Experiment 20
Consumer Chemistry: Vitamin C in Fruit Juices
The Task
The goal of this experiment is to determine the concentration of vitamin C in a range of different fruit juices (fresh and preserved) using titration and to rank these sources of vitamin C.
Skills
At the end of the laboratory session you should be able to: * use a pipette correctly, * use a pipette filler safely, * manipulate a burette and carry out a quantitative titration properly, * weigh a sample accurately, * understand and utilise error analysis.
Other Outcomes * You will extract vitamin C from a number of types of fresh fruit and bought juices. * You will present a conclusion concerning the ranking of different sources of vitamin C that includes clear reference to their interpretation of the error analysis. * You will explore the stability of vitamin C in solution and relate this to differences between fresh and preserved juices.
Introduction
Vitamin C is a water-soluble compound that is essential for life. It is involved in many processes in the human body, including: the production of collagen in the connective tissue; the synthesis of dopamine, noradrenaline and adrenaline in the nervous system; and the synthesis of carnitine, which is important in the transfer of energy to the cell mitochondria.
A deficiency in vitamin C causes scurvy, a disease that affected sailors in the 16th - 18Centuries. It was discovered that fresh fruit, e.g. limes and oranges, or sauerkraut (preserved cabbage) provided the sailors with protection from scurvy.
In Australia and New Zealand, the recommended daily intake (RDI) of Vitamin C is 60 mg. The Nobel-prize winning scientist, Linus Pauling (1901 - 1994), believed in regular mega doses of vitamin C, but this is still regarded as unorthodox in conventional medicine. Vitamin C is often used as an antimicrobial and antioxidant in foodstuffs. It was first isolated in 1928 and in 1932 it was proved to be