Determination of perfluoro-alkyl acids in different water matrices by means of direct injection LC-MS/MS analysis

Perfluoroalkyl acids (PFAAs) are characterized by high resistance to physical, chemical and biological degradation and a worldwide contamination of environmental matrices, including all water compartments, resulted from their extensive use for a wide range of industrial and commercial applications since the 1950s. In 2006, some regulatory restrictions have been promulgated both in United States and Europe in order to discipline the use of perfluorooctanesulphonic acid (PFOS) and perfluorooctanoic acid (PFOA), which were, until then, the most industrially employed chemicals among PFAAs. The direct injection (DI) approach is an interesting alternative to extraction/clean-up procedures, such as solid phase extraction, since it allows to minimize the sample contamination due to its manipulation, to ensure high analytical throughput and to overcome any possible recovery issues related to the variety of physicochemical characteristic of these molecules (such as chain length and acidic moiety). However, the injection of relatively large volume of sample, together with the absence of the preconcentartion/purification steps, could translate into strong matrix effect which can negatively affect method accuracy and/or sensitivity. This study aimed to evaluate the feasibility of the DI-LC-MS/MS approach for the analysis of selected carboxylic and sulphonic PFAAs in several water matrices (i.e. drinking water, groundwater, river water, lake water and wastewater). Method detection limits achieved in this study were found in the range 0.014-29 ng L-1, resulting to be lower or comparable to those obtained with the same approach, or by means of SPE procedure. For the first time, the presence of PFAAs in water samples - ranging from sub ng L-1 to tens of ng L-1 - has been determined in a number of rural, urban and industrial areas of Tuscany, Italy.