GB 20802-2017Feed additive-Cupric methionine complex (chelate) (English PDF)

4.2.1 Reagents and solutions

4.2.1.1 Methanol.

4.2.1.2 Trichloromethane.

4.2.1.3 Dithizone solution in chloroform (10 µg/mL) Weigh 1 mg of dithizone and dissolve in 100 mL of chloroform (4.2.1.2).

4.2.1.4 pyridine.

4.2.2 Identification method Weigh 1.0g sample, extracted with 25mL methanol (4.2.1.1), filtered, the filtrate was taken 0.1mL, sequentially added dithizone trichloromethane dissolved Liquid (4.2.1.3) 3mL, the test solution shall not appear cloudy, precipitation phenomenon; then add pyridine (4.2.1.4) 0.5mL, blue liquid test solution shall not appear.

4.3 Determination of copper content

4.3.1 Principle After digestion with nitric acid and hydrochloric acid, the sample was complexed with copper ions with ethylenediaminetetraacetic acid (EDTA) at a pH of 5, Pyridylazo) -2-naphthol (PAN) indicator indicates the end point of the titration, calculated from the volume of disodium ethylenediaminetetraacetate standard solution consumed Copper content.

4.3.2 Reagents and materials

4.3.2.1 Nitric acid.

4.3.2.2 Hydrochloric acid.

4.3.2.3 ammonia solution. Ammonia water = 1 9.

4.3.2.4 acetic acid - sodium acetate buffer solution (pH = 5) .82g of sodium acetate plus 25mL of acetic acid, diluted with water to.200mL.

4.3.2.5 disodium edetate standard titration solution (EDTA-2Na) .c (EDTA-2Na) = 0.02mol/L. 4.3.2.6 1- (2-Pyridylazo) -2-naphthol (PAN) indicator

0.2 g of 1- (2-pyridylazo) -2-naphthol (PAN) was dissolved in 100 mL of 95% Ethanol.

4.3.3 Analysis steps Weigh 0.25g sample, accurate to 0.0001g, placed in 250mL conical flask, add 3mL nitric acid (4.3.2.1) and 3mL hydrochloric acid (4.3.2.2), heated to near dry, after cooling, add 20mL water heated to near dry, add water after cooling 80mL, with ammonia solution (4.3.2.3) tune The solution pH is about 5, then the solution was dark blue, added acetic acid - sodium acetate buffer solution (4.3.2.4) 10mL and PAN indicator (4.3.2.6) 3 drops, then heated to boil, while hot Disodium ethylenediaminetetraacetate standard titration solution (4.3.2.5) titration to yellowish green end. At the same time, another 250mL Erlenmeyer flask, a blank test, in addition to not adding the sample, the other types of operations and the amount of reagents and measurement are measured The same test.

4.3.4 Calculation and representation of results The copper content in the sample X1 is mass fraction, the value is expressed in%, and can be calculated according to the formula (1). X1 = (V1-V0) × c1M1 × 10-3 m1 × 100 (1) In the formula. V0

--- titration blank solution consumption of disodium edetate standard titration solution (4.3.2.5) of the volume in milliliters (mL); V1

--- titration sample solution consumption of disodium edetate standard titration solution (4.3.2.5) of the volume in milliliters (mL); c1

--- disodium edetate standard titration solution (4.3.2.5) concentration in units of moles per liter (mol/L); M1

--- molar mass of copper in grams per millimolar (g/mol) (M1 = 63.55); m1

--- sample quality, in grams (g). The arithmetic mean of the two parallel determination results is the determination result, and the result is retained to one decimal place. The absolute difference between the two measurements is not more than 1%. Determination of methionine content 4.4

4.4.1 Principle Excess iodine solution is added accurately in neutral medium, two iodine atoms are added to the sulfur atom of methionine, the excess iodine solution is treated with sulfur Substitution of sodium sulfate standard titration solution back to the sample from the consumption of sodium thiosulfate standard titration solution volume calculated methionine content of the sample.

4.4.2 Reagents and materials

4.4.2.1 Potassium iodide.

4.4.2.2 hydrochloric acid solution .6mol/L.

4.4.2.3 Sodium hydroxide solution .20%.

4.4.2.4 sulfuric acid solution. Sulfuric acid water = 15.

4.4.2.5 potassium dihydrogen phosphate solution .200 g/L.

4.4.2.6 dipotassium hydrogen phosphate solution .200 g/L.

4.4.2.7 iodine solution .c (1/2I2) = 0.1mol/L.

4.4.2.8 sodium thiosulfate standard titration solution .c (Na2S2O3) = 0.1mol/L.

4.4.2.9 Starch indicator solution .10g/L.

4.4.3 Analysis steps Weigh 1.5g sample, accurate to 0.0001g, placed in a 100mL beaker, add 50mL water, 3mL hydrochloric acid solution (4.4.2.2), plus Heat dissolved, with sodium hydroxide solution (4.4.2.3) to adjust the pH greater than or equal to 13, boiled 3min, cooled and moved into 250mL volumetric flask, Dilute to the mark, take the supernatant filtration, accurately remove 50mL filtrate in iodine bottle, add 50mL of water, with sulfuric acid solution (4.4.2.4) tune A pH of 7 was added and 10 mL potassium dihydrogen phosphate solution (4.4.2.5), 10 mL dipotassium hydrogen phosphate solution (4.4.2.6), 2 g potassium iodide (4.4.2.1), Shake, accurately add 50mL iodine solution (4.4.2.7), evenly, in the dark place 30min, with sodium thiosulfate standard titration solution (4.4.2.8) drops Set until the solution color changes from dark blue to light blue, add 3 mL of starch indicator solution (4.4.2.9) and continue titration until the solution blue disappears. At the same time, take another 100mL beaker and 250mL Erlenmeyer flask, a blank test, in addition to without the sample, the other operations and add the reagent species Class and quantity are the same with the test.

4.4.4 Calculation and representation of results The content of methionine in sample X2 is calculated by mass fraction, the value is expressed in%, and can be calculated according to formula (2). X2 = (V2-V3) × c2M2 × 10-3 × 5 m2 × 100 (2) In the formula. V2

--- titration blank solution consumed sodium thiosulfate standard titration solution (4.4.2.8) of the volume in milliliters (mL); V3

--- titration test solution consumed sodium thiosulfate standard titration solution (4.4.2.8) volume, in milliliters (mL); c2

--- sodium thiosulfate standard titration solution (4.4.2.8) the actual concentration in units of moles per liter (mol/L); M2

16.8 Methionine /% >=

78.0 Chelation rate /% >=

95 Table 1 (continued) Project Indicators Moisture /% <=