Determination Of Intraparticle Mass Transfer Parameters Of Liquid Chromatography And Application Of Simplified General Rate Model

High Performance Liquid Chromatography is a highly effective separation method used widely in biochemical and Pharmaceutical fields. In practice, the remarkable effect of intraparticle mass transfer processes in column on separation result has been extensively studied by many chromatographic researchers. So far, there have been many reports focusing on the problem. However, some difficulties baffle the researchers and prevent them from understanding further the intraparticle mass transfer processes in chromatographic column. First, the General Rate (GR) model is necessary to describe detailedly the mass transfer processes in column, but the parameters involved in GR model are difficult to determine accurately. Second, the numerical calculation of GR model is complicated and time consuming. Thus, the practical application of GR model, especially the application in complicated chromatographic systems, is limited.In this dissertation, the identification of intraparticle mass transfer parameters involved in GR model is discussed. And the moment analysis method is adopted in this work. Because the accurate measuring result of the third central moment is difficult to obtain, the factors which result in the error of measurement of the third central moment of eluted band profiles are investigated experimentally in this work. The experimental conditions for the measurement of the third central moment have been optimized. Under this improved condition, the third central moments of band profiles are measured with their relative standard deviations below than 10%. Further analysis about the measurement results of the third central moments indicates thatμ3u0 4(whereμ3 is the third central moment of band profile and u0 the surperficial velocity of mobile phase) is always proportional to u0 under all the experimental conditions in this work. And then it can be deduced that the external mass transfer coefficient is proportional to u0 according to the measurement results of the moments and the moment equations of GR model calculated in this work,. Consequently, the intraparticle mass transfer parameters can be determined from the measurement result of the second central moments of band profiles which can be measured accurately in practice.Secondly, the Modified Equilibrium-Dispersion (MED) model equivalent to the GR model is developed based on the moment equations of GR model deduced in this work. Although the first and second moments of the band profiles calculated from MED model are same with those from GR model, the equivalence between the two models is investigated under the conditions of different levels of intraparticle mass transfer parameters, nonlinearity and velocity of mobile phase, respectively. And the results show that the band profiles calculated from the two models always match well with each other. Therefore, the numerical solution of the GR model can be substituted by that of the MED model to simplify the calculation of GR model greatly.At last, the effects of intraparticle mass transfer parameters on the separation region and performance parameters of SMB (Simulated Moving Bed) are discussed in this work. The MED model above is adopted to replace the GR model as the mathematical model for the single column of SMB, and the separation regions (99% purity) as well as the purities, recoveries and enrichments of separation products of SMB are calculated under different levels of intraparticle mass transfer parameters. The calculated results indicate the following conclusions. The effect of effective diffusivity on SMB process is always more remarkable than that of external mass transfer coefficient. Both nonliearity and intraparticle mass transfer process influence the separation region of SMB obviously. The separation region of SMB shrinks, while the recovery and enrichment of separation products increases with the decrease of intraparticle mass transfer parameters.