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Experiment 6

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Experiment 6
(1) Answer to Question in lab manual. NO introduction/background etc.

1. What is the retention time for caffeine?
Retention time for caffeine : 4.149+4.142+4.152+4.1454 = 4.15 2. What is the retention time for benzoic acid?
Retention time for caffeine : 2.651+2.817+2.857+2.9274 = 2.81

3. How are the retention times for caffeine and benzoic acid related to their chemical structure and the nature of the chromatographic system?
The retention time of caffeine and benzoic are related due to the presence of a hydroxyl group. The hydroxyl group impart polarity and induce dipole-dipole forces between the benzoic acid and the column. Thus, benzoic acid, being polar, are retarded by the column and will come out of the column with a longer retention time. 4. What is the peak width of caffeine?
Peak Width = Area of peakHeight of peak x 2
Peak width of caffeine at 75ppm: 2304120272024 x 2 = 16.94
Peak width of caffeine at 100ppm: 3135638373010 x 2 = 16.81
Peak width of caffeine at 150ppm: 4546077539388 x 2 = 16.86
Peak width of caffeine at 200ppm: 6155195725789 x 2 = 16.96

Average peak width of caffeine: 16.94+16.81+16.86+16.964 = 16.89

5. What is the peak width of benzoic acid?
Peak Width = Area of peakHeight of peak x 2
Peak width of benzoic acid at 75ppm: 56940825861 x 2 = 44.04
Peak width of benzoic acid at 100ppm: 77970236817 x 2 = 43.36
Peak width of benzoic acid at 150ppm: 110568848555 x 2 = 45.54
Peak width of benzoic acid at 200ppm: 148854358107 x 2 = 51.23

Average peak width of benzoic acid: 44.04+43.36+45.54+51.234 = 46.04 6. Calculate the resolution of caffeine and benzoic acid.
R = 2∆tWA+WB = 2(4.15-2.81)46.04+16.89 = 0.043 min/nm 7. Construct a calibration curve of the caffeine peak are versus concentration.

8. What is the linear regression line for the calibration curve of caffeine?

9. Construct a
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