A Comparative Study Of Equilibrium Plate Theory And Non-equilibrium Plate Theory

The development of chromatographic technique depends on the improvement of chromatographic instrument, but the improvement and progress of chromatographic instrument is based on the development of chromatographic theory. Therefore, theory research and development is a key factor for developing chromatographic technique.In this paper, we try to use Martin's plate theory as a foundation, and interpret the process of chromatographic separation from two dynamic ways. Each way is developed into a chromatographic theory, called new non-equilibrium plate theory and extended equilibrium plate theory, respectively. The main research work is summarized as follows:Firstly, Pai's parcel model is discussed in detail, and the disadvantages are analyzed. By using the parcel model experience and basing on the Fick's first diffusion law, a new non-equilibrium plate theory is proposed. The realistic non-equilibrium mass transfer process between mobile phase and stationary phase is fully taken into consideration, and a new parameter called degree coefficient of completeness of equilibrium DN is introduced to describe the degree of deviation from equilibrium partition. With the aid of computer program, chromatographic peaks are successfully simulated by the new non-equilibrium plate theory, and the effects of various parameters are discussed.Secondly, Martin's plate theory is deeply analyzed and evaluated. We assume that the partition of sample between two phases isn't instantaneously achieved within unit plate height but through a short chromatographic column. This multiple of changed equilibrium plate height to unit plate height is called equivalent plate height multiple, ME. Different chromatographic separation can be viewed as the result of equilibrium partition within various equilibrium plate heights. Thus, Martin's plate theory is developed into extended equilibrium pate theory. With the aid of computer program, chromatographic peaks are also successfully simulated by the extended equilibrium plate theory.Thirdly, peak shapes simulated by the above theories are taken a systematically comparison from qualitative and quantitive aspects. Finally, a conclusion has been achieved, when the typical parameters of the two theories meet a relation ME=2/DN-1, there exists nearly no differences between the peak shapes simulated by the two theories, which indicates that equilibrium partition or non-equilibrium partition doesn't exert influences on chromatographic elution in linear chromatography. Therefore, this conclusion demonstrates that Martin's assumption of―perfect equilibrium being established within a plate‖isn't a restricted condition for describing practical separation processes. With this conclusion, equilibrium partition problem can wholly replace non-equilibrium partition problem in chromatographic theory research, which will offer great convenience in practical study.