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Biomedical subjects

K Bester

Publications and source records attributed to K Bester.

12 recordsLinked to original sources
PubMed2006

Elimination of macrolides, tiamulin, and salinomycin during manure storage.

The extensive use of veterinary drugs in livestock farming increases the risk that these compounds end up in the environment when manure is used as fertilizer. This study focuses on the fate of antibiotics in liquid manure tanks before the liquid manure is spread on fields. A 180-day degradation experiment of four commonly used antibiotics erythromycin, roxithromycin, salinomycin, and tiamulin in liquid manure was performed. The resulting half-lives during manure storage were calculated as follows: 41 days for erythromycin, 130 days for roxithromycin, and 6 days for salinomycin. A first-order degradation rate was calculated for these three antibiotics. The concentration of tiamulin remained unchanged during the entire experiment. No degradation of tiamulin was detected even after 180 days.

Animals↗
PubMed2004

Organophosphorus flame retardants and plasticisers in surface waters.

Organophosphates used as flame retardants, plasticisers and lubricants such as tris-(2-chloro-, 1-methyl-ethyl)-phosphate (TCPP), tris-(2-chloroethyl)-phosphate (TCEP) or tris-(2-chloro-, 1-chloromethyl-ethyl)-phosphate (TDCP), tri-n-butylphosphate (TnBP), tri-iso-butylphosphate (TiBP), triphenylphosphate (TPP) and tris-(butoxyethyl)-phosphate (TBEP) have been analysed in several rivers and sewage treatment plant (STP) effluents. The concentrations in the River Ruhr are 20-200 ng/l TCPP, 13-130 ng/l TCEP, about 50 ng/l TDCP, 10-200 ng/l TBEP and up to 40 ng/l TPP. The STP effluents exhibit concentrations up to 400 ng/l TCPP, 130 ng/l TCEP, about 120 ng/l TDCP and 500 ng/l TBEP, respectively. The main sources for the load of organophosphates are sewage treatment plants, but not all contribute equivalent to the amount of inhabitants they serve.

Environmental Monitoring↗
PubMed2004

Organophosphate flame retardants and plasticisers in wastewater treatment plants.

Previous studies have revealed that chlorinated and non-chlorinated organophosphorous flame retardants and plasticisers are important contaminants in German surface waters and it has been demonstrated that wastewater treatment plants contribute to the emission of these substances. In this study temporal development as well as elimination efficiency were determined in two wastewater treatment plants (STP) in the Ruhr/Rhine area at different stages of the wastewater treatment process. The samples were analysed for the non-chlorinated organophosphate esters tri-n-butylphosphate (TnBP), tri-iso-butylphosphate (TiBP), tris-(butoxyethyl)-phosphate (TBEP) and triphenylphosphate (TPP) and the chlorinated organophosphate esters tris-(2-chloro, 1-methylethyl)-phosphate (TCPP), tris-(2-chloro-, 1-chloromethylethyl)-phosphate (TDCP) and tris-(2-chloroethyl)-phosphate (TCEP). The study showed that there were significant differences in the elimination of chlorinated and non-chlorinated organophosphorous flame retardants. The elimination rates ranged from 57-86% for TiBP, TnBP and TBEP at both STP's. No elimination of the chlorinated flame retardants TCPP, TDCP and TCEP was observed in any of the sampled STPs. At both STPs the first treatment steps and the final filtration did not contribute to the elimination of the non-chlorinated organophosphorous flame retardants while the aeration step did. At both STPs the efficiency of the cleaning process concerning the flame retardants was comparable. Thus the type of construction of the STP was not relevant for the elimination of these substances. Additionally a strong day-to-day variation was observed, while in one STP a temporal trend for TCPP during the week was found.

Environmental Monitoring↗
PubMed2003

Triclosan in a sewage treatment process--balances and monitoring data.

In a German sewage treatment plant that processes 200000 m(3) wastewater per day, the concentrations of 2,4,4'-trichloro, 2'-hydroxy-phenylether (triclosan) in the in-flowing ( approximately 1000 ng x l(-1)) as well as in the out-flowing water ( approximately 50 ng x l(-1)) are compared to the concentrations measured in sludge (1200 ng x g(-1)). Considering the mass flow of water and sludge in the respective plant, balances including water and sludge are calculated. Thirty percent of the triclosan is sorbed with weak bonds to the sludge, while some amounts are sorbed as bound residues in the sludge. About 5% is dissolved in the out-flowing water. Thus most of the in-flowing material is not recovered as the parent compound but it is likely that it is transformed to other metabolites or unrecovered bound residues. These data are compared to the monitoring of sewage sludge of 20 different plants in this region, most of which are smaller, though. The concentrations found in these sludges vary from 1000-8000 ng x g(-1).

Adsorption↗
PubMed2002

Bioassay-directed chemical analysis of River Elbe surface water including large volume extractions and high performance fractionation.

A bioassay-directed fractionation and identification (toxicity identification evaluation procedure) was performed on extracts of 10 1 River Elbe water samples. The experimental method included a SDB-1 solid phase extraction followed by RP-HPLC fractionation and subfractionation. Chemical analysis by GC-MS as well as acute toxicity testing using a luminescent bacteria assay were conducted in the respective fractions. Many substances were identified, among which were pesticides and pharmaceuticals, but many compounds remained unknown.

Chromatography, High Pressure Liquid↗
PubMed2001

New method for rapid solid-phase extraction of large-volume water samples and its application to non-target screening of North Sea water for organic contaminants by gas chromatography-mass spectrometry.

A method has been developed that allows the solid-phase extraction of microorganic compounds from large volumes of water (10 l) for non-target analysis of filtered seawater. The filtration-extraction system is operated with glass fibre filter candles and the polymeric styrene-divinylbenzene sorbent SDB-1 at flow-rates as high as 500 ml/min. Recovery studies carried out for a couple of model substances covering a wide range of polarity and chemical classes revealed a good performance of the method. Especially for polar compounds (log Kow 3.3-0.7) quantitative recovery was achieved. Limits of detection were between 0.1 and 0.7 ng/l in the full scan mode of the MS. The suitability of the method for the analysis of marine water samples is demonstrated by the non-target screening of water from the German Bight for the presence of organic contaminants. In the course of this screening a large variety of substances was identified including pesticides, industrial chemicals and pharmaceuticals. For some of the identified compounds their occurrence in marine ecosystems has not been reported before, such as dichloropyridines, carbamazepine, propyphenazone and caffeine.

Gas Chromatography-Mass Spectrometry↗
PubMed2001

How to overcome matrix effects in the determination of pesticides in fruit by HPLC-ESI-MS-MS.

A high-performance liquid chromatographic method, with electrospray ionisation tandem mass spectrometry (HPLC-ESI-MS-MS) for detection, has been developed for the determination of thiabendazole, carbendazime, and phenylurea pesticides in fruit matrices. During the validation process the method was tested for matrix effects, blanks, and the stability of the system. Considerable unspecific matrix effects in the ESI (+) process were detected by comparing standard calibration, and matrix calibration, although blank values were very low and the specific calibration functions showed only small standard deviations. This effect was overcome by using a more complex clean-up, i.e. an additional size-exclusion step.

Calibration↗
PubMed2001

Preparation and certification of a reference material on PCBs in pig fat and its application in quality control in monitoring laboratories during the Belgian "PCB-crisis".

In this article, the production and validation of a new certified reference material "PCBs in animal fat" for the control of the maximum level of 200 ng/g setup by the European Communities for veterinary products from Belgium is described. Three materials are established: a blank, one material with about 100 ng/g and one with about 200 ng/g (sum of seven PCBs). Data on the production and certification are given. Additionally, this material was used as an unknown test material in the quality assurance program of the Belgium meat monitoring system (before the certification of the material). While the certification was performed with an uncertainty of less than 10%, the round robin exhibited larger deviations. However, these deviations were less than 20% for most of the 30 participating laboratories. Only two had significantly higher deviations.

Adipose Tissue↗
PubMed2001

Nonylphenols, nonylphenol-ethoxylates, linear alkylbenzenesulfonates (LAS) and bis (4-chlorophenyl)-sulfone in the German Bight of the North Sea.

Nonylphenols and nonylphenol-ethoxylates were detected in the water and sediment samples from the German Bight of the North Sea. Additionally bis (4-chlorophenyl)-sulfone and linear alkylbenzenesulfonates (LAS) were detected in marine waters. Proof of identification is given by comparison of spectral and chromatographic data from the compounds in sample extracts to those obtained from pure standards. In extracts obtained from water samples taken in 1990 and 1995 the concentrations of nonylphenols and bis-(4-chlorophenyl)-sulfone were compared for each year. The concentrations of nonylphenols in seawater varied from 0.7 to 4.4 ng/l while in the Elbe estuary about 33 ng/l were found. In water samples taken in 1998 nonylphenol-polyethoxylates could not be determined, whereas LAS concentrations of 30 ng/l were confirmed by HPLC-MS/MS. The concentrations of bis (4-chlorophenyl)-sulfone ranged from 0.18 to 2.2 ng/l. In sediment samples LAS concentrations of 39-109 ng/g dry weight were determined.

Alkanesulfonic Acids↗
PubMedDate not supplied

Chlorostyrenes in fish and sediment samples from the river Elbe.

Chlorinated styrenes were identified in fish (bream) and sediment samples from the river Elbe. Four hexachlorostyrenes, four heptachlorostyrenes (concentrations in fish 1-10 ng/g wet weight) and octachlorostyrene (10-45 ng/g wet weight) were analysed. The gas chromatographic retention times and the electron impact (EI) mass spectra of the respective hepta- and hexachloro congeners found in the environment as well as those of some synthesised compounds are presented and discussed. The comparison of the chromatograms from the samples in the upper part of the river with those from the estuary revealed a possible difference in the pattern of chlorostyrenes.

Animals↗