Identification of genotoxic transformation products by effect-directed analysis with high-performance thin-layer chromatography and non-target screening

Summary The widespread use of the pharmaceutical metformin for diabetes therapy has led to finding its way into many surface waters up to the μg L−1 range and subsequently into different water treatment processes. In this study, metformin was treated with hypochlorite on the laboratory scale, and the resulting transformation products were investigated with the umu assay in a microtiter plate, where a genotoxic effect was detected. For the characterization of this genotoxic effect, the sample was separated using high-performance thin-layer chromatography (HPTLC), and 29 zones over the whole retardation area were extracted from the HPTLC plate with the thin-layer chromatography-mass spectrometry (TLC-MS) Interface. Then, the umu assay was performed again with each extracted zone, such that the genotoxic effect in the sample could be assigned to a certain zone. By the measurement of this effective zone with high-performance liquid chromatography with high-resolution mass spectrometry and by performing a non-target screening, the effective substance could be identified as a cyclic dehydro-1,2,4-triazole derivate with an intense yellow color. This substance formerly was found by Armbruster et al. (Water Research, 2015), which is a major transformation product of chlorine-treated metformin.