It is generally believed that multicomponent stationary phases, or mixed stationary phases, show the average effect of individual pure phases in gas chromatography (GC). Investigations have shown the existence of a synergistic effect in some mixed GC stationary phases and about 18 articles have been published since 1996.[1,2] Some chromatographic properties of the mixtures, such as separation factor (a), retention factor (k'), elution order of Grob test regent, and McReynolds constants, are not the simple addition of the chromatographic properties of the two pure phases. These values of mixed stationary phases may be greater or less than either of the pure stationary phases. It is different from general experimental results. The positive synergistic effect is very useful in the separation of some substance pairs.