Gas Chromatography Lab

Data and Conclusions: The purpose of this experiment was to learn how to use distillation and gas chromatography to separate and identify different compounds from a given mixture. There are several kinds of distillation methods. However, the method that we used in this experiment was fractional distillation. This method is used when trying to separate two different volatile compounds whose boiling points differ by 40-50°C or more. If the boiling points are too close, this method will not work because the two compounds will begin evaporating at close temperatures and will condense down to the receiving flasks at relatively the same times. This will not create an ideal separation. The apparatus used for this type of distillation
Because of this, I hypothesized that all of fraction A and most of fraction B consisted of the low boiling point compound. As I raised the temperature of the hotplate, I was able to collect fraction C, and I predicted that it was composed of mostly the high boiling point liquid. To test this, the experiment called for the use of gas chromatography. The chromatography would not only show the relative concentrations of each compound in the fraction, but could also help confirm the identification of the compounds we thought were in the fractions based on the temperatures that each liquid boiled. Before trying to guess the correct compounds of the mixture, one must run each individual fraction through the machine to clearly see the composition of each. Gas chromatography works because as the liquid runs through the machine, its different components run through and exit at different times due to changes of temperatures that measure high and low boiling points. The machine records these using peaks of retention time that identify these different components. After obtaining this data, there was enough information to choose a reasonable match for each of the components. Once both the fractions and the guessed compound were mixed, the retention recordings should
For cyclohexane I mixed it with fraction A, since it predominantly consisted of my low boiling point liquid, and observed two peaks in my results. Therefore I concluded that cyclohexane was the low boiling point liquid. However, for the second liquid I guessed heptane first, and my results showed three peaks. Knowing that I had guessed wrong, I tested toluene mixed with my fraction C and only got two peaks. The high boiling point liquid proved to be