阅读说明：本技术 一种斐林氏溶液以及糖蜜中总糖的测定方法 (Method for determining total sugar in Fehling solution and molasses ) 是由 熊玉兰 张冲 余志全 韩礼 吴小波 杨秀兰 李涛 于 2019-10-17 设计创作，主要内容包括：本发明提供了一种斐林氏溶液以及糖蜜中总糖的测定方法,解决了现有技术中需先进行预滴定,检验时间偏长的技术问题。它包括A溶液和B溶液,所述B溶液以1000mL计：含酒石酸钾钠364g,氢氧化钠100g,亚铁氰化钾10g-20g,余量为水。本发明的斐林氏溶液,应用其进行单糖滴定检测,取消了次甲基蓝指示剂的加入,并且取消了预滴定,直接进行滴定,减少了操作步骤,都节约了检验时间；滴定终点为蓝色刚好褪去,溶液颜色变为土黄色,蓝色褪去瞬间溶液变为土黄色,终点容易观察,且不会返色；实验精度和准确度均得到明显提高。(The invention provides a method for measuring total sugar in a Fehling solution and molasses, which solves the technical problems that in the prior art, pre-titration is needed firstly and the detection time is long. The solution A comprises a solution A and a solution B, wherein the solution B is measured by 1000 mL: comprising 364g of potassium sodium tartrate, 100g of sodium hydroxide, 10-20 g of potassium ferrocyanide and the balance of water. The Fehling solution is used for monosaccharide titration detection, the addition of a methylene blue indicator is omitted, pre-titration is omitted, titration is directly carried out, operation steps are reduced, and the detection time is saved; the titration end point is that blue just fades, the color of the solution changes into earthy yellow, the solution changes into earthy yellow when the blue fades, the end point is easy to observe, and the solution does not fade; the experimental precision and accuracy are both obviously improved.)

1. A fimbrian solution comprising a solution a and a solution B, characterized in that: the B solution is measured by 1000 mL: comprising 364g of potassium sodium tartrate, 100g of sodium hydroxide, 10-20 g of potassium ferrocyanide and the balance of water.

2. A fimbrian solution according to claim 1, characterized in that: the B solution is measured by 1000 mL: comprising 364g of potassium sodium tartrate, 100g of sodium hydroxide, 12-18 g of potassium ferrocyanide and the balance of water.

3. A fimbrian solution according to claim 2, characterized in that: the B solution is measured by 1000 mL: comprising 364g of potassium sodium tartrate, 100g of sodium hydroxide, 15g of potassium ferrocyanide and the balance of water.

4. A fimbrian solution according to any one of claims 1 to 3, wherein: the preparation method of the solution B comprises the following steps:

(1) weighing potassium sodium tartrate, sodium hydroxide and potassium ferrocyanide according to the proportion;

(2) mixing potassium sodium tartrate and sodium hydroxide, and dissolving with water to prepare a solution I; dissolving potassium ferrocyanide in water to prepare a solution II;

(3) and (3) mixing the solution I and the solution II prepared in the step (2), then diluting the mixture to 1000mL by using water, and uniformly mixing.

5. The fimbrian solution of claim 4, wherein: the A solution is measured by 1000 mL: containing CuSO₄•5H₂O69.278g, and the balance being water.

6. The fimbrian solution of claim 5, wherein: the preparation method of the solution A comprises the following steps: weighing CuSO according to proportion₄•5H₂And O, adding water to dissolve, diluting to 1000mL, and filtering for later use.

7. A method for determining total sugar in molasses is characterized by comprising the following steps: in performing a monosaccharide titration assay, the use of a fimbrine solution according to any one of claims 1 to 6 for performing a monosaccharide titration assay.

8. The method for determining total sugar in molasses according to claim 7, characterized in that: the monosaccharide titration detection method comprises the following specific steps:

① adding 5mL of the solution B into a 250mL conical flask, adding 5mL of the solution A, and then adding 30mL-40mL of distilled water;

② heating to boil and keeping boiling for 2min, immediately and rapidly dripping monosaccharide liquid to be detected from a dropper under boiling state until the blue color of the solution in the conical flask just fades and turns into khaki, which is the end point.

9. The method for determining total sugar in molasses of claim 8, wherein in step ①, distilled water is added in an amount such that the total amount of the solution in the erlenmeyer flask after titration is 60 mL.

10. The method for determining total sugar in molasses according to claim 8 or 9, wherein in step ②, the liquid to be tested is quickly dropped from a dropper, and the time taken for dropping until blue color just fades is less than or equal to 1 min.

Technical Field

The invention relates to a method for determining total sugar in molasses, in particular to a method for determining total sugar in a Fehling solution and molasses.

Background

Molasses is a viscous, black brown and semi-fluid substance, is a byproduct of sugar industry, and has different compositions according to different sugar-making raw materials and processing conditions.

The inspection of total sugar (calculated as invert sugar) in molasses is based on the industry standard of entry and exit inspection and quarantine of the people's republic of China: SN/T1540-2005 molasses inspection protocol appendix C inspection for Total sugars. And (3) checking the principle: the molasses is hydrolyzed, the original invert sugar in the sample and the invert sugar generated after hydrolysis have reducibility, and the reducing substances are measured by a Lane-Ey-non constant volume method. Firstly, a sample is treated, impurities with reducibility such as nonsugar and calcium salt in the sample are removed by lead acetate and a deleading agent, and disaccharide is converted into reducibility monosaccharide by hydrochloric acid. Reducing bivalent copper into univalent copper in a Filin solution with certain alkalinity by monosaccharide, thereby obtaining the content of reducing substances.

Molasses → hydrolysis → reducing sugar (disaccharide) → hydrochloric acid → reducing sugar (monosaccharide) → fihling's solution → end point (divalent copper Cu)²⁺Reduction to monovalent copper Cu⁺)。

Preparation of a standard fihn a solution: weighing copper sulfate (CuSO)₄·5H₂O)69.278g, dissolved in water and weighed to 1000mL, filtered and reserved. Preparation of a fihn's B solution: 346g of potassium sodium tartrate and 100g of sodium hydroxide are weighed, mixed, dissolved by a small amount of water, diluted to 1000mL, placed overnight and filtered for later use.

The detection titration comprises the following steps:

① pre-titration, namely accurately sucking 5mL of the Filin's A solution and the B solution into a 250mL conical flask respectively, adding about 30mL of water, placing the bottles on an asbestos net, heating the bottles until boiling, keeping the boiling temperature for 1min, adding 1 drop of 10g/L methylene blue indicator, boiling the bottles for 1min, immediately titrating the bottles with the prepared monosaccharide liquid to be detected until the blue color is just faded, and thus obtaining the end point.

The reason for carrying out the pre-titration is that the titration reaction speed is high, the titration is completed within 1min from the titration to the end point, the end point is not easy to observe, and the time requirement cannot be met if the pre-titration is not carried out firstly.

② formal titration, adding monosaccharide liquid about 0.5mL less than the pre-titration, boiling for 1min, adding 1 drop of methylene blue indicator, boiling for 1min, and titrating with the monosaccharide liquid to be detected to the end point.

The applicant has found that the prior art has at least the following technical problems:

1. the pre-titration is required first, and the detection time is long.

2. The difference between the requirements of the pre-titration and the formal titration is about 0.5mL, and the actual operation is not easy to grasp, so that the experimental precision is low.

3. The terminal point is blue and just fades, fade the instant and hardly hold, and blue very easily turns back the look (because this titration reaction requires to keep the boiling state, divalent copper reduces to monovalent copper when titrating the terminal point, blue just fades, becomes brick red, when taking up the erlenmeyer flask and carefully seeing the terminal point, the temperature reduces slightly, monovalent copper is oxidized into divalent copper promptly in the air, cause the color reversion, be difficult to judge the terminal point), because of receiving the influence of people's eye color discernment ability, the terminal point is very easily dripped, lead to that the inspection result is on the high side, the experimental accuracy is on the low side.

Disclosure of Invention

The invention aims to provide a Fehling solution to solve the technical problems that in the prior art, pre-titration is needed firstly and the detection time is long. The technical effects that can be produced by the preferred technical scheme in the technical schemes provided by the invention are described in detail in the following.

In order to achieve the purpose, the invention provides the following technical scheme:

the invention provides a Fehling solution, which comprises a solution A and a solution B, wherein the solution B is measured by 1000 mL: comprising 364g of potassium sodium tartrate, 100g of sodium hydroxide, 10-20 g of potassium ferrocyanide and the balance of water.

Further, the B solution is measured by 1000 mL: comprising 364g of potassium sodium tartrate, 100g of sodium hydroxide, 12-18 g of potassium ferrocyanide and the balance of water.

Further, the B solution is measured by 1000 mL: comprising 364g of potassium sodium tartrate, 100g of sodium hydroxide, 15g of potassium ferrocyanide and the balance of water.

Further, the preparation method of the solution B comprises the following steps:

(1) weighing potassium sodium tartrate, sodium hydroxide and potassium ferrocyanide according to the proportion;

(2) mixing potassium sodium tartrate and sodium hydroxide, and dissolving with water to prepare a solution I; dissolving potassium ferrocyanide in water to prepare a solution II;

(3) and (3) mixing the solution I and the solution II prepared in the step (2), then diluting the mixture to 1000mL by using water, and uniformly mixing.

Further, the solution A is measured by 1000 mL: containing CuSO₄·5H₂O69.278g and the balance of water.

Further, the preparation method of the solution A comprises the following steps: weighing CuSO according to proportion₄·5H₂And O, adding water to dissolve, diluting to 1000mL, and filtering for later use.

According to the method for determining total sugar in molasses, provided by the invention, when monosaccharide titration detection is carried out, the monosaccharide titration detection is carried out by using the Fehling solution.

Further, the specific steps of monosaccharide titration detection are as follows:

① adding 5mL of the solution B into a 250mL conical flask, adding 5mL of the solution A, and then adding 30mL-40mL of distilled water;

② heating to boil and keeping boiling for 2min, immediately and rapidly dripping monosaccharide liquid to be detected from a dropper under boiling state until the blue color of the solution in the conical flask just fades and turns into khaki, which is the end point.

Further, in step ①, distilled water is added in an amount such that the total volume of the solution in the flask after titration is 60 mL.

Further, in the step ②, the liquid to be detected is quickly dropped from the dropper, and the time taken for the titration until the blue color just fades is less than or equal to 1 min.

Based on the technical scheme, the embodiment of the invention can at least produce the following technical effects:

the Fehling solution provided by the invention is unchanged from the Fehling A solution; the Fehling B solution is a mixed solution of potassium sodium tartrate, sodium hydroxide and potassium ferrocyanide; when the total sugar in the molasses is measured, the monosaccharide titration detection is carried out by using the total sugar, the addition of a methylene blue indicator is cancelled, the operation steps are reduced, and the detection time is saved; in addition, the pre-titration is cancelled, and the titration is directly carried out, so that the operation steps are reduced, and the inspection time is further saved; in addition, the titration end point is that blue just fades, the color of the solution becomes earthy yellow, the solution becomes earthy yellow when the blue fades, the end point is easy to observe, and the color cannot return; the experimental precision and accuracy are both obviously improved.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.