Chromatography is a technique used to separate and analyze chemicals. It was initially discovered in the early 1900's by chemist Mikhail Tsvett who was researching chlorophyll to separate plant pigments.1 The components undergoing separation are divided into two phases, a stationary phase, and a mobile phase. The stationary phase does not move while the mobile phase, which includes the sample, passes through the stationary phase. Different chemicals are impeded at different rates through the stationary phase based on individual properties which make them unique.2
[...] There are also less intermolecular forces in Freon 22, as evidenced by the lower boiling point when compared to Freon 123. The shorter retention time directly affects the ban width which was shorter for Freon 22 because the less time the component spends in the column the less time there is for interactions to take place between the Freon 22 and the stationary phase which generates a shorter ban width. Gas chromatography requires a carrier gas, a column, and a detector. [...]
[...] Results The gas flow rate (linear gas velocity) for our homemade chromatograph was calculated using the formula ū = where ū is the average linear gas velocity (in centimeters/second), L is the length of the gas chromatograph column (in centimeters), and tA is the average retention time for air (in seconds) ū = 29.5 cm / 4s Linear gas velocity = ū = 7.4 cm/s 11 For each halocarbon the green-blue flame appeared, intensified, and disappeared as portrayed in Figure 1. [...]
[...] The commercial chromatograph uses a flame ionizing detector which identifies ions in the sample based on their mass This experiment was designed to separate Freon 123 form Freon 22 in a mixture of the two halocarbons first by using our homemade gas chromatograph, then by using the commercial gas chromatograph, and then compare the two methods and the data measured from both pieces of equipment.6 Being able to separate components is an important method used by scientists today. Common uses of chromatography include determining drug content in urine and alcohol in blood samples, testing for water pollution, detecting bombs, and separating and testing histamines and antibiotics.7 Prior to performing this experiment I thought the components would successfully separate from one another and Freon 22 would have the shorter retention time than Freon 123 because it is a smaller molecule. [...]
[...] Using the commercial gas chromatograph we identified the unknown concentrations of the two halogens Freon 22 and Freon 123 to be 181.985 ppm and 207.126 ppm respectively. References McNair, H.M. & Miller, J.M., Basic Gas Chromatography; Wiley-Interscience Publication: New York, 1998; pp. 1-18, 39-40. Oxtoby, D.W. & Nachtrieb, N.H., Principles of Modern Chemistry; Saunders College Publishing; Fort Worth, 1996; pp.196-199. Brown, T. E., LeMay, H. E. & Bursten, B.E., Chemistry: The Central Science; Prentice Hall: Upper Saddle River, NJ, 2005; pp Paper Chromatography, Peter Piper Publishing Inc April 2003. [...]
[...] The column of the commercial gas chromatograph is 2 meters, much longer than that of the homemade ones, which were 20 cm long.6 A longer column increases the degree of separation of the components and provides a much more efficient. The homemade column was packed with Tide and is shorter due to the large amounts of pressure needed to force the sample through the column. The difference in column length causes both the retention time and ban width to be greater for the commercial gas chromatograph. [...]
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