Gas chromatography is a helpful technique to separate and analyze volatile compounds. In this experiment, ethanol and pentanol are both nonpolar, so they are separated based on their boiling points. Ethanol has a higher boiling point than pentanol, so it elutes first and its peaks can be seen first on all the chromatograms (Figures 1, 2, 4, and 5). It is useful to be able to separate ethanol and determine its percentage, like in this experiment, in the case of alcohol concentration in beer. The purpose of the calibration plot of ethanol solutions made during Week 1 was to obtain a direct correlation between the percent ethanol in a sample and its average ethanol peak area (Figure 3). The R2 value of the graph was 0.9973, indicating that the data obtained during Week 1 was precise and accurate (Figure 3). The linear trendline from the calibration plot, y=0.0687x+0.1683, can be used to determine the unknown percent ethanol in the extraction sample (Figure 3). From the determination of the percent ethanol in the extraction sample, the partition coefficient can be calculated. …show more content…
If K had been less than one, then the aqueous layer would have contained the most ethanol. However, with a K value of 2.1, it was determined that the organic layer contained the most ethanol. From this information, it was concluded that the injections during Week 2 should come from the organic layer. It was only necessary to determine K in Week 1 because the partition coefficient is calculated after the solute has all been extracted, which happened in Week 1. Not all of the ethanol was extracted in Week 2 and the other ingredients in beer could have skewed the partition