Analysis and determination of amino acid additives

First, feed grade L-lysine hydrochloride

Identification

1. Reagents and solutions ninhydrin: 0.1% solution; silver nitrate: 0.1 mol/L solution; nitric acid: 1+9 solution; ammonium hydroxide: 1+2 solution.

2. Operation steps Identification of amino acids: Weigh 0.1 g of sample, dissolve in 100 ml of water, take 5 ml of this solution, add 1 ml of ninhydrin solution, heat for three minutes, add water 20 ml, let stand for 15 minutes, solution It is purple. Identification of chloride: 1 g of the sample was weighed, dissolved in 100 ml of water, and a silver nitrate solution was added to produce a white precipitate. Adding dilute nitric acid, the precipitate does not dissolve; another white precipitate is taken, an excess of ammonia hydroxide solution is added, and the precipitate is dissolved.

Determination of L-lysine hydrochloride content

1. Reagents and solutions formic acid; glacial acetic acid; mercury acetate: 6% glacial acetic acid solution; α-naphthol phenylmethanol indicator: 0.2% glacial acetic acid solution; perchloric acid: about 0.1 mol/L glacial acetic acid standard solution .

2. Procedure The sample was dried at 105 ° C to a constant weight in advance, and 0.2 g of the dried sample was weighed, weighed to 0.0002 g, 3 ml of formic acid and 50 ml of glacial acetic acid were added, and 5 ml of a solution of mercury acetate in glacial acetic acid was added. Add 10 drops of α-naphthol phenylmethanol indicator solution and titrate with 0.1 mol/liter of chloric acid in glacial acetic acid standard solution. The sample solution changes from orange to yellow green and is the end point of titration. In the same way, another blank test was performed to correct it.

3. Calculation of results

C4H14N2O2·HCl)/m×100

Where C: concentration of perchloric acid standard solution, mol / liter;

V1: volume of perchloric acid standard solution consumed by the sample, ml;

V2: volume of perchloric acid standard solution consumed by the blank test, ml;

m: sample quality, gram;

0.09132: grams per mmol of lysine hydrochloride.

2. Determination of feed grade DL-methionine

Identification

1. Reagents and solutions anhydrous copper sulfate: sulfuric acid saturated solution; sodium hydroxide: 1 + 5 aqueous solution; glycine: 1 + 100 solution; sodium nitroferrocyanate: 1 + 10 solution; hydrochloric acid: 1 + 5 solution; Ninhydrin: 2% solution; sodium acetate.

2. Operation steps Weigh 25m of sample, add 1ml of anhydrous copper sulfate saturated sulfuric acid solution, appear yellow; weigh 5mg of sample, add 5ml of water to dissolve 2ml of sodium hydroxide solution, shake and mix, add 1 A milligram of aminoacetic acid solution, 0.3 ml of sodium nitroferrocyanate solution, and then fully shaken and mixed, placed at 35-40 ° C for 10 minutes, ice-cooled for 2 minutes, added 10 ml of dilute hydrochloric acid solution, shaken and mixed, the solution was red. Weigh 1 g of the sample, dissolve it in 30 ml of water, take 1 ml of the test solution, add 1 ml of ninhydrin solution and 100 mg of sodium acetate, and heat to boiling, the solution is blue-violet.

Determination of methionine content

1. Reagents and solutions Dipotassium hydrogen phosphate; potassium dihydrogen phosphate; potassium iodide; iodine: 0.05 mol/L solution; soluble starch: 0.5% solution; sodium thiosulfate: 0.1 mol/L solution.

2. Operation steps Weigh 0.3 g sample, put it into a stoppered flask, add 100 ml of water, 2 g of dipotassium hydrogen phosphate, 2 g of potassium dihydrogen phosphate, 2 g of potassium iodide, mix and dissolve by shaking, and add 0.05 mol/accurately. 50 ml of iodine solution was added, and the mixture was shaken well after shaking. After standing for 30 minutes, 1 ml of the starch test solution was used as an indicator, and excess iodine was titrated with a 0.1 mol/liter sodium thiosulfate solution, and the blank test was performed in the same manner. . 0.1 mol/L sodium thiosulfate solution per 1 ml = 7.460 mg C5H11NO2S.

3. Calculation results

C5H11NO2S=)/m×100

Where K: milligrams per milliliter of sodium thiosulfate

V1: volume of sodium thiosulfate consumed by the sample, ml;

V2: volume of sodium thiosulfate consumed by the blank test, ml;

m: sample mass, gram.