阅读说明：本技术 一种饲料中水溶性氯化物含量的快速检测方法 (Method for rapidly detecting content of water-soluble chloride in feed ) 是由 王凤麟 梁洪慧 冯建文 谭会泽 赵江涛 陈丹 向娜娜 于 2020-05-19 设计创作，主要内容包括：本发明涉及饲料检测领域,具体涉及一种饲料中水溶性氯化物含量的快速检测方法。在本检测方法中,待测样品通过重金属盐沉淀有机物质后,再过滤,在滤液中添加过量硝酸银,使样品中氯离子完全转化成氯化银沉淀下来,再用硫氰酸铵标准液滴定溶液中过量硝酸银,即可计算出样品中氯化物含量。本检测方法检测耗时短、操作简便、灵敏度高,适用于全价配合饲料、浓缩饲料中水溶性氯化物含量的快速检测。(The invention relates to the field of feed detection, in particular to a method for rapidly detecting the content of water-soluble chloride in feed. In the detection method, after organic substances of a sample to be detected are precipitated by heavy metal salts, filtering is carried out again, excessive silver nitrate is added into filtrate, so that chloride ions in the sample are completely converted into silver chloride to be precipitated, and then the excessive silver nitrate in the solution is titrated by ammonium thiocyanate standard solution, so that the chloride content in the sample can be calculated. The detection method has the advantages of short detection time, simple and convenient operation and high sensitivity, and is suitable for quickly detecting the content of the water-soluble chloride in the complete compound feed and the concentrated feed.)

1. A method for rapidly detecting the content of water-soluble chloride in feed is characterized by comprising the following steps:

step 1, weighing a sample, putting the sample into a glass container, and sequentially adding V_aWith a volume of V_bStirring the zinc acetate solution uniformly to obtain a first sample solution;

step 2, filtering the first sample liquid in the step 1 to obtain a filtrate;

step 3, taking the volume V in the step 2_cAdding nitric acid and saturated ferric ammonium sulfate solution into the flask, adding excessive silver nitrate solution to generate precipitate, and shaking the flask to coagulate the precipitate to obtain a second sample solution;

step 4, dropwise adding an ammonium thiocyanate standard titration solution into the second sample liquid in the step 3 for titration until reddish brown appears in the second sample liquid and the reddish brown is kept for 30s and does not fade, and recording a titration volume V of the ammonium thiocyanate standard titration solution₁；

And 5, replacing the filtrate obtained in the step 2 with water as a blank solution, repeating the operations of the step 3 and the step 4, carrying out a blank test, and recording the volume V of the ammonium thiocyanate standard titration solution consumed by the blank solution₀；

And 6, calculating the content X of the water-soluble chloride in the sample according to the following formula:

in the formula: v₀-volume of blank spent ammonium thiocyanate standard titration solution, ml;

V₁-the volume of sample consumed ammonium thiocyanate standard titration solution, ml;

V_a-volume of potassium ferrocyanide solution, ml;

V_b-volume of zinc acetate solution, ml;

V_c-volume of filtrate, ml;

c-concentration of ammonium thiocyanate standard titration solution, mol/L;

m-weight of sample, g.

2. The method for rapidly detecting the content of the water-soluble chloride in the feed according to claim 1, which is characterized by comprising the following steps:

step 1, weighing 2-8 g of a sample, putting the sample into a 300-500 ml high beaker, adding 100ml of potassium ferrocyanide solution, adding 50ml of zinc acetate solution, and stirring in a stirrer for 15-20 min to obtain a first sample solution;

step 2, filtering the first sample liquid in the step 1 to obtain a filtrate;

step 3, putting 25ml of the filtrate obtained in the step 2 into a 150ml Erlenmeyer flask, adding 5ml of nitric acid and 2ml of saturated solution of ferric ammonium sulfate into the Erlenmeyer flask, adding 15ml of silver nitrate solution to generate a precipitate, and shaking the Erlenmeyer flask to coagulate the precipitate to obtain a second sample solution;

step 4, dropwise adding an ammonium thiocyanate standard titration solution into the second sample liquid in the step 3 for titration until reddish brown appears in the second sample liquid and the reddish brown is kept for 30s and does not fade, and recording a titration volume V of the ammonium thiocyanate standard titration solution₁；

And 5, replacing the filtrate obtained in the step 2 with water as a blank solution, repeating the operations of the step 3 and the step 4, carrying out a blank test, and recording the volume V of the ammonium thiocyanate standard titration solution consumed by the blank solution₀；

And 6, calculating the content X of the water-soluble chloride in the sample according to the following formula:

in the formula: v₀-volume of blank spent ammonium thiocyanate standard titration solution, ml;

V₁-the volume of sample consumed ammonium thiocyanate standard titration solution, ml;

c-concentration of ammonium thiocyanate standard titration solution, mol/L;

m-weight of sample, g.

3. The method for rapidly detecting the content of water-soluble chloride in feed according to claim 2, wherein the concentration of the potassium ferrocyanide solution is 5.3 g/L.

4. The method for rapidly detecting the content of water-soluble chloride in feed according to claim 2, wherein the concentration of the zinc acetate solution is 21.9 g/L.

5. The method for rapidly detecting the content of water-soluble chloride in the feed according to claim 2, wherein the concentration of the silver nitrate solution is 0.1 mol/L.

6. The method for rapidly detecting the content of water-soluble chloride in the feed according to claim 2, wherein the concentration C of the standard titration solution of ammonium thiocyanate is 0.1 mol/L.

7. The method for rapidly detecting the content of water-soluble chloride in the feed according to claim 2, wherein the mass of the sample weighed in the step 1 is 5 g.

8. The method for rapidly detecting the content of the water-soluble chloride in the feed according to claim 2, wherein the stirring time in the step 1 is 20 min.

Technical Field

The invention relates to the field of feed detection, in particular to a method for rapidly detecting the content of water-soluble chloride in feed.

Background

Common salt, chemical name of sodium chloride, is one of basic substances for maintaining normal water and salt metabolism in animals, can increase appetite, enhance digestion and promote metabolism, but excessive common salt can cause animal poisoning. The detection of the sodium content in the feed is not easy, and the content of the salt in the feed is converted by detecting the content of water-soluble chloride in the feed.

At present, in the feed manufacturing industry of China, the method for detecting the chloride in the feed comprises the following steps:

(1) preparing a sample solution containing organic matters: weighing 5g of sample, transferring to a 500ml volumetric flask, adding 400ml of water at a temperature of about 20 ℃ and 5ml of potassium ferrocyanide solution, stirring, then adding 5ml of zinc acetate solution, mixing, shaking in a shaker for 30min, diluting to the mark with water, and mixing.

(2) Titration: transferring a certain volume of filtrate into a triangular flask, adding a saturated solution of nitric acid and ammonium ferric sulfate, and dripping 2 drops of standard titration solution of ammonium thiocyanate from a burette filled with standard titration solution of ammonium thiocyanate to a scale of 0 into the triangular flask; titrating with silver nitrate standard titration solution until the reddish brown disappears, and adding 5ml of excessive silver nitrate standard titration solution; the excess silver nitrate solution was titrated again with the previously remaining ammonium thiocyanate standard titration solution.

The above detection method has the following drawbacks:

1. in the step (1), the volumetric flask is a large-belly long-neck volume quantitative vessel, after 400ml of water is added into a 500ml volumetric flask, the liquid level approaches the bottleneck, so that the stirring is difficult, the uniform mixing is difficult during the oscillation, the oscillation time can be only prolonged for achieving the uniform mixing, and the detection consumes too long time. The sample to be detected is feed, and contains a large amount of solid matters lighter than water, and after oscillation, the solid matters float on the bottleneck and cover the scale marks of the volumetric flask, so that the sample is difficult to be accurately diluted to the scale marks by water, and the detection deviation is increased.

2. In the step (2), two standard titration solutions, namely an ammonium thiocyanate standard titration solution and a silver nitrate standard titration solution, are required, so that the titration difficulty and the use of the standard titration solutions are increased, the quantification process is not easy to operate, the steps are complicated and time-consuming, the requirement on operators is high, and the requirement on rapid supervision and inspection work in the current feed production cannot be met.

Disclosure of Invention

The invention aims to provide a method for rapidly detecting the content of water-soluble chloride in feed, so as to overcome the defects of difficult operation, complexity and long time consumption in the prior art.

The technical scheme adopted for solving the technical problem is to provide a method for rapidly detecting the content of water-soluble chloride in feed, which comprises the following steps:

step 1, weighing a sample, putting the sample into a glass container, and sequentially adding V_aWith a volume of V_bStirring the zinc acetate solution uniformly to obtain a first sample solution;

step 2, filtering the first sample liquid in the step 1 to obtain a filtrate;

step 3, taking the volume V in the step 2_cAdding nitric acid and saturated ferric ammonium sulfate solution into the flask, adding excessive silver nitrate solution to generate precipitate, and shaking the flask to coagulate the precipitate to obtain a second sample solution;

step 4, dropwise adding an ammonium thiocyanate standard titration solution into the second sample liquid in the step 3 for titration until reddish brown appears in the second sample liquid and the reddish brown is kept for 30s and does not fade, and recording a titration volume V of the ammonium thiocyanate standard titration solution₁；

And 5, replacing the filtrate obtained in the step 2 with water as a blank solution, repeating the operations of the step 3 and the step 4, carrying out a blank test, and recording the volume V of the ammonium thiocyanate standard titration solution consumed by the blank solution₀；

And 6, calculating the content X of the water-soluble chloride in the sample according to the following formula:

in the formula: v₀-volume of blank spent ammonium thiocyanate standard titration solution, ml; v₁-the volume of sample consumed ammonium thiocyanate standard titration solution, ml; v_a-volume of potassium ferrocyanide solution, ml; v_b-volume of zinc acetate solution, ml; v_cVolume of filtrate, ml, C concentration of standard titration solution of ammonium thiocyanate, mol/L, m weight of sample, g.

According to the method for rapidly detecting the content of the water-soluble chloride in the feed, provided by the invention, after heavy metal salts precipitate organic substances in a sample to be detected, filtering is carried out again, excessive silver nitrate is added into filtrate, so that chloride ions in the sample are completely converted into silver chloride to be precipitated, then the residual silver nitrate in the solution is titrated by using the ammonium thiocyanate standard solution, the volume difference of the blank solution and the sample solution which consume the ammonium thiocyanate standard solution is utilized, and the chloride content in the sample can be calculated according to a calculation formula. The detection method has the advantages of short detection time, simple and convenient operation and high sensitivity, and is suitable for quickly detecting the content of the water-soluble chloride in the complete compound feed and the concentrated feed.

In some embodiments, the rapid detection method specifically comprises the following steps:

step 1, weighing 2-8 g of a sample, putting the sample into a 300-500 ml high beaker, adding 100ml of potassium ferrocyanide solution, adding 50ml of zinc acetate solution, and stirring in a stirrer for 15-20 min to obtain a first sample solution;

step 2, filtering the first sample liquid in the step 1 to obtain a filtrate;

step 3, putting 25ml of the filtrate obtained in the step 2 into a 150ml Erlenmeyer flask, adding 5ml of nitric acid and 2ml of saturated solution of ferric ammonium sulfate into the Erlenmeyer flask, adding 15ml of silver nitrate solution to generate a precipitate, and shaking the Erlenmeyer flask to coagulate the precipitate to obtain a second sample solution;

step 4, dropwise adding an ammonium thiocyanate standard titration solution into the second sample liquid in the step 3 for titration until reddish brown appears in the second sample liquid and the reddish brown is kept for 30s and does not fade, and recording a titration volume V of the ammonium thiocyanate standard titration solution₁；

And 5, replacing the filtrate obtained in the step 2 with water as a blank solution, repeating the operations of the step 3 and the step 4, carrying out a blank test, and recording the volume V of the ammonium thiocyanate standard titration solution consumed by the blank solution₀；

And 6, calculating the content X of the water-soluble chloride in the sample according to the following formula:

in the formula: v₀-volume of blank spent ammonium thiocyanate standard titration solution, ml; v₁The volume (ml) of the standard titration solution of ammonium thiocyanate consumed by the sample, the concentration (mol/L) of the standard titration solution of ammonium thiocyanate, and the mass (g) of the weighed sample.

In some embodiments, the concentration of the potassium ferrocyanide solution is 5.3 g/L.

In some embodiments, the concentration of the zinc acetate solution is 21.9 g/L.

In some embodiments, the silver nitrate solution has a concentration of 0.1 mol/L.

In some embodiments, the concentration C of the standard titration solution of ammonium thiocyanate is 0.1 mol/L.

In some embodiments, the sample weighed in step 1 has a mass of 5 g.

In some embodiments, the stirring time in step 1 is 20 min.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a flow chart of a method for rapidly detecting the content of water-soluble chloride in feed according to an embodiment of the invention.

Detailed Description

Exemplary embodiments that embody features and advantages of the invention are described in detail below in the specification. It is to be understood that the invention is capable of other embodiments and that various changes in form and details may be made therein without departing from the scope of the invention and the description and drawings are to be regarded as illustrative in nature and not as restrictive.