EFFECT OF PH ON ANTIOXIDANT CAPACITYGroup Members: Ng Aik Yang (2A1) Siah Zhi Xuan (2A1) Darryl Hwang (2A2) Timothy Loe (2A3)

HYPOTHESIS

Hypothesis : The higher the pH, the faster the reaction between antioxidants and free radicals.Null Hypothesis:pH does not affect antioxidant capacity.

RATIONALE

To investigate if Alkaline water really helps antioxidants function better to counter the free radicals in our body

METHODOLOGY

Chemicals used:•Different kinds of antioxidants (aqueous). E.g. red tea, ginger tea, vitamin C solution•2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS)•Hydrochloric acid (HCl)•Sodium Hydroxide (NaOH)•Salt Solution (NaCl)

METHODOLOGY

Chemicals needed:• ABTSMolecular Formula: C18H18N4O6S4 . NH3

• Frequently used by the food industry and agricultural researchers to measure the antioxidant capacities of foods• Blue solution, but converted to a colorless solution

after reactions with antioxidants

METHODOLOGY

Put 3ml of ABTS into a cuvette

Test for light absorbance level by putting the cuvette into the UV-Vis Spectrometer, and record the results

Add 25µl of antioxidants of varying pH level into the cuvette of ABTS

1 minRecord the light

absorbance level

WHAT HAPPENS

• Antioxidants from the solution will react with the free radicals in the ABTS

• The ABTS would turn from blue to colorless gradually as the antioxidants react with the ABTS.

• The higher the colour intensity of the solution, the more light will be absorbed.

• Thus, by measuring the light absorbance, we can see how much of the ABTS has reacted.

VARIABLES

Constant Independent DependentVolume of ABTS(3ml)

pH value of antioxidant

Amount of light absorbed(Amount of ABTS that reacted in 1min)

Volume of antioxidant(25µl)Duration of reaction (1min)

EXPERIMENT PROCEDURES

• 4 beakers of the various antioxidants with varying pH values (adjusted with the chemicals, NaOH and HCl)

• pH meter used to measure pH• 3 beakers with NaCl solution (control)• One unchanged solution• Add in 3 ml of ABTS into cuvettes and test the

absorbance • Put the 25µl of antioxidant in, and start timing • And after shaking, put it in the UV-Vis Spectrometer

and wait for 1min • Observe and recorded results obtained

*Light absorbance = (light absorbance of ABTS with chemicals - original light absorbance of ABTS) divided by original light absorbance of ABTS × 100%

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GINGER

2 3 4 5 6 7 8 9 101.50%

2.00%

2.50%

3.00%

3.50%

4.00%

4.50%

5.00%

5.50%

6.00%

6.50%

7.00%

7.50%

8.00%

Ginger

Mean

pH

Ligh

t Ab

sorb

ance

• Has a trend that a high pH leads to a higher light absorbance, showing that it has a higher antioxidant capacity

• Light absorbance relatively low

GINGER

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RED TEA

2 3 4 5 6 7 8 9 10 1165.00%

67.50%

70.00%

72.50%

75.00%

77.50%

80.00%

82.50%

85.00%

87.50%

Red Tea

Mean

pH

Ligh

t Ab

sorb

ance

• Shows a similar trend with Ginger• Error bars can show that range of results defy trend• Subjective conclusion

RED TEA

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CHRYSANTHEMUM TEA

4 4.5 5 5.5 6 6.5 7 7.5 880.00%81.00%82.00%83.00%84.00%85.00%86.00%87.00%88.00%89.00%90.00%91.00%92.00%93.00%94.00%95.00%96.00%97.00%98.00%

Chrysanthemum Tea

Mean

pH

Ligh

t Ab

sorb

ance

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TIE GUAN YIN

2 3 4 5 6 7 8 9 1093%

94%

95%

96%

97%

98%

99%

100%

Tie Guan Yin

Mean

pH

Ligh

t Ab

sorb

ance

• Both showed two similar dips in terms of graphs.• Error bars show that results between the 5 tests we

took were rather consistent• In this case, pH does not affect antioxidant capacity

TIE GUAN YIN

CHRYSANTHEMUM TEA

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GINGER (EXTENDED)

2 3 4 5 6 7 8 9 10 11 12

-10.00%

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

Ginger Tea

Mean

• General trend shows that antioxidant capacity decrease then increases slowly throughout, with a drastic increase between pH 9.7 – pH 10.5

GINGER (EXTENDED)

CONCLUSION

• pH does not affect antioxidant capacity for antioxidant bodies like tea

• Different antioxidant bodies might react differently to the ABTS

• Alkaline water does not really help antioxidants function better to counter free radicals in our body

• Acid-base homeostasis, part of human homeostasis concerning the proper balance of pH, already adjusts the body for anti-oxidant capacity to work at its peak.

• Our results fulfill the null hypothesis which would be that pH does not affect antioxidant capacity.

CHALLENGES WE FACED

• Adjustments of the pH for antioxidant bodies such as fruits

• Varying the pH by the number of drops instead

Problems faced Actions taken Effectiveness and Improvements

New to the concepts and barely understood anything when we embarked on the project

We had to do a lot of research to understand facts as well as learn how to use lab apparatus such as the UV-Spectrometer

We picked up new skills during the course of the project

Bumps along the project, such as the adjustments of pH for certain antioxidant bodies

Improve the quality of other experiments in order to make up for the losses of “quantity”

Allowed us to have concrete explanations for the conclusions, training our critical thinking and analytical skills.

GENERAL REFLECTIONS

WORKS CITED

• ABTS. In Wikipedia. Retrieved from http://en.wikipedia.org/wiki/ABTS

• Wikipedia. [Image ABTS molecule structure]. Retrieved from http://en.wikipedia.org/wiki/File:ABTS.png

• Fairy-water watertec Co. Ltd. [Image alkaline water machine]. Retrieved from http://www.ro-filter.com/images/products/ALKALINE_WATER_IONIZER_MANUFACTURER.jpg

THANK YOU FOR YOUR KIND ATTENTION!