Laboratory Report: Experiment 3 Analysis of commercial vitamin C tablets Name: Cheung Chun Hin, Harry Class: 6L 12 Date: 14-10-2009 Objective: To determine the content of vitamin C in commercial tablets redox titration and back titration Principle of method: Vitamin C, which is ascorbic acid, reacts with iodine rapidly in an acidic medium. We will use this reaction in conjunction with a starch indicator to determine the number of moles of Vitamin C present. The solution stays colorless until all the ascorbic acid has been oxidized. The objective of this study was to determine the vitamin C content in artificially prepared juices of orange, grapes, apple and mango juices of two different local companies i. Iodine is chosen because it is a weak oxidizing agent so it will not oxidize substances other than the ascorbic acid in the sample of fruit juice. At large doses vitamin C causes problems such as diarrhea and the induction of kidney stones.
Procedure for Determining Vitamin C Purpose The goal of this laboratory exercise is to determine the amount of vitamin C in samples, such as fruit juice. The end point of the titration has been achieved when the blue color remains in the solution for at least 30 seconds. Proper techniques and calculation regarding blank titration is also shown. The titration can be performed using just iodine solution and not iodate, but the iodate solution is more stable and gives a more accurate result. Ascorbic acid levels in matured ripe and unripe sweet oranges Citrus sinensis , lemons Citrus lemonum and grapefruits Citrus grandis were investigated using redox titration involving oxidation-reduction conversion of ascorbic acid.
It has several types like acid-base titrations and redox titrations. Conversely, the substance that accepts gains electrons experiences a decrease in oxidation number and is said to be reduced. Then add drops of iodine solution until you notice a color change; observe the color. To detect the end point you will add starch to the solution in the flask at the beginning of the titration. Add water and protons to the equations as appropriate. Vitamin C is also involved in iron metabolism, and many believe that very large doses are effective in preventing or curing the common cold. Many fruits and vegetables contain vitamin C, but cooking destroys the vitamin, so raw citrus fruits and their juices are the main source of ascorbic acid for most people.
The result reveals that G. The method used in the present study was found to be cheap, accurate and could be easily practice in routine analysis. Determination of Vitamin C by an Iodometric Titration Purpose: The goal of this lab is to determine the concentration of vitamin C in juices and Real Lemon. There was only a small change in all the biochemical parameters studied on storage up to the period of 4 hrs. Titrations are a common laboratory method — and factorial method — of chemical analysis that is widely used to determine unknown concentrations of a reactant. Many fruits and vegetables contain vitamin C, but cooking destroys the vitamin, so raw citrus fruits and their juices are the main source of ascorbic acid for most people. For each titration calculate the number of moles of ascorbic acid in 1 mL of juice.
Using the burets properly dispence 2. Its aqueous solutions are rapidly oxidized by air; this reaction is accelerated in basic solution and in the presence of iron and copper ions. In chemical analysis, the amount of an object is determined using a process called titration. The endpoint or equivalence point is at the appearance of the beige color. This experiment tested for the vitamin C content in fresh fruit juices and commercially sold drinks. Pauling 1901 - 1994 received the Nobel Prize in Chemistry in 1954, the Nobel Prize for Peace in 1962, and barely missed the Nobel Prize in Biology that was awarded to Watson and Crick. Vitamin C is a fairly strong reducing agent and decolorizes many dyes.
The limit of quantitation was 1. A deficiency of vitamin C results in a disease called scurvy, which is characterized by weakness, swollen joints, bleeding gums and loose teeth, and delayed healing of wounds. Add 1 mL of starch indicator solution, 1 mL of 6 M acetic acid, and 1. We found that the lowest content of vitamin C was 617. Excess iodine I¬2 reacts with iodide ions I- to make a triiodide ion I3- which forms a very intense blue color when it comes into contact with starch. Among all fresh juices studied mango was found to have highest total sugar content 14.
The maximum concentration of Ascorbic acid was found in green chilli: i. As long as there is ascorbic acid present iodine will react with it. It was the first vitamin to be prepared in pure form. Theoretical Background Whereas acid-base reactions involve the transfer of a proton, oxidation-reduction or redox reactions involve the transfer of electrons from one substance to another, resulting in changes in oxidation numbers of two or more elements in the chemical reaction. Ball-and-stick model of the L -ascorbic acid vita. This experiment makes use of an oxidation-reduction reaction in which elemental iodine oxidizes ascorbic acid.
Moreover, it was also observed that the artificial preserved juices contain lesser amounts of vitamin C as compare to freshly prepared juices. It is involved in the synthesis of collagen, which constitutes about one-third of the total protein in the human body. Be sure to label the flasks correctly so that you know the exact concentration of juice in each flask. The reason for waiting 30 seconds is that some blue color might form before ascorbic acid has a chance to react with the iodine; if so, it will take a little while for ascorbic acid to react with the iodine that was in the starch-iodine complex. Spectrophotometric method used in this study was based on the kinetic reaction between Vitamin C and methylene blue. Since vitamin C is a weak acid and also a good reducing agent, either type of reaction might be used. Introduction: Although most mammals can synthesize vitamin C, or ascorbic acid C6H8O6 , from sugars, man must ingest considerable quantities of this substance.
Vegetables are generally boiled for cooking or stored in refrigerators. All other rankings in the hypothesis were correct. If there are solid parts, filter them before titration. Chemistry of Vitamin C The chemical name for vitamin C is L-ascorbic acid. You can assert that, if the solution holds its color for 30 seconds, you have reached the endpoint. Ascorbic acid vitamin C is a water-soluble micronutrient required for multiple biological functions. These results showed that freezing or boiling of vegetables causes significant loss of available Ascorbic acid contents, especially boiling.