Extraction of perfluorinated compounds from food matrices using fluorous solvent partitioning

Perfluorinated compounds (PFCs) such as perfluorooctane sulfonic acid (PFOS) have emerged as a new class of global environmental pollutant; they bioaccumulate and are persistent in the environment and in wildlife. Fluorine-fluorine interactions have been investigated as a means to isolate PFCs for mass spectrometric quantification. A novel sample extraction and cleanup procedure has been developed for fat-containing samples based on fluorous liquid-liquid extraction (F-LLE) in a triphasic solvent system consisting of hybrid:fluorous:organic solvent (trifluoroethanol:perfluorohexane/dichloromethane-saturated with water). This system partially separates fluorous from non-fluorous compounds, allowing removal of co-extractants, which had previously resulted in liquid chromatography mass spectrometry (LC-MS/MS) peak suppression preventing low-level detection of PFCs. The developed F-LLE was coupled with an existing extraction protocol allowing the limits of detection of PFCs to be lowered an order of magnitude for high fat samples. The developed workflow was used to show the absence of a range of eleven PFCs in nine UK and one Irish cheese samples. This representative application demonstrates a new application of fluorous-organic extraction in sample cleanup for measurement of fluorinated analytes in food, environment and broader analytical chemistry.