Direct-injection suppressed ion chromatography-mass spectrometry with online preconcentration for short- and ultra short-chain perfluoroalkyl carboxylic acids in fresh water

Abstract

This work developed a novel analytical method to detect short- and ultra-short chain perfluoroalkyl carboxylic acids (PFCAs) in freshwater samples by direct injection using ion chromatography mass spectrometry (IC-MS). Ultra-short chain PFCAs, including trifluoroacetic acid (TFA), are often present in aqueous environments at higher concentrations than longer chain PFCAs, however there are currently a limited number of methods that can analyze them. Detection limits ranged between 1.3 and 2.8 ng L⁻¹ (ppt) of the PFCAs (C2–C6) analyzed and were comparable to those of other LC-MS and GC-MS methods. The precision of this method ranged from 0.4–7.6% for all the PFCAs (C2–C6). An advantage of this method is that small samples sizes under 1 mL can be used. This method was applied to real freshwater samples including tap water, precipitation, lake water, and river water. TFA was detectable in most of the samples with online pre-concentration and no other additional pretreatment sample preparation; however, method performance decreased in samples with high conductivity. A new unidentified isobaric interferent for TFA was present in most of the freshwater samples.