Extraction and identification of lecithin.

. Objective: To deepenstructure and properties of phospholipids.
2. Master the principles and methods of lecithin extraction and identification.
, the principle of experiment . Phospholipids are an important component of biological
tissues
cells, mainly found in plant tissues such as soybeans and animal liver, brain, spleen, heart and other tissues, especially in egg yolk content (about 10%.) Lecithin and cerebral phospholipids are soluble in ether and not in acetone, which can be separated from neutral fat by this property, in addition, lecithin can be soluble in ethanol and cerebral phospholipids insoluble, using this property can separate lecithin and cerebral phospholipids.
newly extracted lecithin is white, and when in contact with air, the unsaturated fatty acids it contains are oxidized to make lecithin yellowish-brown. Lecithin can be decomposed into fatty acids, glycerin, choline and phosphates after being hydrolysed by alkali.
Glycerin and potassium sulphate co-heat, can produce acrylic with a special odor, phosphate in acidic conditions with ammonium niobate, the production of yellow phosphate precipitation, choline under the further action of alkali to produce colorless and with ammonia and fishy smell of methylene. In this way, lecithin can be identified by testing the decomposition products., instruments and
reagents instruments
small
beech

test tube
.
reagents
. 1. Egg yolk
2. Red stone
test paper 3. 95% ethanol
10% sodium hydroxide solution
5. Ammonium diphate reagent dissolved 6g ammonium niobate in 15mL distilled water, added 5mL of ammonia water, and another 24mL of thick nitric acid dissolved in 46mL distilled water, the two mixed after one day.
6. Acetone
. 7. Ether
8. 3% bromine carbon tetrachloride solution 9. Potassium sulphate 4, operation step(i) lecithin extraction
said to take about 10g egg yolks in a small berries, add warm 95% ethanol 30mL, mix well, cool down after

. If the filter is still cloudy, it can be refiltered until it is completely transparent. Place the filter liquid in the evaporative dish, steam in the water bath, the resulting dry is lecithin.
(ii) the solubility of lecithin
take
dry
test tube, add a little lecithin, then add 5mL ether, stir with a stick to dissolve lecithin, drip into acetone 3 to 5mL, observe the experimental phenomenon.
(iii) the identification of lecithin
. 1. The test of methamphetamine
take a dry test tube, add a small amount of extracted lecithin and 2 to 5mL sodium hydroxide solution, put in a water bath
heat
15min,
put a piece of red stone test paper at the mouth of the tube to observe whether the color has changed, and smell its odor. The heated solution is filtered and the filter is used for inspection below.
2. Unsaturated test
take a clean test tube, add 10 drops of the above filter, and then add 1 to 2 drops of 3% bromine carbon tetrachloride solution, shake the test tube, to observe what phenomenon occurs.
3. Phosphoric acid test
take a clean test tube, add 10 drops of the above filter and 5 to 10 drops of 95% ethanol solution, and then add 5 to 10 drops of ammonium diphate reagent, observe the phenomenon;
4. Test of glycelin
Take a clean test tube, add a little lecithin and 0.2g potassium sulfate, clamp with the test tube and heat it slightly on a small fire, so that lecithin and potassium sulphate melt, and then heat centrally, when there is water vapor released, smell what smell. .