Derivatization and liquid chromatography–UV–tandem mass spectrometric analysis of perfluorinated carboxylic acids

The presence of perfluorocarboxylates (PFCAs) in the environment is of increasing concern due to their possible toxicity to humans and bioaccumulation in organisms. PFCAs are frequently found in river water, sediment and organisms and sometimes even in groundwater. In order to quantitatively determine these PFCAs, a fast derivatization coupled with a liquid chromatography–ultraviolet detector–electrospray ionization-tandem mass spectrometry (LC–UV–ESI-MS/MS) method was developed. The PFCAs were quantitatively converted to their corresponding phenacyl esters using p-bromophenacyl bromide as the derivatization reagent. Under optimized reaction conditions, the conversion yield of the PFCAs ranged from 86 to 92% with low %RSD. The typical derivatization product (p-bromophenacyl bromide perfluorooctanoate) was characterized by 1H NMR, 13C NMR, FT-IR and mass spectrometry. UPLC with a BEH C18 column and CAN/H2O (8/2, v/v) as a mobile phase were used to separate the derivatives. The analytes were completely eluted within 6 min and multidimensional detection using UV at 260 nm and ESI–MRM in the negative ion mode were carried out. Bromide isotopic characteristic fragment ions appeared in the first Q1 scans, and four daughter ions of the MRMs at m/z [M−H − 222]−, [M−H − 250]–, [M−H − 278]− and [M−H − 316]− were used for quantification and confirmation. The mass spectral information ensured accurate identification of the analytes even when the sample matrices were complex. The method successfully eliminated the PFCAs background problems originating from polymeric parts in liquid chromatographic systems. The LODs of the method were lower than 5 ng mL−1, and the relative standard deviation (RSD%) values ranged from 5.2 to 9.8%. The method was successfully applied for the quantification of PFCAs in river water contaminated by industrial wastewater, and this indicated that the method was useful in the determination of PFCAs in environmental samples.