Vitamin A measurement: color method.

the principles of . Vitamin
A (retinol) is a fat-soluble vitamin that produces an unstable blue substance in a chloroform solution called Carr-price reaction, which can be used for qualitative identification and quantitative determination of vitamin A, and the depth of the resulting color is directly related to the amount of vitamin A in the solution. A 120nm wavelength
can be measured at
620nm wavelength using a 10th 100-degree photometric for a certain period of time.reagents
equipment first, reagents sodium sulfate without water;25% chlorpyride-chloroform solution: 25g of
drided
is dissolved in 100mL of chloroform, and brown bottles are stored in light.vitamin A standard liquid: accurately called standard vitamin A, placed in
capacity bottle
, dissolved with chloroform, with 100 IU / mL standard liquid., the materialfish liver oil.III, equipmenttest tube
1.5×15cm (×10); pipe pipe 10mL (×1), 1 mL (×11); capacity bottle 25mL (×10), with plug conical bottle 250mL (×1), research, light dlight meter.method 1, production standard curvedilute vitamin A standard liquid chloroform into different concentrations of standard series (e.g. 10,20,30,40,50,60,70,80,90,100IU/mL). Take the same number of color cups, add 1mL chloroform and 1mL standard liquid, each tube added a drop of acetic anhydride, into a standard color column.
is chloroform at a wavelength of 620nm. The standard color column is moved sequentially to the optical path, quickly adding 9mL terse-chloroform solution to measure the absorption within 6 seconds. The standard graph is drawn with the absorbance as the ordinate and the vitamin content as the horizontal coordinate., sample determination the use of grinding method to measure the content of vitamin A.grinding: precisely called 2-5g sample, placed in the research, add 3-5 times the weight of the sample of sodium a waterless sulfate, carefully ground to the sample moisture is completely absorbed.extraction: carefully move the above abrasive into the tapered bottle with plugs, accurately add 50-100mL ether, cover the plug, shake hard for 2 minutes, so that the sample variety of vitamin A dissolved in ether, the cone bottle placed in ice water 1-2h, until the ether liquid clarified.Concentrate: Take the clarification ether extract 2-5mL, put it in a color tube, steam it out in a 70-80C water bath, immediately add chloroform 1mL dissolved residue, add 1 drop of acetic anhydride and 9mL trifide, mix well, measure its absorbent value within 6 seconds.the amount of vitamin A in the tube to be measured from the standard curve, and then the content of vitamin A in the sample was measured according to the dilution relationship.Note: (1) Vitamin A is highly susceptible to light damage and should be tested in low light.
and equipment used to quantify vitamin A must be absolutely dry. Trace moisture can make triclosal, no longer react with vitamin A, and appear cloudy. Adding 1-2 drops of acetic anhydride to the test tube removes trace amounts of inhaled water.
(2) chloroform should be free of decomposition or it will destroy vitamin A.
.