Thermal and forced hydrolytic degradation studies of flonicamid and its photolysis in Egyptian clay-loam soil

The present study investigated the stability of Teppeki 50% WG (a flonicamid formulation) during forced thermal degradation at (35, 40, 45, and 54°C); forced acidic and alkaline hydrolysis in 1.0, 0.1, and 0.01N HCl and NaOH; and photolysis in clay-loam soil. The results showed that flonicamid active ingredient was significantly degraded (15.83 %) after storage at 54 °C after 14 weeks and its shelf-life decreased to 1/3 that of its shelf-life at 35°C. Acidic hydrolysis of flonicamid increased its shelf–life and half-life to 18.65 and 252.05 days in 1.0 N HCl which is almost 5 times that in 0.01 N HCl. Nonetheless, the shelf–life and half-life of flonicamid in the alkaline media was reduced to 0.57 and 7.72 days and 0.07 and 0.95 days in 0.01 N and 1.0 N NaOH, respectively. The half-life for flonicamid’s dissipation in clay-loam soil (pH 8.59) was 2.46 days. Generally, the kinetics of flonicamid degradation followed the first-order model being dependent upon the initial concentration. During the thermal degradation and acidic and alkaline hydrolysis of flonicamid, the byproducts rendered indicated the cleavage and rearrangement of the side chain however, they indicated that the pyridine ring remained stable. Nevertheless, the dissipation of flonicamid in soil was effective in the cleavage of the pyridine ring. This may be attributed to the macro and micro content available in soil tested which played a role in this molecule transformation.