Determination of the concentration of vitamin C by using DCPIP test

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Practical investigation
Determination of the concentration of vitamin C
by using DCPIP test
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Apparatus required
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Materials required
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DCPIP Dichlorophenol-indophenol
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Juices from different sources
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Squeeze the fruits and get the juices
in this way?
or in this way?
or
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Juices must be freshly prepared
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Which one of them gets more vitamin C ?
Notice that while Kiwi fruit is rich in vitamin
C, it is not a citrus fruit.
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Citrus fruits are rich in vitamin C.
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A few steps in titration
Juice titrates against DCPIP solution
DCPIP solution changes to pink colour
DCPIP solution changes to colourless
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How to transfer 1 ml of DCPIP solution to a test
tube by using pipette?
How to titrate vitamin C solution against 1 ml of
DCPIP solution
How to titrate juice against 1 ml of DCPIP
solution
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Precaution
Drop size must be constant. Press the squeezing
pipette gently.
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The pipettes must be carefully cleaned by
distilled water and rinsed with the solution to
be taken up.
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During determination, the dropper must be held
vertical and the fruit juice should not flow down
the side of the test tube.
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At least three experimental trials must be taken
and the average number of drops calculated.
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Question
To decolourize the DCPIP solution
Which one gets more vitamin C in it ?
Answer juice A
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How to work out the concentration of vitamin C in
different juices?
Concentration of standard solution
Concentration of vitamin C in fruit juice
Volume of standard solution Volume of fresh
juice
X
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Notice that mathematically, it is an inverse
relation, ?? !