Determination of artificial sweeteners in sewage sludge samples using pressurised liquid extraction and liquid chromatography–tandem mass spectrometry

An analytical method for the determination of six artificial sweeteners in sewage sludge has been developed. The procedure is based on pressurised liquid extraction (PLE) with water followed by solid-phase extraction (SPE) and subsequent liquid chromatography–tandem mass spectrometry analysis. After optimisation of the different PLE parameters, extraction with aqueous 500 mM formate buffer (pH 3.5) at 80 °C during a single static cycle of 21 min proved to be best conditions. After a subsequent SPE, quantification limits, referred to dry weight (dw) of sewage sludge, ranged from 0.3 ng/g for acesulfame (ACE) to 16 ng/g for saccharin (SAC) and neohespiridine dihydrochalcone. The trueness, expressed as recovery, ranged between 72% and 105% and the precision, expressed as relative standard deviation, was lower than 16%. Moreover, the method proved its linearity up to the 2 μg/g range. Finally, the described method was applied to the determination of the artificial sweeteners in primary and secondary sewage sludge from urban wastewater treatment plants. Four of the six studied artificial sweeteners (ACE, cyclamate, SAC and sucralose) were found in the samples at concentrations ranging from 17 to 628 ng/g dw.