RESUMEN
To separate chlorogenic acid from low concentration ethanol and explore the influence of Donnan effect and solution-diffusion effect on the nanofiltration separation rule. The experiment showed that solution pH and ethanol volume percent had influences on the separation of chlorogenic acid. Within the pH values from 3 to 7 for chlorogenic acid in 30% ethanol, the rejection rate of chlorogenic acid was changed by 70.27%. Through the response surface method for quadratic regression model, an interaction had been found in molecule weight cut-off, pH and ethanol volume percent. In fixed nanofiltration apparatus, the existence states of chlorogenic acid determinedits separation rules. With the increase of ethanol concentration, the free form chlorogenic acid was easily adsorbed, dissolved on membrane surface and then caused high transmittance due to the solution-diffusion effect. However, at the same time, due to the double effects of Donnan effect and solution-diffusion effect, the ionic state of chlorogenic acid was hard to be adsorbed in membrane surface and thus caused high rejection rate. The combination of Box-Behnken design and response surface analysis can well optimize the concentrate process by nanofiltration, and the results showed that nanofiltration had several big advantages over the traditional vacuum concentrate technology, meanwhile, and solved the problems of low efficiency and serious component lossesin the Chinese medicines separation process for low concentration organic solvent-water solution.
RESUMEN
Objective: Response surface analysis and regulating Donnan effect methodology were used to optimize the matrine concentration by nanofiltration techonology. Methods: On the basis of single factor experiment results, molecular weight cut-off (MWCO) of nanofiltration membrane, concentration and pH were selected as influencing factors to evaluate the retention rate of matrine and total alkaloids with Box-Behnken central composite experiment design, and then, the optimal concentration parameters were calculated in the conditions of pH 6-7 to regulate Donnan effect between alkaloids and nanofiltration membrane. Results: The retention rate of matrine was of positive relevance with the ethanol concentration. The optimal concentration parameters were as follows: cutting off molecular weight of 150, pH of 6.19, concentration of 204.3 μg/mL, ethanol concentration of 15%, the retention rate of matrine and total alkaloids were 94.41% and 97.63%, respectively. Conclusion: The combination of ethanol regulation Donnan effect and response surface analysis can well optimize the concentration process of S. flavescens extract by nanofiltration, and the results provide the references for nanofiltration concentration for heat-sensitive Chinese materia medicia.