Millions of people around the world have been suffering from Alzheimer’s disease (AD) everyday. Rivastigmine tartrate is a potential AD drug. A crystallization process can enhance purities of rivastigmine tartrate properly. Predictive models for solubilities of rivastigmine tartrate will improve subsequent industrial crystallization process design. In this work, the solubility of rivastigmine tartrate in (H2O?+?isopropanol), (H2O?+?ethanol), and (H2O?+?acetonitrile) binary solvent systems in the temperature range of 278.15–333.15 K under atmospheric pressure was measured and investigated by employing the analytical stirred-flask method. Binary solvent systems of rivastigmine tartrate overcame drawbacks of mono-solvent crystallization systems, such as high viscosity. Three thermodynamic models, including modified Apelblat equation, the general cosolvency model, and the Jouyban–Acree model, were employed to correlate with the obtained experimental solubility data. Moreover, the calculations of apparent thermodynamic properties of rivastigmine tartrate dissolution process involving the Gibbs free energy, enthalpy, and entropy were accomplished by using the van’t Hoff analysis. Among the three models, the modified Apelblat equation is the most suitable one for predicting the solubility behavior of rivastigmine tartrate in binary solvent systems. Based on the data from modified Apelblat equation, a crystallization process of (H2O?+?ethanol) binary solvent mixture was developed.
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Three isomers of mono-caffeoylquinic acid, specifically, 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid and 5-O-caffeoylquinic acid, were successfully isolated from a crude extract of tobacco (Nicotiana tobaccum L.) wastes using continuous resin-based pre-separation and preparative high-performance liquid chromatography (HPLC). The extract of tobacco wastes was continuously pre-separated by resin-based columns packed with D101 and XAD-4, yielding total mono-caffeoylquinic acids with a purity of 67.71% and a recovery rate of 90.06%. Variables affecting resolution and productivity of three mono-caffeoylquinic acid isomers in preparative HPLC (i.e. mobile-phase composition, pH, flow rate and loading amount) were studied. The optimum chromatographic conditions were determined to be a mobile phase consisting of 15% (v/v) methanol and aqueous acetic acid with a pH of 4.5, a flow rate of 4.0 mL/min, a loading amount of 4 mL and a detection wavelength of 360 nm. From 300 mg of loading sample, 56.3 mg of 3-O-caffeoylquinic acid, 92.8 mg of 5-O-caffeoylquinic acid and 73.1 mg of 4-O-caffeoylquinic acid were obtained in a single run, each with a purity of over 98% by HPLC. The structures of the isolated compounds were elucidated by ESI-MS, (1) H-NMR and (13) C-NMR spectral data. 相似文献