Evaluation of photocatalytic degradation of imidacloprid in industrial water by GC-MS and LC-MS

The insecticide Imidacloprid was oxidized in water at 50 mg/L, under photocatalytic TiO2 in presence of formulating agents. Analysis of oxidized solutions was performed with both GC-Ion Trap-MS using either EI and CI as ionization modes and LC-Atmospheric Pressure Chemical Ionization (APCI)-MS in order to confirm and evaluate the decay of Imidacloprid and the presence of degradation products (DPs). LC-APCI-MS techniques allowed the monitoring of Imidacloprid and 6-chloronicotinic acid along the degradation process. GC-MS techniques allowed the detection of five DPs, three of which were unequivocally identified. Other complementary techniques such as Total Organic Carbon (TOC) and Ion Chromatography (IC) allowed the evaluation of the mineralization degree achieved. A tentative degradation pathway of Imidacloprid under photocatalysis is proposed. After 450 minutes of irradiation, none of the DPs or Imidacloprid were detected. Nearly total mineralization was achieved after 700 minutes of irradiation.