Gunjan Kashyap et al., Jour. of Sci. Res. in Phar. 2012, 1(2), 77-78
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Research Article ISSN: 2277-9469
Analysis of Vitamin C in Commercial and Naturals substances by Iodometric Titration found in Nimar and Malwa regeion Gunjan Kashyap * and Mangla Dave Gautam Department of Chemistry, Govt. Holkar Science College, Indore, (MP), India.
Received on: 01-06-2012; Revised on: 01-06-2012; Accepted on: 013-06-2012
ABS TRACT Vitamin C or ascorbic acid is important for the human body. It prevents scurvy, which is caused by lack of vitamin C in the body which can affect muscles weakness, swollen and bleeding of gums, loss of teeth and bleeding under the skin as well as its deficiency is responsible for tiredness and depression. Therefore our objectives is to study and compare vitamin C content in two commercial juices and two natural f ruit (mango and orange) found in Malwa and Nimar region using titration method. Beside that, comparing vitamin C content determined and to that stated on the label for each fruit juice sample. To relate the amount of vitamin C present at the time of consumption based on the expired date. Sample to determine vitamin C is orange juice and mango juice in commercial fruit juice on different expiry date. From different expiry date can get different shelf life before expired days. Method to determine vitamin C in commercial fruit juice is titration method with iodine solution. Titration method is a ccurate and precision method compares another methods. From the result the higher amount of vitamin C was guava about 188 g/100mL for nature fruit pulp and 22.25 g/100mL for commercial fruit juice and for mango 26 g/100mL for nature fruit pulp and 14.50 g/100mL for commercial fruit juic e. However mango juice and orange juice were suitable to drinking as they contain higher % of vitamin C content. As per our analysis, the long er shelf life before expiry, the higher amount of vitamin C in fruit juice. Key words: Ascorbi c acid, Commercial fruit juice, Titration, Iodine solution. INTRODUCTION Fruit juices are liquid naturally contained in fruit or vegetables tissue. Juices are prepared by me chanically squeezing or macerating fresh fruits or vegetables without the application of heat or solvents [1]. The labels on fruit juice package may be misleading as the companies may underestimate or overestima te the actual content. Thus, the problem is that the consumers do not know the actual amount of vitamin C in the fruit juices, unless the amount of vitamin C is stated on the label of the package.
Excess iodine (I2) reacts with iodide ions (I-) to form triiodide ion (I3-) which forms a very intense blue color when it reacts starch [3-4]. This colour is due to incorpora tion of the ions within the molecular structure of the starch. I2 + I- → I3To detect the end point, starch must be added at the beginning of the titration in the conical flask. When all ascorbic a cids have finished, the excess of iodine solution will react the starch to form blue-black colour in the solution. I3- + starch → starch (I3-)
Fig. 1: Structure of L-Ascorbic acid Vitamin C can determine by acid-base reaction or oxidationreduction reaction. Vitamin C is a weak acid and a good reducing agent. Iodine is a weak oxidizing agent, so that it will not oxidize substances other than the ascorbic acid in the sample of fruit juice. As a strong reducing agent, vitamin C will reduce I2 to I- very easily. The excess of iodine react the starch as indicator to perform the amount of vitamin C is finishing in redox reaction [2]. In this reaction, the ascorbic acid molecule gains oxygen (in the form of OH groups). Each iodine atom in the I 2 molecule accepts an electron and become a negatively charge to form iodide ion. Thus that, the ascorbic acid molecule was oxidized and the iodine molecule was reduced. C 6H8O 6 + I2 + 2H2O → C 6H10O 8 + 2I - + 2H+
*Corresponding author: Gunjan Kashyap Department of Chemistry, Govt. Holkar Science College, Indore, (MP), India. Mobile No.: +919424513627 E-Mail:
[email protected]
Vitamin C in fresh and freeze dried herbal juices using direct titration me thod with iodine solution in acidic potassium iodide. The limit of detection (LOD) and limit of quantitation (LOQ) was 2.2 and 7.26 mg. After 4 weeks, vitamin C content has found to be reduced from 469 to 338 ppm or 27.9 % for freeze-dried guava and from 1798 to 1727 ppm or 3.9 % for freeze-dried emblic myrobolan. The vitamin C content in fresh juice is greater than in freeze-dried sample while the stability of vitamin C in the freeze-dried sample is greater than in freeze-dried juice after 4-week storage. The method used is another titration method where vitamin C in commercial fruit juices was titrated against a queous sodium dichlorophenolindophenol with starch as indicator. The sodium dichlorophenolindophenol solution was standardized with sodium thiosulphate will concentration of 0.01 N in a matrix of potassium iodide (50%) and HCI (1 N) using starch as indicator. The amounts of vitamin C determined in the samples were between 24 to 430 ppm of juice. METHOD AND METERIALS Determination vitamin C concentration involves iodine and iodate solution in a redox titration method. When iodine solution is a titrant, vitamin C is oxidized to form dehydroascorbic acid while the iodine is reduced to iodide ions. When all vitamin C has finish ed, the excess iodine solution will react will starch solution to form blue-black colour as endpoint of titration (ascorbic a cid + I2→ 2I- + dehydroascorbic acid). This method is a straight forward compared to the alternative method using iodate as the titrant Potassium iodate stable compared to
Journal of Scientific Research in Pharmacy 2012, 1(2)
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Gunjan Kashyap et al., Jour. of Sci. Res. in Phar. 2012, 1(2), 77-78 iodine and it does not have to be standardized as it is a primary standard. The iodine solution needs to be standardized with pure vitamin C or potassium thiosulphate because iodine is unstable. In the alternative method, iodate solution (IO3 -) is added into acidic solution containing iodide ions (I-) where an oxidationreduction reaction occurs. The iodate ions are reduced to form iodine while the iodide ions are oxidized to form iodine [5]. The overall reaction between iodate and iodide is. The endpoint of sample was blue-black starch-iodine complex when excess iodine reacts with the starch as indicator in the solution. The list or reagents (Anal Grade) and materials used are: potassium iodide (KI) ,potassium iodate (KIO3) , 3 M sulfuric acid. Ascorbic acid 1 % starch solution, Commercial fruit juices sample and fruit.
Standardisation of the iodine solution with the vitamin C standard solution: 25 mL of vitamin C solution was pipetted into a 125 mL Erlenmeyer flask. 10 drops of 1% starch solution were added and then titrated against iodine solution until blue-black colour was observed. Titrations were repeated four times.
Preparation of iodine solution: 5.00 g potassium iodide (KI) and 0.268 g potassium iodate (KIO3) were dissolved into 500 mL beaker with 200 mL of distilled water. 30 mL of 3 M sulfuric acid was added into the beaker and then diluted with distilled water until 500 mL solution.
Titration method was accurate and precise method to determine vitamin C compared other methods as high pressure liquid chromatography [HPLC] method and enzymatic methods. Using titration method, it was not suitable for detection of vitamin C in the coloured sample because it was difficult to find blue-black colour at endpoint after starch was added in titration method. The molarity of iodine solution was determined by standardisation method. Three sets of titration were carried out. The result of the average value of vitamin C in each fruit juice samples are tabulated in Table 1.
Preparation of vitamin C standard solution: 0.250 g ascorbic acid was dissolved in the beaker with 100 mL distilled water. The solution was transferred into 250 mL volumetric flask and diluted to the mark will distilled water.
Titration of juice samples: 25 mL of juice samples were pipetted into a 125 mL Erlenmeyer flask. Following by 10 drops of 1% starch solution and titrated against iodine solution until blue-black colour was observed. Titrations were repeated four times. RESULT AND DISSCUSSION
Table No. 1: Total Vitamin c Content in Natural and synthetic samples S. No. 1. 2. 3. 4.
Samples Orange Mango Orange juice Mango juice
Condition Fresh Fresh Fresh Fresh
Temperature (300C) (30 0C) (30 0C) (30 0C) (30 0C)
REFRENCES: 1. Arya, S.P., Mahajan, M., and Jain, P. Photometric methods for the determination of Vitamin C. Analytical Sciences. 1998: 14; 889-895. 2. Brody, T. Nutritional Biochemistry; Academic Press: san Diogo, CA. 1994; pp. x and 450-9.
Total Vitamin- c (mg/100g) 48 29 32 26
3. Block, G. Epidemiologic evidence regardingvitamin C and cancer. American Journal of Clinical Nutrition. 1991: 54; 1310S-14S. 4. Block, G. The data support a role forantioxidants in reducing cancer risk. Nutrition Reviews. 1992: 50(7); 207-13. 5. Biswas S.K. and Mannan M.A. Determination of vitamin C (ascorbic acid) in some fruits and vegetables; B. J. Sci. & Ind. Res. 1996: 1; 31.
Source of suppor t: Nil, Conflict of interest: None Declared
Journal of Scientific Research in Pharmacy 2012, 1(2)
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