[Studies on the matching relation of homologues between experimental points and parameters in retention equation in...

The matching relation between the number of experimental points and that of parameters of retention equations employing two, three, and four parameters of stoichiometric displacement model for the retention (SDM-R) of homologue in liquid chromatography has been investigated. When two experimental points were used, the retention of the homologue of N-alkylphthalimides were predicted by equations with two, three, and four parameters. The predicted values were found to fit the experimental values, although the predicted values by equation of two parameters were found to be better than that by others. Comparison was also made among the retention models proposed by Snyder, Lu Peichang, and Schoenmakers, and it is found the foregoing points have been proved. With the increase in the number of experimental points, the deviation of the predicted results of equation with multi-parameters decreased, while that by equation of two parameters did not significantly decrease. The linear correlation between the parameters of all of those equations employed in this study and the carbon number of the homologue was also discussed. The parameters from equation of two parameters was found to follow the carbon rule of a homologue. On the contrary, the parameters from the equation with multi parameters were found not to follow.