Thermogravimetric analysis as a rapid and simple method to determine the degradation degree of soy biodiesel

• Thermogravimetric analysis is used for measuring the biodiesel oxidation degree.
• A very small amount of biodiesel is required for determining its oxidation degree.
• Biodiesel pre-treatment is not needed to apply thermogravimetric analysis.
• Thermogravimetry is a simple alternative for monitoring biodiesel oxidation.

This work describes the use of the residual mass observed in a thermal decomposition curve for a soy biodiesel sample as a measure of its degradation degree. The difference in thermal stability between esters and oxidation products is the key point to make the determination. Using residual mass, the acceptance or rejection of a biodiesel becomes a non-subjective process and does not require knowledge of the biodiesel oxidation process. The residual mass data were compared with those of kinematic viscosity, UV spectroscopy and nuclear magnetic resonance. The good agreement found between these data justifies the utilization of this method to determine the biodiesel oxidation degree.