Trace-level determination of sweeteners in sewage sludge using selective pressurized liquid extraction and liquid chromatography-tandem mass spectrometry

The occurrence of sweeteners in the environment has become a matter of concern due to the possibility of adverse effects on human health and wildlife species. One of the routes by which sweeteners enter the environment is through sewage sludge. Therefore, a method was developed with a selective-pressurized liquid extraction (S-PLE) followed by liquid chromatography-tandem mass spectrometry for the simultaneous determination of eight sweeteners in sewage sludge. The chromatographic separation was achieved in less than ten minutes using an amide polar-embedded reversed-phase column. Due to the high matrix effect present in the sample, an extensive study was conducted in order to overcome this issue, with C18 in-cell and solid-phase extraction (Oasis HLB) as a clean-up method. S-PLE/SPE recoveries at two levels of concentration (50 μg/kg and 1000 μg/kg in dry weight (d.w.), n = 5) were higher than 61%. Repeatability and reproducibility at the same concentrations (%RSD, n = 5) were lower than 11% and 16%, respectively. The limits of detection were 10 μg/kg (d.w) for all compounds, except for cyclamate (5 μg/kg (d.w.)). The method was successfully applied to sewage sludge samples from three sewage treatment plants located in Catalonia (Spain). Of the eight compounds, five were determined in all of the samples analysed, with acesulfame and saccharine being recorded at the highest concentrations of up to 481 μg/kg and 591 μg/kg (d.w.), respectively.