Gas chromatography triple quadrupole mass spectrometry method for monitoring multiclass organic pollutants in Spanish sewage treatment plants effluents

In Spain, although more than 50% of urban wastewaters are currently being treated, only half of them are subjected to biological treatments and only 3% undergo advanced treatment technologies. Consequently, the application of more exhaustive wastewater treatment protocols, including the use of new and improved technologies, the application of wider and integrated quality control and water reuse strategies are a priority. We have used as a reference, the European Water Framework Directive (WFD; Directive 2000/60/CE), which establishes a framework for Community action in the field of water policy, setting a list of priority compounds to be monitored in water in order to evaluate their levels. The aim of the present study is to develop and validate a multi-residue method for the analysis of 57 multi-class organic contaminants in wastewater samples using gas chromatography coupled to triple quadrupole mass spectrometry and apply it to evaluate the presence of such compounds in different wastewater treatment plants. The proposed method is based on a sample treatment using liquid–liquid extraction with n-hexane followed by identification, confirmation and quantitation with gas chromatography tandem mass spectrometry using a triple quadrupole analyzer operating in the selected reaction monitoring mode. Three MS/MS transitions were selected for unambiguous confirmation of the target chemicals. The method was validated at two different concentration levels (15 and 150 ng L−1) obtaining recovery rates in the range 70–110% in most cases. The limits of quantitation obtained for most of the compounds tested were in the low nanogram per liter range (below 3 ng L−1 in all cases). Treated and untreated effluent wastewater samples of different origin (industrial, coastal and urban) provided by several sewage treatment plants (STPs) located throughout Spain were tested. Results so far showed that most of the samples assayed did not contain large amount of these contaminants. Hexachlorobenzene was found to be the more frequently detected contaminant in the studied samples, although at levels below 5 μg L−1.