"
Vitamin C Concentration Assay
(By Anne Marie Helmenstine, Ph.D)
1. Add 25.00 ml of vitamin C standard solution to a 125 ml Erlenmeyer flask.
2. Add 10 drops of 1% starch solution.
3. Rinse your buret with a small volume of the iodine solution and then fill it. Record the initial volume.
4. Titrate the solution until the endpoint is reached. This will be when you see the first sign of blue color that persists after 20 seconds of swirling the solution.
5. Record the final volume of iodine solution. The volume that was required is the starting volume minus the final volume.
6. Repeat the titration at least twice more. The results should agree within 0.1 ml.
7. You titrate samples exactly the same as you did your standard. Record the initial and final volume of iodine solution required to produce the color change at the endpoint.
