Methylgroup interaction of hydrocarbon stationary phases and hydrocarbon solutes

The temperature dependency of the retention behaviour of some alkanes with squalane as stationary phase has been measured at a very high precision level, at temperatures from 30 to 90°C. Besides the retention index itself [1], its temperature dependency appears to be a source of information about structure. By comparing the retention indices on squalane and on octadecene-1 at 50°C it is seen that indices of all branched alkanes have higher values on the former. Retention indices of the same alkanes on nC28, nC32, nC36 and on squalane as stationary phases, calculated from published specific retention volumes [7] also show the tendency of increasing index with increasing methyl content of the stationary phase. For explanation of the observed phenomena a model for methyl interaction isdescribed