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Jacked Up! Measuring Caffeine & Benzoic Acid Concentrations

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on 3 December 2013

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Transcript of Jacked Up! Measuring Caffeine & Benzoic Acid Concentrations

Jacked Up! Measuring Caffeine & Benzoic Acid Concentrations In Soft Drinks
By Ryan Arrigo, Matt DiNardo, Taylor Fish, Maggie Pope, and Martha Whamond
Experimental Design Part 1
We created a standard solution of 100 mg/L benzoic acid and 200 mg/L standard of caffeine as well as a .1 M HCl solution.
We then prepared standards of the benzoic acid (2-10mg/L) and caffeine (4-20mg/L) from the stock solution by adding HCl: two charts
One benzoic acid standard and one caffeine standard was selected and the absorbance spectrum was measured for each using the Jasco Spectrophotometer
Lambda max for each spectrum was determined and the values recorded as the λmax benzoic acid and λmax caffeine
The absorbance of all 10 solutions was measured under both the λmax benzoic acid and λmax caffeine
Calibration curves were then created using the data in order to calculate the absorptivity of both species at λmax benzoic and λmax caffeine
Critical Analysis
Percent error
Mello Yello- .0816 mg/mL at 33% error
Mt. Dew- .047 mg/mL at 69% error
Nos- .669 mg/mL at 107% error
Red bull- .341 mg/mL at .88% error

Error
An outlier was found when constructing the calibration curve for the caffeine,altering data found with calculations using the Lambda max of caffeine.
The addition of HCl and the dilution could have allowed error when finding the original concentration through the dilution equation.
If the soft drinks were not completely decarbonated it could have skewed data in the spectrophotometer.
The drinks had to be strained before running through the Spectrophotometer. If they were not 100% clear it would alter their absorbance.

Analysis
Even though the data was off and exhibited a large error, we had no procedural issues so the experiment was a success.
Introduction/ Background
Caffeine and benzoic acid are organic compounds found in beverages that give the boost that is responsible for “waking you up”. In this lab, we wanted to measure the amount of caffeine and benzoic acid in common soft drinks. As organic molecules, caffeine and benzoic acid exhibit absorbance bands in the UV region of the electromagnetic spectrum with a lamda max between 200-400 nm. Because of this, the concentration of these two compounds can be determined through spectrophotometer analysis and the use of calibration curves.
Conclusion
Experimental Design Part 2
Part 2: Experimentation with different soft drinks
We selected 4 different soft drinks to test for their caffeine and benzoate concentration: Nos, Red Bull, Mello Yello, and Mountain Dew
The drinks were de-carbonated and then filtered
The drinks were diluted by adding 3 mL of .1M HCl and diluted to 100mL
An absorbance spectrum was then recorded using the Jasco Spectrophotometer at each λmax

Results
Original Concentration in Undiluted samples
Mello Yello
Caffeine: 0.0816mg/mL
Benzoic acid: 0.316mg/mL

Mountain Dew
Caffeine: 0.047mg/mL
Benzoic acid: 0.617mg/mL

NOZ
Caffeine: 0.669mg/mL
Benzoic acid: 0.045mg/mL

Red Bull:
Caffeine: 0.341mg/mL
Benzoic acid: 0.149mg/mL


Our data followed the trend in that Nos has the most caffeine, followed by Red Bull, Mt. Dew, and Mello Yello. Even though some experimental data had high percent error, they still follow this major trend showing that we were able to calculate the concentrations of benzoic acid and caffeine in these soft drinks.
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