Occurrence of the antidiabetic drug metformin in sewage and surface waters in Germany

The antidiabetic drug metformin is among the pharmaceuticals with the highest production numbers world-wide. This paper presents first data on the occurrence of metformin in sewage and surface waters in Germany. Analysis of metformin is based on pre-concentration of the analyte onto a polymeric solid-phase material and subsequent determination by liquid chromatography and tandem mass spectrometry. Applying the method to sewage and surface waters, recoveries >90% and limits of detection of 10 ng L-1 could be achieved by pre-concentration of a sample volume of only 10 mL. Measurements in sewage and surface waters showed an almost ubiquitous presence of metformin in the aquatic environment. The measured concentration levels in sewage treatment plant influents correlate nicely to the prescription numbers for metformin in Germany. During sewage treatment a significant reduction of metformin concentrations was observed which seems to be mainly due to microbial degradation. Despite this significant elimination during sewage treatment, metformin was found in all river waters under investigation. Concentration levels depend on the sewage fraction of the receiving waters and for most rivers are in the range of several 100 ng L-1, i.e. in the same order of magnitude or even higher than for other relevant pharmaceutical residues.