Experiment 10 Caffeine in Soda Drinks
Harleen Bansal A2101 July 28th, 2015 Abstract Caffeine 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. Introduction Caffeine is added to approximately 70% of soft drinks available in the market, and manufacturers justify this by claiming that caffeine caffeine is the primary source of flavour in their drinks. However, 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, Bel l, 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 sol ution 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 Results Drink
Amount of Crude Caffeien (mg/L) 92
Coke Class Data Drink
Coke
Amount of crude caffeine (mg/50ml)
Melting Point (Degrees Celcius)
Diet Coke 85.4
Pepsi 175.4
Pepsi One 102.6
Pepsi Max
245.6
Crude Caffeine
Purified Caffeine
229.4-233.5
232.9-235.4
269.8
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 reversephase 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).
