Thermodynamic analysis of the thermal stability of sulphonamides in milk using liquid chromatography tandem mass spectrometry detection

Abstract

[EN] The present study investigates the kinetics of the degradation of eight sulphonamides in skimmed milk when heated at 60, 70, 80, 90 and 100 degrees C using an LC-MS/MS methodology. To determine the thermal stability of these compounds, the first-order kinetic model was applied and the activation energies, half-lives and degradation percentages were calculated. Application of kinetic equations to the different heat treatments used in dairy processing indicates that sulphonamides are very stable during pasteurisation (63 degrees C; 30 min and 72 degrees C; 15 s) as well as UHT sterilisation (140 degrees C; 4 s). In contrast, the calculations performed with the kinetic model estimated losses in concentrations between 6.5% (sulfadimethoxine) and 85.1% (sulfamethazine) for the sterilisation at 120 degrees C for 20 min. The existence of thermodynamic compensation was also tested for sulphonamide degradation. Results show that enthalpy and entropy values displayed a good linear relationship, and thermodynamically we can establish that the thermal degradation of sulphonamides in skimmed milk exhibits enthalpy-entropy compensation.