A digestion method for the determination of total nitrogen in tobacco and tobacco products by continuous flow method

Abstract

The present invention provides a digestion method for the determination of total nitrogen in tobacco and tobacco products by continuous flow method, comprising the following steps: balancing the moisture of tobacco or tobacco products in an oven, and then crushing and sieving to obtain a sample to be tested; weighing the sample to be tested into a digestion tube, and adding a catalyst for promoting the digestion of tobacco and tobacco products into the digestion tube; placing the digestion tube on a digestion furnace for digestion, and taking it out after the digestion is completed and the temperature drops; taking it out after the digestion is completed, adding distilled water, shaking evenly and transferring it to a volumetric flask without loss and shaking well for constant volume, and filtering to prepare a test solution for on-machine detection. The digestion method of the present invention can greatly shorten the digestion time for the determination of total nitrogen in tobacco and tobacco products by continuous flow method while ensuring the accuracy and reliability of the total nitrogen detection results.

Description

Technical Field

[0001] The present invention relates to the technology for determining total nitrogen in tobacco and tobacco products, and particularly to a digestion method for determining total nitrogen in tobacco and tobacco products by continuous flow method. Background Art

[0002] Total nitrogen is the general term for nitrogen contained in various nitrogen-containing compounds in tobacco leaves, such as proteins, amino acids, nicotine, volatile bases, chlorophyll, etc. The nitrogen in tobacco leaves directly affects the suction quality of cigarette products and the evaluation of sensory smoking quality. Therefore, the use of a rapid and accurate method for determining the total nitrogen content has always been a research hotspot in the tobacco and tobacco products industry.

[0003] At present, the industry standard YC / T 161-2002 continuous flow method is still used as a reference for determining total nitrogen in reconstituted tobacco by papermaking method. In this method, mercury oxide, potassium sulfate and sulfuric acid are used as catalysts. At a certain temperature and time, the tobacco leaves are strongly heated and decomposed by digestion, and nitrogen is converted into ammonia and combined with sulfuric acid to remain in the digestion solution, completing the digestion work for total nitrogen determination. Among them, mercury oxide, as a highly toxic chemical, not only poses a threat to human and environmental safety, but also has certain difficulties in procurement and use. At present, copper sulfate has been proven to be a safer catalyst alternative to mercury oxide. Experiments and related research have shown that YC / T 161-2002 cannot completely digest tobacco products such as finished reconstituted tobacco sheets, probably due to problems such as the amount of catalyst used and the digestion temperature and time being insufficient.

[0004] Based on this, it is particularly important to find a suitable catalyst, the amount of catalyst used, and the digestion temperature control parameters on the basis of ensuring accurate test results. Summary of the Invention

[0005] The purpose of the present invention is to propose a digestion method for determining total nitrogen in tobacco and tobacco products by continuous flow method, aiming at the problems of long time in the current total nitrogen determination method and inaccurate determination results for tobacco products such as reconstituted tobacco sheets. This digestion method can significantly shorten the digestion time for determining total nitrogen in tobacco and tobacco products by continuous flow method while ensuring accurate and reliable total nitrogen test results.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: a digestion method for determining total nitrogen in tobacco and tobacco products by continuous flow method, comprising the following steps:

[0007] (1) Sample preparation: Balance the moisture of the pretreated tobacco or tobacco products in an oven, and then crush and sieve to obtain the test sample;

[0008] (2) Weighing: Weigh the test sample into a digestion tube and add a catalyst to promote the digestion of tobacco and tobacco products;

[0009] (3) Digestion: Place the digestive tract on a digestion furnace for digestion. After digestion is completed and the temperature drops, take it out.

[0010] (4) Shaking: After digestion is completed and taken out, add distilled water, and use an ultrasonic shaking device to quickly and stably shake the digestive juice evenly.

[0011] (5) Transfer and preparation for analysis: After digestion is completed and taken out, add distilled water, shake it evenly, transfer it to a volumetric flask without loss, shake it well to make up the volume, and filter it to prepare the sample solution for analysis.

[0012] Further, the pretreatment of the tobacco or tobacco product in step (1) is as follows: for white slice samples, randomly select no less than 100 g of samples, pick out the white slices that do not meet the requirements, and measure the white slice rate; for abnormally sliced samples, spread out the randomly selected samples, pick out the samples with abnormal slicing such as overly fragmented or irregularly shaped slices, and measure the abnormal slicing rate; for powder-shedding samples, take 50 g of samples for cutting into shreds, place them on a 20-mesh sieve, shake the sieve left and right until no powder falls, collect the shredded samples, weigh them, and measure the powder-shedding rate. Ensure that the white slice rate, abnormal slicing rate, and powder-shedding rate are controlled within a certain range, and use the five-point sampling method to take samples to make them representative for detection.

[0013] Further, the tobacco product in step (1) is a finished product of reconstituted tobacco leaf flakes.

[0014] Further, the temperature of the oven in step (1) is 40 - 60 °C, and the moisture balance time is 1.5 - 2.5 h.

[0015] Further, the mesh number of the sieve through which the crushed tobacco and tobacco product in step (1) pass is 40 mesh.

[0016] Further, the catalyst reagent in step (2) is a low-toxic and low-harm chemical reagent, including potassium sulfate, copper sulfate, and sulfuric acid. The dosage ratio of the sample to be measured, potassium sulfate, copper sulfate, and sulfuric acid is 0.9995 - 0.1005 g : 1.9995 - 2.0005 g : 0.16 - 0.2 g : 5 mL; the concentration of the sulfuric acid is 95.0 - 98.0%.

[0017] Further, the digestion in step (3) includes two steps. The first step is at 190 - 210 °C for 30 - 40 min, and the second step is at 420 - 430 °C for 125 - 135 min; after digestion, it is taken out after cooling to 20 - 70 °C.

[0018] Further, in step (3), a digestion device with the function of collecting and recycling the tail gas of total nitrogen digestion is used. For example, a digestion device for continuously flowing method to determine the total nitrogen in tobacco and tobacco products, which has the function of collecting and recycling the tail gas of total nitrogen digestion.

[0019] Furthermore, the ultrasonic shaking device in step (4) has an ultrasonic frequency of 100-150 KHz, an ultrasonic time of 5-9 min, a shaking frequency of 200-300 r / min, and a shaking time of 5-12 min.

[0020] Furthermore, in step (5), the ratio of the sample to be tested to distilled water is: 0.9995-0.1005 g: 20-40 mL.

[0021] Furthermore, a digestion device for determining total nitrogen in tobacco and tobacco products by a continuous flow method comprises an upper water reservoir, a lower water reservoir, a first instantaneous flow meter, a second instantaneous flow meter, a hose, a vacuum pump, an exhaust gas outlet device, a digestion furnace, a digestion tube and a valve, wherein the bottom surface of the upper water reservoir is higher than the exhaust gas outlet device, and the exhaust gas outlet device is higher than the top surface of the lower water reservoir; the digestion tube is placed on the digestion furnace, the exhaust gas outlet device comprises a collecting cavity and a plurality of rubber plugs arranged below the collecting cavity, the rubber plug can be stuck on the opening of the digestion tube, the rubber plug can achieve the sealing of the digestion tube, the rubber plug is provided with a hole, and the inside of the digestion tube is connected with the collecting cavity through the hole provided on the rubber plug;

[0022] The bottom outlet of the upper water reservoir is connected to the inlet of the lower water reservoir through a first hose, and the bottom outlet of the lower water reservoir is connected to the inlet of the upper water reservoir through a second hose; the first hose is provided with a first instantaneous flow meter and a valve, and the second hose is provided with a second instantaneous flow meter and a vacuum pump; the exhaust gas outlet device is connected to the middle part of the first hose through a third hose, and the third hose is connected to the first hose close to the lower water reservoir at an obtuse angle.

[0023] Furthermore, the valve is arranged at one end of the first hose close to the upper water reservoir.

[0024] Furthermore, the valve is a twist valve.

[0025] Furthermore, the first instantaneous flow meter is arranged at one end of the first hose close to the upper water reservoir to reduce the interference of exhaust gas on the flow meter.

[0026] Furthermore, the height difference between the bottom surface of the upper water reservoir and the top surface of the lower water reservoir is 1.40-1.55m.

[0027] Working principle of the above device: Weigh the sample to be tested into the digestion tube, place it on the digestion furnace, and insert the rubber stopper of the tail gas export device onto the digestion tube against the digestion tube opening to form a closed environment. Open the twisting valve, and the water in the upper reservoir flows into the lower reservoir through the first hose. At this time, a negative pressure environment is created in the third hose connected to the first hose. Subsequently, turn on the digestion furnace, and the tail gas generated during the total nitrogen digestion process in the digestion tube is collected into the collection chamber of the tail gas export device through the rubber stopper. The tail gas sequentially passes through the collection chamber, the third hose, and the first hose and enters the lower reservoir. Turn on the vacuum pump to transfer the water in the lower reservoir to the upper reservoir. During the operation of the total nitrogen digestion tail gas collection water circulation device, the flow rate of the second instantaneous flowmeter should be slightly greater than that of the first instantaneous flowmeter to achieve water circulation.

[0028] Further, the ultrasonic shaking device for determining the total nitrogen in tobacco and tobacco products used in step (4) for shaking includes: a control panel, a chassis, an ultrasonic cell, a lifting column, a support plate, a lower support frame, an upper support frame, a buffer spring, a bottom plate, a rotary oscillator, and a hydraulic system;

[0029] A bottom plate is arranged at the inner bottom of the chassis, and a rotary oscillator and a hydraulic system are fixed on the lower surface of the bottom plate;

[0030] An ultrasonic cell is arranged inside the chassis and above the bottom plate. The ultrasonic cell is fixed to the side wall of the chassis and is used to hold ultrasonic water; shaking holes are respectively arranged at the four corners of the chassis; the lifting column includes a sleeved outer column and an inner column. The outer column is fixed in the shaking hole, and the inner column passes through the outer column and is connected to the upper surface of the bottom plate; the control panel is arranged on the outer side wall of the chassis; the control panel is electrically connected to the ultrasonic cell drive structure, the rotary oscillator, and the hydraulic system respectively;

[0031] A plurality of first digestion tube holes are provided on the upper support frame. The arrangement of the plurality of first digestion tube holes enables the upper support frame to insert multiple digestion tubes simultaneously. A buffer spring is coaxially arranged above each first digestion tube hole. One end of the buffer spring is fixed on the upper support frame, and the other end is used to support the outer edge of the digestion tube. The opening of the digestion tube is thickened and protruded. When the digestion tube is placed and during the shaking process, the buffer spring can play a buffering role to prevent the digestion tube from being damaged due to severe friction with the upper and lower support frames; a plurality of second digestion tube holes are provided on the support plate, and the plurality of first digestion tube holes correspond to the plurality of second digestion tube holes one by one, that is, the digestion tube can sequentially pass through the digestion tube holes provided on the buffer spring support frame and the digestion tube holes provided on the support plate to achieve fixation;

[0032] The lower support frame is fixed at the top of the four inner columns, and the upper support frame cooperates with the lower support frame; the support plate is fixed at the upper 1 / 3 of the four inner columns of the lifting column.

[0033] Further, a scale line is marked at the lower end of the digestion tube.

[0034] Further, a positioning line is marked in the middle and lower part of the inner column of the lifting column.

[0035] Further, a lifting column lifting adjustment knob (for controlling the hydraulic system), a lifting column rotation speed adjustment knob (for controlling the rotary shaker), an ultrasonic time adjustment knob, and an ultrasonic intensity adjustment knob (for controlling the ultrasonic cell drive structure) are respectively arranged on the control panel.

[0036] Further, a limiting device is arranged on the upper support frame and / or the lower support frame to facilitate the accurate engagement of the upper support frame and the lower support frame.

[0037] The working principle of the ultrasonic shaking device for determining the total nitrogen in tobacco and tobacco products: The operation of the ultrasonic shaking device is mainly completed by two functional supports. One is the ultrasonic dissolution function, and the other is the oscillating and mixing function. After ultrasonic treatment, the digestion solution is fully dissolved and then oscillated to complete uniform mixing.

[0038] A digestion method for continuously flowing method to determine the total nitrogen in tobacco and tobacco products according to the present invention includes a specific catalyst and dosage combination and digestion temperature control parameters, and has the following advantages compared with the prior art:

[0039] (1) The catalyst for promoting the digestion of tobacco and tobacco products in the present invention is copper sulfate, potassium sulfate, and sulfuric acid. Mercuric oxide, a highly toxic and high-risk reagent in the industry standard YC / T 161-2002, is replaced by copper sulfate. On the premise of ensuring the same catalytic effect, it has high operability and safety.

[0040] (2) The catalyst and dosage combination for promoting the digestion of tobacco and tobacco products in the present invention: The dosage ratio of the sample to be measured, potassium sulfate, copper sulfate, and sulfuric acid is 0.9995 - 0.1005 g: 1.9995 - 2.0005 g: 0.16 - 0.2 g: 5 mL. This reagent dosage can meet the complete digestion of tobacco and tobacco products such as reconstituted tobacco leaves, and has high general applicability.

[0041] (3) The digestion temperature control parameters for continuously flowing method to determine the total nitrogen in tobacco and tobacco products according to the present invention include two procedures. The first procedure is 190 - 210 °C for 30 - 40 min, and the second procedure is 420 - 430 °C for 125 - 135 min. This digestion temperature control parameter is greatly shortened compared with the digestion time recommended by the current supplier. The digestion time recommended by the current supplier is 5 h for 2 procedures, and the digestion time of the present invention is 2.6 - 2.9 h for 2 procedures. While ensuring accurate test results, it can reduce the waste of water and electricity resources and reduce the safety problems caused by too long digestion time.

[0042] (4) The special production process of reconstituted tobacco by the papermaking method requires special catalytic conditions for the determination of total nitrogen in its products. The present invention is an improvement of the digestion method based on YC / T 161-2002 Tobacco and Tobacco Products - Determination of Total Nitrogen - Continuous Flow Method. Therefore, the present invention not only meets the detection requirements for the determination of total nitrogen in reconstituted tobacco by the papermaking method but also greatly shortens the detection time.

[0043] (5) The digestion device for the determination of total nitrogen in tobacco and tobacco products by the continuous flow method has a simple, reasonable and compact structure. It takes away the tail gas through water flow, meets the tail gas emission requirements for total nitrogen digestion detection, and at the same time, the circulating water circulates between the upper water reservoir and the lower water reservoir, which can also effectively reduce the waste of water resources.

[0044] (6) The ultrasonic shaking device for the determination of total nitrogen in tobacco and tobacco products can not only ensure a stable shaking frequency and rate of the digestion tube, but also accelerate the dissolution of the digestive juice in the digestion tube by adding an ultrasonic function with specific parameters; this device can process a large number of samples at the same time, and compared with manually processing a single digestion tube, the sample processing efficiency and detection stability are greatly improved.

[0045] In summary, the catalyst and its dosage combination and digestion temperature control parameters of the present invention can make the results of the determination of total nitrogen in tobacco and tobacco products by the continuous flow method accurate, greatly shorten the digestion time, make the operation process safer, and achieve more resource conservation. Description of the Drawings

[0046] Figure 1 It is a schematic structural diagram of the digestion device for the determination of total nitrogen in tobacco and tobacco products by the continuous flow method;

[0047] Figure 2 It is a schematic structural diagram of the tail gas export device;

[0048] Figure 3 It is a schematic structural diagram of the ultrasonic shaking device for the determination of total nitrogen in tobacco and tobacco products;

[0049] Figure 4 It is a schematic structural diagram of the digestion tube;

[0050] Figure 5 It is a schematic structural diagram of the upper support frame with the digestion tube placed on it;

[0051] Figure 6 It is a schematic structural diagram after the bottom plate is turned over;

[0052] Figure 7 It is a schematic structural diagram of the bottom plate. Detailed Embodiments

[0053] The following further illustrates the present invention in conjunction with embodiments:

[0054] Embodiment 1

[0055] This embodiment discloses a verification method for the digestion of total nitrogen in tobacco and tobacco products by continuous flow method using the laboratory control sample A of the National Tobacco Quality Supervision and Inspection Center. The specific steps are as follows:

[0056] (1) Weighing: Weigh 0.1 g of laboratory control sample A into a digestion tube; then weigh 0.20 g of copper sulfate and 2.00 g of potassium sulfate quantitatively, and measure 5 mL of sulfuric acid and add them into the digestion tube in sequence.

[0057] (2) Digestion: Place the digestion tube on a digestion furnace with set digestion temperature control parameters. The digestion temperature control parameters include two programs. The first program is 200 °C for 30 min, and the second program is 420 °C for 130 min. After digestion, take out the digestion tube after the temperature of the digestion furnace drops to 20 °C.

[0058] (3) Shaking: Add 30 mL of distilled water into the digestion tube, and use an ultrasonic shaking device for the determination of total nitrogen in tobacco and tobacco products to shake well. The ultrasonic frequency is 100 KHz, the ultrasonic time is 5 min, the shaking frequency is 200 r / min, and the shaking time is 12 min.

[0059] (4) Instrument detection: After uniformly oscillating and shaking well, transfer it to a 100 mL volumetric flask without loss and shake well to make up the volume. After filtration, prepare a test solution for instrument detection.

[0060] The total nitrogen content of the laboratory control sample A measured by the digestion method for the determination of total nitrogen in tobacco and tobacco products by continuous flow method in this embodiment is 1.60 ± 0.01%, and its certified value is 1.60 ± 0.08%.

[0061] In step (2), the digestion uses a digestion device with a function of collecting and recycling the tail gas of total nitrogen digestion, as Figure 1 and 2 shown, which includes an upper water reservoir 11, a lower water reservoir 10, a first instantaneous flowmeter 21, a second instantaneous flowmeter 22, a vacuum pump 4, a tail gas export device 5, a digestion furnace 6, a digestion tube 7 and valves. The bottom surface of the upper water reservoir 11 is higher than the tail gas export device 5, and the tail gas export device 5 is higher than the top surface of the lower water reservoir 10; the height difference between the bottom surface of the upper water reservoir 11 and the top surface of the lower water reservoir 10 is 1.40 - 1.55 m. The upper water reservoir holds 10 - 30 L of tap water. The inner diameters of the 3 hoses are 65 - 80 mm. The digestion tube 7 is placed on the digestion furnace 6. The tail gas export device 5 includes a collection chamber, and a plurality of rubber plugs matched with the digestion tube 7 are fixed below the collection chamber, that is, the rubber plugs can be stuck on the opening of the digestion tube 7, and the rubber plugs can seal the digestion tube 7. A hole is provided in the rubber plug, and the inside of the digestion tube 7 communicates with the collection chamber through the hole in the rubber plug.

[0062] The bottom outlet of the upper water reservoir 11 is communicated with the inlet of the lower water reservoir 10 through a first flexible hose, and the bottom outlet of the lower water reservoir 10 is communicated with the inlet of the upper water reservoir 11 through a second flexible hose 32; a first instantaneous flowmeter 21 and a valve are arranged on one end of the first flexible hose close to the upper water reservoir 11, and the valve is a turning valve 8. A second instantaneous flowmeter 22 and a vacuum pump 4 are arranged on the second flexible hose 32; the tail gas discharging device 5 is communicated with the middle of the first flexible hose through a third flexible hose 33, and the third flexible hose 33 is connected to the first flexible hose close to the lower water reservoir 10 in an obtuse angle connection mode.

[0063] The working principle of the above device: Weigh the sample to be measured in the digestion tube, place it on the digestion furnace, and insert the rubber stopper of the tail gas discharging device onto the digestion tube opening facing the digestion tube mouth to form a closed environment. After everything is ready, open the turning valve, and the water in the upper water reservoir 11 flows into the lower water reservoir 10 through the first flexible hose. At this time, the third flexible hose communicated with the first flexible hose is in a negative pressure environment; then start the digestion furnace 6, and the tail gas generated during the total nitrogen digestion process in the digestion tube 7 is collected into the collection chamber of the tail gas discharging device 5 through the rubber stopper, and the tail gas passes through the collection chamber, the third flexible hose, and the first flexible hose in sequence and enters the lower water reservoir 10; open the vacuum pump 4 to transfer the water in the lower water reservoir 10 to the upper water reservoir 11. During the working process of the total nitrogen digestion tail gas collection and water circulation device, the flow rate of the first instantaneous flowmeter 21 is 0.50 - 0.55 m / s, and the flow rate of the second instantaneous flowmeter 22 is slightly greater than that of the flowmeter 21 to achieve water circulation.

[0064] The total nitrogen digestion tail gas collection and water circulation device can directly carry away the tail gas generated during the total nitrogen digestion process through flowing water at a certain flow rate, avoid the overflow of tail gas, and reduce the harm to the environment. At the same time, the circulating water circulates between the upper water reservoir 11 and the lower water reservoir 10, which can effectively reduce the waste of water resources.

[0065] The ultrasonic shaking device for determining the total nitrogen in tobacco and tobacco products used in step (3), as Figures 3 - 7 shown, includes: a control panel 20, a chassis 12, an ultrasonic cell 13, a lifting column 16, a support plate 17, a lower support frame 19, an upper support frame 23, a buffer spring 24, a bottom plate 25, a rotary oscillator 26, and a hydraulic device 27;

[0066] A bottom plate 25 is arranged at the inner bottom of the chassis 12, and a rotary oscillator 26 and a hydraulic device 27 are fixed on the lower surface of the bottom plate 25; the shaking and lifting column driving structure of the ultrasonic shaking device for determining the total nitrogen in tobacco and tobacco products is the rotary oscillator 26 and the hydraulic device 27.

[0067] An ultrasonic pool 13 is arranged inside the chassis 12 and above the bottom plate 25. The ultrasonic pool 13 is fixed to the side wall of the chassis 12 and is used to hold water for ultrasound. Shaking holes 28 are respectively arranged at the four corners of the chassis 12. The lifting column 16 includes an outer column and an inner column, the outer column is fixed in the shaking hole 28, and the inner column passes through the outer column and is connected to the upper surface of the bottom plate 25. A positioning line 31 is marked on the middle and lower part of the inner column of the lifting column 16.

[0068] A control panel 20 is arranged on the outer wall of the chassis 12; the control panel 20 is electrically connected to the ultrasonic pool driving structure, the gyroscopic oscillator 26 and the hydraulic device 27 respectively; the control panel 20 is respectively provided with a lifting column 16 lifting adjustment button (for controlling the hydraulic device 27), a lifting column 16 speed adjustment button (for controlling the gyroscopic oscillator 26), an ultrasonic time adjustment button and an ultrasonic intensity adjustment button (for controlling the ultrasonic pool driving structure).

[0069] The upper support frame 23 is provided with a plurality of first digestive tube holes. The arrangement of the plurality of digestive tube holes enables the upper support frame 23 to simultaneously insert a plurality of digestive tubes 7. A buffer spring 24 is coaxially arranged above each of the first digestive tube holes. One end of the buffer spring 24 is fixed to the upper support frame 23, and the other end is used to support the outer edge of the digestive tube 7. The tube mouth of the digestive tube 7 is thickened and protruding. When the digestive tube is placed and during shaking, the buffer spring 24 can play a buffering role to avoid severe friction between the digestive tube and the upper and lower support frames and damage to the digestive tube 7 and the device; the lower end of the digestive tube 7 is marked with a scale line 30.

[0070] The support plate 17 is provided with a plurality of second digestive tract holes 29, and the plurality of first digestive tract holes correspond to the plurality of second digestive tract holes 29 one by one, that is, the digestive tract 7 can sequentially pass through the buffer spring 24, the first digestive tract holes provided on the upper support frame 23, and the second digestive tract holes 29 provided on the support plate 17 to achieve fixation;

[0071] The lower support frame 19 is fixed on the top of the four inner columns, and the upper support frame 23 cooperates with the lower support frame 19; a limiting device is provided on the upper support frame 23 and / or the lower support frame 19 to facilitate the accurate engagement of the upper support frame 23 and the lower support frame 19. The support plate 17 is fixed at the upper 1 / 3 of the inner column of the four lifting columns 16.

[0072] Working principle of the ultrasonic shaking device for determining total nitrogen in tobacco and tobacco products: The operation of the ultrasonic shaking device is mainly supported by two functions, one is the ultrasonic dissolution function, and the other is the oscillation and shaking function. After ultrasound, the digestive fluid is fully dissolved, and then oscillated to complete the mixing.

[0073] Operation steps: Take out the digestive tube that has been cooled to room temperature after digestion, add 30-50ml of distilled water one by one, and then place it in the ultrasonic shaking device. The upper support frame 23, the lower support frame 19 and the support plate 17 can fix the digestive tube 7. Set the program, which is divided into two stages. The first stage is the ultrasonic stage. The ultrasonic frequency is 100-150KHz, and the ultrasonic time is 5-9min. Start the ultrasonic function, and the hydraulic system realizes the lowering of the inner column of the lifting column 16 until the inner column positioning line 31 drops to the upper edge of the outer column. At this time, the scale line of the digestive tube is just submerged under the water level of the ultrasonic pool; after the ultrasonic is finished, enter the second stage, that is, the shaking stage, the shaking frequency is 200-300r / min, and the shaking time is 5-12min. Start the shaking function, the lifting column rises to be out of the ultrasonic pool, and then performs a circular motion in the shaking hole in a counterclockwise direction. After the shaking is finished, take out the digestive tube, and the entire ultrasonic shaking process is finished.

[0074] Example 2

[0075] This embodiment discloses a digestion method verification for determining total nitrogen in tobacco and tobacco products by continuous flow method using laboratory control sample B of the National Tobacco Quality Supervision and Inspection Center as raw material. The specific steps are as follows:

[0076] (1) Weighing: Weigh 0.1 g of laboratory control sample B into the digestive tube; then weigh 0.16 g of copper sulfate, 2.00 g of potassium sulfate, and 5 mL of sulfuric acid into the digestive tube.

[0077] (2) Digestion: The digestion tube is placed in a digestion furnace with set digestion temperature control parameters for digestion. The digestion temperature control parameters include two programs, the first program is 200°C for 30 minutes, and the second program is 420°C for 130 minutes. After the digestion is completed, the digestion furnace temperature is lowered to 70°C and then taken out.

[0078] (3) Shaking: Add 30 mL of distilled water into the digestive tube and shake it evenly using an ultrasonic shaking device. The ultrasonic frequency is 100 kHz, the ultrasonic time is 7 min, the shaking frequency is 250 r / min, and the shaking time is 8 min.

[0079] (4) On-machine testing: After evenly shaking, transfer the solution to a 100 mL volumetric flask without damage, shake to volume, and filter to prepare the test solution for on-machine testing.

[0080] In this embodiment, the total nitrogen content of the laboratory control sample B determined by the continuous flow method for determining the total nitrogen of tobacco and tobacco products is 2.11±0.01%, and the certified value is 2.13±0.11%.

[0081] Example 3

[0082] This example discloses a method for verifying the digestion method for determining the total nitrogen in tobacco and tobacco products by continuous flow method using reconstituted tobacco product A as the raw material. The specific steps are as follows:

[0083] (1) Sample preparation: The reconstituted tobacco product A obtained by the five-point sampling method is subjected to moisture equilibration in an oven at 40 °C for 2 h, and then it is crushed and sieved through a 40-mesh sieve. The sieved sample is the test sample.

[0084] (2) Weighing: Weigh 0.1 g of reconstituted tobacco product A into a digestion tube; then weigh 0.2 g of copper sulfate and 2.00 g of potassium sulfate quantitatively, and measure 5 mL of sulfuric acid and add them into the digestion tube in sequence.

[0085] (3) Digestion: Place the digestion tube on a digestion furnace with set digestion temperature control parameters for digestion. The digestion temperature control parameters include two programs. The first program is 200 °C for 30 min, and the second program is 420 °C for 130 min. After digestion is completed, the temperature of the digestion furnace drops to 50 °C and then it is taken out.

[0086] (4) Shaking: Add 30 mL of distilled water into the digestion tube, and use an ultrasonic shaking device to shake it evenly. The ultrasonic frequency is 150 KHz, the ultrasonic time is 5 min, the shaking frequency is 200 r / min, and the shaking time is 5 min.

[0087] (5) Instrument detection: Add 30 mL of distilled water into the digestion tube, shake it evenly, transfer it to a 100 mL volumetric flask without loss, shake it well and make up the volume, and filter it to prepare the test solution for instrument detection.

[0088] The total nitrogen content of reconstituted tobacco product A determined by the digestion method for determining the total nitrogen in tobacco and tobacco products by continuous flow method in this example is 1.60 ± 0.01%, and its true value is 1.60 ± 0.02%.

[0089] Example 4

[0090] This example discloses a method for verifying the digestion method for determining the total nitrogen in tobacco and tobacco products by continuous flow method using reconstituted tobacco product A as the raw material. The specific steps are as follows:

[0091] (1) Sample preparation: The reconstituted tobacco product A obtained by the five-point sampling method is subjected to moisture equilibration in an oven at 60 °C for 2 h, and then it is crushed and sieved through a 40-mesh sieve. The sieved sample is the test sample.

[0092] (2) Weighing: Weigh 0.1 g of reconstituted tobacco product A into a digestion tube; then weigh 0.2 g of copper sulfate and 2.00 g of potassium sulfate quantitatively, and measure 5 mL of sulfuric acid and add them into the digestion tube in sequence.

[0093] (3) Digestion: Place the digestive tract on a digestion furnace with the set digestion temperature control parameters. The digestion temperature control parameters include two programs. The first program is 200 °C for 40 minutes, and the second program is 430 °C for 130 minutes. After digestion, take it out after the temperature of the digestion furnace drops to 20 °C.

[0094] (4) Shaking: Add 30 mL of distilled water into the digestive tube, and use an ultrasonic shaking device to shake well. The ultrasonic frequency is 100 KHz, the ultrasonic time is 9 minutes, the shaking frequency is 300 r / min, and the shaking time is 5 minutes.

[0095] (5) Instrument detection: Transfer it to a 100 mL volumetric flask for uniform oscillation and dilution to volume without loss, and make it into a test solution for instrument detection after filtration.

[0096] In this example, the total nitrogen content of the reconstituted tobacco product A determined by the digestion method for determining the total nitrogen in tobacco and tobacco products using the continuous flow method is 1.59 ± 0.01%, and its true value is 1.61 ± 0.02%.

[0097] It can be seen from Examples 1-4 that the application of the digestion method of the present invention in the determination of total nitrogen in tobacco and tobacco products by the continuous flow method has the total nitrogen detection results within the range of the true values of each sample, its operation process is safe, the digestion time is greatly shortened, and the detection results can be timely feedback.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A digestion method for the determination of total nitrogen in tobacco and tobacco products by continuous flow method, characterized in that, It includes the following steps: (1) Sample preparation: The pretreated tobacco or tobacco product is subjected to moisture equilibration in an oven, and then pulverized and sieved to obtain a sample to be tested; (2) Weighing: Weigh the sample to be tested into a digestion tube and add a catalyst to promote the digestion of tobacco and tobacco products; the catalyst reagent consists of potassium sulfate, copper sulfate and sulfuric acid, and the dosage ratio of the sample to be tested, potassium sulfate, copper sulfate and sulfuric acid is 0.1 g: 1.9995 - 2.0005 g: 0.16 - 0.2 g: 5 mL; the concentration of the sulfuric acid is 95.0 - 98.0%; (3) Digestion: Place the digestion tube on a digestion furnace for digestion. After digestion is completed and the temperature drops, take it out; the digestion includes two steps. The first step is at 190 - 210 °C for 30 - 40 min, and the second step is at 420 - 430 °C for 125 - 135 min; after digestion, it is taken out when it cools to 20 - 70 °C; Use a digestion device for the determination of total nitrogen in tobacco and tobacco products by continuous flow method, and this device has the function of collecting and recycling the tail gas of total nitrogen digestion; The digestion device for the determination of total nitrogen in tobacco and tobacco products by continuous flow method includes an upper reservoir, a lower reservoir, a first instantaneous flowmeter, a second instantaneous flowmeter, a hose, a vacuum pump, a tail gas export device, a digestion furnace, a digestion tube and a valve. The bottom surface of the upper reservoir is higher than the tail gas export device, and the tail gas export device is higher than the top surface of the lower reservoir; the digestion tube is placed on the digestion furnace. The tail gas export device includes a collection chamber and a plurality of rubber stoppers arranged below the collection chamber. The rubber stoppers can be stuck on the opening of the digestion tube, and the rubber stoppers can seal the digestion tube. There are holes on the rubber stoppers, and the inside of the digestion tube is communicated with the collection chamber through the holes arranged on the rubber stoppers; The bottom outlet of the upper reservoir is connected to the inlet of the lower reservoir through a first hose, and the bottom outlet of the lower reservoir is connected to the inlet of the upper reservoir through a second hose; a first instantaneous flowmeter and a valve are arranged on the first hose, and a second instantaneous flowmeter and a vacuum pump are arranged on the second hose; the tail gas export device is connected to the middle of the first hose through a third hose, and the third hose is connected to the first hose near the lower reservoir in an obtuse angle connection mode; (4) Shaking: After digestion is completed and taken out, add distilled water, and use an ultrasonic shaking device to quickly and stably shake the digestion solution evenly; for the ultrasonic shaking device, the ultrasonic frequency is 100 - 150 KHz, the ultrasonic time is 5 - 9 min, the shaking frequency is 200 - 300 r / min, and the shaking time is 5 - 12 min; (5) Transferring and loading onto the machine: After shaking evenly, transfer the digestion solution to a volumetric flask without loss, shake well and make up the volume, and filter to prepare a sample solution to be tested for on - machine detection.

2. The digestion method for determining total nitrogen in tobacco and tobacco products by continuous flow method according to claim 1, characterized in that, In step (1), the temperature of the oven is 40 - 60 °C, and the moisture equilibration time is 1.5 - 2.5 h.

3. The digestion method for determining total nitrogen in tobacco and tobacco products by continuous flow method according to claim 1, characterized in that, The mesh number of the sieved tobacco and tobacco products in step (1) is 40 mesh.

4. The digestion method for determining total nitrogen in tobacco and tobacco products by continuous flow method according to claim 1, wherein In step (4), the dosage ratio of the sample to be tested and distilled water is: 0.1 g: 20 - 40 mL.

5. According to the digestion method for the determination of total nitrogen in tobacco and tobacco products by continuous flow method as claimed in claim 1, characterized in that, Step (4) The ultrasonic shaking device is an ultrasonic shaking device for the determination of total nitrogen in tobacco and tobacco products, comprising: a control panel, a chassis, an ultrasonic cell, a lifting column, a support plate, a lower support frame, an upper support frame, a buffer spring, a bottom plate, a rotary oscillator and a hydraulic system; A bottom plate is provided at the inner bottom of the chassis, and a rotary oscillator and a hydraulic system are fixed on the lower surface of the bottom plate; An ultrasonic cell is provided above the bottom plate inside the chassis. The ultrasonic cell is fixed to the side wall of the chassis and is used for containing ultrasonic water. Shaking holes are respectively provided at the four corners of the chassis. The lifting column comprises an outer column and an inner column sleeved thereon. The outer column is fixed in the shaking hole, and the inner column passes through the outer column and is connected to the upper surface of the bottom plate. The control panel is arranged on the outer side wall of the chassis. The control panel is electrically connected to the ultrasonic cell driving structure, the rotary oscillator and the hydraulic system respectively; A plurality of first digestion tube holes are formed in the upper support frame. The arrangement of the plurality of digestion tube holes enables the upper support frame to insert multiple digestion tubes simultaneously. A buffer spring is coaxially arranged above each first digestion tube hole. One end of the buffer spring is fixed to the upper support frame, and the other end is used for supporting the outer edge of the digestion tube. The mouth of the digestion tube is thickened and protruded. When the digestion tube is placed and during the shaking process, the buffer spring can play a buffering role to prevent the digestion tube from being damaged due to violent friction with the upper and lower support frames. A plurality of second digestion tube holes are formed in the support plate. The plurality of first digestion tube holes correspond to the plurality of second digestion tube holes one by one, that is, the digestion tube can sequentially pass through the digestion tube holes formed in the buffer spring support frame and the digestion tube holes formed in the support plate to achieve fixation; The lower support frame is fixed to the tops of the four inner columns, and the upper support frame is matched with the lower support frame. The support plate is fixed at the upper 1 / 3 of the four inner columns of the lifting column.

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