阅读说明：本技术 一种吡唑酮有效成分的检测方法 (Method for detecting active ingredients of pyrazolone ) 是由 陈安源 罗芳 杨伦花 张美艳 郑越晴 王舒萍 于 2018-08-15 设计创作，主要内容包括：本发明属于化合物检测领域,具体公开了一种吡唑酮有效成分的检测方法,所述检测方法为通过碘取代反应方法来检测反应体系中的吡唑酮类有效成分,所述检测方法包括待检样品溶解、滴定和空白校正。在滴定过程中,滴定溶液与待检样品反应时在待检样品的苯环上发生了两个氢位取代,并且不会出现假性终点,因此检测检测结果更加准确,同时此检测方法操作简单,对检测设备和检测环境要求也不高。(The invention belongs to the field of compound detection, and particularly discloses a method for detecting pyrazolone active ingredients. In the titration process, when the titration solution reacts with the sample to be detected, two hydrogen substitution occurs on the benzene ring of the sample to be detected, and no false end point occurs, so that the detection result is more accurate, and meanwhile, the detection method is simple to operate and has low requirements on detection equipment and detection environment.)

1. A method for detecting pyrazolone effective components is characterized in that iodine and pyrazolone substances are subjected to substitution reaction to detect the pyrazolone effective components in a reaction system.

2. The method for detecting pyrazolone active ingredient according to claim 1, comprising the steps of:

(1) weighing a pyrazolone sample in a container, adding distilled water for dispersing, adding a sodium carbonate solution, and stirring to fully dissolve the pyrazolone sample to obtain a dissolved solution;

(2) adding a sodium bicarbonate solution into the dissolved solution in the step (1), and continuously stirring to obtain a mixed solution;

(3) adding a color developing agent into the mixed solution, titrating by using an iodine standard solution, and taking a titration end point when the solution changes color;

(4) carrying out blank test in the same way;

(5) calculating the content of the pyrazolone effective component in the sample according to a formula shown in a formula (I):

omega% (. C. (V-V blank). M/M. (100))

In formula (I): c is the actual concentration of the iodine standard titration solution, mol/l;

v ═ the volume of iodine standard titration solution consumed by titrating the sample, ml;

V_{air conditioner}The volume of iodine standard titration solution consumed for the blank test, ml;

m is the mass of the phenylpyrazolone product equivalent to 1mol/l iodine standard titration solution, g/mol;

m is the sample mass, g.

3. The method for detecting a pyrazolone active ingredient according to claim 1 or 2, wherein the color-developing agent is a starch indicator.

4. A method for detecting pyrazolone active ingredients according to any one of claims 1-3, characterized in that a concentration of the color-developing agent added is 8-12 g/l, and a volume ratio of the color-developing agent to the mixed solution is 0.5-1.5: 6.

5. A method for detecting pyrazolone active ingredients according to any one of claims 1-4, characterized in that a concentration of the color-developing agent added is 10-12 g/l, and a volume ratio of the color-developing agent to the mixed solution is 1-1.5: 6.

6. The method for detecting pyrazolone active ingredient according to any one of claims 1-5, wherein the mass ratio of sodium carbonate in the added sodium carbonate solution to the sample to be detected is 50-60: 100;

preferably, the mass ratio of the added sodium carbonate solution to the sample to be detected is 53-58: 100.

7. The method for detecting pyrazolone active ingredients according to any one of claims 1 to 6, wherein the mass ratio of sodium bicarbonate in the added sodium bicarbonate solution to a sample to be detected is 1-3: 1;

preferably, the mass ratio of the sodium bicarbonate in the sodium bicarbonate solution to the sample to be detected is 2-3: 1.

8. The method for detecting pyrazolone active ingredient according to any one of claims 1 to 7, wherein the concentration of iodine standard solution in the titration process is 0.03-0.06 mol/l.

9. The method for detecting a pyrazolone active ingredient according to any one of claims 1 to 8, which comprises detecting a compound represented by the following general formula (II):

in the formula (II), R is H or-SO₃H. Alkyl or halogen.

10. A method for the detection of a pyrazolone active ingredient according to any one of claims 1-9, in which the compounds of formula (ii) include phenylpyrazolone, p-methylpyrazolone, p-pyrazolone sulfonate and m-pyrazolone sulfonate.

Technical Field

The invention belongs to the field of compound detection, and particularly relates to a method for detecting active ingredients of pyrazolone.

Background

The pyrazolone substance is an important intermediate for synthesizing medicines, pesticide Tyropham, herbicide pyrazolate, dye and the like, has wide application, detects the content of the active ingredients of the pyrazolone in real time in the production process, and has great significance for tracking the reaction process and controlling the product quality, but the prior measuring method of the pyrazolone is rarely reported. The method widely adopted at present is a nitrosation method, and because the nitrosation reaction is carried out on the pyrazolone and a sodium nitrite standard titration solution under an acidic condition, the active ingredient of the pyrazolone in the pyrazolone sample can be detected by using a starch-potassium iodide test paper to check the end point. However, in the detection method, because of nitrosation reaction, the reaction temperature needs to be controlled, the workload is large, meanwhile, starch-potassium iodide test paper is used as an indicator, a false end point exists, the end point is difficult to judge, the detection parallelism is poor, and in addition, NO in the reaction is low^-Due to steric effects, only 1mol substitution occurs, but in actual reaction, two hydrogen sites are substituted, which causes deviation of measurement results. Zhang Li Jie et al disclose a method for quantitatively determining 1, 3-dimethyl-5-pyrazolone by high performance liquid chromatography, through adopting high performance liquid chromatography to quantitatively determine DP (namely 1, 3-dimethyl-5-pyrazolone), the method has good sensitivity, recovery rate and repeatability, but the factors influencing the high performance liquid chromatography technology are more, including mobile phase, detection wavelength, flow velocity, column temperature, fixation and the like, which results in higher analysis cost and longer analysis time, and in addition, the price of the liquid chromatography and the daily maintenance cost are expensive, which also limits the application of the method. Therefore, the detection method for the active ingredients of the pyrazolone is simple to operate, accurate in measurement result and low in detection cost.

The present invention has been made in view of this situation.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the detection method for the active ingredients of the pyrazolone, which has the advantages of simple operation, accurate measurement result and low detection cost.

In order to solve the technical problems, the invention provides a method for detecting pyrazolone effective components, which is a method for detecting the pyrazolone effective components in a reaction system through a substitution reaction of iodine and pyrazolone substances.

In the scheme, after the iodine is added into the solution containing the pyrazolone substance, hydrogen sites on the pyrazolone substance are replaced, when the pyrazolone substance in the reaction system is reacted with the iodine, the micro-excessive iodine in the solution system can perform a color development reaction with the color developing agent, and the detection method is sensitive in color development, and can perform color development with a trace amount of excessive iodine. In the conventional nitrosation detection method, potassium iodide-starch is used as an external indicator, and potassium iodide can be oxidized by air to free iodine under acidic conditions due to strong acidity of a solution in a titrated bath and appear blue with starch to confuse an end point when the acidity of the solution does not reach the end point, so that the real end point needs to be determined by performing a plurality of external tests, and the samples to be detected are lost by the plurality of external tests to increase errors. The detection method of the invention is that the iodine standard solution is directly dripped into the reaction system, the color can be developed by the slight excess iodine, the conditions of false end point and sample loss can not occur, the whole reaction can be completed at room temperature, and the accuracy and operability of the detection result are greatly improved.

Further, the substitution reaction is that two hydrogen position substitutions occur on the pyrazolone substance.

Because the pyrazolone substance has two hydrogen positions for substitution, in the nitrosation process, NO is generated in the reaction^-Due to steric effect, only 1mol of substitution occurs, which also causes deviation of results, and through the iodine substitution method, two hydrogen positions can be substituted simultaneously by utilizing the strong oxidizing property of iodine, thereby more ensuring the accuracy of detection results.

Further, the detection method comprises the steps of sample dissolution to be detected, titration and blank correction.

The white test in the above scheme refers to the result obtained by operating in the same way without adding the sample to be tested or replacing the solution to be tested with an equal amount of solvent. Since titration jump occurs at the end of titration, the titration results need to be corrected with a blank test to reduce errors.

Further, the detection method comprises the following steps:

(1) weighing a pyrazolone sample in a container, adding distilled water for dispersing, adding a sodium carbonate solution, and stirring to fully dissolve the pyrazolone sample to obtain a dissolved solution;

(2) adding a sodium bicarbonate solution into the dissolved solution in the step (1), and continuously stirring to obtain a mixed solution;

(3) adding a color developing agent into the mixed solution, titrating by using an iodine standard solution, and taking a titration end point when the solution changes color;

(4) carrying out blank test in the same way;

(5) calculating the content of the pyrazolone effective component in the sample according to a formula shown in a formula (I):

omega% (. C. (V-V blank). M/M. (100))

In formula (I): c is the actual concentration of the iodine standard titration solution, mol/l;

v ═ the volume of iodine standard titration solution consumed by titrating the sample, ml;

V_{air conditioner}The volume of iodine standard titration solution consumed for the blank test, ml;

m is the mass of the phenylpyrazolone product equivalent to 1mol/l iodine standard titration solution, g/mol;

m is the sample mass, g.

In the scheme, in the titration process, when the oxidation-reduction reaction of the pyrazolone substances and iodine is completed, the iodine in the reaction system slightly excessive can perform a color development reaction with the color developing agent.

The reason why a proper amount of distilled water and distilled water are added before the sample is dissolved in the step (1) is that the sample to be detected is solid powder with small weight, the sample can be uniformly dispersed in the distilled water by adding the distilled water, and the sample can be completely dissolved under the condition that as few solvents as possible are used, so that the influence of the solvents on subsequent titration is reduced.

The addition of the 0.6% sodium bicarbonate solution in the step (2) can buffer the pH value of the solution system to a certain extent, and the change of the pH value is small along with the increase of the titration amount, so that the stability of the titration environment and the titration accuracy are ensured.

The stirring in step (1) and step (2) can be performed by a stirring method known in the chemical field, preferably by a magnetic stirring method, so as to accelerate the dissolution of the sample and promote the uniform stabilization of the solution system.

And (4) blank test in the step (4) refers to the result obtained by operating according to the same method under the condition that a sample to be detected is not added or an equivalent solvent is used for replacing a liquid to be detected. Since titration jump occurs at the end of titration, the titration results need to be corrected with a blank test to reduce errors.

Further, the color developing agent is a starch indicator;

in the reaction, because the pyrazolone solution is beige initially, when the titration is carried out to the reaction end point, a trace amount of excess iodine and starch are easy to generate a blue complex, and a trace amount of blue is slightly brown observed by human eyes in the beige solution and gradually deepens to be blue along with the increase of the iodine amount or the placement in the air. To ensure that the titration value is accurate, when a brownish color is observed, the titration endpoint is determined.

Furthermore, the concentration of the added color developing agent is 8-12 g/l, and the volume ratio of the color developing agent to the mixed solution is 0.5-1.5: 6.

Furthermore, the concentration of the added color developing agent is 10-12 g/l, and the volume ratio of the color developing agent to the mixed solution is 1-1.5: 6.

Further, the mass ratio of the sodium carbonate in the added sodium carbonate solution to the sample to be detected is 50-60: 100;

preferably, the mass ratio of the added sodium carbonate solution to the sample to be detected is 53-58: 100.

Further, the mass ratio of the sodium bicarbonate in the added sodium bicarbonate solution to the sample to be detected is 1-3: 1;

preferably, the mass ratio of the sodium bicarbonate in the sodium bicarbonate solution to the sample to be detected is 2-3: 1.

The sodium bicarbonate solution is added in the scheme, so that the pH value in the solution system can be buffered to a certain extent, the change of the pH value is small along with the increase of the titration amount, and the stability of the titration environment and the titration accuracy are ensured. Preferably, the sodium bicarbonate solution is 0.4-0.8% of sodium bicarbonate by mass.

Further, the concentration of the iodine standard solution in the titration process is 0.03-0.06 mol/l.

Further, the detection method comprises detecting a compound represented by the following general formula (II):

in the formula (II), R is H or-SO₃H. Alkyl or halogen.

In the above scheme, the compounds corresponding to the above general formula are subjected to the reactions shown in formula (iii) and formula (iv) in sequence during the titration by the iodine substitution method:

I₂+2e ═ 2I-formula (iii)

In the reaction, when the reaction of iodine in the reaction system and the pyrazolone substance is finished, a trace amount of excessive iodine can be developed, and the titration end point is obtained, so that a false end point cannot appear.

Further, the compounds in the above formula (II) include phenylpyrazolone, p-methylpyrazolone, p-pyrazolone sulfonate and m-pyrazolone sulfonate.

After the technical scheme is adopted, compared with the prior art, the invention has the following beneficial effects.

1. The detection method is simple to operate, and can be carried out at normal temperature without heating and temperature rise in the detection process;

2. the requirement on detection equipment is low, and the detection can be finished by conventional chemical experimental equipment;

2. in the reaction process, two hydrogen positions are substituted on iodine and pyrazolone substances, so that the deviation is reduced;

3. because trace excess iodine reacts with starch in the reaction, the color can be developed, no false end point occurs, and the measurement result is more accurate

Detailed Description