Question

Chemistry 70A Experiment 5 - Distillation Fall 2019 5. (4 pts) For gas chromatography, what four factors determine the retention time for organic compounds moving through the column?! 6. (2 pts) Cyclohexane was the first compound to "elute" from the the gc column. Suggest some reasons why cyclohexane elutes before toluene.

can I have help on question 5 please?

Answer 1

The factors which influence the retention time: Nature of stationary phases of there is strong attraction to the gas and liquid stationary phase, then the gas will spend more time bonding to it and the retention time will increase. (2) solubility of Gas & of the gas easily dissolves in the liquid stationary phas, then the gas I will spend more time in the liquid and this increases retention time.

Hongee column improves Length of the column's longer columns will inverase the retention time by increasing the time that the gan speeds inside longer olumn also intease the solutions of the bands produced (they will be farther apart) To maintain the valaticity of sample). 1 Temperature in column & By increasing the temperature inside the column, the salubility La gas in liquid citationary phas) sses and this implies that the goo will Hence move the retention faster time will decrease. (carvien gas). (5) How rate of mobile phase & H we increase the mate at which the carrier gas moves, we also increan the rate at which the mixture gas moves. Thus the retention time will decrease. (A high flow rate causes poor separatin) 16) vapour pressure of liquid mixtures nore Vip implics the mixture will mow with more speed of up leas it implies there not complete conversion of liquid into vo Ant of material injected: Aml Amt a tolly injected had no impact on retention 4 too much of the sample is into the peaks show a significant tavir instead of symmetric shape sample on retention waterial is time. injecteds tule shape should be (a dolal. sample injected