阅读说明：本技术 Dha粉剂中过氧化值的测定方法 (Method for measuring peroxide value in DHA powder ) 是由 王程 管乐 代江华 刘洋 周兴旺 熊文英 于 2019-09-25 设计创作，主要内容包括：本发明公开一种方法简单、易于实施的DHA粉剂中过氧化值的测定方法；它包括如下步骤：a.试样去包埋脱溶后在三氯甲烷和冰乙酸中溶解；b.其内的过氧化物与碘化钾反应生成碘并用硫代硫酸钠标液滴定析出；c.公式计算。(The invention discloses a method for measuring peroxide value in DHA powder, which is simple and easy to implement; it comprises the following steps: a. removing embedding and desolventizing of a sample, and dissolving the sample in trichloromethane and glacial acetic acid; b. the peroxide in the solution reacts with potassium iodide to generate iodine, and sodium thiosulfate standard solution is used for dropwise separation; c. and (4) formula calculation.)

1. A method for measuring peroxide value in DHA powder is characterized by comprising the following steps: it comprises the following steps:

a. removing embedding and desolventizing of a sample, and dissolving the sample in trichloromethane and glacial acetic acid;

b. the peroxide in the solution reacts with potassium iodide to generate iodine, and sodium thiosulfate standard solution is used for dropwise separation;

c. and (4) formula calculation.

2. A method for determining peroxide value in DHA powder according to claim 1, wherein: the step a comprises the following steps:

a1, removing embedding and desolventizing the sample, comprising the following steps:

a11, de-embedding: removing outer layer substances wrapping DHA powder;

a12, desolventizing, namely dissolving the ester-like substances in the DHA powder in an organic reagent;

a13, volatilizing the organic reagent by distillation or nitrogen blowing to obtain fat;

2, adding 50ml of distilled water into a 500ml separating funnel, weighing 30g of fat in the separating funnel, and slightly shaking to ensure that the powder is dispersed in the water but is not completely dissolved;

a3, adding 120ml petroleum ether, fully shaking to completely emulsify the mixture;

a4, adding 150ml absolute ethyl alcohol into the emulsion along the glass wall of the liquid separation drain, shaking gently to allow the emulsion to stand and separate, and separating the upper organic phase into V₂、V₃Two parts;

a5, organic phase V₂Drying at 100 deg.C after partial desolventizing to determine oil mass m and organic phase V₃After the part is vacuumized and desolventized at 30 ℃, 30ml of a mixed solution of trichloromethane and glacial acetic acid is added, and the sample is shaken gently to be completely dissolved.

3. A method for determining peroxide value in DHA powder according to claim 1, wherein: the step b comprises the following steps:

b1, adding 1.00ml of saturated potassium iodide solution, sealing the bottle mouth, slightly shaking for 0.5min, standing in the dark for 3min, adding 100ml of water, shaking uniformly, and immediately dripping the precipitated iodine by using corresponding sodium thiosulfate standard liquid;

b2, when the solution is titrated to light yellow, adding 1mL of starch indicator, continuing to titrate and strongly shaking until the blue color disappears, and simultaneously carrying out a blank test, wherein the volume of the sodium thiosulfate standard solution with the consumption concentration of 0.01mol/L in the blank test cannot exceed 0.1 mL.

4. A method for determining peroxide value in DHA powder according to claim 1, wherein: in step c, the formula is as follows:

in the formula:

X₁peroxide value, unit: g/100 g;

V₁sample consumption sodium thiosulfate standard liquid volume, unit: ml;

V₀consumption of the blank by the sodium thiosulfate standard volume, unit: ml;

V₂volume of organic phase to be desolventized and weighed, unit: ml;

V₃volume of organic phase to be desolventized titrated, unit: ml;

m-organic phase V₂The mass of the oil after desolventizing is as follows, unit: g;

c-concentration of sodium thiosulfate standard solution, unit: mol/L;

0.1269-mass of iodine equivalent to that of a sodium thiosulfate standard solution having a concentration of 1.0 mol/L.

The results calculated using this formula are expressed as the arithmetic mean of two independent measurements obtained under repetitive conditions, which must not exceed 10% of the arithmetic mean, with the result remaining a 2-digit significance.

5. A method for determining peroxide value in DHA powder according to claim 3, wherein: in step b1, when the estimated peroxide value in the solution is <0.15g/100g, 0.002mol/L sodium thiosulfate is used; when the estimated peroxide value in the solution was >0.15g/100g, 0.01mol/L sodium thiosulfate was used.

6. A method for determining peroxide value in DHA powder according to claim 5, characterized in that: in step b1, the sodium thiosulfate is sodium thiosulfate pentahydrate.

7. A method for determining peroxide value in DHA powder according to claim 6, characterized in that: in step b1, a standard solution of 0.1mom/L sodium thiosulfate was prepared as follows: weighing 25g of sodium thiosulfate pentahydrate, adding 0.2g of anhydrous sodium carbonate, dissolving in 1000mL of water, slowly boiling for 10min, cooling, standing for 2 weeks, and filtering.

The 0.01mom/L sodium thiosulfate standard solution is prepared as follows: is prepared by diluting 0.1mol/L sodium thiosulfate standard solution with fresh boiled cooling water.

The preparation method of the 0.002mom/L sodium thiosulfate standard solution is as follows: is prepared by diluting 0.1mol/L sodium thiosulfate standard solution with fresh boiled cooling water.

8. A method for determining peroxide value in DHA powder according to claim 3, wherein: in step b2, the starch indicator is prepared as follows: weighing 0.5g of soluble starch, dissolving in 50ml of boiling water, boiling for 3min, and cooling.

9. A method for determining peroxide value in DHA powder according to claim 3, wherein: in step b1, the preparation method of the saturated solution of potassium iodide is as follows: weighing 20g of potassium iodide, adding 10ml of newly boiled and cooled water, shaking uniformly, storing in a brown bottle, and storing in a dark place for later use; the saturated potassium iodide solution is used to ensure that saturated potassium iodide crystals exist.

10. A method for determining peroxide value in DHA powder according to claim 2, wherein: in step a5, in the mixed solution of trichloromethane and glacial acetic acid, trichloromethane: the volume ratio of the glacial acetic acid is as follows: 2: 3.

Technical Field

The invention relates to the technical field of detection of DHA in milk powder, in particular to a method for determining a peroxide value in DHA powder.

Background

At present, the determination of the peroxide value in the DHA powder is generally carried out detection and determination through a third-party detection mechanism, the mode needs to send a sample to the third-party detection mechanism during determination, the efficiency is low in time, the requirement for rapid result output cannot be met, and enterprises cannot carry out determination at any time according to the self requirement in actual production because the enterprises do not master the detection method of the peroxide value in the DHA powder.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, adapt to the practical requirements and provide the method for measuring the peroxide value in the DHA powder, which is simple and easy to implement.

In order to realize the purpose of the invention, the technical scheme adopted by the invention is as follows:

discloses a method for measuring peroxide value in DHA powder, which comprises the following steps:

a. removing embedding and desolventizing of a sample, and dissolving the sample in trichloromethane and glacial acetic acid;

b. the peroxide in the solution reacts with potassium iodide to generate iodine, and sodium thiosulfate standard solution is used for dropwise separation;

c. and (4) formula calculation.

The step a comprises the following steps:

a1, removing embedding and desolventizing the sample, comprising the following steps:

a11, de-embedding: removing outer layer substances wrapping DHA powder;

a12, desolventizing, namely dissolving the ester-like substances in the DHA powder in an organic reagent;

a13, volatilizing the organic reagent by distillation or nitrogen blowing to obtain fat;

2, adding 50ml of distilled water into a 500ml separating funnel, weighing 30g of fat in the separating funnel, and slightly shaking to ensure that the powder is dispersed in the water but is not completely dissolved;

a3, adding 120ml petroleum ether, fully shaking to completely emulsify the mixture;

a4, adding 150ml absolute ethyl alcohol into the emulsion along the glass wall of the liquid separation drain, shaking gently to allow the emulsion to stand and separate, and separating the upper organic phase into V₂、V₃Two parts;

a5, organic phase V₂Drying at 100 deg.C after partial desolventizing to determine oil mass m and organic phase V₃After the part is vacuumized and desolventized at 30 ℃, 30ml of a mixed solution of trichloromethane and glacial acetic acid is added, and the sample is shaken gently to be completely dissolved.

The step b comprises the following steps: .

b1, adding 1.00ml of saturated potassium iodide solution, sealing the bottle mouth, slightly shaking for 0.5min, standing in the dark for 3min, adding 100ml of water, shaking uniformly, and immediately dripping the precipitated iodine by using corresponding sodium thiosulfate standard liquid;

b2, when the solution is titrated to light yellow, adding 1mL of starch indicator, continuing to titrate and strongly shaking until the blue color disappears, and simultaneously carrying out a blank test, wherein the volume of the sodium thiosulfate standard solution with the consumption concentration of 0.01mol/L in the blank test cannot exceed 0.1 mL.

In step c, the formula is as follows:

in the formula:

X₁peroxide value, unit: g/100 g;

V₁sample consumption sodium thiosulfate standard liquid volume, unit: ml;

V₀consumption of the blank by the sodium thiosulfate standard volume, unit: ml;

V₂volume of organic phase to be desolventized and weighed, unit: ml;

V₃volume of organic phase to be desolventized titrated, unit: ml;

m-organic phase V₂The mass of the oil after desolventizing is as follows, unit: g;

c-concentration of sodium thiosulfate standard solution, unit: mol/L;

0.1269-mass of iodine equivalent to that of a sodium thiosulfate standard solution having a concentration of 1.0 mol/L.

The results calculated using this formula are expressed as the arithmetic mean of two independent measurements obtained under repetitive conditions, which must not exceed 10% of the arithmetic mean, with the result remaining a 2-digit significance.

In step b1, when the estimated peroxide value in the solution is <0.15g/100g, 0.002mol/L sodium thiosulfate is used; when the estimated peroxide value in the solution was >0.15g/100g, 0.01mol/L sodium thiosulfate was used.

In step b1, the sodium thiosulfate is sodium thiosulfate pentahydrate.

In step b1, a standard solution of 0.1mom/L sodium thiosulfate was prepared as follows: weighing 25g of sodium thiosulfate pentahydrate, adding 0.2g of anhydrous sodium carbonate, dissolving in 1000mL of water, slowly boiling for 10min, cooling, standing for 2 weeks, and filtering.

The 0.01mom/L sodium thiosulfate standard solution is prepared as follows: is prepared by diluting 0.1mol/L sodium thiosulfate standard solution with fresh boiled cooling water.

The preparation method of the 0.002mom/L sodium thiosulfate standard solution is as follows: is prepared by diluting 0.1mol/L sodium thiosulfate standard solution with fresh boiled cooling water.

In step b2, the starch indicator is prepared as follows: weighing 0.5g of soluble starch, dissolving in 50ml of boiling water, boiling for 3min, and cooling.

In step b1, the preparation method of the saturated solution of potassium iodide is as follows: weighing 20g of potassium iodide, adding 10ml of newly boiled and cooled water, shaking uniformly, storing in a brown bottle, and storing in a dark place for later use; the saturated potassium iodide solution is used to ensure that saturated potassium iodide crystals exist.

In step a5, in the mixed solution of trichloromethane and glacial acetic acid, trichloromethane: the volume ratio of the glacial acetic acid is as follows: 2: 3.

the invention has the beneficial effects that:

the method for measuring the peroxide value in the DHA powder is simple and easy to implement, and the content of the peroxide value in the DHA powder can be quickly detected by the method.

Detailed Description

The invention is further illustrated by the following examples: