Vitamin C and Content of Soft Fruit Drinks - Coursework Example

Vitamin C and Content of Soft Fruit Drinks Vitamin C (ascorbic acid: C6H8O6) is a common component of various fruits and vegetables, especially citrus fruits such as oranges and lemons. This important vitamin serves various different functions in the human body including the maintenance of the integrity of various connective tissues such as those found in the skin, ligaments, and bones and also plays an important role in promoting wound healing[Uni095]. This paper outlines an experimental methodology to ascertain the amount of Vitamin C in different commercially available soft drinks. In order to determine the amount of Vitamin C present in a new range of soft drinks and comparing the Vitamin C content of different soft drinks, titration can be carried out. Titration is a commonly performed experiment which is used to determine the exact concentration of a particular substance in solution. This is achieved by adding increasing amounts of a standard solution of known concentration (the titrant) to a measured quantity of the solution whose concentration one intends to ascertain (the analyte), and determining the end point of the reaction by means of a substance termed as an indicator. Titration can be used to determine the concentration of various substances including several acids and bases. Vitamin C has been found to turn a blue dye clear. Thus, the amount of Vitamin C in a solution can be worked out by titrating the different soft drinks against a fixed amount of the blue dye, which serves as both the titrant and the indicator in this experiment.  Materials Available: Blue dye A solution containing a known amount of Vitamin C (Solution A) A selection of old products: a lemon, orange and blackcurrant drink A selection of new products: a lemon, orange and blackcurrant drink Equipment needed: Burette Pipette, graduated Pipette filler Ehrlenmeyer flask or Beaker Distilled water Burette clamp Stirring rod Procedure: To begin the experiment, the amount of solution which has a known quantity of Vitamin C (labeled as Solution A) needed to turn 1 cm3 of the blue dye colorless has to be determined. To achieve this, a measured quantity, i.e. 1 cm3 of the dye is added to an Ehrlenmeyer flask or beaker with the help of a pipette. Before using the pipette, it is important to ensure that it is thoroughly cleaned and conditioned before being used in order to remove any water droplets or impurities. Conditioning is achieved by rinsing the pipette with a small volume of the solution being transferred (the stock solution) and disposing of the rinsing solution. The pipette is then filled up to the calibration mark with the help of a pipette filler. It is important to remember that most solutions would form a concave meniscus. Thus, while reading a meniscus, the bottom of the meniscus should be read and the meniscus should be kept at eye level in order to avoid parallax errors. Moreover, the meniscus should be read against a uniform background, which can be achieved by placing a white sheet of paper behind the level of the liquid. The dye is now transferred to the conical flask. Once all the solution has drained, the experimenter should touch the tip of the pipette to the side of the flask. This helps in removing the last drop of solution from the pipette and helps in avoiding errors. It is important to keep in mind that one does not need to blow the last drop of solution out of the pipette. As pointed out previously, in this experiment the blue dye serves as both the titrant and the indicator. An indicator is a substance which indicates the pH of a substance and is commonly used to determine the end point of a reaction, which is denoted by a color change of the indicator. The next step is to add the solution A into the beaker drop by drop by means of a burette. The burette is an apparatus which helps in slowly and precisely deliver small measured volumes of a solution to another. It is most commonly used in titration experiments and measures solutions up to an accuracy of half a division or 0.05 cm3 [avo10]. Before using the burette, it should be conditioned the same way as the pipette, by rinsing it with the solution of Vitamin C (Solution A). In addition, it is important to check the tip of the burette for air bubbles as that could lead to an error in the volume readings. Accurate volume measurements are important in order to carry out a successful titration. The burette should be filled by using a funnel, after closing the stopcock at the bottom. Once that is done, solution A is added slowly to the dye, stirring constantly with the help of the stirring rod, until the dye turns colorless. This is the end-point of the reaction. Normally, the experiment is repeated until the successive measurements are within 0.1 cm3 in order to ensure the precision and accuracy of the volume readings and avoiding any errors. Then the average of three values which are within 0.1 cm3 of each other is taken and recorded. The experiment is then repeated for all the other soft drink samples, i.e. the old lemon, orange and blackcurrant drinks and the new lemon, orange and blackcurrant drinks. It is however, important to remember that before each experiment, all the equipment being used should be thoroughly rinsed with tap water initially followed by distilled water, as any impurities left behind would act as contaminants and would alter the results, resulting in errors. The results can then be recorded in a tabular form as depicted below and the comparison of the amount of Vitamin C in the different soft drinks tested can be easily demonstrated and interpreted accordingly. Thus, in this way, the amount of Vitamin C present in different soft drinks can be determined and comparisons can be made regarding the varying amounts of Vitamin C in different soft drinks. Reading 1 Reading 2 Reading 3 Average Solution A Old Lemon Drink (Solution B1) Old Orange Drink (Solution C1) Old Blackcurrant Drink (Solution D1) New Lemon Drink (Solution B2) New Orange Drink (Solution C2) New Blackcurrant Drink (Solution D2) References Uni095: , (University of Maryland Medical Center), avo10: , (avogadro.co.uk, 2010), Read More