Practical report and essay Example | Topics and Well Written Essays - 1500 words

Practical report and - Essay Example This prevents interference of the proteins during analysis. In addition to this, metaphosphoric acid offers stability to ascorbic acid by preventing its decomposition in acidic solution. DCP solution being unstable is stored in dark bottle at 4Â ºC. DCP titrant has to be standardised using known concentration of vitamin C. This helps in accurate determination of the concentration of vitamin C in an unknown solution. Reagents and samples: 2,6-dichlorophenolindophenol (DCP), 2- metaphosphoric acid, glacial acetic acid, standard ascorbic acid, freshly squeezed orange juice, Tropicana pure premium and Growers direct organic Accurately weighed 800 mg of DCP is dissolved in 500ml of previously boiled and cooled distilled water in a 1000 ml volumetric flask. Then the volume is made up to 1000 ml with distilled water. (The solution can last 7 days in fridge, in a dark bottle). Accurately weighed 15 g of Metaphosphoric acid (HPO) was dissolved in 40 ml of glacial acetic acid and 200 ml water. Then the volume was made to 500ml. The resultant solution was filtered. (MPA lasts 7 days in fridge). Accurately weighed 200 mg of L-ascorbic acid was dissolved in 10 ml MPA solution, and then volume was made to 100 ml with distilled water (made up in MPA/glacial acetic solution). 10 ml of resultant solution was diluted to 100 ml with distilled water. (20 mg of ascorbic acid per 100 ml i.e. 0.2mg/ml). 3. Then the solution in the flask was titrated with DCP solution from burette slowly with constant stirring until faint pink colour appeared and persisted. Then burette reading was noted. 3. Then the solution in the flask was titrated with DCP solution from burette slowly with constant stirring until faint pink colour appeared and persisted. Then, burette reading was recorded. Discussion: Most analytical methods exploit ascorbic acid’s ease of oxidation for its estimation. It was seen that the ascorbic acid content of freshly squeezed