Effect of Temperature and Cu2+ on Abscorbic Acid Stability

Effect of Temperature and Cu2+ on Abscorbic unpleasant StabilityEffects of Temperature, pH and Cu2+ on Abscorbic deadly StabilityNAME Sophia Chai Lai JinObjectivesTo perform a selected oxidation-reduction titrimetric procedure.To measure the stability of ascorbic superman under various conditions.IntroductionL-ascorbic sharp as known as Vitamin C is an essential nourishing for humans. L-ascorbic pane of glass is one of the most potent compounds acting as an antioxidant in biological systems by scavenging active oxygen species and reposition radicals. L-ascorbic acid is a well-known water-soluble antioxidant that has a whitening effect and serves as a cofactor of prolinehydroxylase to promote synthesis of collagen. Low intakes cause a nutrient deficiency disease known as scurvy. Scurvy causes general weakness, anemia, gum disease, and skin hemorrhages. The effectiveness of ascorbic acid as a food additive depends on its oxidation to dehydroascorbic acid which effectively destro ys ascorbic acid. Since it is so readily oxidized, it is frequently called the most unstable vitamin.Ascorbic acid may degrade via a number of different mechanisms. anaerobiotic and aerobic pathways have been identified but when oxygen is present, oxidative degradation predominates. Factors that may influence the rate of ascorbic acid degradation include temperature, salt and dulcorate submerging, pH, oxygen concentration, metal catalysts, and enzymes.ApparatusTest tubes, beakers (20 and 250 mL), burets, pipets (1,5 and 10 mL), Erlenmeyer flasks (50 mL), graduated cylinders (10 and 50 mL), hot plate, boiling beads, pH meter, water bath.MaterialsAscorbic acid consequence (0.5 and 10 mg/mL), oxalic acid solution (0.25 M), 2,6-dichloroindophenol (dye) solution, cupric sulphate, (CuSO4.5H2O) solution (10 g/100 mL), genus Glycine buffer (0.1 M, pH 2), carbonate buffer (0.1 M, pH 8), HCl (1 M).Experimental ProcedureAbscorbic Acid Standard Curve9 mL of oxalic acid solution and 1 mL of 1.0 M HCl was transferred to from each one of four Erlenmeyer flask.0.5, 1.0, 1.5 and 2.0 mL of ascorbic acid solution (0.5 mg/mL) was added to each respectively.Each flask rapidly with dye solution was titrate until a light but distinct rose pink colourise persists for at least 5 s.A volume o fdye versus miligrams of ascorbic acid was plotted.Effects of Temperature, pH and Cu2+ on Ascorbic Acid Stability10 mL (duplicate) was prepargond of each of the following solutionAscorbic acid in glycine bufferAscorbic acid in carbonate bufferAscorbic acid in glycine buffer + CuSO4Ascorbic acid in carbonate buffer + CuSO41 mL of ascorbic acid (10 mg/mL), 0.5 mL of CuSO4 and sufficient buffer was added to bring the total volume to 10 mL and well mixed.The pH was recorded for each solution.They was cover and capped loosely and transfer to a boiling water bath. It was boiled for 15 minutes and cooled.Titration was done.Results get across 1 Volume of dye vs miligrams of ascorbic acidAscorbic ac id (0.5 mg/mL)Ascorbic acid in mgVolume of dichloroindophenol used (mL)0.50.2530.41.00.557.11.50.7582.72.01.0114.1Table 2 pH cherish of each solutionSolutionpH value1st set2nd setAscorbic acid + glycine2.062.09Ascorbic acid + carbonate7.247.27Ascorbic acid + glycine + CuSO41.982.00Ascorbic acid + carbonate + CuSO46.176.22Table 3 Volume of dye vs different solutionsSolutionVolume of dichloroindophenol used (mL)Ascorbic acid + glycine5.8Ascorbic acid + carbonate3.3Ascorbic acid + glycine + CuSO42.6Ascorbic acid + carbonate + CuSO41.6CalculationAverage amount of ascorbic acid to titrate with dichloroindophenol in 1 mLY = 113.21x1 = 113.21xX = 0.0088 mg1 mL of dichloroindophenol is required to titrate with 0.0088 mg of ascorbic acidTotal volume of ascorbic acid solution = 10 mLAscorbic acid + glycine solution required 5.8 mL of dichloroindophenol0.0088 mg X 5.8 = 0.05104 mgConcentration of ascorbic acid = 0.005104 mg/mLAscorbic acid + carbonate required 3.3 mL of dichloroindophenol0.0 088 mg X 3.3 = 0.02904 mgConcentration of ascorbic acid= 0.0029 mg/mLAscorbic acid + glycine + CuSO4 required 2.6 mL of dichloroindophenol0.0088 mg X 2.6= 0.02288 mgConcentration of ascorbic acid = 0.002288 mg/mLAscorbic acid + carbonate + CuSO4 required 1.6 mL of dichloroindophenol0.0088 mg X 1.6= 0.01408 mg/mLConcentration of ascorbic acid = 0.001408 mg/mLDiscussionIn this experiment, redox iodometric titration assay was used to determine the amount of concentration of ascorbic acid in each buffer solution. CuSO4 act as the oxidizing reagent in the reaction. Firstly, the dichloroindophenol act as the blue dye allow for oxidized the ascorbic acid when titration begin. The ascorbic acid will be oxidized into another form which is called dehydroascorbic acid. The following figure shows the equation of redox reaction of ascorbic acid and converted to dehydroascorbic acid in the titration.In acid condition, the blue dye will turn the solution into pinkish colour, if the ascorbic acid is present, it will reduce the solution back into colourless compound. The higher the concentration of ascorbic acid, the more dichloroindophenol is needed to oxidize it. Until the titration end point is reached, a persist pink colour solution will be obtained. This indicates that the availability of ascorbic acid has used up for reduction and being oxidized quantitavely by dichloroindophenol. Therefore, from the result in part A standard curve calibration, a straight linear line was achieved. The 2.0 mL of ascorbic acid solution (0.5 mg/mL) required a huge amount of dichloroindophenol to thieve it.From the result obtained, the ascorbic acid-glycine solution tend to have higher concentration of ascorbic acid. Meanwhile in ascorbic acid-carbonate solution has a lower concentration of ascorbic acid. This might due to in alkaline condition it will be more comfortably to oxidized into dehydroascorbic acid. In alkaline condition, the O2 will act as the oxidant to breakdown the ascorbic acid and destabilize it. Therefore, a slightly acidic pH, the antioxidant properties of ascorbic acid tail assembly be maintained.Moreover, in the presence of CuSO4 will degrade the ascorbic acid easily as CuSO4 is a strong oxidizing agent. Cu2+ will catalaze the oxidation and heating also will increase the rate of oxidation. However, at a slight acidic pH such as in citrus juice, the vitamin is more stable.Besides, thermal treatment to the ascorbic acid can degrade and destruct the antioxidant properties of the structure. In boiling water bath, most of the ascorbic acid are believed to be degraded. Therefore, the amount of the concentration of ascorbic acid are found to be lower than the beginning of the experiment.ConclusionThe higher the concentration of ascorbic acid in a solution, the more amount of dichloroindophenol are required to neutralized it. In a very acidic condition, it will degrade the ascorbic acid faster. However in a neutral or alkaline condition in the presence of air, the ascorbic acid will oxidized fast due to the O2 which is an oxidant. High temperature can degrade the antioxidant properties of the vitamin C.Referenceshttp//www.nlm.nih.gov/medlineplus/ency/ word/000355.htmhttp//chemistry.about.com/od/demonstrationsexperiments/ss/vitctitration_4.htmhttp//www.sussexvt.k12.de.us/science/Textbook/LIM_LowRes_Unsecured/NCInv13D.pdfQuestionsExplain the difference in the results between the ascorbic acid-glycine and the ascorbic acid-carbonate buffers, and the effect of pH on ascorbic acid.The ascorbic acid-glycine solution tend to have higher concentration of ascorbic acid. Meanwhile in ascorbic acid-carbonate solution has a lower concentration of ascorbic acid. This might due to in alkaline condition it will be more easily to oxidized into dehydroascorbic acid. In alkaline condition, the O2 will act as the oxidant to breakdown the ascorbic acid and destabilize it. Therefore, a slightly acidic pH, the antioxidant properties of ascorbic acid c an be maintained.Explain the difference in the results between ascorbic acid-glycine buffer and the ascorbic acid-glycine buffer with CuSO4 between ascorbic acid-carbonate buffer and the ascorbic acid-carbonate buffer with CuSO4 model systems.The presence of metal ions such as copper and iron increase the rate of oxidation of ascorbic acid. CuSO4 is strong oxidizing agent. Ascorbic acid form complex with metal ions and reduce metal ion into metal. Therefore, the addition of CuSO4 has lowered the amount of dichloroindophenol which required to titrate with the ascorbic acid solution.