Experiment 10 Caffeine in Soda Drinks
Harleen Bansal
A2101 July 28th, 2015
AbstractCaffeine content was determined in Coke, Diet Coke,
Pepsi, Pepsi One, and Pepsi Max by
separating crude caffeine via extraction in a separatory funnel,
filtering the extraction, evaporating the solvent, and purifying by
vacuum sublimation. After examining and comparing caffeine
contents, Pepsi One contained more caffeine than Coke.
IntroductionCaffeine is added to approximately 70% of soft
drinks available in the market, and manufacturers
justify this by claiming that caffeine is the primary source of
flavour in their drinks. However, it was found that only 8% of cola
consumers could detect the difference in flavour between high and
low caffeine content in soda samples (Griffiths and Venotica,
2000). As a central nervous-system active drug, it has stimulatory
and other physiological effects (Chou and Bell, 2007). Methods of
extracting caffeine include isocratic reverse-phase
high-performance liquid chromatography (Chou and Bell, 2007) and
annular centrifugal contractors (Zhou et al. 2006). The melting
point of caffeine is 236.1 degrees and the boiling point of
dichloromethane is 39.8 degrees (CRC Handbook of Chemistry and
Physics). For this experiment, dichloromethane was an excellent
solvent because it has a low boiling point and caffeine is more
soluble in this solution compared to water. This produces two
immiscible layers of liquid when dichloromethane is added to a
caffeine containing product making it sufficiently easier to
separate the caffeine as the dichloromethane is then evaporated to
extract crude caffeine.
In this experiment, caffeine content in several cola drinks was
found to determine whether Pepsi One contained more caffeine than
Coke. The amount of caffeine was determined through liquid-liquid
extraction, solvent removal via evaporation, and purification by
vacuum sublimation.
Experimental Procedure Refer to experimental design form
ResultsDrink Amount of Crude Caffeien (mg/L)
Coke 92
Class Data
Drink Coke Diet Coke Pepsi Pepsi One Pepsi Max
Amount of crude caffeine (mg/50ml)
85.4 175.4 102.6 245.6 269.8
Crude Caffeine Purified Caffeine
Melting Point (Degrees Celcius)
229.4-233.5 232.9-235.4
Discussion The amount of crude caffeine found in Coke was 92mg/L
while Pepsi One was found to
contain 245.6mg/L. Thus, the amount of crude caffeine was
greater in Pepsi One compared to Coke. The beverage that contained
the most caffeine was Pepsi Max and the least caffeine was found in
Coke.
The procedure for this experiment could be improved to receive
more accurate results by repeating the extractions with the
separator funnel more than three times. This will ensure that most
if not all of the caffeine present in the sample will be extracted
and dissolved in the dichloromethane layer, resulting in a greater
percentage of caffeine when isolated. Other techniques that require
advanced technology and knowledge such as the isocratic
reverse-phase high-performance liquid may also be used to achieve
accurate results.
The melting point ranges for the crude caffeine was 229.4-233.5
and the purified caffeine had a melting range of 232.9-235.4. The
melting point value found in the literature was 236.1. The melting
points found in the lab were both lower than the literature value,
however the purified sample had a melting point that was closer to
this value than the crude sample. Impurities such as foreign
substances present in the caffeine that was extracted interfere
with the forces that hold the solid together, thus giving a value
lower than the melting point found in the literature. The bonds
require less energy to break in an impure sample of caffeine verses
a pure sample.
Bibliography
Chou, K.-H.; Bell, L.N. J. Food Sci. 2007, 6, C337.
Griffiths, R.R.; Venotica, E.M. Archives of a Family Medicine
2000, 8, 9.
Zhou, J.Z.; Zhou, X.Z.; Duan, W.D. Solvent Extraction and Ion
Exchange 2006,2, 251-259.
CRC Handbook of Chemistry and Physics. Caffeine.
http://www.hbcpnetbase.com (accessed July 18, 2015).
CRC Handbook of Chemistry and Physics. Dichloromethane.
http://www.hbcpnetbase.com (accessed July 18, 2015).
