Determination Of Vitamin C Using DCPIP dichlorophenolindophenol


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24.11.2010
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Determination Of Vitamin C Using DCPIP (dichlorophenolindophenol) Essay, Research Paper

A Biological Assay To Determine The Vitamin C Content OF Fresh Fruit Juices Compared To Commercially Sold Juices using DCPIP (dichlorophenolindophenol) as an Indicator

Sinead O’Keeffewords

Table of Contents

Page

Introductionp. 1~3

Materialsp. 3

Proceduresp. 4

Chart Showing the Amount of Fruit Juice Needed in Millilitresp. 5~ 6

To Turn 2ml’s of DCPIP from Blue to Clear with explanation

And analysis

Chart Showing the Different Amount of Each Juice in Millilitresp. 7

Needed to Turn 2ml’s of DCPIP from Blue to Clear with

Explanation

The Amount of Commercially Drinks in Millilitres Needed to p. 8

Fulfill the Required Daily Allowance (RDA) of Vitamin C with

Explanation and analysis

The Amount of Fresh Fruit Juices in Millilitres Needed to Fulfillp. 9

The Required Daily Allowance (RDA) of Vitamin C with analysis

Evaluationp. 9~10

Bibliographyp. 11

Endnotesp. 12

Abstract

Vitamin C (ascorbic acid) is a very important vitamin to the body. Vitamin C promotes healthy teeth and gums, helps absorption of iron, aids in maintenance of normal connective tissue, promotes wound healing, and helps boost the immune system.

With vitamin C being such a useful substance to our bodies, finding good sources of vitamin C is important. Many people today rely on vitamin supplement tablets. But fruit juices, vitamin-supplemented drinks, or vitamin supplemented foods may contain just as much vitamin C as a supplement tablet. Which one is better though, commercially sold drinks or fresh fruit juices? This was the research question: Are commercially sold and popularly consumed juices (in Japan) a good substitute fro fresh fruits in terms of dietary vitamin C?

What this experiment sought to find out was exactly what kind of drink was better in terms of dietary vitamin C. The juices were titrated into a set amount of DCPIP and measuring how many millilitres it took for the DCPIP to turn from blue to clear. The hypothesis was that fresh fruit juices should contain more vitamin C since they had not been heat treated and probably had spent less time on a shelf or being transported than commercially sod drinks. This is important since vitamin C is heat labile. This means that vitamin C is susceptible to change and unstable or that the vitamin C can break down easily if exposed to high temperatures or is kept for a long time on a shelf.

The experiment and results showed that vitamin C is more abundant in fresh fruit juices. This was true for all the juices tested except for lemon. Therefore, it is safe to say that fresh fruit juices tend to contain more vitamin C than commercially bought juices.

Introduction

The body needs a good balance of foods, which must contain carbohydrates, proteins, and fats along with mineral salts, water, fibre, and vitamins. All of these are required in different amounts according to different people. However, there are recommended daily allowances. For example, the recommended daily allowance for vitamin C is 60mg. Vitamins are easily absorbed into the bloodstream from the gut. A diet lacking in any particular vitamin will lead to a deficiency disease. Such diseases are rickets that is caused by lack of vitamin D, and night blindness that is caused by lack of vitamin A. However, these can be remedied by using vitamin supplements if the dietary intake is inadequate.

The aim of the experiment was to see the difference of vitamin C content between fresh fruit juices and commercially sold and popularly consumed juices (in Japan) a good substitute for fresh fruits in terms of dietary vitamin C? This research question was established because in the modern day and age people are too busy, especially in winter, to stock up on fresh fruit and many people rely on commercially sold drinks as a source of vitamins. However, vitamin C, in particular, is known to be labile and therefore likely to be absent from a cooked food diet. In temperate climates, such as Japan or Europe, people ear fresh fruits in summer, but eat tinned, preserved, or cooked foods in the winter. The latter being more susceptible to heat, possibly breaking down the amount of vitamin C in them. This experiment tested for the vitamin C content in fresh fruit juices and commercially sold drinks. This experiment was conducted mostly on citrus fruits because vitamin C is said to be abundant in citrus fruits. The experiment was also performed on non-citrus fruits. The experiment was performed on these two types of fruit drinks because vitamin C contributes to maintaining a healthy body, especially during the winter, when citrus fruits are not in season. AS a result, the amount of vitamin C found in each type of juice would be essential in knowing what drinks to choose during the winter to provide the most or the optimum amount of vitamin C.

Using this information, the following hypothesis was formed. Since vitamin C is labile (meaning susceptible to change and unstable), the commercially sold juices, which have most likely been heat treated and stored in various conditions for various periods of time, should have lower vitamin C content than fresh fruit juices. The commercially sold juices would have most likely been exposed to the conditions leading to the deterioration in the content of vitamin C.

In this experiment the independent variables were the juices that were being tested for their vitamin C content. The volume of each required to make a standard volume of DCPIP (dichlorophenolindophenol) change from blue to clear was measured.1 This was the dependent variable. These juices were first filtered and then titrated using a burette. The fixed variable of the experiment was the amount of DCPIP in each beaker and the room temperature. Both of these remained constant throughout the experiment. The importance of the room temperature being constant and not too high is because otherwise the vitamin C content of any and all the juices may have been altered, since vitamin C is heat labile. Moreover, if the temperature varied, the measured results might have varied also. The DCPIP was carefully made to the concentration of 0.1%. In each case 2 millilitres of DCPIP was taken. The amount, 2 millilitres of DCPIP, was chosen because it was not too much or too little an amount for the reactions to be seen clearly, without taking too much time.

Vitamin C was first discovered because of its absence, during the age of exploration. Sailors on long sea voyages suffered very often from bleeding gums, loosened teeth, and aching joints. These were the symptoms of the disease now called scurvy. It is called scurvy because of “the presence of scurf’s (or scales) on the skin”. It was James Lind that showed that scurvy could be cured and prevented by eating “greens, fresh vegetables, and ripe fruits”. However, it was the Polish biochemist, Casimir Funk, which named the missing group vitamines. He named this because he believed that they contained an amine group. Vitamines means “life amines”. It is from the word that we get the word, vitamin. When vitamin C was finally isolated in 1925, it was given the name ascorbic acid because ascorbic means “no scurvy”.2

Vitamin C has many functions in the body. One of the most important functions is as an antioxidant. This means that it helps prevent oxidation of water-soluble molecules that could otherwise create radicals, which may generate cellular injury, disease, and damage skin cells. It can also be said that it helps neuralise or counteract damage to cells caused by free radicals, which can cause the aging of skin and damage to different cells around the body. Indeed, ascorbic acid (vitamin C) is commonly added to processed food as an antioxidant. 3

In some roles, vitamin C may act as a coenzyme, helping a particular enzyme to do its work, especially where metallic ions play a role. Where there are two oxidation states of metals such as Fe2+ (Iron II) and Fe3+ (Iron III), in the presence of vitamin C the reduced form (Fe2+) prevails. For iron-deficiency anemia, vitamin C helps the absorption of iron (especially the nonheme or vegetable-source iron) from the gastrointestinal tract.4 Specifically, ascorbic acid works as a coenzyme to convert proline and lysine to hydoxyproline and hydroxylysine, both important to the collagen structure. 5

Vitamin C also helps in the stimulation of production of collagen. Collagen is the basis of connective tissue. It is found in ligaments, skin, cartilage, vertebral discs, capillary walls, bones, and teeth. As a result, vitamin C helps heal wound in the ligaments, blood vessels, skin, and cartilage. It also helps prevent hernias as it protects the inside part of the disc in the vertebral discs where hernias may occur. Vitamin C is also used in skin treatments because it softens the skin and prevents or delays the aging of skin.6

It also helps form serotonin which is an important brain chemical, it stimulates adrenal function, it aids in cholesterol metabolism, helps wounds heal, and helps maintain healthy blood vessels.7 In diabetes, vitamin C is commonly used to improve the utilisation of blood sugar and thereby reduce it, but there is no clear evidence that regular vitamin C usage alone can prevent diabetes.8 There are some preliminary reports that ascorbic acid may help prevent cataract formation (probably through its antioxidant effect) and may be helpful in the prevention and treatment of glaucoma, as well as certain cases of male infertility caused from the clumping together of sperm, which decreases sperm function. Ascorbic acid is also said to act as a detoxifier and may reduce the side effects of drugs such as cortisone, aspirin, and insulin; it may also reduce the toxicity of the heavy metals lead, mercury, and arsenic, either by controlling Oxidation State or by facilitating excretion. There are other proposed functions for vitamin C, but they remain controversial. For example, it is said that it aids in the production of interferon, which stimulates the immune system, that it is an antihistamine and therefore prevents or lessens the affects of allergies, and it may help prevent certain forms of cancer.

In short, vitamin C helps prevent scurvy, promotes healthy teeth and gums, helps absorption of iron, aids in maintenance of normal connective tissue, promotes wound healing, and helps boost the immune system. However, vitamin C is also a natural laxative and may help with constipation problems. In fact, the main side effect of too much vitamin C intake is diarrhea. However, this will not happen if you go over the recommended daily allowance (RDA). For this side effect to occur there would have to be a very high consumption of vitamin C, very fast because it is a water soluble molecule.9

Vitamin C is an important substance in the body. This is why it is vital that we take in the right amount of vitamin C by eating or drinking the substances that supply us with it.

Materials

?Fresh grapefruit

?Fresh lemon

? Fresh orange

?Fresh pomegranate

?Fresh apple

?Fresh mikan (tangerine)

?Bottle of C100 Vitamin Lemon drink

?Can of Nichirei Acerola drink

?Bottle of Sawayaka apple juice

?Carton of Zakuro (pomegranate) Water drink

?Carton of grapefruit juice

?Carton of Dole orange juice

?Tin of Sanyo mikan

?Carton of Ringo No Oishii Mizu (Delicious Apple Water)

?Knife

?Cutting board

?Blender

?Lemon squeezer Filter

?Distilled water

?Burette

?DCPIP (0.1%) solution

?Funnel

?White marble tile

?Paper napkins

?14 beakers

?6M hydrochloric acid

?Electronic scales

?Spatula

?Pipette

Procedures

An amount of 0.5g of DCPIP (dichlorophenolindophenol) powder was measured on an electronic scale. Next, 500ml of distilled water were then mixed together to form 500ml of 0.1% DCPIP solution, which was stored in a dark bottle. The solution was a dark blue colour. DCPIP is used for the testing of vitamin C. When tested for vitamin C, a colour change will take place either from blue to clear, or from blue to pink to clear. Once the full colour change is observed, the amount of solution taken to change it can be recorded.

The burette was cleaned thoroughly using hydrochloric acid. The acid was poured in gently so as not to spill while the burette was slowly rotated over a sink. Once this was finished, water was run down the sink so the acid would be diluted and be less harmful to the pipe system. Distilled water was then poured down the burette to make sure the acid was fully rinsed out.

The grapefruit had the juice extracted from it using a regular lemon squeezer. The squeezer was then cleaned using distilled water. The juice was hen filtered using a tea strainer and then a filter paper. The juice was collected in a beaker. This procedure was repeated with an orange, lemon, and a mikan (tangerine). The pomegranate was cut in half and the juice was extracted by squeezing each half using the hand. This juice was also filtered in the same fashion as all the juices. The apple was diced and put into a blender where it was blended until it looked like a puree. This was then filtered and placed into a beaker like the previous juices. All the juices, including the commercially sold ju8ices, were filtered to prevent blockage of the burette.

Next, 16 beakers were each filled with 2ml of 0.1% DCPIP solution. The burette was filled with the fresh grapefruit juice just past the zero line using a funnel to pour it into the burette so the juice would go directly into the burette. The grapefruit juice was then drained until it came exactly to the zero line. Looking at eye level to see if the bottom part of the curvature was exactly at zero checked this.

The grapefruit juice was slowly dripped into the beaker of DCPIP until a clear observation in the colour change was observed. The beaker was swirled gently to ensure mixing. It was properly observed, as a white tile had been placed under the beaker of DCPIP. This made the colour change more clearly visible. The amount of juice taken for a full colour change to take place in the beaker containing DCPIP was recorded.

The burette was then cleaned by pouring distilled water through it twice. The lemon juice was then poured into the burette and the mount of lemon juice taken to observe a clear colour change in the beaker containing DCPIP was recorded. The burette was cleaned once again and the process was repeated with each fresh fruit juice and commercially sold drink.

Data

Chart showing The Amount of Fruit Juice Needed in ml’s to Turn DCPIP From Blue To Clear

Types of JuicesAmount of commercially sold juices in ml needed to turn 2ml’s of DCPIP clearAmount of fresh juices in ml’s needed to turn 2 ml’s of DCPIP clear

Grapefruit50+ ml2.2 ml

Lemon0.13 ml2.0 ml

Orange2.9 ml2.3 ml

Pomegranate50+ ml11.3 ml

Apple1.4 ml23.1 ml

Mikan (tangerine)6.5 ml2.9 ml

The above chart shows how many ml’s of each juice, both commercially sold and fresh, it took to turn 2ml’s of DCPIP clear. All fruits used to make the fresh fruit juices in the experiment were purchased fresh so heat and length of time wouldn’t have affected the vitamin C content too much. All the commercially sold juices were bought on the basis of popularity among teenager’s in Japan. They were bought to represent the likely amount of vitamin C intake that Japanese teenager’s would have during the winter when cooked vegetables would lose a lot of their vitamin C content. The fewer amounts of millilitres of juice it took to turn DCPIP from blue to clear, the larger the amount of vitamin C there was in the drink. In procuring commercial fruit juices, it soon became apparent that all was not what it seemed. Some were heavily supplemented with vitamin C (e.g. the commercially sold lemon drink “C1000 Lemon” and other, while labeled as fruit juices, contained only 10% juice!)

When the commercially sold lemon drink was first measured, the colour changed with a mere 0.1ml of lemon drink, or just four drops. So the experiment was repeated with a one in ten dilution of the lemon drink, this time giving a reading of 1.3ml.

Tinned mikan (tangerine) juice was used and juice prepared for other fruits, i.e. the tin juice was discarded and the mikan sections squeezed and filtered.

The carton of grapefruit juice was labeled as containing 20% real fruit juice. This may be why the amount of ml of juice it took to turn the DCPIP from blue to clear was not established. Over 50ml’s of this grapefruit juice was titrated into the beaker containing DCPIP with little colour change observed. This was shown as more than 50ml on the bar chart, but in each case 75ml was run in without colour change observed. After the DCPIP was too dilute to read the colour. The more than 50ml readings should be interpreted as effectively zero vitamin C content. The juice prepared with a fresh grapefruit showed that there was nearly as much vitamin C content as in the fresh lemon juice. Therefore, real grapefruit is high in vitamin C content.

The lemon drink tested was supposed to provide the daily intake of vitamin C. It only contained 10% real fruit juice. This means that vitamin C that was not naturally produced was inserted into the drink. This is obvious because when compared to the commercially sol lemon juice, the amount of fresh lemon juice needed to turn DCPIP from blue to clear was almost five times the mount of the commercially sold lemon juice.

The commercially sold orange juice contained 100% real fruit juice. It is easy to tell that this juice was either heat treated or old, as it is 100% as real as the fresh orange juice made, but it took 0.6 more ml to turn the DCPIP from blue to clear. The vitamin C content in the commercially sold orange juice was probably broken down a bit by being heat treated and being in storage and on a shelf for too long. It is because vitamin C is heat labile that the vitamin C broke down under these conditions.

The carton of pomegranate ‘water’ contained 10% real juice. More than 50ml of the pomegranate ‘water’ were used to measure the change of DCPIP from blue to clear. On the bar chart it is shown as greater than 50ml though. However, this change was not observed even with that amount of the drink being used, therefore the effective vitamin C content was zero. In the case of fresh pomegranate juice the change in colour was hard to observe/measure as the colour of the pomegranate juice and the pink stage of DCPIP was similar in colour. The difference in colour between the pomegranate juice with the DCPIP pink stage and the pomegranate juice by itself was observed better using a white tile beneath the beaker containing the DCPIP and a beaker of fresh pomegranate juice was place on an other white tile right beside it to make a clearer comparison.

The apple drink (acerola) contained 10% real fruit juice. The acerola apple is different from the common eating apple used in the fresh fruit juice comparison. It is more closely related to the crab apple. It was found, after some more research, that acerola apples have a very high vitamin C content, more so than the common eating apple. Although extra vitamin C may have been introduced into the drink [the package label was not helpful], the vitamin C content was still very high. It contained twenty times the mount of the fresh apple juice tested. Another popular Japanese apple drink called Ringo No Oishii Mizu (delicious apple water) was tested for vitamin C content. It contained 20% real fruit juice made of apples similar to those used for the fresh fruit juice tested. With this apple drink it took 26.9ml before DCPIP turned clear.

The mikan juice extracted from tinned mikan contained 100% real fruit juice. Tinned goods are heat treated, and are normally cooked as part of the canning process. Thins tend to have longer shelf and storage lives too, that would probably account for the decomposition of vitamin C that gave the relatively low reading in comparison to the fresh mikan juice. However, given the famed lability of vitamin C, the readings for canned mikan were surprisingly high and confound the accepted wisdom that “canned fruit contains no vitamin C”.

The graph shows the different amount of each juice in millilitres needed to turn DCPIP from blue to clear. i.e. a lower reading means more vitamin C. Showing it in graph from makes it easier to see the differences between the commercially sold drink in comparison the fresh fruit juice.

The Amount of Each Drink in Millilitres Needed to Fulfill the Required Daily Allowance (RDA) of Vitamin C

Commercially Sold Drinks

DrinkAmount of Juice in ml’s Needed to Turn 2ml’s of DCPIP from blue to clearAmount of Juice in ml’s Needed to Fulfill the RDA of Vitamin C

Lemon (C1000)0.13ml8.4ml

Orange2.9ml187.34ml

Apple (acerola)1.4ml90.44ml

Mikan6.5ml419.9ml

Apple ( Oishii Mizu)26.9ml1737.74ml

The above chart shows the amount of each commercially sold drink needed, in millilitres, to fulfill the required daily allowance (RDA) of vitamin C, which is 60mg of vitamin C. This was figured out because the lemon drink contained 1000mg of vitamin C and was a bottle of 140ml. The following equation was then used to figure out how many millilitres of the lemon drink would provide a person with the RDA for vitamin C.

The amount of mg’s of vitamin C in drink = The required daily allowance

The amount of ml’s of drinkx

1000 = 60

140 x

In this equation x was 8.4. Then 8.4 was divided by 0.13 (the amount of lemon C1000 in ml’s needed to turn DCPIP from blue to clear). The number gotten by doing this was 64.6. This number was then multiplied by the amount of juice, in ml’s, needed to turn DCPIP from blue to clear to get the amount of juice in ml’s needed to fulfill the RDA of vitamin C. This also applies to the next chart.

For the lemon, orange, and apple (acerola) drink, the amounts needed to fulfill the RDA are relatively small. These are amount that could be easily consumed without much effort and disgust. For the mikan and apple drinks, the amounts needed to fulfill the RDA are sizeable in comparison to the lemon, orange, and acerola drinks. Pomegranate and grapefruit juice were not included in this chart since the amount of juice needed to turn DCPIP clear was more than the 75ml’s measured. The amount of apple juice needed to fulfill the RDA is impractical for somebody. Drinking almost two litres of the apple juice in one day would be highly unlikely.

Fresh Fruit Juices

DrinkAmount of Juice in ml’s Needed to Turn 2ml’s of DCPIP from blue to clearAmount of Juice in ml’s Needed to Fulfill the RDA of Vitamin C

Lemon2.0ml129.2ml

Orange2.3ml148.58ml

Apple23.1ml1492.26ml

Grapefruit2.2ml142.12ml

Pomegranate11.3ml729.98ml

For the lemon, orange, mikan, and grapefruit, the amounts needed to fulfill the RDA are relatively small. For the apple and pomegranate and apple juices, the amounts needed to fulfill the RDA are quite large. It would be impractical to drink that much apple juice just to get the RDA of vitamin C. The juice also tasted bad. It would be fairly hard or expensive to get enough pomegranate juice to fulfill the RDA of vitamin C. However, it is also impractical to have about 130 millilitres of fresh lemon juice as it is very sour and not that tasty.

Evaluation

From the two types of drinks (commercially sold drinks and fresh fruit juices), fresh fruit juices tended to contain more vitamin C than the commercially sold juices of the same fruit. The commercially sold juices that had a larger vitamin c content than its equivalent fresh fruit juice were the lemon juice and the first apple juice tested. The lemon juice contained a lot more vitamin C because it was a vitamin C supplement drink for those in the winter with colds that don’t want to drink the hot cough drinks. However, no other commercially sold lemon drink, that wasn’t a vitamin C supplement drink, was found. The first apple drink tested for vitamin C had extra vitamin C added and the type of apple used in the drink had a higher amount of vitamin C than the normal apple, which was used for the fresh fruit juice.

Not all commercially sold drinks had a lower vitamin c content than their equivalent fresh fruit juice. This was especially not expected for the first apple juice tested. Therefore, the hypothesis: since vitamin C is labile (susceptible to change and unstable), the commercially sold juices, which have most likely been heat treated and stored in various conditions for various periods of time, should have lower vitamin c content than fresh fruit juices, was not fully supported. This was due to the fact that assumptions were made on the vitamin C content of apples. It was thought that all apples would have toughly the same vitamin C content, as a result the expected measurements were not as expected. However, this was somewhat remedied by testing a different popular apple drink. The results from this test proved to be like those expected that were stated in the hypothesis.

If the experiment were to be repeated, the most likely change would be to get a wider variation of commercially sold drinks of the same fruit and, if possible, fresher fruit. Testing for the vitamin C content in, for example, three different commercially sold apple drinks may have given a more accurate picture of the vitamin C content in commercially sold apple drinks. The amount of vitamin C broken down in the canning or packaging process, along with the shelf life, may have also become more apparent.

To get more accurate results, the experiment should have been done several times. With all t he results collected an average should have been calculated to give a more concise amount of vitamin C in the drinks tested, but time was limited.

Another thing that would be good to do if the experiment were repeated would be to test how much pure vitamin C (ascorbic acid) it takes to turn DCPIP from blue to clear. This was not achieved because there was no ascorbic acid powder available. Had it been available, it would have been used as a control. As a result, the amount of each juice in millilitres to meet the recommended daily allowance of vitamin C was figured out which served a purpose almost as good as the control method. In some cases it is conceivable that the volume of fruit or commercially sold drinks needed to meet the RDA would not be practicable. In short, it took from 50 – 500 millilitres less of fresh fruit juice than commercially sold drink to fulfill the RDA of vitamin C. This is for all fruits except the lemon and acerola commercially sold drinks as they had vitamin C added.

The results that were accumulated through this experiment were nearly all backed up by the hypothesis, with the exception of the lemon drink comparison for reasons stated earlier on in the paper. The conclusion was made, in answer to the research question: are commercially sold and popularly consumed juices (in Japan) a good substitute for fresh fruits in terms of dietary vitamin C? That commercially sold and popularly consumed juices (in Japan) are not a good substitute for fresh fruits (in the form of juices for the purpose of this experiment). This is because the vitamin C content for all, except the lemon juice and the first apple (acerola) juice tested, was higher in the fresh fruits than it was in the commercially sold drinks. So, it would benefit the majority of teenagers who buy the commercially sold drinks (thinking they contain more vitamin C among other vitamins and minerals) to drink fresh fruit juices if they want the proper amount of vitamin C.

Endnotes

1)”Vitamin C Content of a Lemon ”

The Chemicals of Life

p.47

2)Bates, Chris

“Vitamin C, The Chameleon of the Vitamins”

Biological Science Review

November, 1991, p.11

3)Pitt, George

“The Dark Side of Vitamins”

Biological Science Review

May, 1994, p.38

4) Bates, Chris

“Vitamin C, The Chameleon of the Vitamins”

Biological Science Review

November, 1991, p.12

5)http://www.cforyourself.com

6) http://www.cforyourself.com &

Bates, Chris

“Vitamin C, The Chameleon of the Vitamins”

Biological Science Review

November, 1991, p.12

7)http://www.cforyourself.com

8) “Vitamin C Content of a Lemon”

The Chemicals of Life

p.47

9) http://www.cforyourself.com

Endnotes

1)”Vitamin C Content of a Lemon ”

The Chemicals of Life

p.47

2)Bates, Chris

“Vitamin C, The Chameleon of the Vitamins”

Biological Science Review

November, 1991, p.11

3)Pitt, George

“The Dark Side of Vitamins”

Biological Science Review

May, 1994, p.38

4) Bates, Chris

“Vitamin C, The Chameleon of the Vitamins”

Biological Science Review

November, 1991, p.12

5)http://www.cforyourself.com

6) http://www.cforyourself.com &

Bates, Chris

“Vitamin C, The Chameleon of the Vitamins”

Biological Science Review

November, 1991, p.12

7)http://www.cforyourself.com

8) “Vitamin C Content of a Lemon”

The Chemicals of Life

p.47

9) http://www.cforyourself.com

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