Hey peeps, so whats good? We have been having some labs for biochemistry and the most recent one was to determine the percentage of ascorbic acid (vitamin c) in fruit juice. I went on you tube and found various methods used to demonstrate this and i picked the following so that you could compare the video’s method and the next method I would explain to you.
So ascorbic acid is a water soluble vitamin which is needed for growth and repair of tissues. The vitamin also helps the body to make collagen and a lack in it can lead to a disease known as scurvy. In this experiment the juice is acidified with glacial acetic acid and then water is added to this solution Metaphosphoric acid is then added to this mixture and the solution transferred into a burette. Metephosphoric acid is composed of phosphorous and three oxygen. The acid serves to protect the vitamin c in the soloution against oxidation by the atmosphere. The solution in the burette is then titrated against dichlorophenolindophenol. This is a violet-blue solution which turns colourless when it is reduced. So once enough ascrobic acid is added to the conical flask the colour change will occur and the titre value can be taken. (Titre- difference between final and initial volume of the burette after the titration).
In the video the ascorbic acid in the presence of iodine is oxidized. Sodium thiosulphate is the oxidizing agent.
So it is the same concept but different reagents. In biochemistry there is not only one way to get to the finish line. The race is not for the swift but those who endure to the end.
Hope I was of some help people. Enjoy!