Vitamin c is easy to oxidised by the oxygen in air so

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Vitamin C is easy to oxidised by the oxygen in air, so the food sample should be freshly prepared and kept in the air-tight bottle before use . To aviod extra drop of food sample added to the DCPIP solution until the end point was reached, we should shake the test tube after each drop of food sample added. 3. What are the limitations/difficulties/errors in the experiment? Number of drops of the sample used to decolorize DCPIP solution were recorded in the experiment, however, the volume of each drop may be different , and so it would cause error in calculating the concentration of vitamin C present in the food sample . In the food samples, they may have some other reducing agents, e.g. vitamin E which can reduce/decolorize DCPIP solution. In this case, the calculation of the concentration of vitamin C in the sample will be over estimated . 4. Give some suggestions to improve this experiment. In order to measure the volume of the food sample added accurately, burette should be used in doing the titration. Or we can put the DCPIP solution in the measuring cylinder, and then we can calculate the voulme of the food sample added by subtracting the volume of DCPIP solution initailly from the total volume of solution after the food sample added . DCPIP decolorize to added sample of drop of number DCPIP decolorize to added C vitamin standard of drop of number C vitamin standard the of conc. C vitamin of Conc.
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