Verification of the reversed-phase HPLC model developed on the basis of the generalized charges theory and its application for mobile phase optimization
Nowadays there is a problem of theoretical model suitable for describing the HPLC process and predicting its most important parameters. For the liquid chromatography processes there are special mechanisms of adsoption, «hydrophobic interaction», and competitive sorption. In general, the sorption equilibrium description in liquid chromatography combines the features of the processes of physical adsorption from the rarefied gas medium and strictly competitive ion-exchange. Moreover, solvation processes play an important role in liquid phase. Current theoretical approaches often defining one of the several problems with the others consideration omitting not allowed to create universal and sufficiently convenient model for the wide field of all HPLC considered stationary phases and analytes. In the vast majority of modern and classical concepts including the famous models of Snyder, Soczewinsky and Scott-Kuchera there is a large number of empirical parameters. Previously from the simplified model for weak eluents the phenomenological theory describing the particular cases of the known approaches and having a small number of transferable parameters was developed for the describing of chromatography. The generalized charges theory is used for the transferable parameters evaluation. Formulas for the non-empirical calculation of the basic model parameters are given. The small but undoubted experimental material showing the satisfactory accuracy of a priori theoretical calculations based on the developed model is found in the literature. The theoretical model is applied to the reversed-phase HPLC isocratic system with water-acetonitrile eluent and naphthalene as an analyte. The possibility of optimization of the multicomponent mobile phase with given eluotropic force according to the economic criterion is shown in the paper. It has been held by using the program which was specially designed for research purpose in Python environment. Application of the new composition under the experiment conditions would make possible to achieve almost 40% of economy. The calculation algorithm presented in the article will be a basis for the further HPLC modeling both for describing the behavior of analytes and for choosing the optimal conditions for their separation.