Ultra trace determination of fluorobenzoic acids in tap and reservoir water using solid-phase extraction and gas chromatography–mass spectrometry

A method for the ultra trace analysis of 21 fluorobenzoic acids (FBAs) via GC–MS based on solid-phase extraction (SPE) and derivatization with BF3·MeOH is described. All fluorobenzoic acids were enriched and determined simultaneously. Solid-phase extraction on hydrophilic–lipophilic-balanced reversed-phase cartridges containing a poly(divinylbenzene-co-N-vinylpyrrolidone) polymer allowed a 250-fold enrichment of the acids if 100 mL sample volume is used with extraction efficiencies between 71% and 94%. The method enables the determination of fluorobenzoic acid methyl esters (FBAMEs) down to the range of 6–44 ng L−1 combined with a fast and easy sample-preparation (pH-adjusting prior to SPE and derivatization within 24 h at 64 °C directly in the vial). It uses low amounts of chemicals and is adaptable to larger and smaller sample volumes. Simultaneous extraction and determination of 21 fluorinated aromatic acids in reservoir samples with high salinity confirmed the applicability and reproducibility of the method.

► New method for the derivatization of fluorobenzoic acids using BF3·MeOH.
► New SPE method using a material never used before for this application.
► Quantitative extraction of all commercially available 23 FBAs.
► Determination of all 23 fluorobenzoic acid methyl esters in the ng L−1 range.
► Capability of the method for highly saline reservoir water samples is shown.