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How does pH affect the degradation of ascorbic acid (vitamin C)?
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Justin Bowen
How does pH affect the degradation of ascorbic acid (vitamin C)?
Ascorbic Acid is a known antioxidant molecule and its stability has always been an issue especially for pharma industry which often makes use of AA in formulation. Now as much as pH is a culprit in AA degradation, its only one among other factors like solvent, exposure to light/uv, and the nature of solution (viscous/non-viscous). There are quite a lot of studies on stability of Ascorbic Acid like this one
I normally prepare Ascorbic Acid freshly for each experiment, but it would be an interesting experiment to check the stability of AA for an extended time period at different pH values.
Here is an interesting simulation demonstrating degradation of Ascorbic Acid.
Ascorbic Acid is a known antioxidant molecule and its stability has always been an issue especially for pharma industry which often makes use of AA in formulation. Now as much as pH is a culprit in AA degradation, its only one among other factors like solvent, exposure to light/uv, and the nature of solution (viscous/non-viscous). There are quite a lot of studies on stability of Ascorbic Acid like this one
I normally prepare Ascorbic Acid freshly for each experiment, but it would be an interesting experiment to check the stability of AA for an extended time period at different pH values.
Here is an interesting simulation demonstrating degradation of Ascorbic Acid.
A comment above cites a publication claiming a role for the hydrogen ion in the decomposition of Vitamin C.
I would agree especially if a low pH fosters a Fenton/Fenton-like chemistry. The latter could proceed in the presence of transition metals impurities, which can engage in Fenton chemistry liberating hydroxyl radicals, directly attacking Vitamin C and consuming H+. The chemistry is further promoted in the presence of light/UV (Photo-Fenton).
Also, a role for oxygen leading to reactive oxygen species (like H2O2 which can feed a Fenton reaction).
Dust particles can be rich in metal oxides and air exposure can also be a source of water vapor. So just frequent opening of a container may accelerate decomposition.
Also, elevated temperatures, in general, could impact redox reaction rates, so cold/dry storage may assist in limiting the impact of a reduction of pH on Vitamin C in the presence of metal impurities and exposure to air/water/dust and possible elevated temperatures.
A comment above cites a publication claiming a role for the hydrogen ion in the decomposition of Vitamin C.
I would agree especially if a low pH fosters a Fenton/Fenton-like chemistry. The latter could proceed in the presence of transition metals impurities, which can engage in Fenton chemistry liberating hydroxyl radicals, directly attacking Vitamin C and consuming H+. The chemistry is further promoted in the presence of light/UV (Photo-Fenton).
Also, a role for oxygen leading to reactive oxygen species (like H2O2 which can feed a Fenton reaction).
Dust particles can be rich in metal oxides and air exposure can also be a source of water vapor. So just frequent opening of a container may accelerate decomposition.
Also, elevated temperatures, in general, could impact redox reaction rates, so cold/dry storage may assist in limiting the impact of a reduction of pH on Vitamin C in the presence of metal impurities and exposure to air/water/dust and possible elevated temperatures.
Ascorbic Acid is a known antioxidant molecule and its stability has always been an issue especially for pharma industry which often makes use of AA in formulation. Now as much as pH is a culprit in AA degradation, its only one among other factors like solvent, exposure to light/uv, and the nature of solution (viscous/non-viscous). There are quite a lot of studies on stability of Ascorbic Acid like this one
I normally prepare Ascorbic Acid freshly for each experiment, but it would be an interesting experiment to check the stability of AA for an extended time period at different pH values.
Here is an interesting simulation demonstrating degradation of Ascorbic Acid.
Ascorbic Acid is a known antioxidant molecule and its stability has always been an issue especially for pharma industry which often makes use of AA in formulation. Now as much as pH is a culprit in AA degradation, its only one among other factors like solvent, exposure to light/uv, and the nature of solution (viscous/non-viscous). There are quite a lot of studies on stability of Ascorbic Acid like this one
I normally prepare Ascorbic Acid freshly for each experiment, but it would be an interesting experiment to check the stability of AA for an extended time period at different pH values.
Here is an interesting simulation demonstrating degradation of Ascorbic Acid.
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A comment above cites a publication claiming a role for the hydrogen ion in the decomposition of Vitamin C.
I would agree especially if a low pH fosters a Fenton/Fenton-like chemistry. The latter could proceed in the presence of transition metals impurities, which can engage in Fenton chemistry liberating hydroxyl radicals, directly attacking Vitamin C and consuming H+. The chemistry is further promoted in the presence of light/UV (Photo-Fenton).
Also, a role for oxygen leading to reactive oxygen species (like H2O2 which can feed a Fenton reaction).
Dust particles can be rich in metal oxides and air exposure can also be a source of water vapor. So just frequent opening of a container may accelerate decomposition.
Also, elevated temperatures, in general, could impact redox reaction rates, so cold/dry storage may assist in limiting the impact of a reduction of pH on Vitamin C in the presence of metal impurities and exposure to air/water/dust and possible elevated temperatures.
A comment above cites a publication claiming a role for the hydrogen ion in the decomposition of Vitamin C.
I would agree especially if a low pH fosters a Fenton/Fenton-like chemistry. The latter could proceed in the presence of transition metals impurities, which can engage in Fenton chemistry liberating hydroxyl radicals, directly attacking Vitamin C and consuming H+. The chemistry is further promoted in the presence of light/UV (Photo-Fenton).
Also, a role for oxygen leading to reactive oxygen species (like H2O2 which can feed a Fenton reaction).
Dust particles can be rich in metal oxides and air exposure can also be a source of water vapor. So just frequent opening of a container may accelerate decomposition.
Also, elevated temperatures, in general, could impact redox reaction rates, so cold/dry storage may assist in limiting the impact of a reduction of pH on Vitamin C in the presence of metal impurities and exposure to air/water/dust and possible elevated temperatures.
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