Determination of transformation products formed during water disinfection by chromatographic techniques coupled to quadrupole time-of-flight mass spectrometry

Emerging contaminants is one of the most interesting topics in the scientific community nowadays. Due to the inefficiency in WWTP for eliminating compounds from waters, contaminants go through all the barriers and reach ending waters for re-use. That is the reason why since the last years, the presence of several substances in environmental sources such as waters, is increasing and becoming a human health threat. In this thesis, studies about the degradation of emerging contaminants were performed. In degradation processes, regarding the method, the compounds are transformed into other new structures, with unknown toxicity activity. The elucidation of these new substances, as well the parameters about their toxicity, is also evaluated in this work

Determination of N-Nitrosamines by Gas Chromatography Coupled to Quadrupole–Time-of-Flight Mass Spectrometry in Water Samples

An analytical method based on high-resolution quadrupole–time-of-flight (QToF) mass spectrometry has been developed as an alternative to the classical method, using a low-resolution ion trap (IT) analyzer to reduce interferences in N-nitrosamines determination. Extraction of the targeted compounds was performed by solid-phase extraction (SPE) following the United States Environmental Protection Agency (USEPA) -521 method. First, both electron impact (EI) and positive chemical ionization (PCI) using methane as ionization gas were compared, along with IT and QToF detection. Then, parameters such as limits of detection (LOD) and quantification (LOQ), linearity, and repeatability were assessed. The results showed that the QToF mass analyzer combined with PCI was the best system for the determination of the N-nitrosamines, with instrumental LOD and LOQ in the ranges of 0.2–4 and 0.6–11 ng mL−1, respectively, which translated into method LOD and LOQ in the ranges of 0.2–1.3 and 0.6–3.9 ng L−1, respectively. The analysis of real samples showed the presence of 6 of the N-nitrosamines in influent, effluent, and tap water. N-nitrosodimethylamine (NDMA) was quantified in all the analyzed samples at concentrations between 1 and 27 ng L−1. Moreover, four additional nitrosamines were found in tap and wastewater samplesThis research was funded by Xunta de Galicia (references EM2014/004 and ED431C2017/36), Spanish Agencia Estatal de Investigación (reference CTM2017-84763-C3-R-2), and European Regional Development Fund (FEDER/ERDF) funds. I.C. acknowledges her postdoctoral formation grant from Xunta de Galicia governmentS

Chlorination and bromination of 1,3-diphenylguanidine and 1,3-di-o-tolylguanidine: Kinetics, transformation products and toxicity assessment

This works investigates the chlorination and bromination of two rubber and polymer related chemicals, which have emerged as relevant water contaminants, i.e. 1,3-di-o-tolylguanidine (DTG) and 1,3-diphenylguanidine (DPG). Kinetic constants at different pH values were obtained and modelled, taking into account the pKa values of DTG/DPG and HClO, showing that the maximum reaction rate (kapp > 104 M−1 s−1) is obtained at pH values 8.8 for DPG and 9.1 for DTG. Bromination is also very fast, although unlike chlorination, deviation from the model was observed at neutral pH, which was attributed to formation of metastable transformation product (TP). A total of 35 TPs, corresponding to halogenation, hydroxylation, formation of monophenylguanidine derivatives and cyclization reactions, were tentatively identified. Furthermore it was found that chloroform can be formed up to a 25% molar yield, while dichloroacetonitrile was formed into less than a 3% yield. Several ecotoxicological endpoints were predicted by quantitative structure–activity relationship models (QSAR) for the TPs, some of which were predicted to be more toxic than DPG/DTG. Also a chlorinated solution investigated by a Vibrio Fisheri acute toxicity test, confirmed that toxicity increases with chlorination.This work was supported by the Water Challenges for a Changing World Joint Program Initiative (Water JPI) Pilot Call (ref. WATERJPI2013 – PROMOTE), funded by the Spanish Ministry of Economy and Competitiveness/Spanish Agencia Estatal de Investigación (refs. JPIW2013-117 and CTM2017-84763-C3-2-R) and French Office National de l’Eau et des Milieux Aquatiques (ref. PROMOTE). We also acknowledge the Galician Council of Culture, Education and Universities (ref. ED431C2017/36), Région Nouvelle Aquitaine and FEDER/EDRF funding. Benigno J. Sieira acknwledges the COST (European Cooperation in Science and Technology) Action ES1307 for suporting his research stay in PoitiersS