In-situ collection device and analysis method for organic matters on object surface

Abstract

The invention relates to an in-situ collection device and an analysis method for organic matters on the surface of an object, and belongs to the technical field of analysis and detection. The analysis method of the object surface organic matter comprises the following steps: wiping the surface of a to-be-detected object by using wiping cotton to complete collection of target organic matter; performing thermal desorption on the wiping cotton with the collected target organic matters, performing gas chromatography-mass spectrometry on the target matters obtained by thermal desorption, and determining the content of the target organic matters on the surface of the to-be-detected object. According to the method for analyzing the organic matter on the surface of the object, the target object collected in situ is directly desorbed in a thermal desorption mode, the extraction and concentration enrichment process of a large number of organic solvents in a traditional method can be avoided, the test analysis time is shortened, the test analysis efficiency is improved, and the harm of the organic solvents to the environment and operators is reduced; the labor cost is saved, the test accuracy is higher, and the detection limit is lower.

Description

Technical Field

[0001] The present invention relates to an in-situ collection device and analysis method for organic substances on the surface of an article, belonging to the technical field of analytical detection. Background Art

[0002] The surface of an article is an enrichment area for numerous organic substances and an important medium for human exposure to these pollutants. Additives in materials such as plastics and synthetic wood boards will accumulate on the material surface during use. At the same time, gaseous and particulate organic substances in the air will also deposit on the article surface. When people use or accidentally contact the article surface, these organic substances will adhere to the hands and skin, and then enter the human body through hand-to-mouth exposure and skin absorption pathways.

[0003] In analytical chemistry practice, mainstream techniques tend to use destructive sampling methods. A sample of a quantitative mass or area is selected, refined through processes such as cutting and grinding, and then extracted using a large amount of organic solvents. After the extract is concentrated and enriched, methods such as instrumental analysis are used to determine the concentration of organic substances in the extract, and based on this, combined with the sample area or area density information, the concentration of organic substances per unit area on the article surface is deduced. The implicit premise of this series of steps is that the organic substances are evenly distributed on the surface and inside of the sample, and thus the overall concentration is regarded as a reasonable representative of the surface concentration. However, for articles with different distributions of organic substances on the surface and inside, the applicability of this method is limited. To overcome this problem, dust-free paper or gauze soaked in organic solvents can be used to wipe the test surface, and then the wiped dust-free paper or gauze is extracted with organic solvents, concentrated, and then analyzed on a machine to finally obtain the true concentration of the target substance on the article surface. This method can more accurately characterize the concentration of organic substances on the article surface, but this method requires a complex pretreatment process, consuming a large amount of time, manpower, and material resources. At the same time, the use of a large amount of organic extraction agents will cause harm to operators and the environment. Summary of the Invention

[0004] The purpose of the present invention is to provide an analysis method for organic substances on the surface of an article, which can solve the problems of time-consuming, laborious, and low efficiency in the current detection and analysis of organic substances on the article surface.

[0005] Another purpose of the present invention is to provide an in-situ collection device for organic substances on the surface of an article, which can solve the problems of current destructive sampling and inaccurate characterization of surface concentration; at the same time, the collection device is adapted to a thermal desorption instrument, and after collecting the organic substances, it can be directly subjected to thermal desorption analysis, eliminating the complex organic substance extraction process.

[0006] In order to achieve the above purposes, the technical solution adopted by the analysis method for organic substances on the surface of an article of the present invention is as follows: A method for analyzing organic substances on the surface of an article, comprising the following steps: wiping the surface of the article to be tested with a wiping cotton with a wiping agent to complete the collection of the target organic substances; then thermally desorbing the wiping cotton collected with the target organic substances, and then performing gas chromatography-mass spectrometry analysis on the gas obtained by thermal desorption to determine the content of the target organic substances on the surface of the article to be tested.

[0007] The method for analyzing organic substances on the surface of an article of the present invention directly wipes the surface of the article to be tested to collect the target organic substances, and then thermally desorbs the collected target substances, which can avoid the organic solvent extraction and concentration processes in the traditional method, shorten the test analysis time, improve the test analysis efficiency, reduce the harm of organic solvent volatilization during the extraction process to the environment and operators, save labor costs, and have high test accuracy and low detection limits.

[0008] Preferably, the collection includes pushing out a part of the wiping cotton placed in the sampling tube, dropping the wiping agent and then performing the wiping. After the wiping is completed, the wiping cotton is pushed back into the sampling tube, and then the two openings of the sampling tube are blocked with a porous plug, and then the thermal desorption is directly performed.

[0009] Preferably, the wiping includes a primary wiping and a secondary wiping. The length of the wiping cotton pushed out for the primary wiping is 1 / 4 to 1 / 3 of its total length. After the primary wiping, 1 / 4 to 1 / 3 of its total length is pushed out again for the secondary wiping.

[0010] Preferably, the wiping is performed within a set area, and then the concentration of organic substances on the surface of the test article is calculated by the ratio of the content of the target organic substances to the area.

[0011] Preferably, the method for thermal desorption includes the following steps: pre-purging the wiping cotton collected with the target organic substances, and then thermally desorbing the pre-purged wiping cotton under the action of a carrier gas to obtain a thermally desorbed product; then enriching the thermally desorbed product with a cold trap, and then heating and desorbing the cold trap under the action of a carrier gas. The target organic substances can be various organic substances in the field of detecting organic substances on the surface of articles, including but not limited to dibutyl phthalate (DnBP), diisobutyl phthalate (DiBP), etc.

[0012] Preferably, the temperature of the thermal desorption is 280 to 300 °C, and the time is 8 to 10 min; the temperature for heating and desorbing the cold trap is 300 to 310 °C, and the time is 8 to 10 min; the gas used for pre-purging is an inert gas, the flow rate of the pre-purging gas is 80 to 100 mL / min, and the time is 1 to 8 min; during the thermal desorption, the flow rate of the carrier gas is 50 to 70 mL / min; during the heating and desorbing of the cold trap, the flow rate of the carrier gas is 1 to 3 mL / min.

[0013] The technical solution adopted by the in-situ sampling device for organic matter on the surface of an article of the present invention is as follows: An in-situ sampling device for organic matter on the surface of an article, comprising a sampling tube adapted to a thermal desorption instrument, wherein a wiping cotton is arranged in the sampling tube; it further comprises a porous plug for plugging both ends of the sampling tube and an operating rod, the operating rod is used to partially push out the wiping cotton outside the sampling tube before wiping, and to abut against the inner part of the sampling tube of the wiping cotton during wiping, and to push the wiping cotton back into the sampling tube after wiping.

[0014] The in-situ sampling device for organic matter on the surface of an article of the present invention can complete the in-situ sampling of organic matter on the surface of an article by setting the wiping cotton, the sampling tube and the operating rod and utilizing the mutual cooperation among the various components. The working principle of the in-situ sampling device for organic matter on the surface of an article of the present invention is as follows: Before use, the wiping cotton is pushed out, a quantitative wiping agent is injected, the target is collected through the wiping process between the wiping cotton and the surface to be measured, after collection, the wiping cotton is sent back into the sampling tube, the wiping cotton that has completed sampling in the sampling tube is desorbed by a thermal desorption instrument, and the desorbed target enters a gas chromatograph or a gas chromatography-mass spectrometry instrument for quantitative analysis. According to the absolute mass of the target and the wiping area, the concentration of the target on the surface of the article can be obtained.

[0015] Preferably, the length of the operating rod is less than the length of the sampling tube. Description of the Drawings

[0016] Figure 1 Schematic diagram of the in-situ sampling device for organic matter on the surface of an article in Embodiment 1 of the present invention; The reference numerals are as follows: 1 - sampling tube; 2 - wiping cotton; 3 - filter net; 4 - operating rod. Detailed Embodiments

[0017] The analysis method for organic matter on the surface of an article of the present invention is a pioneering invention. The analysis method for organic matter on the surface of an article of the present invention can complete the collection of the target organic matter through the wiping process of the surface of the article to be measured, and then the collected sample is thermally desorbed, which can avoid the problems of destructive sampling and inaccurate characterization of surface concentration in the traditional method; at the same time, the sampling device is adapted to a thermal desorption instrument, and the organic matter can be directly thermally desorbed and analyzed after collection, saving the complicated organic matter extraction process, improving the test analysis efficiency, reducing the harm of organic solvent volatilization to the environment and operators, saving labor costs, and having high test accuracy and low detection limit.

[0018] The preferred target organic matter in the present invention is semi-volatile organic matter (boiling point between 240 and 400 °C), and it can also be used for organic matter with stronger volatility.

[0019] The gas chromatography - mass spectrometry analysis conditions can be determined in a conventional manner. For example, according to the type of organic matter to be analyzed, a DB - 5 chromatographic column is selected; the temperature - rising program of the gas chromatographic column is: the initial temperature is 40 - 45 °C, maintained for 10 - 15 min, and then raised to 280 - 300 °C at a temperature - rising rate of 10 - 15 °C / min. When performing mass spectrometry analysis, the ion source temperature is 230 °C, the voltage is 70 eV, the quadrupole temperature is 150 °C, and the scanning mode is the full - scan mode.

[0020] Specific embodiments of the in - situ collection device and analysis method for organic matter on the surface of the articles of the present invention are as follows: Example 1 The in - situ collection device for organic matter on the surface of the articles in this example is as Figure 1 shown, and includes a sampling tube 1, a wiping cotton 2, a filter net 3, and an operating rod 4.

[0021] The sampling tube 1 is used to hold the wiping cotton 2. After the wiping cotton 2 wipes the surface of the article, it enters the sampling tube 1, and direct thermal desorption is carried out using a thermal desorption instrument, so as to realize the quantitative analysis of the target organic matter. The material of the sampling tube 1 needs to meet the characteristics of being resistant to organic solvents and high temperatures. Optional materials include but are not limited to stainless steel, quartz, etc.; in this example, the sampling tube is made of quartz, with a length of 88.9 mm, an outer diameter of 6.35 mm, and an inner diameter of 4 mm.

[0022] The wiping cotton 2 is used to collect the target organic matter on the surface of the article by wiping. Before wiping, it is located in the sampling tube 1. When wiping, the operating rod 4 is used to push the wiping cotton 2 out of the sampling tube 1, and then a certain amount of wiping agent is injected onto the wiping cotton 2 and the surface to be tested is wiped. The material of the wiping cotton 2 needs to meet the characteristics of being resistant to organic solvents and high temperatures, and at the same time can adsorb organic matter at room temperature and desorb organic matter at high temperatures. Optional materials include but are not limited to glass fiber, metal fiber, and inert plastic fiber or other porous materials. The filling amount of the wiping cotton 2 is determined according to the density of the filler and the volume of the sampling tube 1, and it is appropriate that it does not exceed half of the volume of the sampling tube. In this example, the wiping cotton is a tuft - like glass fiber, with a mass of 0.8 g, and the diameter of the glass fiber is 75 μm.

[0023] The operating rod 4 is used to push the wiping cotton 2 out before wiping, support the wiping cotton 2 during wiping, and send the wiping cotton 2 back after wiping. The material of the operating rod 4 needs to meet the characteristics of being resistant to organic solvents. Optional materials include but are not limited to quartz, stainless steel, polypropylene, and polytetrafluoroethylene plastic. The length of the operating rod is slightly shorter than that of the sampling tube to prevent the wiping cotton from being pushed out during the wiping process. In this example, the operating rod is made of glass, with a diameter of 3 mm and a length of 86 mm.

[0024] There are two filter meshes 3, which are used to block both ends of the sampling tube 1 after the wiping cotton 2 has collected the target organic matter and entered the sampling tube 1, so as to prevent the wiping cotton fibers or particles from being blown into the analytical instrument when the sampling tube 1 is desorbed in the thermal desorption instrument. The material of the filter mesh needs to meet the characteristics of being resistant to organic solvents and high temperatures. Optional materials include inert metals such as stainless steel and copper, or plastics. In this embodiment, the filter mesh is a stainless steel mesh.

[0025] Embodiment 2 The method for analyzing organic matter on the surface of an article in this embodiment specifically includes the following steps: (1) Place 3 wire frames with a width of 6 cm and a length of 10 cm on a pre-cleaned glass plate to form three relatively closed surfaces to be measured. Then, drop a solution containing 20 ng of DnBP and 20 ng of DiBP on the surface area of the glass plate enclosed by each wire frame. The solvent in the solution is ethyl acetate. After dropping, let it stand. After the solvent in the solution has completely evaporated, a surface to be measured with a known organic matter content is formed on the surface area of the glass plate enclosed by the wire frame (the surface to be measured).

[0026] (2) Prepare the sampling device in Embodiment 1. The device includes a sampling tube, wiping cotton, a filter mesh, and an operating rod. The sampling tube is made of quartz, with a length of 88.9 mm, an outer diameter of 6.35 mm, and an inner diameter of 4 mm. The wiping cotton is flocculent glass fiber with a mass of 0.8 g and a glass fiber diameter of 75 μm. The filter mesh is a stainless steel mesh. The operating rod is made of glass, with a diameter of 3 mm and a length of 86 mm.

[0027] After preparation, completely insert the flocculent wiping cotton into the sampling tube to form a columnar wiping cotton with a length not exceeding half of the sampling tube length. During sampling, use the operating rod to push the columnar wiping cotton from one end of the sampling tube to the other end until 1 / 3 of the length of the columnar wiping cotton is outside the sampling tube. Use a micro syringe to inject 100 μL of a wiping agent onto the wiping cotton outside the sampling tube (the type of the wiping agent is determined according to the substance to be collected. For weakly polar substances, solvents such as n-hexane and ethyl acetate can be selected. For substances with slightly stronger polarity, solvents such as methanol and acetone can be selected; the amount of the wiping agent should be just enough to moisten the wiping cotton. The wiping agent in this embodiment is ethyl acetate). Due to the osmotic migration effect, the wiping agent will gradually soak the entire wiping cotton.

[0028] Then, use the operating rod to press against one end of the wiping cotton located inside the sampling tube, and wipe the surface to be measured with known organic matter content from top to bottom and from left to right. After wiping, use the operating rod to continue pushing the columnar wiping cotton inside the sampling tube outwards until 2 / 3 of the length of the columnar wiping cotton is outside the sampling tube. Then, continue to use the operating rod to press against one end of the wiping cotton located inside the sampling tube, and use the part of the wiping cotton outside the sampling tube that has not wiped the surface to be measured to wipe the surface to be measured with known organic matter content from top to bottom and from left to right again; then use the operating rod to push all the wiping cotton back into the sampling tube, and insert filter meshes at both ends of the sampling tube to complete the collection of the target organic matters (DnBP and DiBP) on the surface to be measured.

[0029] (3) Use a thermal desorption instrument to thermally desorb the sampling tube containing the target organic matters. The desorbed target organic matters enter the chromatographic column of the gas chromatography - mass spectrometry (GC - MS) instrument for separation, and the separated substances enter the mass spectrometer for analysis to obtain the mass spectrometry signal intensity of the target organic matters. In this embodiment, the thermal desorption instrument used is the TD - 100xr model of Markes International Company, and the GC - MS instrument is the 7890B - 5977B model of Agilent Company. The chromatographic column used for gas chromatography is the DB - 5 model, with dimensions of 30m × 0.32mm × 0.32μm.

[0030] Among them, the process of thermal desorption using the thermal desorption instrument includes the following steps: 1) Pre - purge the sampling tube with helium at a flow rate of 100 mL / min for 5 min to remove the ethyl acetate solvent in the wiping cotton inside the sampling tube; 2) Heat the sampling tube at a high temperature of 300°C for 10 min under a helium gas flow rate of 50 mL / min; 3) The desorbed target organic matters are first enriched by the cold trap on the path, and then the cold trap desorbs the target organic matters at a high temperature of 310°C for 10 min under a helium gas flow rate of 2 mL / min.

[0031] The test conditions for quantitative analysis using the gas chromatography - mass spectrometry instrument include: the initial temperature of the gas chromatography column oven is 40°C, maintained for 10 min, and then increased to 280°C at a heating rate of 10°C / min; the ion source temperature of the mass spectrometer is 230°C, the voltage is 70 eV, the quadrupole temperature is 150°C, and the full - scan mode is adopted.

[0032] (4) Prepare 4 sampling devices that are exactly the same as the sampling device in step (2). Then, use a micro syringe to inject standard solutions of DnBP and DiBP with gradient differences onto the glass wool in the sampling tubes of the 4 sampling devices, so that the 4 sampling tubes contain 2, 10, 30, and 50 ng of the target substances respectively. Then, plug filter meshes at both ends of the sampling tubes, and then use a thermal desorption instrument to thermally desorb the sampling tubes collecting the target organic substances according to the method in step (3), and make the desorbed target organic substances enter a gas chromatography-mass spectrometry (GC-MS) instrument for analysis to obtain the signal intensities of the target organic substances. Then, based on the signal intensities and the masses of the known target substances, establish a quantitative calibration curve for the signal response relationship.

[0033] (5) Use the corresponding relationship between the mass of the target organic substance and the mass spectrometry peak intensity in step (4) and the mass spectrometry peak intensity of the target organic substance detected in step (3) to calculate the mass of the target organic substance on the surface to be measured. The test results show that the contents of DnBP and DiBP on the 3 surfaces to be measured formed on the glass plate in step (1) are 19.2 ± 0.9 ng and 18.4 ± 1.6 ng respectively, and the deviation between the measured values and the theoretical values is within 10%.

[0034] The traditional wiping method includes at least one ultrasonic or Soxhlet extraction step for the wiped dust-free paper or gauze, and this process takes at least half an hour; the volume of the extracted solution is usually large (more than 10 mL), and the concentration of the target substance in it is relatively low. Therefore, it is necessary to further concentrate it to 1 mL or less by means such as nitrogen blowing, and the concentration step takes at least two hours; only after the above extraction and concentration treatments can instrumental analysis be carried out. In contrast, the present invention directly conducts instrumental analysis after wiping the sample without a pretreatment step. Specifically, the thermal desorption instrument can effectively desorb the target substance from the wiping material and introduce it into the quantitative analysis instrument within half an hour, thereby increasing the overall analysis efficiency by more than five times.

[0035] More critically, the direct thermal desorption technique avoids the dilution effect of organic solvents and significantly reduces the detection limit of the method. Taking the absolute detection limit of the target analyte by the quantitative analysis instrument as 1 ng (below this concentration, it cannot be detected) as an example, the present invention can directly detect the target substance as low as 1 ng on the wiped surface. If the traditional method of extracting after wiping the surface containing 1 ng of the target substance is used, and the final concentrated volume is 0.5 mL, then the concentration of the target substance in the extract is 0.002 ng / μL. Calculated according to the commonly used injection volume of 1 μL when testing the solution by gas chromatography-mass spectrometry, only 0.002 ng of the target substance enters the final quantitative instrument, which is far below the detection limit and thus cannot be detected. In other words, when using the traditional solution extraction method, the target analyte on the wiped surface needs to be higher than 500 ng to be quantitatively detected. Accordingly, the detection method of the present invention reduces the detection limit by two orders of magnitude compared with the traditional method.

Claims

1. A method for analyzing organic matter on the surface of an object, characterized in that: The following steps are involved: Use a cotton pad with a wiper to wipe the surface of the object to be tested to complete the collection of target organic matter; The wiping cotton collected with the target organic matter is then subjected to thermal desorption, and the gas obtained by the thermal desorption is then subjected to gas chromatography-mass spectrometry analysis to determine the target organic matter content on the surface of the object to be tested.

2. The method for analyzing organic matter on the surface of an object according to claim 1, characterized in that: The collection includes pushing out the wiping cotton part placed in the sampling tube, adding a wiping agent and then wiping, pushing the wiping cotton back into the sampling tube after wiping is completed, and then using a porous plugging material to block the openings at both ends of the sampling tube, and then directly performing the thermal desorption.

3. The method for analyzing organic matter on the surface of an object according to claim 2, characterized in that: The wiping includes primary wiping and secondary wiping. The wiping cotton pushed out by the primary wiping is 1 / 4 to 1 / 3 of its total length. After the primary wiping, another 1 / 4 to 1 / 3 of its total length is pushed outward for secondary wiping.

4. The method for analyzing organic matter on the surface of an object according to claim 1, characterized in that: The wiping is performed within a set area, and then the concentration of organic matter on the surface of the test article is calculated by the ratio of the target organic matter content to the area.

5. The method for analyzing organic matter on the surface of an object according to claim 1, characterized in that: The thermal desorption method comprises the following steps: pre-purging a wiping cotton collected with target organic matter, and then thermally desorbing the pre-purged wiping cotton under the action of a carrier gas to obtain a thermal desorption product; then enriching the thermal desorption product with a cold trap, and then heating and desorbing the cold trap under the action of a carrier gas.

6. The method for analyzing organic matter on the surface of an object according to claim 5, characterized in that: The temperature of the thermal desorption is 280-300°C, and the time is 8-10 min; the temperature of the cold trap for heating desorption is 300-310°C, and the time is 8-10 min; the gas used for pre-purge is an inert gas, the flow rate of the pre-purge gas is 80-100 mL / min, and the time is 1-8 min; during thermal desorption, the flow rate of the carrier gas is 50-70 mL / min; when the cold trap is heated for desorption, the flow rate of the carrier gas is 1-3 mL / min.

7. An in-situ collection device for organic matter on the surface of an object, characterized in that: It includes a sampling tube adapted to a thermal desorption instrument, in which a wiping cotton is arranged; it also includes a porous plugging object and an operating rod for sealing the openings at both ends of the sampling tube, wherein the operating rod is used to poke the wiping cotton part out of the sampling tube before wiping, and to press against the part of the wiping cotton inside the sampling tube when wiping, and to push the wiping cotton back into the sampling tube after wiping.

8. The in-situ collection device for organic matter on the surface of an object as claimed in claim 7, characterized in that: The length of the operating rod is shorter than the length of the sampling tube.

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