TGA investigation of the volatilisation of fipronil at elevated temperatures

•TGA was used to study the thermal behaviour of the insecticide fipronil.•Sublimation and evaporation enthalpies were determined.•Vapour pressure predicted by TGA could be accurate to within 12%. In the present work, thermogravimetric analysis (TGA) was used to study the vaporisation behaviour of fipronil in the temperature range of 150 to 230 °C, i.e., below and above the melting point of the insecticide. The sublimation and evaporation rates were measured using isothermal thermogravimetric analysis. The vapour pressure was estimated assuming that the ideal gas law holds and that the rate of mass loss can be accounted for by the variation of the evaporation rate with liquid depth within the sample crucible and the vapour diffusion coefficient for the evaporating compound into the nitrogen gas. From this, the sublimation enthalpy was determined to be 120 ± 4 kJ⋅mol−1, while the enthalpy of evaporation was 72 ± 5 kJ mol−1. Separate measurements using benzoic acid indicated that the vapour pressure predicted by the thermogravimetric method employed could be accurate to within about 12%.