Dirk Löffler

Analytical method for the determination of the aminoglycoside gentamicin in hospital wastewater via liquid chromatography–electrospray-tandem mass spectrometry

A method for the determination of gentamicin residues in hospital wastewater has been developed using kanamycin as a surrogate standard. The method consists of solid-phase extraction (SPE) and detection by ion-pair chromatography with electrospray tandem mass spectrometry (LC-ES-tandem MS). The SPE was performed on a weak cation exchanger. Filtration should be avoided in the sample preparation, otherwise a significant loss of gentamicin occurs. Chromatographic separation on a C18-column was achieved using a ternary eluent containing methanol, water and 1(-1) heptafluorobutyric acid solution. Mean relative recoveries of the analytes in hospital wastewater varied between 107 and 111%. The limit of quantification (LOQ) was 0.20 microg l(-1) in hospital wastewater. Gentamicin was found in native hospital wastewater in a concentration range between 0.4 and 7.6 microg l(-1).

Environmental risk assessment of ivermectin: A case study.

The veterinary parasiticide ivermectin was selected as a case study compound within the project ERAPharm (Environmental Risk Assessment of Pharmaceuticals). Based on experimental data generated within ERAPharm and additional literature data, an environmental risk assessment (ERA) was performed mainly according to international and European guidelines. For the environmental compartments surface water, sediment, and dung, a risk was indicated at all levels of the tiered assessment approach. Only for soil was no risk indicated after the lower tier assessment. However, the use of effects data from additional 2-species and multispecies studies resulted in a risk indication for collembolans. Although previously performed ERAs for ivermectin revealed no concern for the aquatic compartment, and transient effects on dung-insect populations were not considered as relevant, the present ERA clearly demonstrates unacceptable risks for all investigated environmental compartments and hence suggests the necessity of reassessing ivermectin-containing products. Based on this case study, several gaps in the existing guidelines for ERA of pharmaceuticals were shown and improvements have been suggested. The action limit at the start of the ERA, for example, is not protective for substances such as ivermectin when used on intensively reared animals. Furthermore, initial predicted environmental concentrations (PECs) of ivermectin in soil were estimated to be lower than refined PECs, indicating that the currently used tiered approach for exposure assessment is not appropriate for substances with potential for accumulation in soil. In addition, guidance is lacking for the assessment of effects at higher tiers of the ERA, e.g., for field studies or a tiered effects assessment in the dung compartment.

Environmental fate of the anthelmintic ivermectin in an aerobic sediment/water system.

This study investigated the long-term fate of (3)H-ivermectin and its metabolites in aerobic sediment/water systems. Total radioactivity in sediment and water was measured by Liquid Scintillation Counting and Radio-HPLC was used for determination of transformation products. The test system, containing a cooling and a water trap, showed excellent applicability for studying environmental fate of (3)H-labelled compounds. A complete mass balance was obtained over the whole duration with total recoveries ranging from 91.3% to 98.8%. In water, a DT(50)-value of ivermectin of <6h and a DT(90)-value of 16.8 d were obtained. The DT(50)-value of ivermectin in the entire system was 127 d. Maximum distribution coefficients were calculated to K(d)=160 L kg(-1) and K(oc)=3550 L kg(-1). The fraction of bound residues increased to a maximum percentage of 30.4% after 188 d. In total about 31.3% of the initially applied ivermectin were transformed after 188 d. Two transformation products ivermectin monosaccharide and ivermectin aglycone, could be identified in samples from day 100 and 188, respectively. However, additional peaks which were observed in the radio-chromatograms indicate that several other transformation product are formed.