Ascorbic Acid as Antioxidant

Abstract

The use of ascorbic acid as a food additive is well known in health fields because it is a natural substance that is present in many fruits and vegetables, especially citrus fruits. Its beneficial actions in living beings is frequently associated with its inhibitory action of oxidative biochemical processes. On the other hand, it has also been found to inhibit the corrosion of metal alloys despite the fact that the metals in contact with acidified aqueous media react with the hydrogen ions to give molecular hydrogen and metal derivatives.When checking in our laboratory that the juice of different citrus fruits and solutions of ascorbic acid and citric acid cause this effect on different technological metals and also check the protective action of ascorbic acid on the superficial atmospheric oxidation of carbonaceous particles, such as those of graphene or graphite, the idea arose to analyze the inhibitory effect of the anodic solution of a known system easy to study using electrochemical techniques that could be model of the inhibitory mechanism caused by ascorbic acid. In this work the inhibitory effect of ascorbic acid on copper anodic dissolution is studied by means of spectrum-electro-gravimetric techniques, since the Cu / acid solution system is a relatively simple model of possible utility to interpret the inhibitory effect of ascorbic acid on other more complicated systems.The spectro-electro-gravimetric studies are useful to explain the corrosion and electrodeposits kinetics of copper in acid media [1,2]. If we analyze the mass evolution at open circuit potential of copper in sulfuric and ascorbic media, it is showed that in the chase of sulfuric media the mass decreases, but the process is slower at the end attending to the passive layer formation. However, when we analyze the mass evolution for the ascorbic acid dissolution, we can see that the mass grows proportionally to the acid concentration. First, takes place the adsorption on non-charged species over the electrode surface. This fact increases the rigidity over the electrode surface decreasing the values of the motional resistance. When the electrochemical process begins, there is an accumulation of copper ions over the electrode surface. The accumulation of copper ions allows the catalytic oxidation of the ascorbic acid.1) D. Giménez-Romero, C. Gabrielli, J.J. García-Jareño, H. Perrot, F. Vicente Electrochemical quartz crystal microbalance study of copper electrochemical reaction in acid medium containing chlorides,. J. Electrochem. Soc. 153 (2006) J32-J39.2) A. Cuenca, J. Agrisuelas, J.J. García-Jareño, F. Vicente, Oscillatory Changes of the Heterogeneous Reactive Layer Detected with the Motional Resistance during the Galvanostatic Deposition of Copper in Sulfuric Solution, Langmuir.31(46) (2015) 12664-12673.