阅读说明：本技术 苯乙烯含量的测定方法及其应用 (Method for measuring styrene content and application thereof ) 是由 房彩琴 李秋荣 艾相豪 高剑琴 刘慧娜 张�成 董栋 张宁 于 2019-11-19 设计创作，主要内容包括：本发明属于分析技术领域,具体涉及一种样品中苯乙烯含量的测定方法,其包括：称取一定质量的待消解样品,加入浓硝酸进行微波消解,将样品中的苯乙烯消解转化为包含多种硝基苯甲酸的消解液；将消解液制备为样品待测液,进行高效液相色谱测试,获得样品待测液的液相色谱图；通过样品待测液的液相色谱图中各硝基苯甲酸对应的峰面积结合四种硝基苯甲酸的标准曲线计算得到样品待测液中四种硝基苯甲酸的质量浓度,根据公式(I)进行计算。简化了前处理步骤,使前处理更简单、快速；排除了同类物质的干扰,实验重复性、重现性好,准确度高；解决了高含量苯乙烯的测定结果不准确的难题。(The invention belongs to the technical field of analysis, and particularly relates to a method for measuring styrene content in a sample, which comprises the following steps: weighing a certain mass of a sample to be digested, adding concentrated nitric acid to perform microwave digestion, and digesting and converting styrene in the sample into a digestion solution containing multiple nitrobenzoic acids; preparing the digestion solution into a sample solution to be detected, and performing high performance liquid chromatography to obtain a liquid chromatogram of the sample solution to be detected; and (3) calculating by combining the peak area corresponding to each nitrobenzoic acid in the liquid chromatogram of the sample to be detected with the standard curves of the four nitrobenzoic acids to obtain the mass concentrations of the four nitrobenzoic acids in the sample to be detected, and calculating according to the formula (I). The pretreatment steps are simplified, so that the pretreatment is simpler and quicker; the interference of similar substances is eliminated, and the experiment repeatability, the reproducibility and the accuracy are high; the problem of inaccurate determination result of high content styrene is solved.)

1. A method for measuring styrene content is characterized by comprising the following steps,

weighing a certain mass of a sample to be digested, adding concentrated nitric acid to perform microwave digestion, and digesting and converting styrene in the sample into a digestion solution containing multiple nitrobenzoic acids;

preparing the digestion solution into a sample solution to be detected, and performing high performance liquid chromatography to obtain a liquid chromatogram of the sample solution to be detected;

calculating the mass concentration of the four kinds of nitrobenzoic acid in the liquid to be detected by combining peak areas corresponding to the 2-nitrobenzoic acid, the 3-nitrobenzoic acid, the 4-nitrobenzoic acid and the 3, 5-dinitrobenzoic acid in a liquid chromatogram of the liquid to be detected of the sample with standard curves of the four kinds of nitrobenzoic acid, calculating according to a formula (I),

in the formula:

x represents the content percent of styrene in a sample to be digested;

C₂the mass concentration of the 2-nitrobenzoic acid in the sample solution to be detected is mg/mL according to the standard curve;

C₃the mass concentration of the 3-nitrobenzoic acid in the sample solution to be detected is mg/mL according to the standard curve;

C₄the mass concentration of 4-nitrobenzoic acid in the sample solution to be detected is mg/mL according to the standard curve;

C_3,5obtaining the mass concentration of 3, 5-dinitrobenzoic acid in the sample solution to be detected by a standard curve, mg/mL;

v, determining the volume of the sample to be detected to be mL;

m-sample mass to be digested, mg.

2. The method according to claim 1, wherein the step of preparing the digestion solution as a sample solution to be tested comprises: adjusting the pH value of the digestion solution to 0.95-1.05 by using a sodium hydroxide solution and nitric acid, extracting by using an organic solvent incompatible with water to obtain an organic extract, back-extracting the organic extract by using saturated salt water, reserving the organic extract, fixing the volume, and uniformly mixing to obtain the sample solution to be detected.

3. The process according to claim 2, characterized in that the organic solvent is selected from ethers, hydrocarbons or halogenated hydrocarbons.

4. The method of claim 1, wherein, in the high performance liquid chromatography test,

the chromatographic columns used were: c18 reversed phase chromatographic column, particle size 5 μm, inner diameter 2.0-4.6 mm, column length 100-250 mm;

the detector is an ultraviolet visible light detector, and the detection wavelength is 220 nm-250 nm;

and (3) chromatographic detection conditions: the mobile phase is selected from methanol-ammonium acetate water solution, gradient elution is carried out, the flow rate is 1mL/min, the column temperature is 35-40 ℃, and the sample injection volume is 5-10 mu L.

5. The method of claim 4, wherein the chromatographic column has a particle size of 5 μm, an inner diameter of 4.6mm, a column length of 150mm, and gradient elution conditions of:

time, min Methanol, is% An aqueous solution of ammonium acetate, and,％ 0 8 92 15 8 92 17 30 70 22 30 70 25 8 92 30 8 92

。

6. the method according to any one of claims 1-5, further comprising, prior to the microwave digestion:

weighing a certain amount m₁Extracting the sample to be detected, filtering the extracted sample to be detected, and drying the sample to be detected to constant weight m₂Obtaining a dried sample, namely the sample to be digested;

calculating the content Y of the solvent extract in the sample to be detected according to a formula (II),

in the formula:

m₁the mass of the sample to be tested before extraction, in g,

m₂extracting and drying to constant weight sample mass, unit g,

calculating the content Z of the styrene in the sample to be detected according to the formula (III),

7. use of a method according to any one of claims 1 to 5 for detecting the styrene content of a phenolic resin.

8. Use of the method of claim 6 for detecting styrene content in a rubber or rubber composition.

Technical Field

The invention belongs to the technical field of analysis, and particularly relates to a quantitative analysis method for styrene content in a sample, in particular to a quantitative analysis method for styrene content in phenolic resin and rubber.

Background

Phenolic resins are polycondensation products of phenols and aldehydes, and are generally classified into two main categories, namely thermoplastic and thermosetting types, and are specifically applied to the rubber industry, and the phenolic resins can be classified into an adhesion type, a bonding type, a reinforcing type and a vulcanization type according to different use functions of the phenolic resins. In order to reduce the cost or obtain the green, environment-friendly and high-performance resin, various resin manufacturers can modify phenolic resin, and styrene modified phenolic resin is one of the phenolic resin. Phenol, resorcinol, alkylphenol, etc. have high reactivity, can react with aldehydes sufficiently, and styrene is added to control the reactivity of molecules and the length of molecular chains and generate a resin structure with stable and fixed molecular weight distribution. The analysis of the mixing amount of the styrene in the phenolic resin has important guiding significance for competitive product analysis of resin production plants and judgment of resin performance of rubber product plants.

The styrene-butadiene rubber is obtained by random copolymerization of styrene and butadiene monomers, and the chain links of the styrene-butadiene rubber comprise four structural units of styrene, 1, 2-polybutadiene, cis-1, 4-polybutadiene and trans-1, 4-polybutadiene. Wherein, the styrene endows the rubber material with certain strength and abrasion resistance. The level of styrene in the composition during rubber processing directly affects the properties of these materials, and it is therefore important to accurately determine the level of styrene in the rubber and rubber compositions.

At present, the test methods for detecting the styrene content include: infrared spectroscopy, thermogravimetric analysis, pyrolysis gas phase method, refractive index method, ozone decomposition method, spectrophotometric method. The common method for quantifying the content of the styrene is a gas phase method and a spectrophotometric method after digestion, wherein the gas phase method is used for measuring a styrene monomer which can be gasified, and cannot be used for measuring bound styrene which is difficult to gasify; the invention patent with publication number CN105628804A discloses a method for detecting styrene content by ultra-high performance liquid chromatography, which is used for detecting residual styrene in a sample and can not detect combined styrene in the sample; the digested products containing bound styrene such as bound styrene, high styrene resin, styrene block copolymer and the like in rubber are measured by a spectrophotometric method, the content of styrene is measured by combining an empirical formula and a known sample correction coefficient through the absorbance of three groups of nitro, benzene ring and sodium formate in an ultraviolet visible region, although the empirical formula is corrected by a known sample, each sample has difference, the measurement result of the method is inaccurate and has large errors due to overhigh styrene content in the sample, and the measurement result of the method is interfered by the presence of other aromatic substances in the method.

Disclosure of Invention

In order to eliminate the interference of other aromatic substances on the measurement result of the styrene content and accurately quantify the styrene content in a high-content styrene sample, the invention provides a method for quantifying the styrene content by using a liquid chromatography. The specific operation mode is as follows: and (3) nitrifying styrene in the sample into 2-nitrobenzoic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid and 3, 5-dinitrobenzoic acid by using a microwave digestion instrument under the conditions of high temperature and high pressure, wherein the 4-nitrobenzoic acid is a main digestion product. And (3) extracting nitrobenzoic acid from the digestion solution, feeding the obtained product into a liquid chromatograph, separating each digestion product through a liquid chromatographic column, and calculating the content of each nitrobenzoic acid by using a standard curve method so as to calculate the content of styrene in the sample.

The method for measuring the styrene content provided by the embodiment of the invention comprises the following steps,

weighing a certain mass of a sample to be digested, adding concentrated nitric acid to perform microwave digestion, and digesting and converting styrene in the sample into a digestion solution containing multiple nitrobenzoic acids;

preparing the digestion solution into a sample solution to be detected, and performing high performance liquid chromatography to obtain a liquid chromatogram of the sample solution to be detected;

calculating the mass concentration of the four kinds of nitrobenzoic acid in the liquid to be detected by combining peak areas corresponding to the 2-nitrobenzoic acid, the 3-nitrobenzoic acid, the 4-nitrobenzoic acid and the 3, 5-dinitrobenzoic acid in a liquid chromatogram of the liquid to be detected of the sample with standard curves of the four kinds of nitrobenzoic acid, calculating according to a formula (I),

in the formula:

x represents the content percent of styrene in a sample to be digested;

C₂the mass concentration of the 2-nitrobenzoic acid in the sample solution to be detected is mg/mL according to the standard curve;

C₃the mass concentration of the 3-nitrobenzoic acid in the sample solution to be detected is mg/mL according to the standard curve;

C₄the mass concentration of 4-nitrobenzoic acid in the sample solution to be detected is mg/mL according to the standard curve;

C_3,5obtaining the mass concentration of 3, 5-dinitrobenzoic acid in the sample solution to be detected by a standard curve, mg/mL;

v, determining the volume of the sample to be detected to be mL;

m-sample mass to be digested, mg.

Further, the step of preparing the digestion solution into the sample solution to be tested comprises the following steps: adjusting the pH value of the digestion solution to 0.95-1.05 by using a sodium hydroxide solution and nitric acid, extracting by using an organic solvent incompatible with water to obtain an organic extract, back-extracting the organic extract by using saturated salt water, reserving the organic extract, fixing the volume, and uniformly mixing to obtain the sample solution to be detected.

Further, the organic solvent is selected from ether, hydrocarbon or halogenated hydrocarbon.

Further, in the high performance liquid chromatography test,

the chromatographic columns used were: c18 reversed phase chromatographic column, particle size 5 μm, inner diameter 2.0-4.6 mm, column length 100-250 mm; the detector is an ultraviolet visible light detector, and the detection wavelength is 220 nm-250 nm; and (3) chromatographic detection conditions: the mobile phase is selected from methanol-ammonium acetate water solution, gradient elution is carried out, the flow rate is 1mL/min, the column temperature is 35-40 ℃, and the sample injection volume is 5-10 mu L.

Further, the chromatographic column has the particle size of 5 μm, the inner diameter of 4.6mm, the column length of 150mm, and the gradient elution conditions are as follows:

time, min	Methanol, is%	Aqueous ammonium acetate solution,%)
			0	8	92
15	8	92
			17	30	70
22	30	70
			25	8	92
30	8	92

。

The method can be used for detecting the content of the styrene in the phenolic resin.

Further, before the microwave digestion, the method also comprises the following steps:

weighing a certain amount m₁Extracting the sample to be detected, filtering the extracted sample to be detected, and drying the sample to be detected to constant weight m₂Obtaining a dried sample, namely the sample to be digested;

calculating the content Y of the solvent extract in the sample to be detected according to a formula (II),

in the formula:

m₁-mass of sample to be tested, g, before extraction;

m₂extracting and drying to constant weight sample mass g;

calculating the content Z of the styrene in the sample to be detected according to the formula (III),

the above-described method of the present invention can be used for detecting the content of styrene in a rubber or a rubber composition.

The method for measuring the styrene content in the sample provided by the embodiment of the invention simplifies the pretreatment steps, so that the pretreatment is simpler and quicker; the interference of similar substances is eliminated, and the experiment repeatability, the reproducibility and the accuracy are high; the problem of inaccurate determination result of high content styrene is solved.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention and to enable other features, objects and advantages of the invention to be more fully apparent. The drawings and their description illustrate the invention by way of example and are not intended to limit the invention. In the drawings:

FIG. 1 is a standard curve of 2-nitrobenzoic acid in example 1 of the present invention, in which the ordinate represents the mass concentration (in mg/mL) of the mixed standard series solution and the ordinate represents the peak area;

FIG. 2 is a standard curve of 4-nitrobenzoic acid in example 1 of the present invention, in which the ordinate represents the mass concentration (in mg/mL) of the mixed standard series solution and the ordinate represents the peak area;

FIG. 3 is a standard curve of 3-nitrobenzoic acid in example 1 of the present invention, in which the ordinate represents the mass concentration (in mg/mL) of the mixed standard series solution and the ordinate represents the peak area;

FIG. 4 is a standard curve of 3, 5-dinitrobenzoic acid in example 1 of the present invention, in which the ordinate represents the mass concentration (in mg/mL) of the mixed standard series solution and the ordinate represents the peak area;

FIG. 5 is a liquid chromatogram of a standard substance in an example of the present invention;

FIG. 6 is a liquid chromatogram of one of the replicates of example 1 of the present invention; and

FIG. 7 is a liquid chromatogram of one of the replicates of example 2 of the present invention.

Detailed Description

The method for measuring the styrene content in the sample provided by the embodiment of the application comprises the following steps:

firstly, weighing a certain mass of a sample to be digested, adding concentrated nitric acid for microwave digestion, and digesting and converting styrene in the sample into a digestion solution containing 2-nitrobenzoic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid and 3, 5-dinitrobenzoic acid. The quality of the sample is preferably 50-200mg, the dosage of the concentrated nitric acid is preferably 5-7mL, hydrogen peroxide can be added into the sample which is not easy to oxidize for improvement, the dosage of the hydrogen peroxide is preferably 1mL, the digestion equipment is preferably a microwave digestion tank, the digestion condition is preferably power of 400-1600W, the digestion temperature is preferably 150-180 ℃, the temperature is increased to the digestion temperature within 45min and is kept for 30min, and the solution is naturally cooled to room temperature (25 ℃) after digestion is completed, so that the digestion solution is obtained.

When the method is used for detecting the content of the styrene in the phenolic resin, the oil-free rubber or the oil-free rubber composition, the sample to be detected can be directly taken as the sample to be digested for microwave digestion; when the method is used for detecting the content of the styrene in the oil-extended rubber or the oil-extended rubber composition, a sample to be detected needs to be subjected to microwave digestion after extraction or extraction, and the specific method can be that a certain amount m is weighed₁Extracting the sample to be detected, filtering the extracted sample to be detected, and drying the sample to be detected to constant weight m₂And obtaining a dried sample, namely the sample to be digested, for microwave digestion. The content Y,%, of the solvent extract in the sample to be tested can be calculated according to the formula (II). Wherein the proportion of the sample and the extraction solvent adopted in the extraction process is (0.5-5.0g) sample/(8-30 mL) extraction solvent; the extraction solvent is preferably acetone or a mixture of acetone-chloroform. When the sample to be detected is raw styrene butadiene rubber or rubber composition rubber compound containing styrene butadiene rubber, acetone is selected as a solvent; when the sample to be detected is the vulcanized rubber of the rubber composition containing the styrene butadiene rubber, a mixture of acetone and trichloromethane is selected as a solvent, and the volume ratio of the acetone to the trichloromethane is 20: 80-50: 50, preferably 30: 70-35: 65.

The extraction method in the above method is preferably microwave extraction, and the conditions are set as follows: 220V +/-10% of a power supply; the ambient temperature is 15-30 ℃; the relative humidity is 20-80%, the power is 400-.

Then, the last one isAnd preparing the digestion solution prepared in the step into a sample solution to be detected, and performing high performance liquid chromatography to obtain a liquid chromatogram of the sample solution to be detected. The step of preparing the digestion solution into the sample solution to be tested can be specifically that the pH value of the digestion solution is adjusted to 0.95-1.05 by using a sodium hydroxide solution and nitric acid, an organic solvent which is incompatible with water is used for extraction to obtain an organic extract, the organic extract is back extracted by using saturated salt water, the organic extract is reserved, constant volume is performed, and the sample solution to be tested is prepared. Wherein the organic solvent is selected from ether, hydrocarbon or halogenated hydrocarbon, preferably petroleum ether, diethyl ether, C₅～C₈Alkane and C₅～C₈Most preferred among them is diethyl ether or cyclohexane. The pH value of the digestion solution indicated in the step can be measured by a pH meter, and 0.1% thymol blue can also be used.

Finally, calculating the mass concentrations of the four nitrobenzoic acids in the liquid to be detected by combining peak areas corresponding to the 2-nitrobenzoic acid, the 3-nitrobenzoic acid, the 4-nitrobenzoic acid and the 3, 5-dinitrobenzoic acid in a liquid chromatogram of the liquid to be detected of the sample with standard curves of the four nitrobenzoic acids, calculating according to a formula (I),

in the formula:

x represents the content percent of styrene in a sample to be digested;

C₂the mass concentration of the 2-nitrobenzoic acid in the sample solution to be detected is mg/mL according to the standard curve;

C₃the mass concentration of the 3-nitrobenzoic acid in the sample solution to be detected is mg/mL according to the standard curve;

C₄the mass concentration of 4-nitrobenzoic acid in the sample solution to be detected is mg/mL according to the standard curve;

C_3,5obtaining the mass concentration of 3, 5-dinitrobenzoic acid in the sample solution to be detected by a standard curve, mg/mL;

v, determining the volume of the sample to be detected to be mL;

m-sample mass to be digested, mg.

When the method is used for detecting the styrene content in the phenolic resin, the oil-free rubber or the oil-free rubber composition, the obtained styrene content X in the sample to be digested is the styrene content in the sample to be detected.

When the above method is used for detecting the styrene content in an oil-extended rubber or an oil-extended rubber composition, it is necessary to calculate the styrene content Z in units% in a sample to be tested according to formula (III).

Wherein in the high performance liquid chromatography test, the used chromatographic columns are as follows: c18 reversed phase chromatographic column, particle size 5 μm, inner diameter 2.0-4.6 mm, column length 100-250 mm; the detector is an ultraviolet visible light detector, and the detection wavelength is 220 nm-250 nm; and (3) chromatographic detection conditions: the mobile phase is selected from methanol-ammonium acetate water solution, gradient elution is carried out, the flow rate is 1mL/min, the column temperature is 35-40 ℃, and the sample injection volume is 5-10 mu L.

The drawing method of the standard curves of the four nitrobenzoic acids can be as follows: accurately weighing a certain amount of 2-nitrobenzoic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid and 3, 5-dinitrobenzoic acid respectively, placing the weighed materials into the same volumetric flask, dissolving the materials in an organic solvent, and fixing the volume to prepare a mixed standard solution. Accurately measuring mixed standard solutions with different volumes to prepare a mixed standard series solution, measuring by adopting a high performance liquid chromatography to respectively obtain the retention time of the 2-nitrobenzoic acid, the 3-nitrobenzoic acid, the 4-nitrobenzoic acid and the 3, 5-dinitrobenzoic acid and the peak area at a specified wavelength, drawing a standard curve by taking the mass concentration of the mixed standard series solution as a vertical coordinate and the peak area as a horizontal coordinate, wherein the adopted organic solvent is preferably one of ether, methanol and acetonitrile.

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The microwave digestion tank used in the embodiment of the invention is a MARS240/50 microwave extraction-digestion instrument, and the HPLC adopted is an LC-20A high performance liquid chromatograph of Shimadzu.