Solubility and solution thermodynamics of flofenicol in binary PEG 400 + water systems

• Solubility of florfenicol in PEG 400 + water solvent mixture at various temperatures.
• Prediction of solubility data in the selected mixed solvent.
• Evaluation of thermodynamic properties including standard enthalpy, entropy and Gibbs energy change of solution.

The solubility of florfenicol in PEG 400 + water solvent mixture was measured at seven temperatures from 293.15 K to 316.25 K. The modified Apelblat equation the General Single model and the Hybrid model were used to fit the experimental solubility data. The thermodynamic functions were obtained from the combination of the modified van’t Hoff equation with the modified Apelblat model, including standard enthalpy, entropy and Gibbs energy change of solution. Results showed that: the mole solubility of florfenicol in binary PEG 400 + water solvent mixture increased with the increasing temperature and the mole fraction of PEG 400; the overall mean percentage deviation (OMPD) obtained from the modified Apelblat equation, the General Single model and the Hybrid model were 3.22, 3.73, 6.52, respectively. Thus, the modified Apelblat equation can give further accuracy and reliability of the solubility of florfenicol in the selected solvent systems than the other two fitted models. The solution process for florfenicol was always endothermic and the driving mechanism was mainly classified as the following three kinds in the temperature range from 293.15 K to 316.25 K: entropy-driving (from 0.0000 to 0.0064 in mole fraction of PEG 400), enthalpy and entropy driving (from 0.0064 to 0.0138 in mole fraction of PEG 400), enthalpy driving (from 0.0138 to 0.0458 in mole fraction of PEG 400).

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