Thursday, October 20, 2011

IB Chemistry Biology IA on Vitamin C quantification using Iodometric Titration or UV spectrophotometer

IB Chemistry Biology on Vitamin C quantification using UV spectrophotometer at 266nm


1. Sodium oxalate (0.0056M) - dissolving 0.075g sodium oxalate in 100ml pH 5 buffer
2. Vit C (0.001M ), prepared by dissolving 0.018g of Vit C in 100ml sodium oxalate solution
3. Perform 2 fold dilution on 0.001M Vit C.
4. Add 1 ml Vit C into a quartz cuvette and 2ml of sodium oxalate ( as a stabiliser )
5. Leave for 10 mins
6. Prepare a blank with 1ml water and 2 ml ammonium oxalate
7. Set up UV spectrophotometer at 266nm and quantify.
Result shown below
Latest journal published in April, accurate way to quantify Vit C. 
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* Oxalate solution used as  stabiliser and pH around 5 as both affect the stability of Vitamin  C


Short video on Vitamin C quantification using UV spectrophotometer
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Vitamin C quantification using iodometric titration
  • Potassium iodate as oxidising agent in burette
  • Potassium iodide as reducing agent , starch and vitamin C (reducing agent) in conical flask
  • End point is blue black colouration
  • Chemical equation below
  • KIO3 + 5KI + 6H+ --> 3I2 + 6K+ + 3H2O
  • 3C6H8O6 + 3I2  --> 3C6H6O6 + 6I- + 6H+
  • Mole ratio KIO3:Vitamin C = 1 :3




Video on Iodometric Titration for Vitamin C quantification


IA Research question for Chemistry/ Biology on Degradation/decomposition of Vit C

  • Effect of heavy metals salts like Pb2+or Cu2+ 
  • Effect of pH and temperature 
  • Duration and exposure to light or UV light
  • Aerobic or anaerobic degradation
  • Effect/presence of different sugar and oxidising agent 

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