A matrix effect-free method for reliable quantification of perfluoroalkyl carboxylic acids and perfluoroalkane sulfonic acids at low parts per trillion levels in dietary samples

• In recent exposure modeling studies diet has been identified as the dominant pathway of human exposure to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). However, the paucity of highly sensitive and accurate analytical data to support these studies means that their conclusions are open to question. Here a novel matrix effect-free method is described for ultra-trace analysis of perfluoroalkyl carboxylic acids (PFCAs, all homologues from perfluorohexanoic acid to perfluorododecanoic acid) and perfluoroalkane sulfonic acids (PFSAs, perfluorohexane and perfluorooctane sulfonic acid) in dietary samples of varied composition. The method employs ion pair extraction of the analytes into methyl tert-butyl ether and subsequent solid phase extraction clean-up on Florisil and graphitized carbon. Instrumental analysis was undertaken using ultra performance liquid chromatography coupled to tandem mass spectrometry. Special care was taken to avoid procedural blank contamination and potential contamination sources were elucidated. The performance of the method was evaluated for five different food test matrices including a duplicate diet sample. Method detection limits in the low to sub pg g-1 range were obtained for all target analytes, which are 5-100 times more sensitive than previously reported for duplicate diet samples. The method provided recoveries consistently between 50 and 80% for all analytes in the food matrices tested and effects of co-extracted matrix constituents on ionization were found to be negligible. Acceptable precision, defined as percentage relative standard deviation <30%, was achieved for all analytes. Accurate quantification at ultra-trace levels was demonstrated by a method intercomparison study with an independent recently developed method. For the first time the presence of long-chain PFCAs in duplicate diet samples is reported. The method presented here can thus support an improved assessment of dietary exposure to PFCAs and PFSAs. Re-analysis of duplicate diet samples, which had been previously analyzed using another older analytical methodology, indicated that human exposure to PFOA and PFOS from dietary sources may previously have been overestimated

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Environmental Sciences (hsv//eng)

Nyckelord

food

diet

human exposure

perfluoroalkyl acids

PFOA

PFOS

Applied Environmental Science

tillämpad miljövetenskap

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)