A total of 10 municipal drinking water samples were taken from households across London, UK, from the 23 rd until the 31 st of March 2022 (GPS coordinates in Table ). Cold water was collected in 30 mL Nalgene polypropylene bottles (Sigma-Aldrich) after having been rinsed three times; it was subsequently frozen at -20 o C and kept in the dark. The same procedure was used to collect and store ultrapure water to be used as process blanks. For method performance evaluation and comparison, a single tap water sample was collected in a 1 L Schott bottle from the laboratory supply (measured pH = 7.5) and employed for all preparations. For SPE, Isolute PE-AX in bulk and polypropylene single fritted SPE cartridges (10 mL reservoir, polyethylene frits) were purchased from Biotage (Uppsala, Sweden). 500 mg mass of this silica-based strong anion exchange in the acetate form was packed into polypropylene cartridges and conditioned with 4 mL of methanol followed by 4 mL of ultrapure water. Subsequently, 10 mL of sample was loaded. The cartridges were then washed with 8 mL of a ultrapure water:methanol solution 9:1, dried, and eluted with a 0.2 M ammonium bicarbonate solution in ultrapure water:methanol 1:9. The eluates were then evaporated to dryness at 38 C, and reconstituted with 100 L of ultrapure water:methanol 1:1 (injection solvent). All extracts were then transferred to 9 mm screw top clear glass Verex vials from Phenomenex (San Juan, USA) with 9 mm Solid Top Polyethylene caps from Restek (Bellefonte, USA) and 0.2 mL glass inserts from VWR for injection onto the LC-HRMS.