DCPIP Solution

Loopy · Post by **Loopy** » 21 Jun 2006, 15:35

I have recently had the request for DCPIP Solution for testing for vitamin C but have discovered that it is not readily available ie phosphoric acid not available to make up the DCPIP soln. Has anyone got any ideas/suggestions/alternatives/recommendations for this basic food test?
Lou P.

estelle · Post by **estelle** » 22 Jun 2006, 09:27

I had a request yesterday for DCPIP. Luckily I had some in my chemical store, it is the first time I have had a request for it in the two years I've been here. If you aren't in a hurry Q stores sell it, item no. 811302 about $19 for a gram but a little bit goes a long way.
Are you using science focus books? We only started using them late last year and this is why I had the request for DCPIP as well as benedicts solution (which I discovered doesn't keep so I don't think it is worth buying as a made up solution unless you use it a lot).
Estelle

Nikki · Post by **Nikki** » 22 Jun 2006, 10:32

Hi Estelle

When you say Benedicts solution could you give me more information please. On another topic stream I have been asking about storage life of chemicals and solutions, some of which have been here quite some time and some solutions that have been made up since before I started working here almost 2 years ago. I am trying to clean out the chem store so that I dont have alot of stuff on the shelves that is no good but also have to be careful as due to the limited funds at our school it may be hard to replace.

Cheers
Nikki

Mother · Post by **Mother** » 22 Jun 2006, 11:38

Hi Nikki
Here is a really simple prac.to test for Vitamin C without using DCPIP.

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.
Student Connections:
Students are able to explore the world of vitamins through this simple experiment.Some points for further discussion and further investigation:
* Were there any surprising results?
* Compare the information on the labels of containers.
*Can you devise a way of testing solid foods?
*Explain the importance of Vitamin C in the diet and why it is important?
*Investigate why Aboriginal people didn't get scurvy before European settlement.(Discuss the background to this question,e.g. which, if any,of the foods tested are native to Australia.
I haven't tried this experiment yet.Would be interested to know what success you had!!
Cheers
Mother

Loopy · Post by **Loopy** » 22 Jun 2006, 12:24

Hi Estelle,
Yes we are using Science Focus as text books although this is the first year we have had year 8 and year 10 (the school only opened in 2004). Glad to know another school is at the same stage as us. Thanks for the tip of Q Stores for DCPIP soln.

Nikki · Post by **Nikki** » 22 Jun 2006, 12:29

Hi Mother

We already do an experiment similar to this using different types of OJ to investigate how much Vitamin C is in each compared to Vit C tablets dissolved. It is very interesting as it is quite clear that fruit drinks have very little vit c and other 100% juices have much more. Most students a quite suprised at how large the difference is.

Cheers
Nikki

Mother · Post by **Mother** » 23 Jun 2006, 10:31

Loopy wrote:I have recently had the request for DCPIP Solution for testing for vitamin C but have discovered that it is not readily available ie phosphoric acid not available to make up the DCPIP soln. Has anyone got any ideas/suggestions/alternatives/recommendations for this basic food test?
Lou P.

Hi Louise
I posted an untested recipe for Vitamin C without using DCPIP but sent it to Nikki instead, sorry.I'm sure you will find it
Mother

Loopy · Post by **Loopy** » 26 Jun 2006, 10:42

Thanks Lee,
I did get your recipe and will definitely give it a go.
Lou P.

estelle · Post by **estelle** » 26 Jun 2006, 11:42

Hi Nikki,
Re the benedicts solution. I did some more research and found that the benedicts solution plus Vit C has to be heated to get a reaction. I tried putting about 3 mL of crushed Vit C and water solution and 3 mL of benedicts solution in a TT and heated it over a bunsen, it turned an orange colour in a short time showing that there is Vit C. So the benedicts solution which the teacher told me was old and didn't react was actually OK.

I also tried the starch/iodine/vit C mix and that works as well. It went from Starch- white to purple after adding the iodine and white again with the addition of a Vit c solution.
Estelle

lada · Post by **lada** » 29 Jun 2006, 14:41

The orange-red colour of heated benedict soln. id a positive test for glucose. Lada

Post by **RosalieM** » 29 May 2007, 13:46

I have had this same problem - needing DCPIP tomorrow! We can hold off till we order some next week, but I was wondering if anyone has tried the iodine and starch experiment suggested in an earlier post. Does it just test for the presence of vitamin c or do you need different amounts to make it change colour? If we test 4 different juices, can we expect that some juices will need more drops than others to have a reaction?
Rosalie

lizzieb · Post by **lizzieb** » 30 May 2007, 09:02

Hi Rosalie,

I have some DCPIP in stock - been here longer than my 4 years, so don't know how 'good' it is.
Also have phosphoric acid.
Give me a ring if you want some.

Liz

smiley · Post by **smiley** » 30 May 2007, 09:31

Our seniors use Vit C tablets to make a standard solution. If you use a 1000mg Vit C tablet, crush it and make a 100mL solution, then this can become your standard. Then you can test, for example, 10mL of the standard and compare 10mL of other juices, by counting how many drops/mLs it takes to change the purple colour of the starch/iodine solution back to white. The more it takes, obviously the less Vit C is present.

Cheers, Kristin

Alice · Post by **Alice** » 30 May 2007, 10:26

Hi everyone

We've done the Vit C prac for many years.

We use 2,6, Dichloroindophenol (DCPIP) powder. The powder has been on the shelf over 10 years and is still OK. You can buy the powder from Chem Supply.

The recipe we use is:

0.1g DCPIP solid in 100g distilled water. You have to make fresh as it deteriorates. (over a number of weeks) It's blue and goes clear if Vit C is present.

Alice

Robbie · Post by **Robbie** » 30 May 2007, 11:34

We are using DCPIP bought in 1984 and it is still OK. However, we only make it up with water. Why do you need Phosphoric Acid? Just curious...

Benedict's bought in the 1980s is still giving good results.

Robbie

Loopy · Post by **Loopy** » 31 May 2007, 09:32

Hey Robbie,
The phosphoric acid is part of the recipe given in "The Laboratory" for an extraction solution. I didn't read down far enough to see just the solution recipe. Regardless, CSIS rates DCPIP solution as a year 11-12 use only. I think the Starch/Iodine/Vit C experiment given by Mother has been the easiest option for the juniors and works well.
Lou P.

Post by **RosalieM** » 08 Jun 2007, 10:19

Hi all,
I followed the directions given by Mother earlier in this topic and it didn't work at all. Any ideas on why this might be? I think we will go back to using DCPIP next year!
Rosalie

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It didn't work!