Method for detecting content of benzene-series organic matters in rubber tube

Abstract

The invention relates to the technical field of substance analysis and detection, and particularly discloses a method for detecting the content of benzene-series organic matters in a rubber tube, which comprises the following steps of: performing adsorption extraction on a sample by adopting a magnetic stirring adsorption extraction rod, and simultaneously detecting the benzene-series organic matters in the rubber tube in combination with GC-MS (Gas Chromatography-Mass Spectrometer) equipment, according to the method, the adsorption and extraction conditions and the detection conditions are optimized according to the specific rubber tube sample, high-sensitivity and high-precision detection of the benzene-series organic matters in the rubber tube is finally realized, and the detection limit of the benzene-series organic matters in the rubber tube can reach 0.1-0.5 mu g / kg.

Description

Technical Field

[0001] The invention relates to the technical field of material analysis and detection, and in particular to a method for detecting the content of benzene-based organic matter in a rubber tube. Background Art

[0002] Rubber hoses can be seen everywhere in daily life, such as car radiator elbows, vacuum cleaner hoses, household tap water pipes, etc.; in the industrial field, rubber hoses are even more indispensable, such as hoses in chemical reactors, connecting pipes for laboratory instruments and equipment, etc. Rubber hoses are tubular rubber products made of rubber as the main raw material, usually composed of inner and outer layers of rubber and skeleton materials. The rubber component in rubber hoses is mostly synthetic rubber, because synthetic rubber has a wider range of performance regulation space and better processing performance. In the production process of rubber hoses, in order to improve its performance or processability, some chemicals may be added, which may contain benzene organics. For example, some plasticizers, antioxidants or other additives may contain benzene organic components such as benzene, toluene, ethylbenzene, and xylene. In addition, the solvents used in the production process may also contain benzene organics, which may remain in the rubber hose during processing. However, benzene organics may have acute or chronic poisoning effects on the human body, affecting the nervous system, hematopoietic system, respiratory system, etc., and long-term exposure may even cause cancer. Generally speaking, qualified rubber hose products should comply with relevant national or industry standards and have strict restrictions on the content of benzene-based organic matter.

[0003] Gas chromatography is a commonly used method for detecting benzene-based organics, which has the characteristics of high sensitivity and high resolution. The gas chromatograph can accurately measure the concentration of different benzene-based organics by evaporating the sample into a gaseous state and injecting it into a chromatographic column for separation and quantitative analysis. Although the existing detection methods have made certain progress in the detection of benzene-based organics in rubber hoses, there are still some problems that need to be solved. For example, for some complex samples, such as benzene-based organics in rubber hoses, the separation effect may be limited due to the presence of multiple coexisting compounds or compounds with similar structures, which may lead to reduced accuracy of the detection results; although methods such as gas chromatography have high sensitivity, for some low-concentration target compounds, the detection sensitivity still needs to be further improved. In addition, factors such as background noise and detector sensitivity may also affect the sensitivity and detection limit of the analysis; effective sample pretreatment methods are essential for removing interfering substances, enriching target compounds and improving analytical sensitivity.

[0004] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a method for detecting the content of benzene-based organic matter in a rubber hose, aiming to solve the problems of low efficiency, low sensitivity and poor accuracy in the existing methods for detecting the content of benzene-based organic matter in a rubber hose.

[0006] The technical solution of the present invention is as follows:

[0007] A method for detecting the content of benzene-based organic matter in a rubber hose, comprising the steps of:

[0008] The rubber tube to be tested is crushed into pieces of 1*1 mm, and 5-10 g is weighed and placed in a glass bottle. 50-100 ml of acetone is added to the glass bottle, and the glass bottle is ultrasonically treated for 30-60 min and then sealed.

[0009] The activated magnetic stirring adsorption extraction rod is placed in a glass bottle, and magnetically stirred at a speed of 800-1000 r / min for 30-90 min at 30-50° C. to complete the extraction of benzene-based organic matter in the rubber tube, wherein the benzene-based organic matter includes benzene, toluene, ethylbenzene, m-xylene and o-xylene;

[0010] The magnetic stirring adsorption extraction rod is taken out and placed in a desorption tube of a GC-MS device, the desorption tube is heated to a predetermined temperature and purged with dry helium, so that the benzene organic matter extracted on the magnetic stirring adsorption extraction rod is volatilized and enters the cold hydrazine along with the carrier gas, and then enters the GC-MS device for detection after secondary desorption to obtain a response value of the rubber tube to be tested;

[0011] Weigh 0.02 g each of benzene, toluene, ethylbenzene, m-xylene, and o-xylene in a 100 mL volumetric flask, dilute with acetone to obtain a mixed standard stock solution, and refrigerate for later use. Take 1 mL of the mixed standard stock solution and add it to a 100 mL volumetric flask and dilute with acetone to obtain a mixed standard intermediate solution with a concentration of 2 mg / L.

[0012] Weigh 0.2mL, 0.4mL, 0.6mL, 0.8mL, 1.0mL, and 1.5mL of the mixed standard intermediate solution into a 20mL volumetric flask, dilute to volume with acetone, and shake well to obtain a standard working solution with a concentration of 0.02mg / L-0.15mg / L;

[0013] The standard working solution is passed into a GC-MS device for measurement, and a standard working curve is drawn with the mass concentration of each target compound as the abscissa and the peak area of ​​each target compound as the ordinate;

[0014] According to the response value of the rubber tube to be tested and the standard working curve, the concentration of the target compound in the rubber tube to be tested is calculated: M = (Ab)×V , where M is the target compound in the rubber tube to be tested

[0015] a×m

[0016] The concentration of the target compound is in mg / kg; A is the peak area of ​​the target compound in mAu*s; b is the intercept of the standard working curve; V is the amount of acetone used as the extractant for the rubber tube to be tested, in L; a is the slope of the standard working curve; m is the mass of the rubber tube to be tested, the target is kg.

[0017] The method for detecting the content of benzene-based organic matter in the rubber tube, wherein the extraction coating in the magnetic agitation adsorption extraction rod is polydimethylsiloxane with a film thickness of 0.5-1.0 mm, and the activation step of the magnetic agitation adsorption extraction rod is: activating for 2-5 hours in a nitrogen environment with a flow rate of 120-150 mL / min, and the activation temperature is 200-280°C.

[0018] The method for detecting the content of benzene-based organic matter in the rubber tube comprises the following steps: extracting the benzene-based organic matter in the rubber tube by magnetic stirring at a speed of 900 r / min for 60 min at 40° C.

[0019] The method for detecting the content of benzene-based organic matter in the rubber tube comprises the following steps: taking out the magnetic stirring adsorption extraction rod and placing it in a desorption tube of a GC-MS device, heating the desorption tube to a predetermined temperature and purging it with dry helium, so that the benzene-based organic matter extracted on the magnetic stirring adsorption extraction rod is volatilized and enters the cooling step along with the carrier gas, wherein the predetermined temperature is 280°C, the desorption time is 4 minutes, and the cooling temperature is -30°C.

[0020] The method for detecting the content of benzene-based organic matter in the rubber tube, wherein the temperature of the secondary desorption is increased to 300° C. at a heating rate of 15° C. / s, and the secondary desorption time is 5 minutes.

[0021] The method for detecting the content of benzene-based organic matter in the rubber tube, wherein in the GC-MS equipment, the conditions of the chromatograph are set as follows: the chromatographic column temperature is maintained at 45°C for 2 minutes, increased to 150°C at 8°C / min, and then increased to 250°C at 4°C / min, maintained for 5 minutes, the carrier gas is helium, and the flow rate is 1.2 mL / min.

[0022] The method for detecting the content of benzene-based organic matter in the rubber hose, wherein, in the GC-MS equipment, the conditions of the mass spectrometer are set as follows: electron impact ion source (EI), ionization energy is 70eV; mass scanning range is 45-400m / z; chromatography-mass spectrometry transmission temperature is 300°C.

[0023] The method for detecting the content of benzene-based organic matter in the rubber hose comprises the following steps: before calculating the concentration of the target compound in the rubber hose to be tested, a blank experiment GC-MS test is first performed, that is, no rubber hose sample is added, and the acetone solvent is directly subjected to GC-MS test to obtain a blank response value. After the blank response value is subtracted from the response value of the rubber hose to be tested, the concentration of each target compound in the rubber hose to be tested is calculated according to the standard working curve to eliminate interference from the instrument and the acetone solvent.

[0024] Beneficial effects: The present invention adopts a magnetic stirring adsorption extraction rod to perform adsorption extraction on the sample, and combines with a GC-MS device to simultaneously detect the benzene-based organic matter in the rubber tube, and optimizes the adsorption extraction conditions and detection conditions according to the specific sample of the rubber tube, and finally achieves high sensitivity and high precision detection of the benzene-based organic matter in the rubber tube. The detection limit of the present invention for the benzene-based organic matter in the rubber tube can reach 0.1-0.5μg / kg. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flow chart of a method for detecting the content of benzene-based organic matter in a rubber hose.

[0026] Figure 2 This is the full scan chromatogram of the rubber tube fragment sample when acetone was used as the extraction solvent without optimizing the conditions.

[0027] Figure 3 The graph is a graph showing the variation of the extraction efficiency (measured in peak area) with the extraction temperature in Example 1.

[0028] Figure 4 The figure is a graph showing the variation of the extraction efficiency (measured in peak area) with the extraction time in Example 1.

[0029] Figure 5 This is a full scan chromatogram of the rubber tube fragment sample after the conditions in Example 1 were optimized. DETAILED DESCRIPTION

[0030] The present invention provides a method for detecting the content of benzene organic matter in a rubber hose. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] See also Figure 1 , Figure 1 The present invention provides a flow chart of a method for detecting the content of benzene-based organic matter in a rubber hose, as shown in the figure, which comprises the steps of:

[0032] S10, crush the rubber tube to be tested into 1*1 mm pieces, weigh 5-10 g of the pieces and put them into a glass bottle, add 50-100 ml of acetone into the glass bottle, perform ultrasonic treatment for 30-60 min, and then seal the bottle;

[0033] S20, placing the activated magnetic stirring adsorption extraction rod into a glass bottle, and magnetically stirring at a speed of 800-1000r / min for 30-90min at 30-50°C to complete the extraction of benzene organic matter in the rubber tube, wherein the benzene organic matter includes benzene, toluene, ethylbenzene, m-xylene and o-xylene;

[0034] S30, taking out the magnetic stirring adsorption extraction rod and placing it into the desorption tube of the GC-MS device, heating the desorption tube to a predetermined temperature and purging it with dry helium, so that the benzene organic matter extracted on the magnetic stirring adsorption extraction rod is volatilized and enters the cold hydrazine along with the carrier gas, and then enters the GC-MS device for detection after secondary desorption to obtain the response value of the rubber tube to be tested;

[0035] S40, weigh 0.02 g each of benzene, toluene, ethylbenzene, m-xylene, and o-xylene in advance into a 100 mL volumetric flask, dilute to volume with acetone to obtain a mixed standard stock solution, and refrigerate for later use, take 1 mL of the mixed standard stock solution, add it to a 100 mL volumetric flask, dilute to volume with acetone, and obtain a mixed standard intermediate solution with a concentration of 2 mg / L;

[0036] S50, weigh 0.2mL, 0.4mL, 0.6mL, 0.8mL, 1.0mL, and 1.5mL of the mixed standard intermediate solution into a 20mL volumetric flask, dilute to volume with acetone, and shake well to obtain a standard working solution with a concentration of 0.02mg / L-0.15mg / L;

[0037] S60, passing the standard working solution into a GC-MS device for measurement, and drawing a standard working curve with the mass concentration of each target compound as the abscissa and the peak area of ​​each target compound as the ordinate;

[0038] S70, calculating the concentration of the target compound in the rubber tube to be tested according to the response value of the rubber tube to be tested and the standard working curve: M= (Ab)×V , where M is the number of

[0039] a×m

[0040] The concentration of the target compound is in mg / kg; A is the peak area of ​​the target compound in mAu*s; b is the intercept of the standard working curve; V is the amount of acetone used as the extractant for the rubber tube to be tested, in L; a is the slope of the standard working curve; m is the mass of the rubber tube to be tested, the target is kg.

[0041] Specifically, in this embodiment, the rubber tube to be tested is first crushed into 1*1mm fragments, 5-10g is weighed and placed in a glass bottle, and then 50-100ml of acetone is added to the glass bottle and ultrasonic treatment is performed for 30-60min before sealing. Crushing the rubber tube into 1×1mm fragments can significantly increase its specific surface area, exposing more internal surfaces. A larger specific surface area means that the solvent acetone can contact the rubber tube fragments more fully, which is beneficial to the penetration and diffusion of the solvent acetone and improves the extraction efficiency; ultrasonic treatment generates cavitation bubbles in the solvent, which will generate a strong impact force when they burst, which helps to destroy certain structures inside the rubber tube and make it easier for benzene organic matter to be released; at the same time, the cavitation effect can also promote the exchange of substances between the solvent and the rubber tube fragments, accelerating the dissolution of benzene organic matter. In this embodiment, acetone is selected as the extraction solvent to dissolve the benzene-based organic matter in the rubber tube to be tested because the molecular structure of acetone contains a polar carbonyl (C=O) bond, which makes it have moderate polarity. This polarity characteristic enables acetone to efficiently dissolve benzene-based organic matter such as benzene, toluene, ethylbenzene, m-xylene and o-xylene, and its own chemical properties are stable.

[0042] In this embodiment, a magnetic stirring adsorption extraction rod is used to adsorb and extract benzene organic matter in the rubber tube to be tested. The magnetic stirring adsorption extraction rod is usually called a stir bar search extraction (SBSE) rod, which is a new type of tool for sample pretreatment and is widely used in trace analysis in the fields of environment, food, medicine, etc. The magnetic stirring adsorption extraction rod is mainly composed of three core parts: an iron core, a glass shell and an extraction coating. The iron core is the power source of the stirring rod, which is driven to rotate by the magnetic field of the magnetic stirrer, driving the entire stirring rod to stir in the sample solution, thereby achieving the extraction of the target analyte; the glass shell is used to isolate the iron core and the extraction coating to avoid the metal catalysis in the iron core causing the coating to degrade, while providing sufficient mechanical strength to protect the internal iron core and the extraction coating; the extraction coating is the core part of the magnetic stirring adsorption extraction rod, which is used to adsorb or absorb the target analyte in the sample, and its volume is much larger than the fiber head of solid phase microextraction (SPME), so it has a higher recovery rate and a larger sample capacity. The extraction coating in the magnetic agitation adsorption extraction rod described in this embodiment is polydimethylsiloxane with a film thickness of 0.5-1.0 mm, and the activation step of the magnetic agitation adsorption extraction rod is: activation for 2-5 hours in a nitrogen environment with a flow rate of 120-150 mL / min, and the activation temperature is 200-280° C. Nitrogen is an inert gas, which can effectively prevent the coating from being oxidized during the activation process. At the same time, the flow rate of nitrogen is controlled within the range of 120-150 mL / min, which can ensure that the surface of the extraction rod is evenly heated and cooled; the activation temperature is selected within the range of 200-280° C., which can ensure that the residue on the surface of the coating is effectively removed, and at the same time, it will not be too high to cause damage to the coating. This temperature range can also promote the molecular movement inside the coating, which helps to restore its adsorption performance; the activation time is controlled within the range of 2-5 hours, which can ensure that the extraction rod is fully activated, and at the same time, it will not be too long to cause unnecessary energy consumption and time waste.

[0043] In the process of using magnetic stirring adsorption extraction rod to adsorb and extract benzene organic matter in the rubber tube to be tested, temperature, rotation speed, and stirring time will affect the adsorption effect. From the perspective of extraction thermodynamics, increasing the temperature can reduce the distribution coefficient of the target analyte (benzene organic matter) between the extraction solution and the coating, thereby affecting the extraction efficiency of the coating for the target analyte; from the perspective of extraction kinetics, increasing the temperature can accelerate the mass transfer rate between the target analyte and the coating and shorten the time to reach extraction equilibrium. Within the temperature range of 30-50℃, the coating will not be lost or the target analyte will not volatilize too quickly due to excessively high temperature, nor will the mass transfer rate and extraction efficiency be affected due to excessively low temperature. This temperature helps to maintain the stability of the extraction system and ensure the smooth progress of the extraction process. Rotation speed can improve adsorption efficiency and rate, promote adsorbent (extraction rod coating) and adsorbate (benzene organic matter) to fully contact, improve the utilization rate of adsorption sites, stirring effect helps to break the diffusion limit of adsorbate in solution, and promote its uniform distribution on the adsorbent surface. However, too high rotation speed may produce excessive shear force, resulting in adsorbent particles breaking or agglomeration, but reducing the effective adsorption area, affecting adsorption efficiency. In the present embodiment, the rotation speed range of 800-1000r / min can avoid unnecessary damage to the adsorbent while ensuring the adsorption efficiency, and help to shorten the time to reach extraction equilibrium and improve extraction efficiency. Extraction time is one of the main factors affecting the extraction efficiency of each component in the sample. In theory, the extraction efficiency increases with the increase of extraction time, and the time required for different substances to reach equilibrium is different, but too long extraction time will make the method lack practical application value. In the present embodiment, within the time range of 30-90min, most benzene organics have been able to reach extraction equilibrium or close to equilibrium, thereby ensuring extraction efficiency.

[0044] In the present embodiment, the magnetic agitation adsorption extraction rod is taken out and placed in the desorption tube of the GC-MS device, the desorption tube is heated to a predetermined temperature and purged with dry helium, so that the benzene organics extracted on the magnetic agitation adsorption extraction rod are volatilized and enter the cold hydrazine with the carrier gas, and enter the GC-MS device for detection through secondary desorption to obtain the response value of the rubber tube to be tested. Wherein, whether the benzene organics adsorbed on the magnetic agitation adsorption extraction rod can be completely desorbed is related to the accuracy of the experimental results. Under the same SBSE conditions, desorption temperature, desorption time and cold hydrazine temperature are the main experimental parameters that affect the transfer of benzene organics from the extraction rod to the GC-MS device. This embodiment is proved by experiments that when the predetermined temperature is 280°C, the desorption time is 4min, and the cold hydrazine temperature is -30°C, the total peak area of ​​the target benzene organics obtained is the largest, indicating that under this condition, the desorption efficiency of benzene organics from the magnetic agitation adsorption extraction rod is the highest.

[0045] In this embodiment, the temperature of the secondary desorption is raised to 300° C. at a heating rate of 15° C. / s, and the secondary desorption time is 5 min. Experiments have shown that under this condition, the secondary desorption efficiency is the highest.

[0046] In this embodiment, in the GC-MS equipment, the conditions of the chromatograph are set as follows: the chromatographic column temperature is maintained at 45°C for 2 minutes, increased to 150°C at 8°C / min, and then increased to 250°C at 4°C / min, and maintained for 5 minutes; the carrier gas is helium with a flow rate of 1.2 mL / min; the conditions of the mass spectrometer are set as follows: electron impact ion source (EI), ionization energy is 70 eV; mass scanning range is 45-400 m / z; chromatography-mass spectrometry transmission temperature is 300°C.

[0047] This embodiment uses a magnetic stirring adsorption extraction rod to adsorb and extract the sample, and combines with a GC-MS device to simultaneously detect the benzene-based organic matter in the rubber tube, and optimizes the adsorption extraction conditions and detection conditions according to the specific sample of the rubber tube. Finally, high-sensitivity and high-precision detection of benzene-based organic matter in the rubber tube is achieved. The detection limit of the present invention for benzene-based organic matter in the rubber tube can reach 0.1-0.5μg / kg.

[0048] The present invention will be further explained below by means of specific embodiments:

[0049] Example 1

[0050] 1. Experimental instruments: Gerstel Twister stirring rod, Gerstel TDU-3 thermal desorption device, Gerstel glass thermal desorption tube, Gerstel CIS cold injection system; 6890N gas chromatograph, 5973N mass spectrometer; 78-I constant temperature heating magnetic stirrer.

[0051] 2. Experimental reagents: acetone; benzene, toluene, ethylbenzene, m-xylene, o-xylene.

[0052] 3. Optimization of experimental conditions:

[0053] 3.1 Extraction solvent optimization:

[0054] 5 g of rubber tube fragment sample was weighed and placed in four 100 mL glass bottles, which were numbered 1-4. Bottles 1-2 used 50 mL of acetone as the extraction solvent, and bottles 3-4 used 50 mL of acetonitrile as the extraction solvent. The gas chromatography-mass spectrometry analysis in the scheme of the present invention was carried out under exactly the same conditions. The extraction effects of the two extraction solvents were compared by peak effect and peak area. The full scan chromatogram when acetone was used as the extraction solvent is shown in FIG. Figure 2 As shown. Figure 2It can be seen that when acetone is used as the extraction solvent, the benzene series organics can be well extracted and separated; while when acetonitrile is used as the extraction solvent, the peaks of the benzene series organics will be bifurcated, so acetone is selected as the extraction solvent in this embodiment.

[0055] 3.2 Optimization of extraction temperature of magnetic stirring adsorption extraction rod:

[0056] The extraction temperature will directly affect the extraction amount and extraction rate of the extraction coating, so the effects of 30℃, 40℃ and 50℃ on the adsorption effect were investigated. From the curve of extraction efficiency (measured in peak area) changing with extraction temperature (such as Figure 3 As shown in the figure, it can be seen that with the increase of temperature, the amount of target components detected gradually increases, and the chromatographic peak area gradually increases. When the extraction temperature is 40°C, the target analytes have a higher extraction efficiency. When the temperature reaches 50°C, the extraction efficiency decreases, which may be related to the volatilization of some low-boiling point substances.

[0057] 3.3 Optimization of extraction speed of magnetic stirring adsorption extraction rod:

[0058] This example examines the adsorption of five benzene-based organic compounds by the extraction rod at rotation speeds of 800, 900 and 1000 r / min, using the peak area as a measurement indicator. The larger the peak area, the greater the adsorption. The experimental results show that the peak areas of the five benzene-based organic compounds increase first and then decrease with the increase in rotation speed. At a rotation speed of 900 r / min, the peak areas of the five benzene-based organic compounds are close to the highest, so the preferred rotation speed in this example is 900 r / min.

[0059] 3.4 Optimization of extraction time of magnetic stirring adsorption extraction rod:

[0060] At 40°C, the same samples were weighed separately, the stirring speed was controlled at 900r / min, and the extraction time was selected at 25min, 35min, 45min, 60min, 70min, and 80min. The sum of the chromatographic peak areas under different time conditions was obtained to determine the optimal extraction time. The results are shown in Figure 4 As shown in the figure, it can be seen that with the extension of extraction time, the sum of chromatographic peak areas gradually increases within 25-60 minutes. After 60 minutes, the increase of peak area slows down and finally stabilizes. Considering the experimental cycle and work efficiency, the optimal extraction time is 60 minutes.

[0061] 3.5 Optimization of desorption conditions of magnetic stirring adsorption extraction rod:

[0062] Whether the benzene organics adsorbed on the extraction rod can be completely desorbed is related to the accuracy of the experimental results. Under the same SBSE conditions, the three experimental conditions of thermal desorption temperature (A), desorption time (B) and cold hydrazine temperature (C) are the main experimental parameters affecting the transfer of benzene organics from the extraction rod to the gas chromatograph. This embodiment adopts the orthogonal experimental method, and experiments are conducted on three influencing factors at three different levels to develop an orthogonal experimental table as shown in Table 1.

[0063] Table 1 Orthogonal experimental factor-level table

[0064] level Thermal desorption temperature (A) Desorption time (B) Cold hydrazine temperature (C) 1 250 3 0 2 280 4 -20 3 300 5 -30

[0065] The experimental results show that the factors that affect the experimental results are: cold hydrazine temperature, thermal desorption temperature and desorption time. The best experimental level combination is A2B2C3, that is, SBSE is desorbed at 280℃ for 4min and supplemented at a cold hydrazine temperature of -30℃, and the total peak area of ​​benzene organics is the largest.

[0066] 4. Based on the optimization of the experimental conditions in step 3, determine the testing steps of the rubber tube to be tested:

[0067] The activated magnetic stirring adsorption extraction rod is placed in a glass bottle, and magnetically stirred at a speed of 900 r / min for 60 minutes at 40° C. to complete the extraction of benzene-based organic matter in the rubber tube, wherein the benzene-based organic matter includes benzene, toluene, ethylbenzene, m-xylene and o-xylene;

[0068] The magnetic stirring adsorption extraction rod is taken out and placed in the desorption tube of the GC-MS equipment. The desorption tube is heated to 280°C and purged with dry helium. The desorption time is 4 minutes. The benzene organic matter extracted on the magnetic stirring adsorption extraction rod is volatilized and enters the cold hydrazine with the carrier gas. The cold hydrazine temperature is -30°C. After secondary desorption, it enters the GC-MS equipment for detection. The temperature of the secondary desorption is increased to 300°C at a heating rate of 15°C / s. The secondary desorption time is 5 minutes, and the response value of the rubber tube to be tested is obtained.

[0069] 5. Develop a standard working curve and determine the detection limit:

[0070] The standard working solution is passed into the GC-MS equipment for determination, and the mass concentration of each target compound is used as the horizontal coordinate, and the peak area of ​​each target compound is used as the vertical coordinate to draw the standard working curve. It can be seen from the standard working curve that the five benzene organic compounds are all within the mass concentration range of 0.02mg / L-0.15mg / L of the standard working solution, and the peak area and its mass concentration show a good linear relationship, and the correlation coefficient r is greater than 0.99. The quantitative ion peak signal-to-noise ratio S / N=3 of each target compound is combined with the dilution multiple of the sample pretreatment to calculate the detection limit. The results are shown in Table 2, wherein the present embodiment uses 3 times the signal-to-noise ratio as the detection limit (LOD) of the method, LOD=3S / N, where S is the signal intensity of the target compound in the rubber tube to be tested, and N is the noise intensity.

[0071] Table 2 Detection limit of benzene organic matter (μg / kg)

[0072]

[0073]

[0074] The national standard method uses a gas chromatograph with FID to measure five benzene-based organic compounds, while this embodiment uses a stirring rod adsorption extraction to selectively adsorb the five benzene-based organic compounds, reducing the interference of impurities, and the combination of gas chromatography and mass spectrometry significantly improves the detection sensitivity, so the detection limit obtained is lower.

[0075] 6. Comparison of the determination of actual samples with the standard method

[0076] The rubber tube to be tested is measured using the national standard method and the steps determined in step 4 of this embodiment. The gas chromatogram obtained by the test method of this embodiment is as follows: Figure 5 The comparison of the detection results of the two methods is shown in Table 3.

[0077] Table 3 Comparison of test results

[0078]

[0079] from Figure 5 As can be seen from Table 3, the national standard method has a higher detection limit than the method of this embodiment and cannot detect low-concentration benzene-based organics. The method of this embodiment can be used to find that benzene-based organics are still used in some rubber hoses, but the contents of these five benzene-based organics do not exceed the national standards.

[0080] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for detecting the content of benzene organic matter in a rubber hose, characterized in that: Includes steps: The rubber tube to be tested is crushed into pieces of 1*1 mm, and 5-10 g is weighed and placed in a glass bottle. 50-100 ml of acetone is added to the glass bottle, and the glass bottle is ultrasonically treated for 30-60 min and then sealed. The activated magnetic stirring adsorption extraction rod is placed in a glass bottle, and magnetically stirred at a speed of 800-1000 r / min for 30-90 min at 30-50° C. to complete the extraction of benzene-based organic matter in the rubber tube, wherein the benzene-based organic matter includes benzene, toluene, ethylbenzene, m-xylene and o-xylene; The magnetic stirring adsorption extraction rod is taken out and placed in a desorption tube of a GC-MS device, the desorption tube is heated to a predetermined temperature and purged with dry helium, so that the benzene organic matter extracted on the magnetic stirring adsorption extraction rod is volatilized and enters the cold hydrazine along with the carrier gas, and then enters the GC-MS device for detection after secondary desorption to obtain a response value of the rubber tube to be tested; Weigh 0.02 g each of benzene, toluene, ethylbenzene, m-xylene, and o-xylene in a 100 mL volumetric flask, dilute with acetone to obtain a mixed standard stock solution, and refrigerate for later use. Take 1 mL of the mixed standard stock solution and add it to a 100 mL volumetric flask and dilute with acetone to obtain a mixed standard intermediate solution with a concentration of 2 mg / L. Weigh 0.2mL, 0.4mL, 0.6mL, 0.8mL, 1.0mL, and 1.5mL of the mixed standard intermediate solution into a 20mL volumetric flask, dilute to volume with acetone, and shake well to obtain a standard working solution with a concentration of 0.02mg / L-0.15mg / L; The standard working solution is passed into a GC-MS device for measurement, and a standard working curve is drawn with the mass concentration of each target compound as the abscissa and the peak area of ​​each target compound as the ordinate; According to the response value of the rubber tube to be tested and the standard working curve, the concentration of the target compound in the rubber tube to be tested is calculated: M = (Ab)×V , where M is the target compound a×m in the rubber tube to be tested The concentration of the target compound is in mg / kg; A is the peak area of ​​the target compound in mAu*s; b is the intercept of the standard working curve; V is the amount of acetone used as the extractant for the rubber tube to be tested, in L; a is the slope of the standard working curve; m is the mass of the rubber tube to be tested, the target is kg.

2. The method for detecting the content of benzene organic matter in a rubber tube according to claim 1, characterized in that: The extraction coating in the magnetic stirring adsorption extraction rod is polydimethylsiloxane with a film thickness of 0.5-1.0 mm. The activation step of the magnetic stirring adsorption extraction rod is: activating in a nitrogen environment with a flow rate of 120-150 mL / min for 2-5 hours, and the activation temperature is 200-280°C.

3. The method for detecting the content of benzene organic matter in the rubber tube according to claim 1, characterized in that: The extraction of benzene organic matter in the rubber tube was completed by magnetic stirring at 900 r / min at 40°C for 60 min.

4. The method for detecting the content of benzene organic matter in a rubber tube according to claim 1, characterized in that: The magnetic stirring adsorption extraction rod is taken out and placed in the desorption tube of the GC-MS equipment, and the desorption tube is heated to a predetermined temperature and purged with dry helium to volatilize the benzene organic matter extracted on the magnetic stirring adsorption extraction rod and enter the cooling step along with the carrier gas. The predetermined temperature is 280°C, the desorption time is 4 minutes, and the cooling temperature is -30°C.

5. The method for detecting the content of benzene organic matter in a rubber tube according to claim 4, characterized in that: The temperature of the secondary desorption was increased to 300°C at a heating rate of 15°C / s, and the secondary desorption time was 5 min.

6. The method for detecting the content of benzene-based organic matter in a rubber tube according to claim 1, characterized in that: In the GC-MS device, the chromatograph conditions were set as follows: the column temperature was maintained at 45°C for 2 min, increased to 150°C at 8°C / min, then increased to 250°C at 4°C / min, and maintained for 5 min; the carrier gas was helium at a flow rate of 1.2 mL / min.

7. The method for detecting the content of benzene organic matter in a rubber tube according to claim 6, characterized in that: In the GC-MS device, the conditions of the mass spectrometer are set as follows: electron impact ion source (EI), ionization energy is 70 eV; mass scanning range is 45-400 m / z; chromatography-mass spectrometry transmission temperature is 300°C.

8. The method for detecting the content of benzene-based organic matter in a rubber tube according to claim 1, characterized in that: Before calculating the concentration of the target compound in the rubber tube to be tested, a blank experiment GC-MS detection is first performed, that is, no rubber tube sample is added, and the acetone solvent is directly subjected to GC-MS detection to obtain a blank response value. After subtracting the blank response value from the response value of the rubber tube to be tested, the concentration of each target compound in the rubber tube to be tested is calculated according to the standard working curve to eliminate interference from the instrument and the acetone solvent.

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