Tobacco volatile organic compound detection device and method

Abstract

The invention relates to the technical field of tobacco detection, in particular to a tobacco volatile organic compound detection device and method. The device comprises a background gas source, a sample part for accommodating a tobacco sample, a detection part for accommodating an electronic nose, a background gas pipeline and a tobacco volatile organic compound pipeline, the sample part is arranged on the tobacco volatile organic compound pipeline; the background gas source is communicated with the detection part through the background gas pipeline and the tobacco volatile organic compound pipeline respectively. The background gas source, the tobacco volatile organic compound pipeline, the sample part and the detection part form a closed-loop detection gas path, so that the gas flow forcibly flows through the tobacco sample to form dynamic headspace circulation, the concentration change of VOCs release is captured in real time, and the problem of gas balance distortion caused by static sampling is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of tobacco detection, and in particular to a device and method for detecting volatile organic compounds in tobacco. Background Art

[0002] In the tobacco industry, testing for volatile organic compounds (VOCs) is of great significance. For example, by testing tobacco VOCs, tobacco quality, such as the maturity and fermentation level of the leaves, can be determined. This helps tobacco producers screen raw materials and improve product quality. Different tobacco varieties have different volatile components, and analyzing the characteristics of these components can be used to identify tobacco varieties. This helps tobacco growers select high-quality varieties suited to local climate and soil conditions. During cigarette production, testing volatile components in cut tobacco can ensure that the quality meets standards. Furthermore, monitoring volatile gases in tobacco storage environments, such as ammonia and hydrogen sulfide, can prevent tobacco from becoming damp, moldy, or contaminated by harmful gases.

[0003] An electronic nose is a sensor system that mimics human olfaction. Its core goal is to quickly and accurately identify and distinguish different odors. Its sensor array consists of gas sensors with varying chemical selectivity, which cross-react to different gases, forming a unique fingerprint. Combined with pattern recognition algorithms, this fingerprint can be used to identify tobacco volatile gases. Patent publication number CN119147700A discloses a chromatographically simulated miniature integrated electronic nose and its applications. The application involves first flushing the sensor array in the chamber with a flow rate of 1000 sccm of N₂ to stabilize the sensor baseline. The sensor array is then exposed to 13 VOCs at a concentration of 10 ppm for 3 minutes. The resistance change of each of the 10 sensors in the miniature integrated electronic nose is measured using a multi-channel benchtop multimeter. Finally, N₂ is passed through the sensor array to flush out the previously introduced VOCs.

[0004] However, this existing technology cannot be directly and effectively applied to the detection of tobacco volatile organic compounds. On the one hand, this is because it can be used for 13 types of VOCs, but there are hundreds of tobacco volatile organic compounds, which are difficult for the electronic nose to directly and effectively identify. On the other hand, in the collection of tobacco volatile organic compounds, most existing technologies use traditional static headspace gas collection methods. Because the gas to be tested must be equilibrated in a sealed container before detection, the dynamic characteristics of the gas concentration are lost. In addition, the background calibration process requires independent gas circuits or manual switching of gas sources, which not only increases hardware costs but also easily introduces baseline drift errors. The existing solenoid valve control system only supports single gas circuit on and off, lacks the ability to dynamically reconstruct the detection gas circuit and background gas circuit, and has insufficient automation. Summary of the Invention

[0005] The present invention aims to solve the above problems and provides a detection device and method suitable for tobacco volatile organic compounds with high recognition accuracy.

[0006] The technical solution to the problem solved by the present invention is, in the first aspect, to provide a tobacco volatile organic compound detection device, comprising a background gas source, a sample portion for accommodating a tobacco sample, a detection portion for accommodating an electronic nose, a background gas pipeline, and a tobacco volatile organic compound pipeline; the sample portion is arranged in the tobacco volatile organic compound pipeline; the background gas source and the detection portion are connected through the background gas pipeline and the tobacco volatile organic compound pipeline, respectively.

[0007] In some preferred embodiments, the background gas source is connected to the background gas pipeline and the tobacco volatile organic compound pipeline via a first solenoid valve; the detection unit is connected to the background gas pipeline and the tobacco volatile organic compound pipeline via a second solenoid valve. Preferably, the first solenoid valve is a two-position three-way solenoid valve; and the second solenoid valve is a two-position three-way solenoid valve.

[0008] In some preferred embodiments, a pressure regulating valve is provided between the background gas source and the first solenoid valve. Preferably, the flow rate adjustment range of the pressure regulating valve is 10-500 mL / min.

[0009] In some preferred embodiments, the electronic nose comprises a top chamber, a sealing ring, a LIG interdigital electrode sensor array, and a bottom chamber that are stacked and connected in sequence, wherein the top chamber is provided with an interface for communicating with the second solenoid valve. Preferably, the LIG interdigital electrode sensor array comprises a substrate, and laser-induced graphene interdigital electrodes, a gas-sensitive conductive coating, and a hydrophobic coating that are sequentially disposed on the substrate. Preferably, the substrate is a polyimide film. Preferably, the hydrophobic coating is a polydimethylsiloxane coating. Preferably, the top chamber is prepared by a laser melting molding process and 3D printing. Preferably, the bottom chamber is prepared by a laser melting molding process and 3D printing.

[0010] In some preferred embodiments, the tobacco volatile organic compound pipeline includes an inlet tube and an outlet tube. One end of the inlet tube is connected to the background gas source via the first solenoid valve, and the other end is suspended above the tobacco sample. One end of the outlet tube is suspended above the tobacco sample, and the other end is connected to the detection unit. Preferably, the inlet tube is closer to the tobacco sample than the outlet tube.

[0011] In some preferred embodiments, the sample portion is provided with a connecting hole for the inlet tube and the outlet tube to be inserted, and a sealing ring is provided on the inner wall of the connecting hole.

[0012] In some preferred embodiments, the device further comprises a housing, wherein the background gas pipeline is disposed within the housing, and the sample unit and the detection unit are disposed on an outer wall of the housing. Preferably, the housing is made of aluminum alloy and is fabricated by sheet metal and laser processing.

[0013] In a second aspect, another object of the present invention is to provide a detection method using the above-mentioned tobacco volatile organic compound detection device, comprising the following steps:

[0014] S1. Pretreatment: Turn on the background gas source and background gas line to flush the electronic nose with background gas at a flow rate of 80-120 mL / min until the rate of change in the electronic nose resistance does not exceed 0.1% / min. This is recorded as the baseline resistance value of the electronic nose.

[0015] S2. Detection: The background gas source and tobacco volatile organic compound (VOC) pipeline are turned on, and the tobacco VOC is delivered to the electronic nose using a background gas carrier gas. The electronic nose is exposed to the VOC for 2 to 4 minutes. The detection resistance value of the electronic nose is obtained, and the rate of change of the detection resistance value relative to the baseline resistance value is calculated.

[0016] The background gas flow rate can be, for example, 80 mL / min, 90 mL / min, 100 mL / min, 110 mL / min, 120 mL / min, preferably 100 mL / min. The exposure time of the electronic nose to tobacco volatile organic compounds can be, for example, 2 minutes, 2.5 minutes, 3 minutes, 3.5 minutes, 4 minutes, preferably 3 minutes.

[0017] In the present application, the pre-processing parameters of the electronic nose are adjusted to make it more suitable for the detection of volatile organic compounds in tobacco.

[0018] In some preferred embodiments, the background gas is an inert gas; preferably, nitrogen.

[0019] In some preferred embodiments, before the electronic nose is flushed with background gas in step S1, the following steps are further included:

[0020] S11. Flushing the electronic nose with background gas until the rate of change of the electronic nose resistance value does not exceed 1% / min;

[0021] S12. Prepare a mixture, wherein the mixture includes non-polar alkanes, weakly polar aromatic hydrocarbons, polar aldehydes and ketones, nitrogen-containing compounds, alcohols, and esters, and the number of carbon atoms of the non-polar alkanes, weakly polar aromatic hydrocarbons, polar aldehydes and ketones, nitrogen-containing compounds, alcohols, and esters is independently 2 to 14; use a background gas carrier gas to deliver the volatile components of the mixture to the electronic nose for flushing until the rate of change of the electronic nose resistance value does not exceed 1% / min.

[0022] After steps S11 and S12 are completed, step S13 is performed. The electronic nose is flushed with background gas at a flow rate of 80-120 mL / min until the rate of change of the electronic nose resistance value does not exceed 0.1% / min, and this is recorded as the baseline resistance value of the electronic nose.

[0023] Before detecting tobacco volatile organic compounds, a mixed volatile substance that simulates the key chemical properties of tobacco volatile organic compounds is used as a probe to activate the surface of the electronic nose sensor, so that the sensor surface reaches adsorption-desorption equilibrium, avoiding irreversible adsorption and signal drift when the electronic nose sensor first comes into contact with tobacco volatile organic compounds, thereby improving the accuracy and stability of the electronic nose in identifying subsequent tobacco volatile organic compounds.

[0024] To mimic the key chemical properties of tobacco VOCs, the mixture contains ingredients ranging from C2 to C14 carbon chains, varying polarity, and different types to ensure effective activation of the electronic nose sensor against tobacco VOCs. Alkanes are inherently non-polar, so the alkane can be selected from at least one of the C2 to C14 alkanes. Weakly polar aromatic hydrocarbons can be selected from at least one of toluene, o-xylene, p-xylene, and benzaldehyde. Polar aldehydes and ketones can be selected from at least one of acetone, acetaldehyde, butanone, nonanal, 2,4-pentanedione, and benzaldehyde. Nitrogen-containing compounds can be selected from at least one of pyridine and quinoline. Alcohols can be selected from at least one of ethanol and isopropanol. Esters can be selected from at least one of ethyl acetate, ethyl formate, and ethyl benzoate. For example, the mixture consists of n-tetradecane, toluene, butanone, quinoline, ethanol, and ethyl acetate.

[0025] The usage ratio of each compound in the mixture is not limited. In some preferred embodiments, the mixture includes, by mass concentration, 30% to 35% non-polar alkanes, 10% to 20% weakly polar aromatic hydrocarbons, 25% to 40% polar aldehydes and ketones, 10% to 15% nitrogen-containing compounds, 5% to 10% alcohols, and 1% to 5% esters.

[0026] The mixture can be purged at once or in batches. In some preferred embodiments, step S12 includes at least three purging stages:

[0027] S121. Low-boiling-point purge: Select compounds and mix them into a first mixture, wherein the boiling point of the first mixture does not exceed 110°C, and the first mixture includes at least non-polar alkanes, weakly polar aromatic hydrocarbons, and polar aldehydes and ketones; use a background gas carrier gas to deliver the volatile components of the first mixture to the electronic nose for purging;

[0028] S122. Medium boiling point purge: selecting compounds to mix into a second mixture, wherein the boiling point of the second mixture is 110-170°C, and the second mixture comprises at least non-polar alkanes, weakly polar aromatic hydrocarbons, and polar aldehydes and ketones; using a background gas carrier gas, the volatile components of the second mixture are delivered to the electronic nose for purge;

[0029] S123. High-boiling-point purge: Select compounds and mix them into a third mixture, wherein the third mixture has a boiling point of not less than 170°C, and the third mixture includes at least non-polar alkanes, weakly polar aromatic hydrocarbons, and polar aldehydes and ketones; use a background gas carrier gas to deliver the volatile components of the third mixture to the electronic nose for purge;

[0030] The nitrogen-containing compound, alcohol compound and ester compound are independently distributed in the first mixture, the second mixture or the third mixture.

[0031] It is understood that the selected compounds are non-polar alkanes with 2 to 14 carbon atoms, weakly polar aromatic hydrocarbons, polar aldehydes and ketones, nitrogen-containing compounds, alcohols, and esters; and the first, second, and third mixtures collectively cover non-polar alkanes, weakly polar aromatic hydrocarbons, polar aldehydes and ketones, nitrogen-containing compounds, alcohols, and esters. By purging tobacco volatile organic compounds (VOCs) in batches and at different boiling points, the electronic nose sensor is trained in a step-by-step manner to improve its recognition accuracy for VOCs.

[0032] The total boiling point or boiling temperature range of the first, second, and third mixtures is affected by the boiling points and amounts of their constituent compounds. In some preferred embodiments, the first mixture consists of hexane, toluene, acetone, and ethanol. Preferably, by mass concentration, the first mixture consists of 25%-35% hexane, 10%-20% toluene, 30%-40% acetone, and 15%-30% ethanol; preferably, the first mixture consists of 30% hexane, 15% toluene, 35% acetone, and 20% ethanol. The second mixture consists of n-decane, xylene, 2,4-pentanedione, and pyridine. Preferably, by mass concentration, the second mixture consists of 25%-35% n-decane, 10%-20% xylene, 30%-40% 2,4-pentanedione, and 15%-30% pyridine; preferably, the second mixture consists of 30% n-decane, 15% xylene, 35% 2,4-pentanedione, and 20% pyridine. The third mixture is composed of n-tetradecane, benzaldehyde, nonanal, quinoline, ethyl benzoate, and ethanol (primarily serving as a solvent for n-tetradecane and quinoline). Preferably, in terms of mass concentration, the third mixture is composed of 15% to 25% n-tetradecane, 10% to 20% benzaldehyde, 30% to 40% nonanal, 5% to 20% quinoline, 15% to 30% ethanol, and 5% to 15% ethyl benzoate; preferably, the third mixture is composed of 20% n-tetradecane, 10% benzaldehyde, 30% nonanal, 15% quinoline, 15% ethanol, and 10% ethyl benzoate.

[0033] In some preferred embodiments, the concentrations of the volatile components of the first mixture, the second mixture, and the third mixture increase. Concentration here refers to the volumetric concentration of the volatile component in the mixture with the background gas, and can be controlled by decreasing the flow rate of the background gas. This step-by-step concentration training method allows for gradual activation of the electronic nose sensor.

[0034] In some preferred embodiments, the flow rate of the background gas in the low-boiling-point purge is 200-300 mL / min, the flow rate of the background gas in the medium-boiling-point purge is 100-200 mL / min, and the flow rate of the background gas in the high-boiling-point purge is 10-100 mL / min. Preferably, the flow rate of the background gas in the low-boiling-point purge is 250 mL / min, the flow rate of the background gas in the medium-boiling-point purge is 150 mL / min, and the flow rate of the background gas in the high-boiling-point purge is 50 mL / min.

[0035] In some preferred embodiments, after each purge stage is completed, the electronic nose is purged with background gas for 10 to 20 seconds, and the background gas flow rate is 400 to 500 mL / min. A large flow of background gas is purged to force the desorption of weakly adsorbed substances. For example, the purge time can be 10 seconds, 11 seconds, 12 seconds, 13 seconds, 14 seconds, 15 seconds, 16 seconds, 17 seconds, 18 seconds, 19 seconds, 20 seconds, preferably 15 seconds. The background gas flow rate can be 400 mL / min, 410 mL / min, 420 mL / min, 430 mL / min, 440 mL / min, 450 mL / min, 460 mL / min, 470 mL / min, 480 mL / min, 490 mL / min, 500 mL / min, preferably 450 mL / min.

[0036] In some preferred embodiments, the gas used to purge the electronic nose in step S122 also includes hydrogen at a volume concentration of 1-2%. The addition of hydrogen suppresses carbonization and deposition. Because the concentration of volatile components in the mixture is low, the amount of volatile components in the mixture can be ignored when calculating the hydrogen flow rate. For example, when the background gas flow rate is 150 mL / min, hydrogen is also introduced at a rate of 1.5-3 mL / min.

[0037] In some preferred embodiments, in a one-time purge embodiment, within 30 seconds before the end of the mixture purge, or in a batch purge embodiment, within 30 seconds before the end of the third mixture purge, carbon dioxide and / or ozone are injected into the electronic nose, wherein the volume concentration of the carbon dioxide is 5-15 ppm and the volume concentration of the ozone is 40-60 ppb. For example, when the flow rate of the background gas in the third mixture purge is 50 mL / min, 0.25-0.75 μL / min of carbon dioxide and / or 0.002-0.003 μL / min of ozone are also introduced within 30 seconds before the end of the purge. Carbon dioxide simulates combustion products, and ozone simulates atmospheric oxidants, further training the sensor's ability to resist cross-response. For example, the concentration of carbon dioxide can be 5 ppm, 6 ppm, 7 ppm, 8 ppm, 9 ppm, 10 ppm, 11 ppm, 12 ppm, 13 ppm, 14 ppm, 15 ppm, preferably 10 ppm. The concentration of ozone can be 40 ppb, 45 ppb, 50 ppb, 55 ppb, 60 ppb, and is preferably 50 ppb.

[0038] Beneficial effects of the present invention:

[0039] 1. The present invention provides a tobacco volatile organic compound detection device, which forms a closed-loop detection gas circuit through a background gas source, a tobacco volatile organic compound pipeline, a sample part, and a detection part, so that the airflow is forced to flow through the tobacco sample to form a dynamic headspace circulation, and the concentration changes of VOCs released are captured in real time, solving the problem of gas balance distortion caused by static sampling. In some embodiments, a first solenoid valve and a second solenoid valve are provided, and the physical characteristics of the normally open channel of the double solenoid valve are utilized to directly construct a direct background gas circuit in the power-off state without the need for an additional filter unit or an independent gas source. In some embodiments, an adjustable airflow pressure regulating valve is provided with a precision flow control of 10~500 mL / min to match the release kinetic characteristics of tobacco VOCs. In some embodiments, an interface is provided on the top cavity of the electronic nose to support plug-and-play electronic nose replacement.

[0040] 2. The present invention provides a method for detecting tobacco volatile organic compounds, which makes it more suitable for detecting tobacco volatile organic compounds by adjusting the preprocessing parameters of the electronic nose. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 1 is a schematic structural diagram of the tobacco volatile organic compound detection device in Example 1;

[0042] Figure 2 This is a data graph obtained after detection in Example 2;

[0043] In the figure: background gas source 1, sample unit 2, detection unit 3, background gas pipeline 11, tobacco volatile organic compound pipeline 12, inlet pipe 121, outlet pipe 122, first solenoid valve 41, second solenoid valve 42, pressure regulating valve 43. DETAILED DESCRIPTION

[0044] The following are specific embodiments of the present invention, which are combined with the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0045] Example 1

[0046] A tobacco volatile organic compound detection device, such as Figure 1 As shown, it includes a shell, a background gas source 1, a sample part 2 for accommodating tobacco samples, a detection part 3 for accommodating the electronic nose, a background gas pipeline 11, a tobacco volatile organic compound pipeline 12, a first solenoid valve 41, a second solenoid valve 42 and a pressure regulating valve 43 with an adjustable flow range of 10~500mL / min.

[0047] The housing is made of aluminum alloy and is equipped with an air source inlet, a VOCs inlet port, a VOCs outlet port, and an electronic nose inlet. The VOCs inlet port, the VOCs outlet port, and the electronic nose inlet are all φ6mm quick-connect connectors.

[0048] The background gas source 1 is a nitrogen tank, which is arranged outside the shell. The background gas source 1 is connected to the gas source inlet on the shell through a first connecting pipe.

[0049] The tobacco volatile organic compound (VOC) pipeline 12 includes an inlet tube 121 and an outlet tube 122. The sample unit 2 is a sample bottle with a sealing stopper. The sealing stopper has two ports for inserting the inlet tube 121 and the outlet tube 122. The ports are equipped with sealing rings. The insertion depth of the inlet tube 121 is greater than that of the outlet tube 122. The sample unit 2 is arranged outside the housing. The inlet tube 121 is connected to the VOCs inlet port, and the outlet tube 122 is connected to the VOCs outlet port.

[0050] The detection part 3 is a fixed frame, and the electronic nose can be placed or clamped on the fixed frame. The electronic nose includes a top chamber, a sealing ring, a LIG interdigital electrode sensor array and a bottom chamber that are stacked and connected in sequence. The top chamber is made by laser melting and 3D printing, and has 4 to 6 through holes and an interface designed on one side. The interface is connected to the electronic nose access port through a second connecting tube. The bottom chamber is also made by laser melting and 3D printing, and has 4 to 6 through holes designed on one side. The sealing ring is a rubber seal, specifically a rectangular rubber film that is laser cut to remove a portion with the same shape as the streamlined groove and four through holes corresponding to the top chamber. The LIG The interdigitated electrode sensor array consists of a flexible polyimide film, grooves formed by laser etching on the PI film, a laser-induced graphene interdigitated electrode array circuit engraved by laser on the PI film, a conductive coating of gas-sensitive material coated on the interdigitated electrode area, and a polydimethylsiloxane (PDMS) coating with a thickness gradient covering the gas-sensitive sensing material; during installation, the top chamber, rubber sealing ring, interdigitated electrode sensor array, and bottom chamber are stacked from top to bottom, the through holes are aligned one by one, and multiple screws are inserted from the through holes on one side of the top chamber inlet pipe, and then tightened with nuts.

[0051] Inside the housing: the air source inlet is connected to the inlet of the pressure-stabilizing valve 43 via a PU tube. The outlet of the pressure-stabilizing valve 43 is connected to the N1 terminal of the first solenoid valve 41. The N2 terminal of the first solenoid valve 41 is connected to the VOCs inlet port via a third connecting tube. The N3 terminal of the first solenoid valve 41 is connected to a fourth connecting tube. The electronic nose inlet is connected to the N1 terminal of the second solenoid valve. The N2 terminal of the second solenoid valve 42 is connected to the VOCs outlet port via a fifth connecting tube. The N3 terminal of the second solenoid valve 42 is connected to the aforementioned fourth connecting tube.

[0052] Based on this, the first connecting pipe, the gas source inlet, the pressure-stabilizing valve 43, the N1 end of the first solenoid valve 41, the N3 end of the first solenoid valve 41, the fourth connecting pipe, the N3 end of the second solenoid valve 42, the N1 end of the second solenoid valve 42, the electronic nose inlet, and the second connecting pipe form the background gas pipeline 11. The first connecting pipe, the gas source inlet, the pressure-stabilizing valve 43, the N1 end of the first solenoid valve 41, the N2 end of the first solenoid valve 41, the third connecting pipe, the VOCs inlet port, the inlet pipe 121, the sample portion 2, the outlet pipe 122, the VOCs outlet port, the fifth connecting pipe, the N2 end of the second solenoid valve 42, the N1 end of the second solenoid valve, the electronic nose inlet, and the second connecting pipe form the tobacco volatile organic compound pipeline 12.

[0053] In addition, a relay control module is also included to control the on and off of the first solenoid valve 41 and the second solenoid valve 43.

[0054] Example 2

[0055] A method for detecting volatile organic compounds in tobacco, using the device of Example 1, comprises the following steps:

[0056] S1. Preprocessing: The relay control module is controlled by the host computer to de-energize the dual valves. The first solenoid valve 41 automatically connects the normally open N1-N3 channel, and the second solenoid valve 42 automatically connects the normally open N3-N1 channel. Nitrogen from background gas source 1 flows through: background gas source 1, gas source inlet, pressure regulating valve 43, N1 terminal of the first solenoid valve 41, N3 terminal of the first solenoid valve 41, N3 terminal of the second solenoid valve 42, N1 terminal of the second solenoid valve 42, and the electronic nose, flushing the electronic nose with background gas nitrogen. The background gas flow rate is 100 mL / min, and the flushing time is 60 seconds. The signal acquisition module records this as the electronic nose's baseline resistance value, R0.

[0057] S2. Detection: Control the double valves to open, the first solenoid valve 41 switches to the N1-N2 path, and the second solenoid valve 42 switches to the N2-N1 path. Airflow path: background gas source 1, gas source inlet, pressure regulating valve 43, N1 end of the first solenoid valve 41, N2 end of the first solenoid valve 41, VOCs air inlet interface, inlet tube 121, sample part 2, outlet tube 122, VOCs air outlet interface, N2 end of the second solenoid valve 42, N1 end of the second solenoid valve 42, electronic nose, to achieve the delivery of tobacco volatile organic compounds to the electronic nose under nitrogen carrier gas, so that the electronic nose is exposed to the tobacco volatile organic compounds for 3 minutes, and the detection resistance value R of the electronic nose is obtained. t Calculate the rate of change of the detection resistance value relative to the reference resistance value ΔR=(R t -R0) / R0. Figure 2 As shown, it can be seen that the detection of tobacco volatile organic compounds is achieved.

[0058] S3. Flushing: The double valves are de-energized again, and the first solenoid valve 41 automatically connects the N1-N3 normally open channel, and the second solenoid valve 42 automatically connects the N3-N1 normally open channel to flush the electronic nose with background gas nitrogen to flush out the tobacco volatile organic compounds previously introduced.

[0059] Example 3

[0060] A method for detecting volatile organic compounds in tobacco, using the device of Example 1, comprises the following steps:

[0061] S1. Pretreatment: S11. The host computer controls the relay control module to de-energize the dual valves. The first solenoid valve 41 automatically connects the normally open N1-N3 channel, and the second solenoid valve 42 automatically connects the normally open N3-N1 channel. Nitrogen from background gas source 1 flows through: background gas source 1, gas source inlet, pressure regulating valve 43, N1 terminal of the first solenoid valve 41, N3 terminal of the first solenoid valve 41, N3 terminal of the second solenoid valve 42, N1 terminal of the second solenoid valve 42, and the electronic nose, flushing the electronic nose with background gas nitrogen. The background gas flow rate is 100 mL / min, and the flushing time is 30 seconds.

[0062] S12. Prepare a mixture by uniformly mixing, by weight, 30 parts hexane, 30 parts n-decane, 20 parts n-tetradecane, 15 parts toluene, 15 parts xylene, 10 parts benzaldehyde, 35 parts acetone, 35 parts 2,4-pentanedione, 30 parts nonanal, 20 parts pyridine, 15 parts quinoline, 35 parts ethanol, and 10 parts ethyl benzoate to obtain a mixture. Place the mixture in sample portion 2.

[0063] Control the dual valves to open, switching the first solenoid valve 41 to the N1-N2 path and the second solenoid valve 42 to the N2-N1 path. The airflow path includes: background gas source 1, gas source inlet, pressure-stabilizing valve 43, N1 end of first solenoid valve 41, N2 end of first solenoid valve 41, VOCs inlet port, inlet tube 121, sample section 2, outlet tube 122, VOCs outlet port, N2 end of second solenoid valve 42, N1 end of second solenoid valve 42, and electronic nose. This creates nitrogen carrier gas, delivering the volatile components of the mixture to the electronic nose for purging. The background gas flow rate is 150 mL / min, and the purge time is 90 seconds.

[0064] S13. De-energize both valves. The first solenoid valve 41 automatically connects the normally open channel N1-N3, and the second solenoid valve 42 automatically connects the normally open channel N3-N1 to flush the electronic nose with background gas nitrogen. The flow rate of the background gas is 100 mL / min, and the flushing time is 60 seconds. This is recorded as the baseline resistance value R0 of the electronic nose.

[0065] S2. Detection: After cleaning and drying the sample part 2, add the tobacco sample. Control the double valves to open, the first solenoid valve 41 switches to the N1-N2 path, and the second solenoid valve 42 switches to the N2-N1 path. Airflow path: background gas source 1, gas source inlet, pressure regulating valve 43, N1 end of the first solenoid valve 41, N2 end of the first solenoid valve 41, VOCs air inlet interface, inlet pipe 121, sample part 2, outlet pipe 122, VOCs air outlet interface, N2 end of the second solenoid valve 42, N1 end of the second solenoid valve 42, electronic nose, to achieve the delivery of tobacco volatile organic compounds to the electronic nose under nitrogen carrier gas, so that the electronic nose is exposed to the tobacco volatile organic compounds for 3 minutes, obtain the detection resistance value Rt of the electronic nose, and calculate the rate of change of the detection resistance value relative to the reference resistance value ΔR=(R t -R0) / R0.

[0066] S3. Flushing: The double valves are de-energized again, and the first solenoid valve 41 automatically connects the N1-N3 normally open channel, and the second solenoid valve 42 automatically connects the N3-N1 normally open channel to flush the electronic nose with background gas nitrogen to flush out the tobacco volatile organic compounds previously introduced.

[0067] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. A tobacco volatile organic compound detection device, characterized by: It comprises a background gas source (1), a sample portion (2) for accommodating a tobacco sample, a detection portion (3) for accommodating an electronic nose, a background gas pipeline (11), and a tobacco volatile organic compound pipeline (12); The sample portion (2) is arranged in the tobacco volatile organic compound pipeline (12); The background gas source (1) and the detection unit (3) are respectively connected through the background gas pipeline (11) and the tobacco volatile organic compound pipeline (12).

2. The tobacco volatile organic compound detection device according to claim 1, characterized in that: The background gas source (1) is connected to the background gas pipeline (11) and the tobacco volatile organic compound pipeline (12) via a first solenoid valve (41); and the detection unit (3) is connected to the background gas pipeline (11) and the tobacco volatile organic compound pipeline (12) via a second solenoid valve (42).

3. The tobacco volatile organic compound detection device according to claim 2, characterized in that: A pressure stabilizing valve (43) is provided between the background gas source (1) and the first solenoid valve (41); the flow rate adjustment range of the pressure stabilizing valve (43) is 10-500 mL / min.

4. The tobacco volatile organic compound detection device according to claim 1, characterized in that: The electronic nose comprises a top chamber, a sealing ring, a LIG interdigital electrode sensor array and a bottom chamber which are stacked and connected in sequence, and the top chamber is provided with an interface for communicating with the second solenoid valve (42).

5. The tobacco volatile organic compound detection device according to claim 1, characterized in that: The tobacco volatile organic compound pipeline (12) comprises an inlet pipe (121) and an outlet pipe (122), wherein one end of the inlet pipe (121) is connected to the background gas source (1) via the first solenoid valve (41), and the other end is suspended above the tobacco sample; one end of the outlet pipe (122) is suspended above the tobacco sample, and the other end is connected to the detection unit (3).

6. The tobacco volatile organic compound detection device according to claim 5, characterized in that: The sample portion (2) is provided with a connection hole for the inlet tube (121) and the outlet tube (122) to be inserted, and a sealing ring is provided on the inner wall of the connection hole.

7. The tobacco volatile organic compound detection device according to claim 1, characterized in that: It also includes a shell, the background gas pipeline (11) is arranged in the shell, and the sample part (2) and the detection part (3) are arranged on the outer wall of the shell.

8. A detection method using the tobacco volatile organic compound detection device according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Pretreatment: Turn on the background gas source (1) and the background gas pipeline (11), and flush the electronic nose with background gas at a flow rate of 80-120 mL / min until the rate of change of the electronic nose resistance value does not exceed 0.1% / min, and record it as the baseline resistance value of the electronic nose; S2. Detection: The background gas source (1) and the tobacco volatile organic compound pipeline (12) are turned on, and the tobacco volatile organic compounds are delivered to the electronic nose using a background gas carrier gas. The electronic nose is exposed to the tobacco volatile organic compounds for 2 to 4 minutes, and a detection resistance value of the electronic nose is obtained, and the rate of change of the detection resistance value relative to the reference resistance value is calculated.

9. The method for detecting volatile organic compounds in tobacco according to claim 8, wherein: The background gas is nitrogen.

10. The method for detecting volatile organic compounds in tobacco according to claim 8, wherein: In step S1, before the electronic nose is flushed with background gas, the following steps are also included: S11. Flushing the electronic nose with background gas until the rate of change of the electronic nose resistance value does not exceed 1% / min; S12. Prepare a mixture, wherein the mixture includes non-polar alkanes, weakly polar aromatic hydrocarbons, polar aldehydes and ketones, nitrogen-containing compounds, alcohols, and esters, and the number of carbon atoms of the non-polar alkanes, weakly polar aromatic hydrocarbons, polar aldehydes and ketones, nitrogen-containing compounds, alcohols, and esters is independently 2 to 14; use a background gas carrier gas to deliver the volatile components of the mixture to the electronic nose for flushing until the rate of change of the electronic nose resistance value does not exceed 1% / min.

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