*3.1. Chemicals*

Urea (CH4N2O) was obtained from Kemaus, Australia. Ammonium oxalate (NH4)2C2O4, nitric acid (HNO3), and methanol (CH3OH) were purchased from Merck, Darmstadt, Germany. Benzoquinone, isopropyl alcohol, titanium (IV) oxysulfate (TiOSO4) and imidacloprid were obtained from Sigma-Aldrich, USA. All reagents were of analytical grade and were used without further purification. Deionized water was used in preparing all aqueous solutions.
