Photocatalytic pilot scale degradation study of pyrimethanil and of its main degradation products in waters by means of solid-phase extraction followed by gas and liquid chromatography with mass spectrometry detection

Aqueous solutions of Pyrimethanil, as technical grade product (TP), with 98 .2% purity, and commercial formulation (CF), containing 40% (w/v) of Pyrime thanil, were submitted to photocatalytic degradation under sunlight in the presence of TiO2 as catalyst in a preindustrial pilot plant. Complete Pyrim ethanil degradation was achieved after ca. 230 min of irradiation, in both TP and CF, but total mineralization was not observed, as was demonstrated b y the TOC values of 3-4 mg/L, measured at the end of the experiments (907 m in). A qualitative and quantitative study of the degradation products (DPs) generated during the process was performed by GC-MS, using El and Cl as io nization modes, and by LC-API-MS, using Atmospheric Pressure Chemical Ioniz ation (APCl) and Electrospray (ES) interfacing techniques. Up to 22 compoun ds could be detected as degradation intermediates. To evaluate the extracti on efficiency of these DPs from the aqueous solution, specially for the mor e polar intermediates, a recovery study was performed with Pyrimethanil and seven of the commercially available DPs. Liquid-liquid extraction (LLE) an d solid-phase extraction (SPE), with different sorbents, were compared. A S PE method using Lichrolut-EN cartridges was selected as the most adequate, but recoveries less than or equal to 60% were obtained for four of the DPs studied (aniline, formamide, 1,3-benzenediol, and 4,6-dimethyl-2-pyrimidina mine). Structure identification of DPs allowed us to propose two main route s in the degradation process. One route involves the attack of hydroxyl rad icals to the pyrimidine and benzene rings with further rings opening and th e other one corresponds to a photoinduced hydrolysis of the molecule by the amine group bonds.