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?
14.Making up aspirin solution accurately
15.Is oxidation of ascorbic acid exo- or endo-thermic?
16.Chemistry behind degradation of vitamin on cooking?
17.Anomalous increase in vitamin C concentration at 80 ^oC
 
B. Colorimetry
1.Colorimetry: iodine stock solution and calibration concentrations?
2.Fruit juices via DCPIP and colorimetry: odd iodine absorption values?
3. How to get from iodine colorimeter reading to concentration of ascorbic acid?
4. Information on using colorimetry to determine vitamin C?
5. Why is sulphuric acid necessary for conversion of iodide to iodine?
6. Using calibration curve with high transmittance values from juice?
7. What filter to use for calibration curve?
 
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.Structure and reduction of DCPIP
11.DCPIP Colour change?
12.How to calculate vitamin concentration in mg?
13.DCPIP titration
14.Half-life of DCPIP?
15.What is the dye factor?
16.Calculation of dye factor
17. Necessary to add HCl only in DCPIP titration?
18. Method for titrating solution from peas?
 
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.Method for iodine titration
20.Iodine titration - best method?
21.How to make up 0.015 M iodine solution?
22.Standarisation of iodine solution
23.Use of acetic acid in NBS titration?
24.NBS titration - method?
25.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
8.How much water to dissolve vitamin C tablet in?
9.Mass of ascorbic acid to make up standard solution?
 
See also our tutorial on Vitamin C investigations

updated: 21 April 2009