Prediction of gas chromatographic retention indices using variable connectivity index

We have re-examined gas chromatographic retention indices of alkanes (48 co mpounds), and alcohols (31 compounds), combining all molecules into a singl e set (n=79) using variable connectivity index (1)chi (f). By varying the w eight for oxygen atom we obtained the regression characterized by the corre lation coefficient r = 0.9933, the standard error s=14.24 retention time un its, and Fisher ratio F = 5695. Use of the simple connectivity index (1)chi , which does not differentiate carbon and oxygen atoms, gives regression wi th the standard error four times larger.