experiment to estimate the content of ascorbic acid

7/28/2019 experiment to estimate the content of Ascorbic Acid

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Ascorbic Acid Saturation Test&

Determination of Ascorbic Acid Content

of Some Fruit Juices.

376 BCH

Miss Tahani Al-shehri


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OBJECTIVES

To measure the concentration of ascorbic acidurine sample after administration of a dose ofascorbic acid.


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Introduction

Vitamin C is a water-soluble vitamin that isnecessary for normal growth and development.

Water-soluble vitamins dissolve in water. Thebody cannot store them. Leftover amounts of thevitamin leave the body through the urine. That

means you need a continuous supply of suchvitamins in your diet.


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Introduction

Ascorbic acid Dehydroscorbic acid


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Functions of Vitamin C

Vitamin C is required for the growth and repairof tissues in all parts of your body.

It is necessary to form collagen

Vitamin C is one of manyantioxidants in thebody

* The body does not manufacture vitamin C on itsown ( Why ? )


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Deficiency of Ascorbic acid

Scurvy


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ascorbic acid saturation test

Administered ascorbic acid is taken up by thetissues until they are saturated, after which thereis a sharp rise in the urinary ascorbic acidexcretion.


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Principle

In a protein-free filtrate of plasma or urine,ascorbic acid has the property of decolorizing ablue dye, dichloro-phenolindophenol DCPIP andthe amount that is decolorized is a measure ofthe amount of the vitamin C present.


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Principle


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Notes

Estimation of urinary ascorbic acid when the

specimen arrives in the laboratory must carried outimmediately .

Ascorbic acid is unstable in urine and a specialbottle containing 20 ml of glacial acetic acid must

be used for the urine collection.

Glacial acetic acid is corrosive and any spilt on theskin should immediately be washed off with a largevolume of water.


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METHOD

1. Measure the volume of the urine.

2. Pipette 5 ml of urine into a 100 ml volumetricflask and make up to the mark with 5% aceticacid.

3. Pipette 5 ml of DCPIP dye solution into a

conical flask.4. Titrate with standard ascorbic acid solution

(0.02 mg/ ml) until the solution just becomescolourless.


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METHOD cont..

5. Calculate how many milligrams of ascorbicacid are equivalent to 5 ml of the dye solution.

6. Pipette 5 ml of dye into a conical flask.

7. Titrate with the dilute urine sample. Thetitration must be done very rapidly, otherwise

slow-reacting reducing substances present inthe urine will contribute to the reduction of thedye

8. Repeat the titrate and take the average


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METHOD cont..

9. Calculate how much ascorbic acid present insample urine diluted

10. Calculate milligrams of ascorbic acid in totalurine collected .


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Results

Volume of urine =.

Mg of ascorbic acid equivalent to 5 ml of the dyesolution =

The conc. Of ascorbic acid present in sampleurine diluted =

Mg of ascorbic acid in total urine collected=

experiment to estimate the content of ascorbic acid

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