4. Sorted FAQs on Vitamin C (ascorbic acid) Investigations

A. Vitamin C degradation
1.Effect of storage: suitable control? DCPIP or iodine titration?
2.Cause of vitamin C decrease in damaged oranges?
3.What happens to vitamin C on boiling broccoli?
4.Effect of refrigeration or damage on vitamin C content of oranges?
5.Effect of temperature on vitamin C in fruit juices: theory?
6.Effect of cooking on vitamin C content: making up solutions?
7.Content in brocolli - effect of cooking
8.How do metals accelerate decomposition of ascorbic acid?
8.Will standard solution of ascorbic acid degrade between 40 - 90 ^oC?
9.Effect of acid on degradation
10.Role of enzymes on oxidation
11.How does light accelerate decomp?
12.Effect of different treatments on degradation
13.Oxidation - reversible?
 
B. Colorimetry
1.Colorimetry: iodine stock solution and calibration concentrations?
2.Fruit juices via DCPIP and colorimetry: odd iodine absorption values?
3. Information on using colorimetry to determine vitamin C?
4. Why is sulphuric acid necessary for conversion of iodide to iodine?
 
C. DCPIP Titrations
1.Methods for DCPIP and NBS titrations?
2.How to standardise DCPIP solution? How to standardise DCPIP?
3.Titration: what indicator to use?
4.How to relate vitamin C % to concentrations of DCPIP or iodine?
5.Is reaction of vitamin C and DCPIP reversible?
6.How is DCPIP used on fruit juice?
7.DCPIP titration of lemon jiuce: effect of citric acid?
8.Effect of heat on vitamin C content: how to use DCPIP?
9.Formula for DCPIP and reaction with vitamin C?
10.How to calculate vitamin concentration in mg?
11.DCPIP titration
12.Half-life of DCPIP?
13.What is the dye factor?
14.Calculating the dye factor
15.Colour change?
 
D. Other methods
1.Effect of pH: does it involve acid-base titration?
2.Vitamin C content of 10 ml orange juice. How much lost in residue?
3.Consistent method for a variety of fruits and veg?
4.Suitable project: effect of boiling and acidifying to protect?
5.Back titration with iodine: how?
6.Will Vitamin C release Fe(III) from oxalate?
7.Advantages and disavantages of methods for vitamin C determination
8.Vitamin C titration: how does oxalic acid stabilise?
9.Orange juice titration with iodine: how does I₂ react?
10.Reaction between ascorbic acid and NBS?
11.Reaction of ascorbic acid and ascorbic acid oxidase?
12.Vitamin C titration: use of phosphoric acid?
13.Background theory?
14.Suggestions for investigating vitamin C or esters?
15.Cabbage: is ascorbic acid oxidase enzyme always present?
16.Phosphoric acid necessary with lemon juice?
17.Leave lemon skin on or peel, for heating?
18.Lemon juice: what other va.riable to study - acid already present?
19.Iodine titration - best method?
20.Use of acetic acid in NBS titration?
21.NBS titration - method?
22.Comparison of methods
 
E.Miscellaneous
1.Role of ascorbic acid in breadmaking
2.Problems with test for Vitamin C in flour?
3.% Vitamin C in tablets?
4.Vit. brocolli - preparation?
5.Function of Vitamin C in peppers
6.Standard solution of Vitamin C - mass needed?
7.Vitamin C in different coloured peppers
 
See also the tutorial on Vitamin C investigations

updated: 07 August 2008