CN109232595B - Rhodamine B free radical fluorescent probe, preparation method and application thereof in free radical detection in production process of acrylic acid and ester - Google Patents
Rhodamine B free radical fluorescent probe, preparation method and application thereof in free radical detection in production process of acrylic acid and ester Download PDFInfo
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Abstract
The invention discloses a rhodamine B free radical fluorescent probe, a preparation method and application thereof in free radical detection in the production process of acrylic acid and ester. The rhodamine B free radical fluorescent probe is a rhodamine B fluorescent probe modified by 4-hydroxypiperidinol oxyradical, and has a structure shown in a formula (I):
Description
Technical Field
The invention belongs to the technical field of fluorescent probes and preparation of acrylic acid and ester, and relates to a rhodamine B free radical fluorescent probe, a preparation method and application of the probe in free radical detection in the production process of acrylic acid and ester.
Background
The rhodamine B derivative has good fluorescence emission, high quantum yield and hole transmission efficiency, and is often used for researching a fluorescent probe or a chemical sensor for detecting metal ions after the structure modification; 4-hydroxypiperidinol oxygen free radical is a free radical type polymerization inhibitor widely used in acrylic acid and ester industries; at present, the rhodamine B derivative modified by 4-hydroxypiperidinol oxyradical is not reported to be used for detecting free radicals.
Acrylic acid is a very important unsaturated organic acid, and acrylic acid and ester mainly refer to acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate and isooctyl acrylate, and are important organic chemical raw materials. The main consumption fields of acrylic acid and ester in China comprise daily use, textile, adhesive, coating, leather and other industries.
The acrylic acid and ester are industrially produced in the 30 s of the 20 th century, and the production method of the acrylic acid and ester is improved for several times, but the production process of the acrylic acid and ester always faces the trouble of polymerization blockage. In the production process of acrylic acid and ester, due to the processes of high-temperature reaction, rectification and the like, the double bonds of the acrylic acid and ester are easy to generate free radicals, so that the free radical polymerization is initiated. Although the polymerization can be delayed by adding a polymerization inhibitor, inhibiting air from polymerization, reducing dead zones and other measures after technical transformation, most of the blockage, stopping and the like caused by polymerization problems are caused by long-term accumulation or implosion of free radical polymerization, which causes great trouble to the production and operation of the whole device.
At present, no research report of a free radical detection reagent in the production process of acrylic acid and ester exists, and polymerization of a device is timely warned by detecting free radicals, so that a polymerization inhibitor or other process parameters are adjusted, and the method has important significance for production of acrylic acid and ester.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a rhodamine B free radical fluorescent probe and a preparation method thereof.
Meanwhile, aiming at the defects of a free radical polymerization monitoring means in the production process of acrylic acid and ester, the application of the probe in free radical detection in the production process of acrylic acid and ester is provided.
A rhodamine B free radical fluorescent probe is a rhodamine B fluorescent probe modified by 4-hydroxypiperidinol oxyradical, and has a structure shown in a formula (I):
a preparation method of a rhodamine B free radical fluorescent probe shown as a formula (I) comprises the following steps: firstly, preparing a compound shown in a formula (IV) by reacting 4-hydroxy-2, 2,6, 6-tetramethyl piperidine nitroxide free radical shown in a formula (II) with 2-aminoethanol shown in a formula (III); then, reacting the compound of formula (IV) with rhodamine B of formula (V) to prepare the rhodamine B free radical fluorescent probe shown in formula (I); the reaction formula is as follows:
the preparation method of the rhodamine B free radical fluorescent probe comprises the following steps:
1) mixing 4-hydroxy-2, 2,6, 6-tetramethyl piperidine nitroxide free radical (ZJ-701) shown in formula (II), 2-aminoethanol shown in formula (III), a catalyst and a solvent, heating and refluxing for 2-6 hours, preferably 3-4 hours, under the protection of nitrogen, cooling to room temperature, adding glacial acetic acid, separating out an orange yellow solid, adding water until the solid is completely dissolved, standing for layering, drying an organic phase, and performing rotary evaporation to obtain a compound shown in formula (IV);
2) mixing rhodamine B shown in a formula (V), a compound shown in a formula (IV) and a solvent, heating and refluxing for 2-6 h, preferably 3h, cooling to room temperature, adding water, extracting by ethyl acetate, drying an organic phase, carrying out rotary evaporation, and purifying to obtain an orange yellow solid, namely the rhodamine B free radical fluorescent probe.
In the step 1), the catalyst is NaH or CaH2Preferably NaH;
in the step 1), the solvent is at least one of toluene and tetrahydrofuran, and toluene is preferred;
in the step 1), the molar ratio of the 2-aminoethanol in the formula (III) to the 4-hydroxy-2, 2,6, 6-tetramethylpiperidine nitroxide radical in the formula (II) is 2-4: 1, preferably 3: 1;
in the step 1), the concentration of the 2-aminoethanol in the formula (III) in a solvent is 0.1-0.2 g/mL, preferably 0.15 g/mL;
in the step 1), the molar ratio of the catalyst to the 2-aminoethanol of the formula (III) is 1-1.5: 1, preferably 1.4: 1;
in the step 1), the molar ratio of the glacial acetic acid to the NaH is 1.5-3: 1, preferably 2: 1;
in the step 1), preferably, 2-aminoethanol, NaH and a solvent are mixed to obtain a 2-aminoethanol solution, then, 4-hydroxy-2, 2,6, 6-tetramethylpiperidine nitroxide free radical shown in the formula (II) is dissolved in the solvent to prepare a solution with the concentration of 0.01-0.1 g/mL, preferably 0.05g/mL, and then, the solution is added into the 2-aminoethanol solution;
in the step 1), after standing and layering, extracting a water phase by using ethyl acetate, and combining the water phase with an organic phase; the organic phase was dried over anhydrous magnesium sulfate.
In the step 2), the molar ratio of rhodamine B in the formula (V) to the compound in the formula (IV) is 2-3: 1, preferably 2: 1;
in the step 2), the concentration of the rhodamine B in the formula (V) in a solvent is 1-2.5 g/mL, and preferably 1.5 g/mL;
in the step 2), the solvent is at least one of absolute ethyl alcohol and absolute acetonitrile, and preferably absolute ethyl alcohol;
in the step 2), the adding amount of water is 200-300 times, preferably 250 times of the mass of rhodamine B in the formula (V); extracting the reaction liquid for 3 times by using ethyl acetate, and combining organic phases, wherein the volume ratio of the reaction liquid to the ethyl acetate is 1-3: 1; the organic phase was dried over 5 wt% anhydrous magnesium sulfate; purifying by silica gel column chromatography, wherein the developing solvent is ethyl acetate and petroleum ether with the volume ratio of 1: 1.
The rhodamine B free radical fluorescent probe is applied to free radical detection in the production process of acrylic acid and ester.
When the rhodamine B free radical fluorescent probe is used for free radical detection in the production process of acrylic acid and ester, the rhodamine B free radical fluorescent probe is complexed with free radicals in a solvent according to the stoichiometric ratio of 1:1, and the ligand fluorescence quantum yield can be increased by 3.4-3.6 times due to the structural change of rhodamine B in the complexing process through the conjugation effect, and the specific expression is that the fluorescence intensity of a fluorescence emission spectrum is increased at 565 nm.
The invention discloses a method for detecting free radicals in the production process of acrylic acid and ester by using a rhodamine B free radical fluorescent probe, which comprises the following steps:
1) the rhodamine B free radical fluorescence probe is prepared by using a solvent with the concentration of 1 multiplied by 10-3～5×10-3g/L, preferably 1X 10-3g/L of fluorescent probe indicator solution;
2) mixing the fluorescent probe indicator solution obtained in the step 1) with a sample to be detected, and detecting the fluorescence emission spectrum change of the solution by using a fluorescence spectrometer;
3) if an increase in fluorescence intensity occurs at 565nm, it is confirmed that the solution contains radicals, and then the concentration of the radicals in the sample to be detected is calculated from the fluorescence titration curve.
In the step 1), the solvent is at least one of absolute ethyl alcohol, acetonitrile, acetone and tetrahydrofuran, and preferably absolute ethyl alcohol;
in the step 2), the mixing mass ratio of the fluorescent probe indicator solution to the sample to be detected is (30-100): (0.5 to 3), preferably 50: 1;
in the step 2), the sample to be detected is a sample in the production process of acrylic acid or acrylic ester, and tower bottom liquid or tower top liquid from an acrylic acid and ester production system; the temperature of a sample to be detected is 15-45 ℃, and preferably 25 ℃;
in the step 3), the method for drawing the fluorescence titration curve comprises the following steps: a radical polymerization initiator, preferably Azobisisobutyronitrile (AIBN), is mixed with a solvent to prepare a gradient concentration (0.1X 10)-3～12×10-3g/L) of the free radical polymerization initiator standard solution, respectively adding the free radical polymerization initiator standard solution into a fluorescent probe indicator solution, detecting the change of a fluorescence emission spectrum of the solution by a fluorescence spectrometer, and drawing a fluorescence titration curve according to the fluorescence intensity of the solution at 565 nm.
In the step 3), if the concentration of the free radicals in the sample to be detected is more than 1000ppm, the polymerization risk in the production process of the acrylic acid or the acrylic ester is proved. And further prevents the polymerization of the system by adjusting polymerization inhibitor or other process parameters.
Acrylic acid and ester are important chemical products, and have important application in the fields of Super Absorbent Polymer (SAP), coating, adhesive, water reducing agent and the like. But because the acrylic acid and the ester have double bond functional groups, the acrylic acid and the ester have high polymerization activity, and the problem of system polymerization is very easy to occur in the production and storage processes, thereby bringing great troubles to the production and the use of the acrylic acid and the ester.
The rhodamine B free radical fluorescence probe has the characteristics of fluorescence identification, interference resistance and low detection limit on free radicals in a system, can effectively detect and monitor the concentration of free radicals generated in the production process of acrylic acid and ester and the concentration of the free radicals in a solution system, and prevents the occurrence of system polymerization.
Drawings
FIG. 1 is a histogram of fluorescence intensity changes of rhodamine B radical fluorescent probe after different substances are added to an ethanol solution (fluorescence changes of the fluorescent probe after different substances are added);
FIG. 2 is a graph showing the change of fluorescence intensity of rhodamine B radical fluorescent probe added with azodiisobutyronitrile of different equivalent weight with the change of radical concentration (fluorescence titration curve: the change of fluorescence intensity of fluorescent probe added with initiator AIBN of different equivalent weight with the change of radical concentration);
FIG. 3 is a bar graph showing the change of fluorescence intensity of methyl ester products with different contents of polymerization inhibitors and different storage periods added to rhodamine B radical fluorescence probe (the change of fluorescence intensity of methyl ester products with different contents of polymerization inhibitors and different storage periods added to fluorescence probe).
Detailed Description
The technical solutions of the present invention are further illustrated in detail by the following examples, which should be understood as merely showing the present invention in more detail, and not limiting the contents of the present invention in any way.
In the following examples, the reagents are analytically pure, Chinese medicine reagents; the water used is deionized water.
The adopted main detection instrument and method are as follows: bruker Avance 300 NMR spectrometer (TMS as internal standard, DMSO-d6 as solvent); LS-55 fluorescence/phosphorescence/luminescence spectrophotometer (Perkinelmer) (excitation 530 nm).
The invention discloses a selective verification method of a rhodamine B free radical fluorescent probe on free radicals, metal ions and monomers, which comprises the following steps:
Wherein, the ethanol solution containing azodiisobutyronitrile and the ethanol solution containing potassium persulfate are firstly placed in an environment of 70 ℃ for 30min, and then all the solutions are detected to detect the fluorescence emission spectrum intensity change under the condition of 30 ℃, as shown in figure 1.
The contrast shows that the fluorescence intensity of the solution containing azodiisobutyronitrile and potassium persulfate is obviously enhanced. As azodiisobutyronitrile and potassium persulfate are used as conventional radical polymerization initiators and can be decomposed to generate radicals at 70 ℃, the fluorescence intensity at 565nm is enhanced by about 1.9 and 2.3 times respectively, and the fluorescence quantum yield is increased by about 3.5 times.
Experiments prove that the rhodamine B free radical fluorescent probe can be complexed with free radicals in an ethanol solution according to the stoichiometric ratio of 1:1, as shown in figure 2, and the fluorescence quantum yield of a ligand can be increased by about 3.5 times due to the structural change of rhodamine B in the complexing process. Therefore, the rhodamine B free radical fluorescent probe has unique fluorescence selectivity, higher sensitivity, lower detection limit and stronger anti-interference capability on free radicals in an ethanol solution.
Preparation of second, rhodamine B free radical fluorescent probe
Example 1
A preparation method of a rhodamine B free radical fluorescent probe comprises the following steps:
1) 2-aminoethanol (1.22g, 20mmol), NaH (1.12g, 28mmol) and toluene (20mL) were combined in a 150mL round bottom flask; then ZJ-701(1.88g, 10mmol) was dissolved in 20mL of toluene and added dropwise to the round bottom flask; the above hybrid system is N2Heating and refluxing for 4h under protection; after the reaction is finished, cooling to room temperature, adding 10mL of glacial acetic acid, precipitating orange-yellow solid, adding a proper amount of cold water until the solid is completely dissolved, separating a toluene layer, extracting an aqueous phase by using ethyl acetate (3X 100mL), drying and filtering an organic phase by using anhydrous magnesium sulfate, and performing rotary evaporation to obtain 2.66g of the compound shown in the formula (IV) and the yield is 85%;
2) adding rhodamine B (1.0g and 2.1mmol), a compound (IV) (0.69g and 3mmol) and 20mL of ethanol into a round-bottom flask, heating and refluxing for 3h, and then adding 40mL of water into the solution; the solution was extracted 3 times with 50mL ethyl acetate, the organic phases were combined and dried over anhydrous magnesium sulfate, filtered and rotary evaporated to give a solid, and the crude product was purified by silica gel column chromatography (developing solvent was ethyl acetate: petroleum ether: 1) to give an orange-yellow solid, i.e., rhodamine B-based radical fluorescent probe, 0.65 g.
High-resolution mass spectrometry: HRMS: calcd for [ M + H ] + C39H5N 4O: 639.8541, respectively; found: 639.3949.
example 2
A preparation method of a rhodamine B free radical fluorescent probe comprises the following steps:
1) 2-aminoethanol (1.83g, 30mmol), NaH (1.2g, 30mmol) and tetrahydrofuran (20mL) were combined in a 150mL round bottom flask; then ZJ-701(1.88g, 10mmol) was dissolved in 20mL tetrahydrofuran and added dropwise to the round bottom flask; the above hybrid system is N2Heating and refluxing for 2h under protection; after the reaction is finished, cooling to room temperature, adding 20mL of glacial acetic acid, precipitating orange-yellow solid, adding a proper amount of cold water until the solid is completely dissolved, separating a toluene layer, extracting a water phase by using ethyl acetate, drying and filtering an organic phase by using anhydrous magnesium sulfate, and performing rotary evaporation to obtain 2.66g of the compound shown in the formula (IV) with the yield of 88%;
2) rhodamine B (2.85g,6mmol), a compound of formula (IV) (0.69g, 3mmol) and 20mL of acetonitrile are added into a round-bottom flask, heated and refluxed for 3h, and then 40mL of water is added into the solution; the solution was extracted 3 times with ethyl acetate (3 × 100mL), the organic phases were combined and dried over anhydrous magnesium sulfate, filtered and rotary evaporated to give a solid, and the crude product was purified by silica gel column chromatography (the developing solvent was ethyl acetate: petroleum ether: 1) to give an orange-yellow solid, i.e., rhodamine B-based radical fluorescent probe, 0.68 g.
High-resolution mass spectrometry: HRMS: calcd for [ M + H ] + C39H5N 4O: 639.8541, respectively; found: 639.3949.
example 3
A preparation method of a rhodamine B free radical fluorescent probe comprises the following steps: 1) 2-aminoethanol (1.22g, 20mmol), CaH2(1.28g, 30mmol) and toluene (30mL) were combined and added to a 150mL round bottom flask; then ZJ-701(1.88g, 10mmol), dissolved in 20mL of toluene, was added drop-wise to the round-bottom flask; the above hybrid system is N2Heating and refluxing for 3h under protection, cooling to room temperature after reaction, adding 10mL glacial acetic acid to precipitate orange solid, adding appropriate amount of cold water to dissolve the solid completely, separating toluene layer, extracting water phase with ethyl acetate (3 × 100mL), and collecting organic phaseDrying and filtering the mixture by using anhydrous magnesium sulfate, and carrying out rotary evaporation to obtain 2.47g of the compound of the formula (IV) with the yield of 79%;
2) adding rhodamine B (1.0g and 2.1mmol), a compound (IV) (0.69g and 3mmol) and 20mL of ethanol into a round-bottom flask, heating and refluxing for 3h, and then adding 40mL of water into the solution; the solution is extracted by ethyl acetate for 3 times, organic phases are combined and dried by anhydrous magnesium sulfate, the solid is obtained by filtration and rotary evaporation, and the crude product is purified by silica gel column chromatography (the developing solvent is ethyl acetate: petroleum ether: 1) to obtain orange yellow solid, namely rhodamine B free radical fluorescent probe, 0.58 g.
High-resolution mass spectrometry: HRMS: calcd for [ M + H ] + C39H5N 4O: 639.8541, respectively; found: 639.3949.
application of rhodamine B free radical fluorescent probe in free radical detection in production process of acrylic acid and ester
Example 4
Monitoring the polymerization condition of the tower kettle of the dehydration tower of the acrylic acid device, wherein the rhodamine B free radical fluorescent probe prepared in the embodiment 1 is adopted, and a sample to be detected is taken from the tower kettle sample of the dehydration tower of a refining system of the acrylic acid device (Mitsubishi technology), and the specific method comprises the following steps:
1) the rhodamine B free radical fluorescent probe prepared in the example 1 is prepared by absolute ethyl alcohol with the concentration of 1 × 10- 3g/L of fluorescent probe indicator solution;
2) drawing a fluorescence titration curve: azodiisobutyronitrile (AIBN) is prepared by absolute ethyl alcohol to have gradient concentration range of 0.1 × 10-3～12×10-3g/L of Azodiisobutyronitrile (AIBN) ethanol standard solution is added into the fluorescent probe indicator solution respectively, the change of a fluorescence emission spectrum of the solution is detected by a fluorescence spectrometer, and a fluorescence titration curve is drawn according to the fluorescence intensity of the solution at 565nm (figure 2);
3) mixing a sample to be detected (at the temperature of 25 ℃) and a fluorescent probe indicator solution according to the mass ratio of 1:50, and detecting the change of a fluorescence emission spectrum of the solution by a fluorescence spectrometer;
4) and (3) detecting to find that the fluorescence intensity of the solution system at 565nm is obviously enhanced, proving that the solution contains free radicals, and then calculating the concentration of the free radicals in the sample to be detected according to a fluorescence titration curve.
By comparing the free radical concentration and the fluorescence titration curve in the graph of fig. 2, the free radical concentration of the system is 843ppm, the free radical content of the system is higher and approaches to the lower limit value of the polymerization risk, the amount of the polymerization inhibitor and the amount of the polymerization inhibiting air of the tower are increased for adjustment, the adjusted tower kettle is sampled, the above steps are repeated for analysis and detection, the free radical content is reduced to 241ppm, the effect is obvious, and the embodiment is proved to effectively monitor the polymerization tendency of the acrylic acid device.
Example 5
Monitoring the polymerization condition of a butyl acrylate device reactor, taking a sample at the outlet of a second reactor of a butyl acrylate device in a plasticizing process as a sample to be detected, and comprising the following specific implementation method:
1) the rhodamine B free radical fluorescence probe prepared in the example 2 is prepared by absolute ethyl alcohol with the concentration of 1 × 10- 3g/L of fluorescent probe indicator solution;
2) mixing a sample to be detected (at the temperature of 25 ℃) and a fluorescent probe indicator solution according to the mass ratio of 1:50, and detecting the change of a fluorescence emission spectrum of the solution by a fluorescence spectrometer;
3) the mixed solution was tested for fluorescence activity by fluorescence spectrometer and found to have a peak at 565nm with pure 10-3The ethanol solution of the fluorescent probe indicator in g/L is obviously enhanced, by comparing a fluorescence titration curve chart 2 of fluorescence intensity and free radical concentration under the same condition, the concentration of the free radical in the reaction liquid is calculated to be 1800ppm, a reaction system has strong polymerization tendency, and the reaction liquid has the phenomenon of viscosity increase from the appearance, measures must be taken immediately, the device immediately adds a ZJ-701 type efficient polymerization inhibitor into a reactor, after three days of operation, the concentration of the free radical detected by the same method is 800ppm, and the viscosity of the reaction liquid returns to normal; effectively avoiding the occurrence of production accidents.
Example 6
Monitoring the polymerization condition of a methyl acrylate storage tank, taking two grades of methyl acrylate products as detection samples, wherein the content of a polymerization inhibitor MQ (p-hydroxyanisole) of grade 1 is 100ppm, the content of a polymerization inhibitor MQ (p-hydroxyanisole) of grade 2 is 15ppm, the storage temperature is 15-16 ℃, and the storage time is 1 month; the specific implementation method comprises the following steps:
1) the rhodamine B free radical fluorescent probe prepared in the example 3 is prepared by absolute ethyl alcohol with the concentration of 1 × 10- 3g/L of fluorescent probe indicator solution;
2) the sample to be tested (temperature 25 ℃) is prepared into 10-3Mixing the g/L ethanol solution with the fluorescent probe indicator solution according to the mass ratio of 1:1, and detecting the fluorescence emission spectrum change of the solution by using a fluorescence spectrometer;
as shown in FIG. 3, the fluorescence intensity is detected, and the methyl ester product with 15ppm of polymerization inhibitor MQ has more free radicals than the methyl ester product with 100ppm of polymerization inhibitor MQ, and the storage time needs to be controlled.
Claims (10)
1. A rhodamine B free radical fluorescent probe is a rhodamine B fluorescent probe modified by 4-hydroxypiperidinol oxyradical, and has a structure shown in a formula (I):
2. a preparation method of a rhodamine B free radical fluorescent probe shown in a formula (I) is characterized by comprising the following steps: firstly, preparing a compound shown in a formula (IV) by reacting 4-hydroxy-2, 2,6, 6-tetramethyl piperidine nitroxide free radical shown in a formula (II) with 2-aminoethanol shown in a formula (III); then, the compound of formula (IV) reacts with rhodamine B of formula (V) to prepare the rhodamine B free radical fluorescent probe of formula (I); the reaction formula is as follows:
the preparation method comprises the following steps:
1) mixing 4-hydroxy-2, 2,6, 6-tetramethyl piperidine nitroxide free radical of formula (II), 2-aminoethanol of formula (III), catalyst and solvent, wherein the catalyst is NaH or CaH2At least one of (a) and (b),heating and refluxing for 2-6 h under the protection of nitrogen, cooling to room temperature, adding glacial acetic acid, and separating out a solid to obtain a compound shown in the formula (IV);
2) and (3) mixing the rhodamine B shown in the formula (V), the compound shown in the formula (IV) and a solvent, and heating and refluxing for reaction for 2-6 hours to obtain the rhodamine B free radical fluorescent probe.
3. The method of claim 2, wherein: heating reflux reaction for 3-4 h in the step 1); and 2) heating reflux reaction for 3 h.
4. The production method according to claim 3, characterized in that:
in the step 1), the catalyst is NaH; the solvent is at least one of toluene and tetrahydrofuran;
the molar ratio of the 2-aminoethanol in the formula (III) to the 4-hydroxy-2, 2,6, 6-tetramethylpiperidine nitroxide radical in the formula (II) is 2-4: 1; the concentration of the 2-aminoethanol in the formula (III) in a solvent is 0.1-0.2 g/mL; the molar ratio of the catalyst to the 2-aminoethanol shown in the formula (III) is 1-1.5: 1; the molar ratio of the glacial acetic acid to the NaH is 1.5-3: 1.
5. The production method according to claim 3, characterized in that: in the step 2), the molar ratio of rhodamine B in the formula (V) to a compound in the formula (IV) is 2-3: 1; the concentration of the rhodamine B in the formula (V) in a solvent is 1-2.5 g/mL; the solvent is at least one of absolute ethyl alcohol and absolute acetonitrile.
6. The application of the rhodamine B free radical fluorescent probe as defined in claim 1 or the rhodamine B free radical fluorescent probe prepared by the preparation method as defined in any one of claims 2-5 in free radical detection in the production process of acrylic acid and acrylate.
7. Use according to claim 6, characterized in that: the method for detecting the free radicals in the production process of acrylic acid and acrylic ester by using the rhodamine B free radical fluorescent probe comprises the following steps:
1) the rhodamine B free radical fluorescence probe is prepared by using a solvent with the concentration of 1 multiplied by 10-3～5×10-3g/L of fluorescent probe indicator solution;
2) mixing the fluorescent probe indicator solution obtained in the step 1) with a sample to be detected, and detecting the fluorescence emission spectrum change of the solution by using a fluorescence spectrometer;
3) if an increase in fluorescence intensity occurs at 565nm, it is confirmed that the solution contains radicals, and then the concentration of the radicals in the sample to be detected is calculated from the fluorescence titration curve.
8. Use according to claim 7, characterized in that:
in the step 1), the solvent is at least one of absolute ethyl alcohol, acetonitrile, acetone and tetrahydrofuran;
in the step 2), the mass ratio of the fluorescent probe indicator solution to the sample to be detected is (30-100): (0.5 to 3).
9. Use according to claim 7, characterized in that: the method for drawing the fluorescence titration curve comprises the following steps: mixing a free radical polymerization initiator and a solvent to prepare a free radical polymerization initiator standard solution with gradient concentration, respectively adding the free radical polymerization initiator standard solution into a fluorescent probe indicator solution, detecting the change of a fluorescence emission spectrum by a fluorescence spectrometer, and drawing a fluorescence titration curve according to the fluorescence intensity of the fluorescence emission spectrum at 565 nm.
10. Use according to any one of claims 7 to 9, wherein: in step 3), if the concentration of free radicals in the sample to be tested is > 1000ppm, there is a risk of polymerization during the production of the acrylic acid or acrylate.
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