For the analysis of hydrocarbonmixtures in GC, the main objective is to obtain the lowest theoretical plateheight which translates to the best possible column efficiency. By adjustingthe column head pressure (which changes the phase velocity) for each run of amixture of samples we can determine the flow rate at which all samples share ahigh efficiency at a certain flow rate. This can be done by constructing VanDemeter plots for each hydrocarbon and locating where all three graphsinteract. This point is the flow rate at which you will receive the bestpossible plate height. In the beginning of this report, it was stated that asthe column pressure decreased, the peaks would narrow but the resolution woulddecrease as a consequence.
Although for the most part the data did show aslight drop in resolution with a lowering of pressure, the peaks actuallybroadened as well. The reasoning for this would be as the CHP is lowered, thelinear velocity does so as well. As a result of this, the various compoundsspent more time in the stationary phase than the gas phase which meant that ittook longer for them to reach the detector, and a wider peak was the result.