Liquid chromatography–high-resolution mass spectrometry workflow for advanced detection of target and suspect PMT substances in municipal and food-industry sludge

The transition toward circular food systems requires the safe reuse of residual streams such as municipal sewage sludge and food-industry sludge (excess aerobic biomass from food-processing wastewater treatment). However, the occurrence of persistent, mobile, and toxic substances (PMTs) poses potential risks to food safety and the environment. Detecting these contaminants is analytically challenging due to their wide polarity range, diverse physicochemical properties, and the limited availability of reference standards. In this study, two chromatographic columns, C18 and pentafluorophenyl (PFP), were first evaluated for their separation performance, followed by a comparison of two sample preparation approaches: solid-phase extraction (SPE) and adapted QuEChERS-based salting-out extraction procedure. The PFP-QuEChERS combination, as the best-performing option, was selected for subsequent analyses. The method was tested against 114 reference standards to delineate its chemical space, of which 74 were reliably covered. Building on this foundation, the workflow was extended to the suspect screening of a curated list of 1910 PMTs from the NORMAN database, prioritized during data acquisition and processing. Application of the workflow to 23 sludge samples demonstrated the ability to determine PMTs when reference standards were available, while also detecting additional suspect compounds beyond the target list. By combining the best-performing chromatographic separation and sample preparation with broad high-resolution mass spectrometry (HRMS) suspect screening, this study provides analytically robust insights for the detection and prioritization of PMTs in sludge, supporting the safe implementation of circular resource use in food production systems.