quantitive estimation of ascorbic acid

• Fatigue
• Insomnia
• Minor capillary bleeding
• Scurvy

Materials:

Method:

1. Use a syringe to transfer 1.0cm3 of DCPIP solution into a test tube.

2. Fill another 1cm3 syringe with 0.1% ascorbic acid solution and, keeping the end of the needle below the surface of the DCPIP, and then carefully add the ascorbic acid solution until the DCPIP is decolourised. Do not shake the mixture; it may gently stirred using the needle.

3. Record the volume of ascorbic acid solution required to decolourise the DCPIP.

4. Afterwards repeat this test with 1.0cm3 of DCPIP solution and a sample of fruit juice e.g. lemon.

5. Record the volume of fruit juice required to decolourise the DCPIP.

6. Finally repeat this procedure with samples of different fruit juices.

Results:

Original Results:

This is my original results table showing the volume required to decolourise the DCPIP solution measured in cm3. It also shows that I did the experiment twice.

Summary Results:

This table shows my average results. To work this out I used my previous results and then divided this by 2 since I got a pair of results from doing the experiment twice.

Concentration of ascorbic acid in the sample of different fruit juices:

This table is showing the concentration of ascorbic acid in each of the fruit juice sample. To work out the concentration I divided the average volume of ascorbic acid solution required to decolourise the DCPIP solution by the average volume of the fruit juice required to decolourise the DCPIP solution.

The Graphs:

I did 2 bar charts which represent my results. My first graph is a bar chart showing the volume required to decolourise the DCPIP solution against the samples of fruit juices. My other graph is showing the concentration of ascorbic acid against the sample of fruit juices.

Conclusion:

My conclusion is that the smaller the volume required for the fruit juices to decolourise the DCPIP solution the higher the concentration of ascorbic acid that is present. My graph gives evidence for this for my results showed that grapefruit had the smallest volume required to decolourise the 0.1% DCPIP solution. Also my results showed that the fruit sample with the highest volume to decolourise the DCPIP solution had the lowest concentration of ascorbic acid present (which was the pineapple in my experiment). I think this is because of the pineapple having a smaller concentration of ascorbic acid means that a higher volume of it is used to decolourise the DCPIP solution. This also is due to the lack of vitamin C that it has.