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Vitamin C concentration

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MEASURING THE VITAMIN C CONTENT IN A VARIETY OF FRUIT AND VEGETABLE JUICES Introduction: Ascorbic acid is commonly known as the vitamin C. The compound has a five-membraned unsaturated lactone ring with two hydroxyl groups attached to the doubly bonded carbons. Vitamin C is required for the formation of intercellular material. It is present in most of the fruits and vegetables. Deficiency of vitamin C leads to scurvy in human. Vitamin C is powerful reducing agent which can reduce DCPIP (2,6-dichlorophenolindophenol) and changes the colour of DCPIP solution from blue to almost colourless. The more vitamin C, the more DCPIP can be decolourized. Research question: What is the ascorbic acid content in fruit and vegetable fruits? Variables: > Independent type of the solution (the juice)- each trial was carried out by using different solutions intended to decolourise DCPIP solution. All solutions were prepared either by squeezing the juice out of fruits and vegetables or by filtering the juice from the carton. Obtained juices were clear and transparent. > Dependent volume of the solution (needed for decolourisation) -certain volume of DCPIP is decolourised by a certain volume of ascorbic acid. Each sample of solution has different concentration of vitamin C therefore the volumes of solution needed for decolourisation of 1 cm3 of DCPIP would differ. ...read more.


7. Add the first sample of solution drop by drop, gently shake the tube after each drop is added and note the number of drops in order to decolourise DCPIP. 8. Continue in the same way with all solutions. Safety: DCPIP is corrosive and toxic. Wash any spills with plenty of water. DCP: Table1: Number of drops of juice solutions needed to decolourise DCPIP. Type of solution Number of drops [�1] Trial 1 Trial 2 Trial 3 Ascorbic acid 8 8 8 Lemon 14 15 14 Old lemon 26 25 25 Tomato 48 49 47 Orange 35 36 36 Rutinoscorbin 14 14 15 Orange juice 18 17 19 Tomato juice 90 88 89 Water Does not decolourise Does not decolourise Does not decolourise At the beginning of the experiment some measurements concerning the dropper were taken. Using the dropper and water I calculated the number of water drops that make 1 cm3. Table2: Number of drops that make 1 cm3 . Volume [cm3�0.05] Drops [�1] Average 1 14 14 14 14 Having this calculated and using the values of measurements from Table1. I calculated the volume of substances needed to decolourise the DCPIP solution. Table3: Average number of drops and volume of the substance needed to decolourise 1 cm3 of DCPIP. ...read more.


In the experiment, some errors and mistakes occurred: * Maturity state- vitamin C concentration decreases during the ripening process. Immature fruit has the highest levels because at a immature state citrus fruits contain more ascorbic acid hence the sour taste of un-ripened citrus fruits. There was no information which provided the state of the ripening process of the fruits/vegetables, therefore the concentration of ascorbic acid can vary (and differences in results and literature might occur). It is difficult to improve that aspect but some ECO shops sell fruits with additional information about their state. * Human error- as the experiment considers only visual aspects, the human error could occur. Eye might have not notice a drop of solution added to DCPIP, two drops could bind and look like they're one etc. To increase the reliability of this method and experiment, I suggest to use two people to watch and count the drops of solution added. Also the state of decolourization is not precise as, again, the human eye can be deceiving. * Uncertainty of the equipment had small influence on the final results. The pipettes used to measure DCPIP volume could have slightly different scales- therefore one pipette should be used for DCPIP volume measure. Literature: i ii iii ?? ?? ?? ?? Gracja Kowalska 2IB ...read more.

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