4.0mg/ml of ascorbic acid
2.0 mg/ml of ascorbic acid
1.0mg/ml of ascorbic acid
0.5mg/ml of ascorbic acid
Orange juice
Sour orange juice
Lemon juice
Test-tubes
Test-tube rack
Procedure:
1. A small syringe was used to add 1ml of DCPIP to a test tube and the test tube was put to stand.
2. A 1ml syringe was filled with 4.0mg/ml of ascorbic acid solution. The solution was then added drop by drop to the DCPIP solution and stirred gently with a glass rod.
3. The number of drops taken to decolorize the DCPIP solution was recorded.
4. The procedure was repeated using fresh samples of DCPIP each time, with the four solutions of ascorbic acid, orange juice, sour orange and lime juice.
5. The results were provided in a table then a graph was plotted of the number of drops of ascorbic acid solution use to decolorized DCPIP against concentration of ascorbic acid solution.
Results:
Table 1. Ascorbic acid concentration and drops of DCPIP.
Table 2. Log of drops for the number of drops and concentration of solution.
Discussion: 2, 6-dichlorophenolindophenol, (DCPIP), a blue chemical compound, can be used as an indicator for Vitamin C (not for other vitamins which are entirely different kinds of chemical). Oxidized DCPIP is blue, reduced DCPIP is colorless. If vitamin C, which is a good reducing agent, is present, the blue dye, which turns pink in acid conditions, is reduced to a colorless compound by ascorbic acid. It required 8 drops of 4.0 mg/ml of ascorbic to decolorize the DCPIP. Then, to decolorize 2.0 mg/ml of ascorbic, it took 19 drops. Hence, an increase in the number of drops for the experiment suggests that the concentration of the ascorbic acids were high.
Sources of Error:
The ascorbic acid was not always dropped directly to the DCPIP solution. It fell to the side of the test tube which made the number of counts inaccurate.
Processed juices may have been used which could alter the results because of the chemicals found in the juices.
Conclusion: The concentration of ascorbic acid in orange juices are high.