Determination of vitamin A by ultraviolet spectrophotometry - Master's thesis

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Determination of Vitamin A by Ultraviolet Spectrophotometry

Key words: vitamin A; ultraviolet spectrophotometer; US instrumentation ; UV-1100; UV-1200

$/></p>1. Principle The isopropanol solution of vitamin A has a maximum absorption peak at 325 nm, and its absorbance is directly proportional to the content of vitamin A. The sensitivity of this method is higher than that of the colorimetric method, and a sample having a vitamin A content of less than 5 Î¼g/g can be determined. The main disadvantage is that many other compounds in the vicinity of 325 nm of the maximum absorption wavelength of vitamin A also have absorption and interference measurement. Therefore, this method is applicable to samples with high purity such as transparent fish oil and vitamin A concentrate. For general samples, the fat must be extracted before saponification, the unsaponifiable fraction is extracted, and the interference is removed by column chromatography. 2. Instrument UV spectrophotometer; US instrumentation ; UV-1100; UV-1200. 3. Reagent 1 isopropanol. 2 Vitamin A standard solution: Weigh 1 g of equivalent cod liver oil equivalent to 50 000 international units of vitamin A, 0.1000 g, dissolved in isopropanol, and dilute to 125 mL. 1 mL of this solution is equivalent to 40 international units (ie 40 IU.mL-1). 4. Determination step 1 standard curve drawing: take vitamin A standard solution (40 IUÂ·mL-1) O. 5. 1.0, 1.5, 2.0, 2.5, 3.0, 4Â·0 mL, in a 10 mL brown volumetric flask, make up to volume with isopropanol. The instrument zero point was adjusted with a blank liquid, and the absorbance was measured at a wavelength of 325 nm on an ultraviolet spectrophotometer, and a standard curve was drawn. 2 sample determination: weigh the appropriate amount of sample, saponification according to the ruthenium trichloride colorimetric method, extraction, washing, concentration, evaporation of the ether layer, quickly dissolved in isopropyl alcohol and transferred to a 50 mL volumetric flask, with isopropanol The volume was measured, and the absorbance was measured at 325 nm of an ultraviolet spectrophotometer, and the equivalent vitamin A content was found from the standard curve. 5. Calculate X=[(c*V)/m]*100 where: Xâ€”â€”sample vitamin A content, IUÂ·(100 g) -1; câ€”â€”vitamin A content obtained from the standard curve, IUÂ· mL-1; V - volume of isopropanol solution of the sample, mL; m - sample mass, g. Key words: vitamin A; ultraviolet spectrophotometer; 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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Determination of vitamin A by ultraviolet spectrophotometry - Master's thesis - Dissertation

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