenwasser-beeinflusste Roh- und Trinkwässer untersucht. Im gesammelten Abwasser des Universitätsklinikums konnten große Mengen der dort verordneten Antibiotika bestimmt werden. Die Antibiotikagehalte reduzierten sich bis in den Rhein durch Abbau, Adsorption an Feststoffe und Verdünnung um mehrere Zehnerpotenzen. Analoge Daten konnten für andere Kläranlagen und Oberflächenwässer ermittelt werden. Im Trinkwasser konnten keine Antibiotika nachgewiesen werden, nur die beiden Antibiotika Erythromycin und Sulfamethoxazol gelangten bis ins Rohwasser, konnten aber durch anschließende Trinkwasseraufbereitungstechniken entfernt werden. Die Substanz Sulfamethoxazol kann hier als Tracer dienen, um rechtzeitig eine Trinkwasserbelastung mit Antibiotikarückständen zu erkennen. Im Bereich der perfluorierten Tenside konnte im Rhein eine durchgehend niedrige Belastung des Wassers ermittelt werden, die Perfluorbutansulfonsäure (PFBS) bildete dabei die Hauptkomponente. Die Ruhr zeigte flussaufwärts stark ansteigende Belastungen mit perfluorierten Tensiden, wobei PFOA mit ca. 80% die Hauptkomponente bildete. Annähernd gleich hohe PFOA-Gehalte wurden auch im Trinkwasser gefunden, das durch künstliche Grundwasseranreicherung mit Ruhr-Wasser gewonnen wird. Durch diese Befunde wurden die Behörden auf eine illegale Industrieabfallentsorgung auf landwirtschaftlichen Flächen am Oberlauf der Möhne (Zufluss der Ruhr) aufmerksam, die zur Verunreinigung des Oberflächen- und des Trinkwassers führte, in deren Folge Konzentrationsobergrenzen für PFT beschlossen wurden, eine Nachrüstung der betroffenen Wasserwerke mit zusätzlichen Aufbereitungsschritten begonnen wurde und eine bundesweit Untersuchungstätigkeit auf perfluorierte Tenside ausgelöst wurde. Die Entdeckung der PFT-Belastung im Trinkwasser an der Ruhr führte zu einer weiteren Optimierung der Anreicherungsmethodik und einem beginnenden Normungsverfahren auf Basis dieser Methode. Durch die vorliegende Arbeit konnten zwei leistungsfähige Multikomponenten-Methoden zur Bestimmung von Antibiotika und perfluorierten Tensiden in wässrigen Matrizes entwickelt werden, mit deren Hilfe eine Belastung der Bevölkerung durch PFOA-kontaminiertes Trinkwasser erkannt und zur Behebung dieses Problems beigetragen werden konnte

Occurrence and temporal variations of TMDD in the river Rhine, Germany

Background, aim, and scope: The chemical substance 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) is a non-ionic surfactant used as an industrial defoaming agent and in various other applications. Its commercial name is Surynol 104® and the related ethoxylates are also available as Surfynol® 420, 440, 465 and 485 which are characterized by different grades of ethoxylation of TMDD at both hydroxyl functional groups. TMDD and its ethoxylates offer several advantages in waterborne industrial applications in coatings, inks, adhesives as well as in paper industries. TMDD and its ethoxylates can be expected to reach the aquatic environment due its widespread use and its physico-chemical properties. TMDD has previously been detected in several rivers of Germany with concentrations up to 2.5 µg/L. In the United States, TMDD was also detected in drinking water. However, detailed studies about its presence and distribution in the aquatic environment have not been carried out so far. The aim of the present study was the analysis of the spatial and temporal concentration variations of TMDD in the river Rhine at the Rheingütestation Worms (443.3 km). Moreover, the transported load in the Rhine was investigated during two entire days and 7 weeks between November 2007 and January 2008. Materials and methods: The sampling was carried out at three different sampling points across the river. Sampling point MWL1 is located in the left part of the river, MWL2 in the middle part, and MWL4 in the right part. One more sampling site (MWL3) was run by the monitoring station until the end of 2006, but was put out of service due to financial constrains. The water at the left side of the river Rhine (MWL1) is influenced by sewage from a big chemical plant in Ludwigshafen and by the sewage water from this city. The water at the right side of the river Rhine (MWL4) is largely composed of the water inflow from river Neckar, discharging into Rhine 14.9 km upstream from the sampling point and of communal and industrial wastewater from the city Mannheim. The water from the middle of the river (MWL2) is largely composed of water from the upper Rhine. Water samples were collected in 1-L bottles by an automatic sampler. The water samples were concentrated by use of solid-phase extraction (SPE) using Bond Elut PPL cartridges and quantified by use of gas chromatography-mass spectrometry (GC-MS). The quantification was carried out with the internal standard method. Based on these results, concentration variations were determined for the day profiles and week profiles. The total number of analyzed samples was 219. Results: The results of this study provide information on the temporal concentration variability of TMDD in river Rhine in a cross section at one particular sampling point (443.3 km). TMDD was detected in all analyzed water samples at high concentrations. The mean concentrations during the 2 days were 314 ng/L in MWL1, 246 ng/L in MWL2, and 286 ng/L in MWL4. The variation of concentrations was low in the day profiles. In the week profiles, a trend of increasing TMDD concentrations was detected particularly in January 2008, when TMDD concentrations reached values up to 1,330 ng/L in MWL1. The mean TMDD concentrations during the week profiles were 540 ng/L in MWL1, 484 ng/L in MWL2, and 576 ng/L in MWL4. The loads of TMDD were also determined and revealed to be comparable in all three sections of the river. The chemical plant located at the left side of the Rhine is not contributing additional TMDD to the river. The load of TMDD has been determined to be 62.8 kg/d on average during the entire period. By extrapolation of data obtained from seven week profiles the annual load was calculated to 23 t/a. Discussion: The permanent high TMDD concentrations during the investigation period indicate an almost constant discharge of TMDD into the river. This observation argues for effluents of municipal wastewater treatment plants as the most likely source of TMDD in the river. Another possible source might be the degradation of ethoxylates of TMDD (Surfynol® series 400), in the WWTPs under formation of TMDD followed by discharge into the river. TMDD has to be considered as a high-production-volume (HPV) chemical based on the high concentrations found in this study. In the United States, TMDD is already in the list of HPV chemicals from the Environmental Protection Agency (EPA). However, the amount of TMDD production in Europe is unknown so far and also the biodegradation rates of TMDD in WWTPs have not been investigated. Conclusions: TMDD was found in high concentrations during the entire sampling period in the Rhine river at the three sampling points. During the sampling period, TMDD concentrations remained constant in each part of the river. These results show that TMDD is uniformly distributed in the water collected at three sampling points located across the river. ‘Waves’ of exceptionally high concentrations of TMDD could not be detected during the sampling period. These results indicate that the effluents of WWTPs have to be considered as the most important sources of TMDD in river Rhine. Recommendations and perspectives: Based also on the occurrence of TMDD in different surface waters of Germany with concentrations up to 2,500 ng/L and its presence in drinking water in the USA, more detailed investigations regarding its sources and distribution in the aquatic environment are required. Moreover, the knowledge with respect to its ecotoxicity and its biodegradation pathway is scarce and has to be gained in more detail. Further research is necessary to investigate the rate of elimination of TMDD in municipal and industrial wastewater treatment plants in order to clarify the degradation rate of TMDD and to determine to which extent effluents of WWTPs contribute to the input of TMDD into surface waters. Supplementary studies are needed to clarify whether the ethoxylates of TMDD (known as Surfynol 400® series) are hydrolyzed in the aquatic environment resulting in formation of TMDD similar to the well known cleavage of nonylphenol ethoxylates into nonylphenols. The stability of TMDD under anaerobic conditions in groundwater is also unknown and should be studied

Construction of an Expression System for Site-Directed Mutagenesis of the Lantibiotic Mersacidin

The lantibiotic (i.e., lanthionine-containing antibiotic) mersacidin is an antimicrobial peptide of 20 amino acids which is produced by Bacillus sp. strain HIL Y-85,54728. Mersacidin inhibits bacterial cell wall biosynthesis by binding to the precursor molecule lipid II. The structural gene of mersacidin (mrsA) and the genes for the enzymes of the biosynthesis pathway, dedicated transporters, producer self-protection proteins, and regulatory factors are organized in a biosynthetic gene cluster. For site-directed mutagenesis of lantibiotics, the engineered genes must be expressed in an expression system that contains all of the factors necessary for biosynthesis, export, and producer self-protection. In order to express engineered mersacidin peptides, a system in which the engineered gene replaces the wild-type gene on the chromosome was constructed. To test the expression system, three mutants were constructed. In S16I mersacidin, the didehydroalanine residue (Dha) at position 16 was replaced with the Ile residue found in the closely related lantibiotic actagardine. S16I mersacidin was produced only in small amounts. The purified peptide had markedly reduced antimicrobial activity, indicating an essential role for Dha16 in biosynthesis and biological activity of mersacidin. Similarly, Glu17, which is thought to be an essential structure in mersacidin, was exchanged for alanine. E17A mersacidin was obtained in good yields but also showed markedly reduced activity, thus confirming the importance of the carboxylic acid function at position 17 in the biological activity of mersacidin. Finally, the exchange of an aromatic for an aliphatic hydrophobic residue at position 3 resulted in the mutant peptide F3L mersacidin; this peptide showed only moderately reduced activity