Prediction of retention for sulfonamides in supercritical fluid chromatography

Properties-retention studies were undertaken on a test library of sulfonamides using supercritical fluid chromatography with CO2-MeOH mobile phases (in the presence or absence of additive) and a 2-ethyl-pyridyl column. Taking a restricted range of retention ratios, k (1 < k < 10) and keeping the proportion of modifier in the mobile phase, φ, above 10%, it was shown that log k varies linearly with φ (R2 > 0.98). From these relationships, the different retention characteristics of the analytes were calculated. Literature studies of quantitative structure–retention relationships (QSRR) showed that these characteristics can be correlated with simple molecular descriptors to derive equations predicting the retention behaviour of new compounds. Measured retention characteristics were found to correlate with total dipole moment, μ, molecular surface area, A, and the electronic charge on the most negatively charged atom, δmin. The correlation of chromatographic measurements with calculated molecular descriptors may allow the prediction of the retention behaviour for an unknown compound provided its properties are known.