Optimization of the gas chromatographic separation of five-membered ring polyarenes with an admixed BPhBT liquid crystal-dexsil 300 stationary phase

A window diagram constructed with the liquid crystal BPhBT in admixtures with the gum phase Dexsil 300 gave the optimum mixing ratio for the gas chromatographic resolution of five-membered ring polycyclic aromatic hydrocarbon solutes. The window diagram was constructed from relative retention data obtained from specific retention volume measurements. Plots of the specific retention volumes versus percentage of BPhBT in the blend were linear to within ± 5% for all solutes. Further, intimately blended phases gave specific retention volumes virtually identical with those of mechanically mixed phases, within experimental error, when the same mixing ratios were compared. This suggests that the liquid crystal is only dispersed (as opposed to dissolved) in Dexsil 300 and that the two phases act independently of each other in the blends. This contention is supported by differential scanning calorimetric measurements. The use of the retention index scheme for the purpose of window diagram construction is shown not to be a valid option for this system.