[Method development for analysis of short-and long-chain perfluorocarboxylates in sewage]

A method using weak anion exchange cartridge for solid phase extraction before high performance liquid chromatography-negative electronspray ionization-tandem mass spectrometry [WAX-SPE + HPLC-ESI(-)-MS/MS] detection has been developed to measure C2-C14 perfluorocarboxylates (PFCAs) in sewages. When the weak anion exchange (WAX) cartridges were used for solid phase extraction (SPE), the better recoveries of short- and long-chain PFCAs (C2-C14) were achieved as the sewage samples were acidified to pH = 3.0 by formic acid, 2% formic acid was used for washing solvent and 1% ammonium hydroxide in methanol was used for elution solvent. The WAX cartridges used for SPE overcame the disadvantages of reverse phase solid phase extraction cartridges, i.e. the recoveries of short-chain PFCAs (C2-C5) were very low. The validity of this method was demonstrated by determination of short- and long-chain PFCAs (C2-C14) in influent of municipal wastewater treatment plant A and B in Shanghai, China. The results indicate that the recoveries of all PFCAs in influent of plant A and B are 56%-121% and 54%-120%, respectively; the recovery relative standard deviations (RSD) of plant A and B are < 11% and < 14%, respectively; and the method detection limits (MDL) and method quantitation limits (MQL) are 0.2-1.0 ng/L and 1.0-5.0 ng/L, respectively. In addition, the perfluorooctanoate (743 ng/L and 837 ng/L, respectively) and trifluoroacetic acid (139 ng/L and 489 ng/L, respectively) are the most and the second most PFCAs found in both plant A and B.