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Ultra trace determination of fluorobenzoic acids in reservoir and ground water using isotope dilution gas chromatography mass spectrometry

The accurate ultra-trace analysis of six fluorobenzoic acids (FBAs) via isotope dilution gas chromatography mass spectrometry through their deuterated analogues is described. North Sea reservoir and ground water samples were spiked with six deuterated FBAs (dFBAs), enriched using solid-phase extraction (SPE) and analysed using GC/MS after derivatisation with BF 3· MeOH. All FBAs were enriched and determined simultaneously. SPE allowed a 250-fold enrichment of the acids if 100 mL of sample volume was used. The method enables the determination of FBAs down to the range of 8–37 ng L −1 with recoveries between 66 % and 85 %. It uses low amounts of chemicals and is adaptable to larger and smaller sample volumes.