The EU Drinking Water Directive (EU 2020/2184) includes maximum limits for total PFAS of 0.5 µg/L. For the sum of 20 PFAS of most concern the maximum limit is 0.1 µg/L, which requires a limit of detection of (LOD) of 30 ng/L for the sum and 1.5 ng/L for the individual compounds. Even when using a modern triple quadrupol HPLC-MS system, a concentration step and is required.

A GERSTEL MultiPurpose Sampler (MPS) and GERSTEL SPExos Online-SPE coupled directly to an LC-MS/MS system can determine PFAS at the required levels by direct injection of water samples. The system is fully automated. Solid phase extraction (SPE) is used as specified in the DIN 38407-42 method. The DIN method list of analytes can easily be expanded to include those in the EU Drinking Water Directive. Key benefits are simplified sample handling, very low solvent consumption, and good reproducibility.

Due to the anionic properties of the analytes to be determined, weak anion exchange (WAX) resins are used. Following analyte concentration, the SPE cartridges are rinsed with solvent and eluted with a solution of ammonia in methanol resulting in analyte focusing on the column head for improved LC separation and MS/MS detection. The SPE cartridge can be replaced after each analysis to eliminate carryover.

Repeated rinse cycles with the rinse solutions added through the sample vial result in the transfer of fine sediment particles to the SPE cartridge where adsorbed PFAS compounds are desorbed and included in the analysis. Even solid sample extracts can be cleaned using the online SPE system after diluting an aliquot of the extract with water inside the syringe. After injection, the syringe is rinsed with solvents and solutions, which are injected to the system after each rinse cycle, eliminating loss through adsorption. The workflow meets the requirements of the DIN 38414-14 method for Determination of selected polyfluorinated compounds (PFC) in sludge, compost and soil.

 

PFAS Online Seminar