Content
Abstract----------------P.4
Objectives---------------P.6
Experiment-------------P.7
Conclusion--------------P.14
Reference----------------P.15
Objectives
Through this project, we would like to find
- the content of the vitamin C in the Vita and Hi-C Corporation of different types of fruit drink;
- the comparison of the content of vitamin C of the same type of fruit juice of Vita brand and Hi-C brand;
- the Best buy fruit drink which contains relatively large amount of vitamin C with the lowest price.
Experiment
Objective
To determine the amount of the ascorbic acid (vitamin C) in the selected fruit juice by titrating with standard DCPIP solution
Theory
Blue 2,6-dichlorophenolindophenol ( DCPIP) dye can oxidize ascorbic acid (vitamin C) and form DCPIPH2 & dehydro-ascorbic acid. The equation of this reaction is shown as following:
+ DCPIP + DCPIPH2
The change of DCPIP with acid is shown as the following:
The blue dye can act as an indicator. Also it can perform the titration against the vitamin C, after adding the certain amount of DCPIP , the vitamin C change to
pink. The pink colour can persist about 10 seconds.
Assumption
1. Only vitamin C in the drink will react with the DCPIP.
2. The oxidation of Vitamin C by air is negligible.
Apparatus
Burette, 10 ml pipette, pipette filler, filter paper, weighting bottle, volumetric flask, beaker, conical flask, magnetic stirrer and heater, electronic balance, filter funnel, and flat-bottomed flask.
Chemical
DCPIP, ascorbic acid, phosphoric acid
Precaution
Vitamin C decomposes over time and on exposure to sunlight and oxygen. The dichlorophenolindophenol solution is unstable and needs to be freshly prepared each time it is used.
Procedure
Preparation of 2,6-dichlorophenolimdophenol solution
-
0.4g of DCPIP was dissolved in 200cm3 of hot deionized water.
-
The solution was then filtered and made the volume up to 1.00 dm3.
- It was then stored in a cool dark place.
Standardisation of the 2,6-dichlorophenolimdophenol solution
-
25.0cm3 of standard ascorbic acid solution (0.2gdm-3 vitamin C) was pipetted to a conical flask
- The dye solution was titrated rapidly from a burette.
- The end point was taken to be when the pink colouration, due to the dye, persists for 10s.
Titration
-
The DCPIP solution was diluted to 1.00 dm3 of the solution.
- The DCPIP solution by filtered using filter funnel.
-
10.0cm3 of the sample was pipetted to a conical flask, and then diluted to 50.0 cm3.
- DCPIP solution as a titre.
- By titration, until the colour change from pink to blue.
-
Repeated the experiment to the ten sample of the test.
Result
Band-A: Hi-C Corporation
Band B : Vita Corporation
Calculation
(I) To find out the relationship between DCPIP and standard ascorbic acid solution
Let xcm3 DCPIP solution is used to 40cm3 of a solution containing 0.1mgcm-3 of ascorbic acid
∴ x cm3 DCPIP ≡ 4 mg ascorbic acid
∴ 1cm3 dye ≡ 4/x mg ascorbic acid
(II) To estimate vitamin C in fruit juice
y cm3 dye =10 cm3 fruit juice
From (i),
1 cm3 dye = 4/x mg ascorbic acid
∴ 10 cm3 beverages contain 4xy/x mg ascorbic acid
250 cm3 beverages contain 100xy/x mg ascorbic acid
The calculated result:
The cost of all the fruit juice samples are $3.5.
Conclusion
All the samples were found to contain more Vitamin C than the recommended daily intake, 30-60 mg.
The vitamin C content of Vita orange juice was found to be the highest among the samples analysed. Since the cost of the each fruit juice sample is the same, so the best buy fruit drink with respect to Vitamin C content was found to be Vita orange juice.
For the same type of fruit juice, Vita brand was found to have a higher Vitamin C content than that of Hi-C brand.
Discussion
The differences of vitamin C content between samples were very small so that the result may not be accurate if a small error, such as adding one more drop of DCPIP solution to the sample juice, was caused.
The Vitamin C content of Hi-C apple juice was exceptional low with respect to other samples. This needs further investigation.
Error
- It should also be noted that the samples of different types of fruit juice have a distinct color of their own which may affect the final effect.
- Some vitamin C in the fruit drink was oxidized by air before the experiment.
Reference
URL:
URL:http://www.vforyourself.com/Overview/Primer/Chemistry/c_tests.html
Books 1:Name: Revised Nuffield Chemistry Options
Author: Andrew Firman
Publisher: Long man Group Limited – Resources Unit 9/11 The Shambles Yorks
Books 2:Name: In search of more solutions (The Royal Society of Chemistry)
Author: Janet Taylor
Publisher: The Royal Society of Chemistry