IA on effect of temperature on polyphenol (tannins) of green tea, using potassium permanganate titration (Lowenthal permanganate).

1. Effect of temp on polyphenol (tannins) of green tea, using potassium permanganate titration (Lowenthal permanganate)
Polyphenols are antioxidants :
- found in blackberry, wines, blueberry, cranberry, grapes, cider, citrus fruits
- tannins (TA), flavonoids, catechins, EGCG, EGC, ECG.
- quantification using potassium permanganate (titration)
- using indigo carmine indicator (blue) to green yellow
Antioxidants that can be quantified using permanganate titration
Procedure:
Potassium permanganate 0.004M (0.02N) was prepared.
0.1% (w/v) indigo carmine indicator 0.1g in 100ml acidified with H2SO4.
End point is greenish yellow.
Limitation : antioxidants like Vit C will be included
Assumption - all antioxidants esp polyphenol will be quantified.
Effect of temp (80,83,88,90,99) will be studied, using water bath.
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1g green tea weighed and placed in tea bag
Green tea was chosen

2. 1g green tea weighed and placed in tea bag
Indicator change from blue to greenish yellow
Procedure:
Potassium permanganate 0.004M (0.02N) was prepared.
0.1% indigo carmine indicator 0.1g in 100ml acidified with H2SO4.
1g tea weighed and placed in tea bag in flask.
20ml water heated to diff temp in water bath.
1g tea and 20ml heated water were added together for 3 mins.
After 3 mins, 2 ml of tea sol was taken out. 2ml water and 200ul of
indigo carmine were added. Blue sol obtained.
Titrated with 0.004M KMnO4 until end point is seen.
Ini and final vol recorded.
Blank titration was done – 2 ml water and 200ul indicator without any antioxidants
Temp/C Ini
vol
Final
vol
Vol (X)
KMnO4
Polyphenol
mg/L TA
80 8.8 9.6 0.8 498
83 1.5 2.3 0.8 498
88 7.2 8.1 0.9 581
90 10.5 11.6 1.1 748
99 12.4 14.6 2.2 1662
Blank (Y) 7.0 7.2 0.2 --
End point
Green tea at diff temp
Total polyphenol (mg/L TA) = (X – Y) x 4.157 x conc KMnO4 (N) x 10000
(0.8 - 0.2) x 4.157 x 0.02 x 10000 = 498mg/L
Formula that can be used. Click here for reference
Total polyphenol (mg/L TA) = (X – Y) x 4.157 x conc KMnO4 (N) x 10000
4.157 – conversion factor to TA equivalents
10000 – conversion factor from % to mg/L of TA.
N – normality for KMnO4 which is 0.02N or 0.004M
X – Vol KMnO4 used
Y – Vol blank titration
TA – tannic acid
Effect of temp on polyphenol (tannins) of green tea, using potassium permanganate titration (Lowenthal permanganate)

3. End point
Total polyphenol (mg/L TA) = (X – Y) x 4.157 x conc KMnO4 (N) x 10000
(0.8 - 0.2) x 4.157 x 0.02 x 10000 = 498mg/L
Formula that can be used. Click here for reference
Total polyphenol (mg/L TA) = (X – Y) x 4.157 x conc KMnO4 (N) x 10000
4.157 – conversion factor to TA equivalents
10000 – conversion factor from % to mg/L of TA.
N – normality for KMnO4 which is 0.02N or 0.004M
X – Vol KMnO4 used
Y – Vol blank titration
TA – tannic acid
Effect of temp on polyphenol (tannins) of green tea, using potassium permanganate titration (Lowenthal permanganate)
1g green tea weighed and placed in tea bag
Temp/C Ini
vol
Final
vol
Vol (X)
KMnO4
Polyphenol
mg/L TA
80 8.8 9.6 0.8 498
83 1.5 2.3 0.8 498
88 7.2 8.1 0.9 581
90 10.5 11.6 1.1 748
99 12.4 14.6 2.2 1662
Blank (Y) 7.0 7.2 0.2 --
0
0.5
1
1.5
2
2.5
80 83 88 90 99 Blank
(Y)
Vol
KMnO4
Temp/C
Temp/C vs Vol KMnO4
0
500
1000
1500
2000
80 83 88 90 99
polyphenol/mg/L
of
TA
Temp/C
Temp/C vs polyphenol/mg/L
of TA
0
500
1000
1500
2000
70 80 90 100 110
Polyphenol/mg/L
of
TA Temp/C
Temp/C vs
polyphenol/mg/L of TA