Isolation of Caffeine from Tea

Date Performed: July 8 & 15, 2012

Ch 22.2 – A Date Submitted: July 23, 2012

Experiment # 3: Isolation of Caffeine from Tea, TLC, and Melting Point Determination

DATA AND RESULTS:

Table 1.1 Raw Data

PROPERTIES | NUMERICAL DATA |

Mass of tea bags (4 Lipton black tea bags) | 10.33g (2.5g each) |

Mass of recovered caffeine in distilling pot | 0.11g (0.03g each bag) |

Caffeine content of tea bags (Unilever, 2012) | 55mg or 0.05g per serving |

Percent Recovery of caffeine | 60% |

Table 1.2 Thin Layer Chromatography

PROPERTIES | LENGTH | RETENTION FACTOR (Rf) |

Standard Caffeine | 15mm | 0.48 |

Sample Caffeine (Spot 1) | 15mm | 0.48 |

Sample Caffeine (Spot 2) | 27mm | 0.87 |

Solvent front | 31mm | |

Table 1.3 Melting Point Determination

SOLUTION | TEMPERATURE (Starts to Melt) | TEMPERATURE (Fully Melts) |

Standard Caffeine | 233.9ºC | 235.8ºC |

Sample Caffeine | 214.2ºC | 225.0ºC |

DISCUSSION

For this experiment, caffeine was isolated from tea by using solid-liquid and liquid-liquid extraction in which these solutions are extracted with solvents of similar polarities and solubility. Nonpolar substances naturally went to the organic layer, while polar substances moved to the aqueous layer. A technique called thin layer chromatography was also used in separating into individual substances and investigating the purity of the sample by allowing the developer (solvent system) to move across the plate, and at the same time, the adsorbent or the silica (SiO2H2O) adsorbs the components of the solution. Lastly, the melting point was determined in order to compare the melting points of both the standard caffeine and the sample retrieved caffeine.

Tea leaves contain several compounds including caffeine, cellulose, chlorophyll, tannic acids, flavonoid pigments. (University of Saskatchewan). Cellulose are insoluble in water, thus, it immediately separates by the addition of hot water. On the other hand, sodium...