Non-isothermal Dehydration Kinetics of Ceftriaxone Disodium Hemiheptahydrate

The non-isothermal dehydration behavior of ceftriaxone disodium (CTXN) hemiheptahydrate, investigated by thermogravimetry-derivative thermogravimetry (TG-DTG), proceeds in two steps: (1) the loss of two and one-half water molecules and (2) the loss of one water molecule. The dehydration kinetics were achieved from the TG-DTG curves by both the Achar method and the Coats-Redfern method with 21 frequently cited basic kinetic models. The dynamic dehydration processes for steps 1 and 2 are best expressed by the Zhuralev-Lesokin-Tempelman equation and the Avrami-Erofeyev equation (n = 1), suggesting a three-dimensional diffusion-controlled mechanism and a nucleation-controlled mechanism, respectively. The corresponding kinetic compensation effects (KCEs) for the two steps are found to be: ln A = 0.354 54 * 10^-6.5733 and ln A = 0.297 66 * 10^-5.47166, respectively.