Abstract
A correlation between the stoichiometric parameter Z in the stoichiometric displacement model for retention (SDM-R) and the parameter S (denoted Sm in the new correlation) in Snyder's empirical equation for isocratic elution reversed-phase high performance liquid chromatography (RPLC) was derived with Taylor translation. The correlation is Sm = Z/(2.3Φm), where Φm is the intermediate value of the activity of the stronger organic solvent in the mobile phase. With the correlation, a more accurate conversion between Z and S can be made, and the physical meaning of the empirical parameter S can be explained by means of that of parameter Z. The correlation was validated with experiment data and data from the literature for a variety of RPLC systems with different solutes and mobile phases. The results indicated that for all solutes, especially for homologues, and mobile phases, a good linear relationship exists between the two parameters. The values of S and Sm were generally found to be similar, but the accuracy of S was generally influenced by the changing composition of the mobile phase. The reason why Sm is more accurate and easily obtained than Sg (the S value obtained from two or more gradient runs) was also explained.
ACKNOWLEDGMENTS
This work was supported in part by the National Natural Science Grants of China (29675017, 39880003) and by Griffith University OSPRO. Qiming Yu is Visting Professor from School of Environmental Engineering, Griffith University, Nathan Campus, Brisbane, Queensland 4111, Australia.