0.1% DCPIP

[Sassi]

Hello labbies!

Do you know if yr 8s are allowed to use this???

[Slartibartfast]

Dichlorphenolindophenol: Moderately toxic if ingested conc. Used to test for vitamin C (solution turns colourless). Your % will be fine.

NR: Not a regulated dangerous good. If you have it you are able to use it for pracs involving Year 11 & 12 students. (not year 8 as I had typed earlier)

[Loopy]

I'm confused folks...(which is not very difficult to achieve let me tell you!)

CSIS lists DCPIP only for Senior use. What gives?

Lou P.

[Slartibartfast]

Doh! I'm sorry I'm having a brain meltdown. I misread the catagory user codes for the said solution.Your correct loopy. Seniors only.

[Sassi]

Thanks heaps guys! I thought so, but apparently it was a compulsary prac in the yr8 syllabus. I guess they will have to do it as a demo then... Oh well, less for me to prepare then!

[Courtney]

This may be a silly question but what is CSIS? We currently do the vit C test with yr 9/10 life science classes.

[Sassi]

CSIS = chemical safety in schools. Its guidelines for safe use and storage of chemicals in schools, put together by the NSW Dept of Edu and training

[Labbie]

Courtney, I believe you in Tas do not use the CSIS, but again, their is talk we may go nation wide with CSIS, but that could take years.

[Courtney]

Ahhh, thank you very much, I am a little less confused now!

[Loopy]

Here is a recipe as given by Mother for Vitamin C testing without using DCPIP and I can say it works a treat!

"Materials required:
Iodine Solution
Starch Solution(1 teaspoon of cornflour dissolved in 1 cup boiling water) made in advance and leave to cool.
This solution is enough for about 8 students.
Test Tubes(enough for each food tested)
Different types of juices e.g.orange juice.lemon juice freshly squeezed.Commercially bought juices and juice drinks,vegetable juice.and Vitamin C tablets to be crushed.
Method:
1. Predict whether each food/drink will contain Vitamin C
2. Place paper towel/newspaper on bench
3. Using an eye dropper put about 20 drops or half teaspoon of starch solution in test tube.
4.Then add 1 or 2 drops of Iodine-the water should turn slightly blue.
5. Add food/drink to the starch-iodine solution.
6. If the blue disappears the food contains Vitamin C. "

So thanks again to Mother and I hope this helps!

Lou P.

[Sassi]

Great! A million thanks each to Loopy and Mother My teachers are very happy indeed!

[smiley]

Actually you can use the Vit C tablet to standardardise your results. Vit C tablets come in 100, 500 or 1000mg. Whichever one you have, crush it and mix it with 100mL water. Then do your iodine/starch reaction, counting drops. Then you can compare that with how many drops your standard solution took to change colour with the other foods being tested.

Cheers, K

[trish armstrong]

Hi, sorry to bring this back up, this is the first time I have had to use this DCPIP. For seniors.
Want to test it for myself, do you have to heat it after you add it to Vit C solution?
I have disolved a Vit C tablet and added a few drops of DCPIP to the solution and the result was that the blue of the DCPIP went clear. So now it looks the same as the solution of Vit c when I started.
Is that the result and how do we convert this to using real food.
Please help, so I can learn. I am abit confused on the earlier posts about using the starch, and the DET has blocked a lot of google sites on this for some unknown reason
Trish

[Ev]

Trish,
Do you have a copy of The Laroratory by Dungey? There is a lengthy explanation in there.

Ev

[RosalieM]

The Vitamin C turns the DCPIP back to clear. The way we do it is we have orange juice of various qualities. The kids measure out 10ml and then count drops of DCPIP one by one until they don't disappear to make a comparison. More vitamin C in the orange juice means more drops of DCPIP before it doesn't go clear anymore. You need to make the DCPIP fresh and Vitamin C decomposes fairly quickly after opening (i read that somewhere...) so the juice should only be opened fresh at the start of the lesson. If you want to take it further, you can use a known concentration of vitamin C (such as from a tablet) and count the drops and then calculate how much vitamin c is in the juices by comparing the drops needed in the unknown to the known. I hope this make sense and helps you.

[rosaliemb]

Thanks for all the info on DCPIP. It came just at the right time as one teacher wants her students to do some sort of comparitive testing of vitamin C content in foods. I have to work out how.
Now, I have DCPIP tablets which say "each tablet has a titration value equivalent to 1ng of ascorbic acid". So what volume of water do I dissolve the tablet in to get 0.1%, presuming this is the strength RosalieM used in her experiment description. OR more details?
Best wishes to all
Rosalie (another one)

[smiley]

Hey Rosalie,

We do the Vitamin C thing with a Iodine/Starch titration. To make a standard solution we crush a 1000mg tablet and make a 1 litre solution with it. Therefore, there is 1mg per mL.
It is a fairly easy alternative, and gets past the colour change issue when kids are determining VitC in colourful foods like strawberries etc. Method is attached.

[Lyn]

Our Y8 has just finished doing basic food tests and have used the DCPIP solution as specified in their textbook Science Dimensions 2 (p.183). The textbook says nothing about it being used as a teacher demonstration. The DCPIP tablets I have are an indeterminate age but still function. The printed information that comes with it has two different methods of making a solution.
Rapid Method - dissolve 1 DCPIP tablet in 30mls of distilled water.
Quantitative Method - dissolve 1 DCPIP tablet in 50ml of distilled water.
Both the above tests are for testing urine.
The method I have used is as described in the Laboratory Manual by B.Dungey which is 1 DCPIP tablet dissolved in 100ml of distilled water.
Lyn.