Retention index prediction from structure

Rohrschneider s approach is able to predict retention index values for solute s with known solute constants (a, through e) [283,288]. These are determined from AI values for the solute on at least five phases of known phase constants and solving the series of linear equations. The retention index of the solute on any phase of known phase constants (X through S ) can then be calculated from Eq. (2.8). The theoretical defects of the method for assigning intermolecular interactions do not apply to the prediction of retention index values. A mean error of about 6 index units was indicated in some calculations. The retention or retention index values for thousands of compounds can be calculated from literature compilations of solute descriptors and the system constants summarized in Tables 2.6 and 2.8 using the solvation parameter model [103]. The field of structure-driven prediction of retention in gas chromatography is not well developed at present and new approaches will likely emerge in the future. 

A plot (Figure 115) of the Apiezon retention index versus boiling point, where known, shows considerably more uniformity despite the variations in structure represented. From such a plot the retention index can be predicted from the boiling point with an average error of 1%, the poorest case being that of tetravinyl tin, where the error is 6%. 

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