Dinitrobenzoquinone method - Determination of fruit vitamin C

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Determination of Vitamin C by Dinitrobenzoquinone Method

Key words: dinitrophenylhydrazine method; fruit vitamin C; US analytical instrument ; UV-1100; UV-1200

$Width="1022" height="796" src="http://i.bosscdn.com/blog/nophoto.gif" /></p> First, the principle: the acid-treated activated carbon to reduce the ascorbic acid Oxidation to dehydroascorbic acid and continued oxidation to diketogulonic acid. The diketogulonic acid is coupled with 2.4-dinitrophenylhydrazine to form a red complex. The intensity of the coloration is proportional to the concentration of the diketone gulonic acid and can be quantified by colorimetry. Second, the reagent: (1) 1% oxalic acid solution. (2) 2% oxalic acid solution. (3) Acid-treated activated carbon: take 200 g of activated carbon, add 10 ml of 10% hydrochloric acid, boil, filter by air, boil with 1000 ml of boiling water, filter, and repeat washing with water until there is no high-priced iron ion in the filtrate (ie 1%) The sulfur solution test is not red) and is dried at 100-120 Â°C. (4) 2% 2.4-dinitrophenylhydrazine solution: 2 g of a 2.4-dinitrophenylhydrazine solution was dissolved in 100 ml of 9N sulfuric acid. (5) 9N sulfuric acid solution: Measure 250 ml of concentrated sulfuric acid, slowly pour into 750 ml of water, and stir while adding water. (6) 10% sulfuric acid solution: 5 g of sulfuric acid was weighed and dissolved in 50 ml of 50% alcohol. (7) 85% sulfuric acid solution: accurately weigh 20 mg of ascorbic acid, dissolved in 1% oxalic acid, and the solution was diluted to 100 ml. Pipette 50 ml of this solution, add 0.1 g of activated carbon, shake for 1 minute, filter and take 5 ml of the above filtrate, and dilute to 100 ml with 1% oxalic acid (this standard use solution contains 10 Î¼g of ascorbic acid per liter). Third, the operation method: (1) sample processing and analysis: weigh the appropriate amount of sample and add an equal amount of 2% oxalic acid solution in the tissue masher into a homogenate. 20 g of the homogenate was diluted to 100 ml with 1% oxalic acid, shaken, and filtered. Take 10 ml of filtrate and add 10 ml of 1% oxalic acid (the amount of filtrate is determined according to the content of ascorbic acid, generally control the concentration of ascorbic acid per ml to 1-lOug), add 1 scoop of activated carbon, shake for 1 minute, and let stand for filtration. Take 2 ml of each filtrate into the sample tube and the sample blank tube, and add 1 drop of sulfuric acid solution to each tube. Add 0.5 ml of 2.4-dinitrophenylhydrazine to the sample tube, sample tube, blank tube of sample, and place in a 37 Â° C incubator for 3 hours. After taking out the sample tube and putting it into human ice water, the sample tube and the blank tube of the sample are placed in an ice bath, and 2 ml of 85% sulfuric acid is added to each tube from the dropping tube, and the tube is shaken while dropping (to prevent the temperature of the solution from rising, The sugar in the solution is charred and turns black). Each tube was taken out in an ice bath, and after standing at room temperature for 30 minutes, the optical density was read at a spectrophotometer wavelength of 540 nm. Based on the measured optical density, the corresponding content is found from the standard curve. UV-1200(2) standard curve drawing: draw 10, 20, 30, 40, 50ml of ascorbic acid standard working solution and dilute to 50ml. These standard solutions contain 2, 4, 6, and 8 per ml. , lOug ascorbic acid. Take 2ml each, place in each standard tube, add 1 drop of sulfuric acid solution and 0.5ml of 2.4-dinitrophenylhydrazine solution, place each tube in the incubator at 30 Â°C for 3-4 hours, take it out and put it on ice. In the bath, 2.5 ml of 85% sulfuric acid was added dropwise to each tube, and the tube was shaken, and then taken out, left for 30 minutes, and the optical density was measured at a wavelength of 540 nm by a spectrophotometer. A standard curve is drawn based on the measured optical density. At the same time, as a reagent blank, a 1% oxalic acid solution 2m1 was added to a reagent blank tube, and the same standard tube was operated. Calculation: milligrams of ascorbic acid per 100 grams of food = C / W Ã— 100C: equivalent to the amount of standard solution (mg) W: the amount of sample solution obtained when measuring is equivalent to the amount of sample (g) IV, Description: (1 After adding 85% sulfuric acid, the test tube was taken out of the water. The color of the solution will continue to darken and must be calculated. After adding sulfuric acid, the colorimetric is allowed within 30 minutes. (2) Sulfuric acid can prevent the oxidation of ascorbic acid and can help the formation of quasi-formation. The concentration of sulfuric acid in the solution must be consistent, otherwise the color will be affected. Key words: dinitrophenylhydrazine method; fruit vitamin C; aesthetic instrument ; UV-1100; UV-1200</p> </div> </div> <div class="tech-detail -share">  <div class="bdsharebuttonbox"> <a href="#" class="bds_qzone" data-cmd="qzone" title="Share to QQ Space"> </a> <a href="#" class="bds_tsina" data-cmd="tsina" title="Share to Sina Weibo"></a> <a href="#" class="bds_weixin" data -cmd="weixin" title="Share to WeChat"></a> <span>Share to:</span> </div> <script>window._bd_share_config = { "common": { "bdSnsKey": { }, "bdText": "", "bdMini": "1", "bdMiniList": false, "bdPic": "", "bdStyle": "2", "bdSize": "16" }, "share" : {} }; with (document) 0[(getElementsByTagName($

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