Uncovering monitoring gaps and novel persistent and mobile substances (PMs) in groundwater using lyophilisation enrichment and SFC-HRMS smart screening.

Persistent and mobile chemicals (PMs) threaten groundwater quality and drinking water safety, yet many remain undetected because analytical methods insufficiently address highly polar and ionic substances, while regulatory frameworks lack monitoring requirements for these compound classes. Here, we developed a supercritical fluid chromatography-high-resolution mass spectrometry-based smart-screen approach that integrates three key prioritisation strategies: (i) sampling site prioritisation, (ii) suspect-level prioritisation through tiered suspect lists, and (iii) candidate prioritisation using stepwise scoring. Additionally, the method achieved the sensitive identification and reliable quantification of PMs in groundwater, with a median limit of quantification of 6.8 ng/L, stable recoveries (75%), and low matrix effects (-12%) across diverse groundwater types. Prioritisation reduced 599 groundwater wells to 10 representative sites, yielding an 8.6-fold reduction in analytical workload while maintaining chemical diversity. The tiered suspect lists and stepwise scoring strategies improved confirmation efficiency and facilitated the detection of substances of high environmental relevance. Collectively, 34 PMs were detected across six substance groups including polar per- and polyfluoroalkyl substances, polyfluorinated inorganic species, transformation products, and amide or ether solvents at concentrations of 0.1-22,300 ng/L. Among these, 16 substances were newly detected in ambient groundwater and four were reported for the first time in any environmental compartment. Several substances (e.g. 2-phenylpropane-2-sulphonic acid) are not classified as persistent under EU regulation on registration, evaluation, authorisation and restriction of chemicals (REACH) yet occur ubiquitously in groundwater, suggesting an underestimation of PMs under aquifer conditions. These findings advance monitoring of PMs, supporting their regulation for groundwater and drinking water protection.