Measurement and correlation of solubility of boscalid with thermodynamic analysis in pure and binary solvents from 288.15 K to 313.15 K

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Highlights

  • The solubility of boscalid in pure solvents and binary solvents was determined.

  • Four thermodynamic models were used to correlate the solubility data of boscalid.

  • The mixing thermodynamics were calculated and discussed based on NRTL model.

Abstract

The solubility of boscalid in five pure solvents, including methanol, ethanol, isopropanol, ethyl acetate and n-propyl acetate, and two binary solvent mixtures, including (ethanol + ethyl acetate) and (isopropanol + ethyl acetate), was determined by a gravimetric method with temperatures ranging from (288.15 to 313.15) K. It turns out that the solubility of boscalid increases with the increasing of temperature in all selected solvents. Moreover, it is interesting that the solubility of boscalid in the two binary solvent mixtures performed a maximum effect with the decreasing mole fraction of ethyl acetate at a given temperature. The solubility of boscalid in pure solvents was correlated by the modified Apelblat model and λh model while that in binary solvent mixtures was correlated by the modified Apelblat model, CNIBS/R-K model and Jouyban-Acree model. It is found that all the models could give satisfactory correlation results with less than 3% of all the ARD values. Furthermore, the thermodynamic properties of the mixing processes in all solvents selected were calculated and discussed based on the NRTL model.

Introduction

Boscalid (C18H12Cl2N2O, CAS Number: 188425-85-6, Fig. 1), developed by BASF, is a broad-spectrum fungicide belonging to the class of succinate dehydrogenase inhibitor fungicides [1]. It is sufficient safety to the vegetation and can control a broad of fungal pathogens in arable and specialized crops including ornamentals [2]. Furthermore, its novel mechanism of action is not easy to produce cross-resistance. So it is worth paying more attention to the new active ingredient [3]. Recently, the research about boscalid has attracted considerable attention mainly on functional mechanism.

Solution crystallization is usually employed as an extremely important step of separation and purification process of boscalid [4]. To a great extent, the physical properties of products, such as purity, particle size distribution and crystalline morphology, will be significantly influenced by operation of crystallization process [5]. Solid-Liquid Equilibrium data which strongly relies on temperature and solution composition strongly affects the development of crystallization processes of boscalid [6] and it is essential to control the super-saturation, particle size, desired polymorphic and yield [7]. However, the solubility data of boscalid has never been systematically reported.

In this work, by using a gravimetric method [8], [9], [10], the solubility of boscalid in methanol, ethanol, isopropanol, ethyl acetate, n-propyl acetate, (ethanol + ethyl acetate), and (isopropanol + ethyl acetate) solvents were experimentally determined with temperatures ranging from 288.15 K to 313.15 K under atmospheric pressure. Moreover, the modified Apelblat model and λh model were employed to correlate the solubility of boscalid in five pure solvents while the modified Apelblat model, CNIBS/R-K model and Jouyban-Acree model were adopted to correlate that in binary solvent mixtures. All the selected thermodynamic models could fit the experimental data well. In addition, based on the NRTL model with activity coefficients consideration, the mixing thermodynamic properties (free Gibbs energy, enthalpy and entropy) of boscalid in different solvents were calculated and discussed.

Section snippets

Materials

Boscalid (≥ 0.990 mass fraction) was purchased from Hubei Kangbaotai Fine-chemicals Co., Ltd., China. The purity of boscalid was determined by high performance liquid chromatography (Agilent 1200, Agilent Technologies, USA). The organic solvents, including methanol, ethanol, isopropanol, ethyl acetate and n-propyl acetate were provided by Tianjin Kewei Chemical Co., Ltd., China and are analytical grade (≥0.995 mass fraction). All materials above were used without any treatment and more detailed

Thermodynamic and correlating models

In this paper, five commonly used solid-liquid phase equilibrium models, including the modified Apelblat model, λh model, NRTL model, CNIBS/R-K model and modified Jouyban−Acree Model, were applied to correlate the solubility of boscalid.

X-ray powder diffraction analysis

To verify that no physicochemical changes occurred during the entire experiment, the raw material and excess samples of boscalid in different solvents were tested by the X-ray powder diffraction (PXRD). And it was found from the PXRD patterns that all the samples used remained constant. Here the PXRD patterns of the raw material and one excess sample were shown in Fig. 2. The result confirmed that boscalid did not show any polymorphism, solvates or amorphous during the whole experimental

Conclusions

In this study, the solubility of boscalid in five pure solvents and two binary solvent mixtures, including (ethanol + ethyl acetate) and (isopropanol + ethyl acetate), was determined by the gravimetric method with temperatures ranging from (288.15 to 313.15) K. From the measured results, it can be found that the solubility of boscalid increases with the increasing of temperature in all solvents tested. Furthermore, at constant temperature, the order of solubility in pure solvents is ethyl acetate > 

Author information

Notes

The authors declare no competing financial interest.

Acknowledgements

The authors are grateful to the financial support of National Natural Science Foundation of China (81361140344, 21676179 and 21376164), Major Science and Technology Program for Water Pollution Control and Treatment (Grant 2015ZX07202-013) and Science and Technology Prospers Sea Project of Tianjin (KJXH2015-01).

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