A quantitative analysis method of tobacco strong polarity vocs

Abstract

The application discloses a quantitative analysis method of strong polarity VOCs of tobacco, which comprises the following steps: S1, the inert gas is used to purge the tobacco, and the tobacco is heated and sampled, and the strong polarity VOCs of the tobacco are collected; S2, the strong polarity VOCs of the tobacco are enriched by using reduced graphene oxide (rGO), and then, the thermal desorption is carried out under the conditions that the inert gas purging flow rate is 10-70 mL / min and the temperature is 250-325 DEG C, and then, the secondary enrichment is carried out at-20 DEG C to-80 DEG C by using a cold trap, and then, the secondary resolution is carried out, and finally, the GC-MS quantitative analysis is carried out. The application uses the reduced graphene oxide (rGO) as the adsorption medium of the thermal desorption of the purging and trapping method, simultaneously adjusts and controls the inert gas purging flow rate of the thermal desorption, the temperature of the thermal desorption, and the temperature of the secondary enrichment and the secondary resolution of the cold trap, establishes the quantitative analysis method of the strong polarity VOCs of the tobacco, and improves the accuracy of the quantitative analysis of the strong polarity VOCs of the tobacco.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of tobacco volatile organic compound analysis and detection, and particularly relates to a quantitative analysis method of strong polar VOCs of tobacco. BACKGROUND

[0002] The strong polar VOCs (volatile organic compounds) of tobacco mainly include acids, aldehydes, ketones, alcohols and the like, which have important contribution to the aroma characteristics of tobacco and are important indicators for quality control of tobacco products. For example, strong polar C1-C6 volatile fatty acids in tobacco have a content of about 0.1-0.2%, which can produce fruit or butter aroma. Strong polar aromatic amino acid degradation products, benzaldehyde, benzyl alcohol and phenethyl alcohol, can increase the smoke density and fullness, and impart sweet, floral and fruity notes to tobacco smoke. The Maillard reaction products of tobacco, furfural and 5-methyl furfural, can provide nutty aroma to tobacco smoke. Therefore, quantitative analysis of the strong polar VOCs of tobacco can help people better control the quality of tobacco products and improve the production and manufacturing methods of tobacco products, which has important economic value.

[0003] At present, most of the quantitative analysis methods of tobacco volatile organic compounds are based on gas chromatography-mass spectrometry (GC-MS). In the quantitative analysis of tobacco volatile organic compounds, purge and trap (P&T) method is further used to extract tobacco volatile organic compounds from complex smoke by thermal desorption and concentrate them for GC-MS analysis. However, the currently commercially available adsorption media for thermal desorption of purge and trap method, such as polymer adsorption medium Tenax TA and graphitized carbon black Carbonxen, have poor enrichment effect on tobacco volatile organic compounds, which leads to that most of them can only be used for qualitative and semi-quantitative analysis of tobacco volatile organic compounds, and it is difficult to accurately quantify tobacco volatile organic compounds, not to mention accurately quantifying strong polar VOCs of tobacco.

[0004] Therefore, it is of great significance to develop a method which can accurately quantify strong polar VOCs of tobacco. SUMMARY

[0005] The present application aims to solve the problem of inaccurate quantitative analysis of strong polar VOCs of tobacco, and provides a quantitative analysis method of strong polar VOCs of tobacco, which uses reduced graphene oxide (rGO) as the adsorption medium for thermal desorption of purge and trap method, and realizes accurate quantitative analysis of strong polar VOCs of tobacco in combination with GC-MS.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A quantitative analysis method of tobacco strong polar VOCs, comprising the following steps:

[0008] S1. Puffing tobacco with inert gas, while heating and sampling, to collect tobacco strong polar VOCs;

[0009] S2. Enriching tobacco strong polar VOCs with reduced graphene oxide (rGO), performing thermal desorption at an inert gas purging flow rate of 10-70 mL / min and a temperature of 250-325 DEG C, then performing secondary enrichment at -20--80 DEG C and secondary resolution with a cold trap, and finally performing GC-MS quantitative analysis.

[0010] When the reduced graphene oxide (rGO) is used as the adsorption medium for thermal desorption of the purging and trapping method, the specific surface area of the rGO is increased through the layered loose structure and the porous three-dimensional structure of the rGO, and the enrichment capacity of the rGO for the tobacco strong polar VOCs is improved. Meanwhile, by adjusting the inert gas purging flow rate for thermal desorption, the temperature for thermal desorption, and the temperature for secondary enrichment and secondary resolution with the cold trap, a quantitative analysis method of the tobacco strong polar VOCs is established, which not only improves the enrichment effect of the tobacco strong polar VOCs, but also prevents the decomposition of the tobacco strong polar VOCs, and improves the accuracy of the quantitative analysis of the tobacco strong polar VOCs.

[0011] In addition, if the temperature for thermal desorption is too high, the decomposition of the tobacco strong polar VOCs is prone to occur, and the accuracy of the quantitative analysis of the tobacco strong polar VOCs is reduced. If the inert gas purging flow rate for thermal desorption is too high, the effect of the subsequent secondary enrichment with the cold trap is reduced, and the loss of the tobacco strong polar VOCs is increased. If the temperature for secondary enrichment with the cold trap is too low, the cold focusing enrichment of the tobacco strong polar VOCs on the cold trap is not conducive.

[0012] Preferably, the tobacco strong polar VOCs include one or more of 2,3,5-trimethylpyrazine, furfural, benzaldehyde, propionic acid, 5-methylfurfural, butyric acid, 2-methylbutyric acid, valeric acid, caproic acid, benzyl alcohol, phenethyl alcohol, anisaldehyde, pentanol, methylheptenone, nonanal, acetophenone, acetic acid, furfuryl alcohol, or hexanal.

[0013] Further preferably, the tobacco strong polar VOCs include one or more of benzaldehyde, benzyl alcohol, phenethyl alcohol, or anisaldehyde.

[0014] Preferably, the inert gas purging flow rate for thermal desorption in step S2 is 30 mL / min.

[0015] Preferably, the temperature for thermal desorption in step S2 is 325 DEG C.

[0016] Preferably, the temperature for secondary enrichment with the cold trap in step S2 is -40 DEG C.

[0017] Preferably, the time of the thermal desorption in step S2 is 8-24 min.

[0018] Further preferably, the time of the thermal desorption in step S2 is 16 min.

[0019] Preferably, the temperature of the secondary resolution in step S2 is 150-300℃.

[0020] Further preferably, the temperature of the secondary resolution in step S2 is 250℃.

[0021] Preferably, inert gas is used for purging when the reduced graphene oxide (rGO) enriches tobacco strong polarity VOCs in step S2, and the flow rate of the inert gas purging is 0.1-0.9 L / min.

[0022] Further preferably, the time of the inert gas purging when the reduced graphene oxide (rGO) enriches tobacco strong polarity VOCs in step S2 is 2-10 min.

[0023] Preferably, the preparation method of the reduced graphene oxide (rGO) in step S2 is: heating reaction of graphene oxide, iron powder and hydrochloric acid in water, and removing excess iron powder after reaction to obtain the reduced graphene oxide.

[0024] Further preferably, the preparation method of the reduced graphene oxide (rGO) in step S2 is: mixing graphene oxide (GO) with water, adding iron powder, stirring and slowly adding hydrochloric acid, stirring, heating and standing, adding concentrated hydrochloric acid to remove excess iron powder, suction filtration, and cleaning with water and anhydrous ethanol alternately, and drying to obtain the reduced graphene oxide (rGO).

[0025] Further preferably, the mass ratio of the graphene oxide (GO) to the iron powder is 1:(10-60).

[0026] Further preferably, the hydrochloric acid is HCl with a mass fraction of 36%.

[0027] Further preferably, the amount of the hydrochloric acid used is 10-30 mL.

[0028] Further preferably, the heating temperature is 30-50℃.

[0029] Preferably, the specific operation of step S2 is:

[0030] (1) The reduced graphene oxide (rGO) is loaded into a thermal desorption tube, and dead glass wool is filled into both ends of the thermal desorption tube, and then aged to obtain an rGO thermal desorption tube for standby use;

[0031] (2) sequentially connecting the gas sampling bag containing tobacco strong polar VOCs, the rGO thermal desorption tube and the sampling pump, enriching the tobacco strong polar VOCs by inert gas purging, then inserting into the thermal desorption warehouse, performing thermal desorption at an inert gas purging flow rate of 10-70 mL / min and 250-325℃, then performing secondary enrichment at-20--80℃ in the cold trap, then performing secondary analysis, and finally performing GC-MS quantitative analysis.

[0032] Preferably, the inert gas is nitrogen.

[0033] Preferably, the device structure used in the sampling of step S1 is as follows, including an inert gas source 1, a first gas guide pipe 2, a sample bottle 3, a vacuum valve 11, a second gas guide pipe 4, a diaphragm pump 5 and a gas sampling bag 6 which are sequentially connected, and a water bath heating tank 7 and a magnetic stirrer 10; the sample bottle 3 is located in the water bath heating tank 7; the magnetic stirrer 10 includes a stirring rod 1001 and a base 1002 of the magnetic stirrer, the water bath heating tank 7 is located on the base 1002 of the magnetic stirrer, and the stirring rod 1001 is located in the inner cavity of the sample bottle 3.

[0034] The inventors found in many experiments that, compared with the existing purging and trapping method sampling device, the quantitative analysis method of the present application can better improve the accuracy of quantitative analysis of tobacco strong polar VOCs when used in cooperation with the device (tobacco strong polar VOCs purging and trapping method sampling device) used in the sampling of step S1.

[0035] Preferably, the temperature of the heating in step S1 is 10-50℃.

[0036] Preferably, the specific operation of step S1 is as follows:

[0037] (1) crushing and freeze-drying the tobacco, placing it in a sample bottle, and sealing it for use;

[0038] (2) purging the tobacco in the sample bottle with inert gas, stirring and heating at the same time, collecting the gas stream containing tobacco strong polar VOCs in the gas sampling bag into which strong polar VOCs internal standard has been injected in advance, standing, and shaking evenly.

[0039] Further preferably, the strong polar VOCs internal standard is cinnamaldehyde.

[0040] Further preferably, the ratio of the volume of the sample bottle to the maximum value of the mass of the tobacco is (30 mL:1 g)-(50 mL:1 g).

[0041] More preferably, the ratio of the volume of the sample bottle to the maximum value of the mass of the tobacco is 50 mL:1 g.

[0042] Compared with the prior art, the present application has the beneficial effects that:

[0043] When the reduced graphene oxide (rGO) is used as the adsorption medium for the thermal desorption of the purge and trap method, the specific surface area of the rGO is increased through the layered loose structure and the porous three-dimensional structure of the rGO, and the enrichment capacity of the rGO for the strong polar VOCs of tobacco is improved; meanwhile, the quantitative analysis method for the strong polar VOCs of tobacco is established by regulating the inert gas purging flow rate of the thermal desorption, the temperature of the thermal desorption, and the temperature of the secondary enrichment and secondary analysis by using the cold trap, so that the enrichment effect of the strong polar VOCs of tobacco is improved, the decomposition of the strong polar VOCs of tobacco is prevented, and the accuracy of the quantitative analysis of the strong polar VOCs of tobacco is improved. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 SEM image of the reduced graphene oxide.

[0045] Figure 2 Structure schematic diagram of the tobacco strong polar VOCs enrichment device, in which: 6-Tedlar gas sampling bag, 8-rGO thermal desorption tube, 9-sampling pump.

[0046] Figure 3 Structure schematic diagram of the tobacco strong polar VOCs purge and trap method sampling device, in which: 1-inert gas source, 2-first gas guide pipe, 3-sample bottle, 4-second gas guide pipe, 5-septum pump, 6-Tedlar gas sampling bag, 7-water bath heating tank, 10-magnetic stirrer, 1001-stirring rod, 1002-base of the magnetic stirrer, 11-vacuum valve.

[0047] Figure 4 Enrichment capacity diagram of the rGO and Tenax TA for butyric acid with different concentrations.

[0048] Figure 5 Tobacco strong polar VOCs peak area statistical diagram of Examples 1 to 4 and Comparative Example 1.

[0049] Figure 6 Tobacco strong polar VOCs peak area statistical diagram of Examples 5 to 8 and Comparative Example 2.

[0050] Figure 7 Tobacco strong polar VOCs peak area statistical diagram of Examples 9 to 12 and Comparative Example 3.

[0051] Figure 8 Tobacco strong polar VOCs peak area statistical diagram of Examples 13 to 16.

[0052] Figure 9 Tobacco strong polar VOCs peak area statistical diagram of Examples 17 to 21.

[0053] Figure 10 Statistical chart of strong polar VOCs peak area of tobacco for Examples 22-26.

[0054] Figure 11 Statistical chart of strong polar VOCs peak area of tobacco for Examples 27-31.

[0055] Figure 12 Statistical chart of strong polar VOCs chromatogram of tobacco for Examples 32-35, wherein 1 is 2,3,5-trimethylpyrazine, 2 is furfural, 3 is benzaldehyde, 4 is propionic acid, 5 is 5-methylfurfural, 6 is butyric acid, 7 is 2-methylbutyric acid, 8 is valeric acid, 9 is hexanoic acid, 10 is benzyl alcohol, 11 is phenethyl alcohol, 12 is anisaldehyde, and IS is cinnamaldehyde. DETAILED DESCRIPTION

[0056] The application will be further described in conjunction with the following examples. These examples are only used to illustrate the application and not used to limit the scope of the application. The experimental methods in the following examples without specific conditions are usually according to the conventional conditions in the art or according to the conditions suggested by the manufacturers; the raw materials, reagents and the like used, if not specifically stated, are all the raw materials and reagents that can be obtained by commercial means from the conventional market. Any non-essential changes and substitutions made by the person skilled in the art on the basis of the present application shall fall within the scope of the present application.

[0057] 1. Preparation method of reduced graphene oxide (rGO) of the application

[0058] 0.05 g of graphene oxide (GO) was mixed with 100 mL of deionized water under ultrasonic for 1 h, iron powder was added, stirring and slowly adding 36% mass fraction of HCl, stirring at 200 rpm for 30 min, heating and standing for 390 min, adding concentrated hydrochloric acid to remove excess iron powder, suction filtration, and washing with water and anhydrous ethanol alternately for 3 times, vacuum drying at 60 ℃ for 12 h, to obtain reduced graphene oxide (rGO);

[0059] Meanwhile, orthogonal optimization experiments were carried out on the mass ratio of GO to iron powder, the amount of 36% mass fraction of HCl used and the heating temperature, and the synthesized rGO was subjected to thermogravimetric analysis (TGA) to test the weight loss rate of rGO at 325 ℃, as shown in Table 1:

[0060] Table 1 Orthogonal optimization experiment of rGO preparation method

[0061]

[0062] From Table 1, it can be seen that the rGO prepared according to the scheme 7 (mass ratio of GO to iron powder 1:60, the amount of 36% HCl used 10 mL, and the heating temperature 50℃) has the smallest weight loss rate at 325℃ and the best thermal stability, and is most suitable as the adsorption medium for the thermal desorption of purge and trap method in the working environment of 250-325℃.

[0063] Therefore, the rGO prepared according to the scheme 7 is used in the examples and comparative examples of the present application, and the rGO prepared according to the scheme 7 is subjected to SEM analysis, as shown in Figure 1 .

[0064] Figure 1 The SEM image of the reduced graphene oxide is shown. The rGO prepared according to the scheme 7 has a layered loose structure, and the overall surface morphology is uniform; the thin two-dimensional rGO sheet layer is curved and folded to form a thermodynamically stable porous three-dimensional particle, which is conducive to increasing the specific surface area of the rGO and improving the enrichment capacity of the rGO for the strong polar VOCs of tobacco.

[0065] 2. Reagents used in the present application and related experimental parameters

[0066] In the detailed description of the present application:

[0067] Each example and comparative example is repeated at least 3 times;

[0068] The internal standard of the strong polar VOCs is cinnamaldehyde;

[0069] The tobacco is provided by Guangdong Tobacco Industry Co., Ltd.;

[0070] The inert gas is high-purity nitrogen;

[0071] The Tedlar gas sampling bag has a capacity of 20L;

[0072] The conditions for GC-MS quantitative analysis are as follows:

[0073] Chromatographic column: DB-WAXetr (30m x 0.25mm x 0.25μm, AGILENT Technologies, Palo Alto, CA, USA); carrier gas: high-purity helium (purity > 99.999%); temperature rising program: 65℃ for 0.5min, 10℃ / min to 100℃, 2℃ / min to 110℃, 5℃ / min to 130℃, 10℃ / min to 176℃, 1℃ / min to 177℃; transfer line temperature: 250℃; ionization energy 70eV; ion source temperature: 250℃; solvent delay time 3min, analyzed in SIM mode.

[0074] Example 1

[0075] This embodiment provides a quantitative analysis method for highly polar VOCs in tobacco, including the following steps:

[0076] S1. A standard solution of highly polar tobacco VOCs was prepared using dichloromethane as a solvent. 40 μL of this standard solution was injected using a microsyringe into a container that had previously injected 40 μL of 1.0 × 10⁻⁶ mol / L 10⁻⁶ mol / L. 4 The Tedlar gas sampling bag containing ng / L of highly polar VOCs internal standard was filled with N2 and allowed to evaporate at room temperature for 15 minutes. The Tedlar gas sampling bag was then shaken to ensure uniform gas distribution, thus obtaining a Tedlar gas sampling bag containing tobacco highly polar VOCs standard gas.

[0077] S2. Specifically as follows:

[0078] (1) 0.04g of reduced graphene oxide (rGO) was loaded into a thermal desorption tube, and deactivated glass wool was filled at both ends of the thermal desorption tube. The tube was heated and aged at 250°C for 5 hours in a thermal desorption device. During the entire aging process, 100mL / min of inert gas was passed through to obtain the rGO thermal desorption tube for later use.

[0079] (2) Figure 2 This is a schematic diagram of a tobacco strong polar VOCs enrichment device, which includes a Tedlar gas sampling bag 6, an rGO thermal desorption tube 8 and a sampling pump 9 connected in sequence.

[0080] like Figure 2 As shown, a Tedlar gas sampling bag containing standard gas of highly polar tobacco VOCs, an rGO thermal desorption tube, and a sampling pump were connected in sequence. The highly polar tobacco VOCs were enriched by purging with inert gas at a flow rate of 0.5 L / min for 8 min. Then, the thermal desorption chamber was inserted, and thermal desorption was performed for 16 min at an inert gas purging flow rate of 30 mL / min and 325 °C. Then, a second enrichment was performed using a cold trap at -40 °C, followed by a second desorption at 250 °C. Finally, GC-MS quantitative analysis was performed.

[0081] The standard solution of highly polar tobacco VOCs includes: pentanol, methyl heptenone, nonanal, furfural, benzaldehyde, propionic acid, 5-methylfurfural, acetophenone, 2-methylbutyric acid, valeric acid, benzyl alcohol, phenethyl alcohol, and anisaldehyde, all with a concentration of 5.0 mg / mL.

[0082] The standard gas for highly polar VOCs in tobacco includes: all with a concentration of 1.0 × 10⁻⁶. 4 ng / L of pentanol, methylheptenone, nonanal, furfural, benzaldehyde, 5-methylfurfural propionate, acetophenone, 2-methylbutyric acid, valeric acid, benzyl alcohol, phenethyl alcohol, and anisaldehyde.

[0083] Examples 2-4 and Comparative Example 1

[0084] Examples 2-4 and Comparative Example 1 provide different quantitative analysis methods of strong polar VOCs in tobacco, which are different from Example 1 only in that the inert gas purge flow rate of the thermal desorption in step S2 is different, and the rest are consistent with Example 1, as shown in Table 2:

[0085] Table 2 Inert gas purge flow rate of thermal desorption in step S2 of Examples 1-4 and Comparative Example 1

[0086] Temperature of thermal desorption (°C) Example 1 30 Example 2 10 Example 3 50 Example 4 70 Comparative Example 1 90

[0087] Examples 5-8 and Comparative Example 2

[0088] Examples 5-8 and Comparative Example 2 provide different quantitative analysis methods of strong polar VOCs in tobacco, which are different from Example 1 only in that the temperature of the thermal desorption, the strong polar VOCs standard solution in tobacco, and the strong polar VOCs standard gas in tobacco in step S2 are different, and the rest are consistent with Example 1, as shown in Table 3:

[0089] Table 3 Temperature of thermal desorption in step S2 of Examples 5-8 and Comparative Example 2

[0090] Temperature of thermal desorption (°C) Example 5 250 Example 6 275 Example 7 300 Example 8 325 Comparative Example 2 350

[0091] In addition, the strong polar VOCs standard solution in tobacco of Examples 5-8 and Comparative Example 2 includes methyl heptenone, nonanal, furfural, benzaldehyde, propionic acid, 5-methyl furfural, butyric acid, acetophenone, 2-methyl butyric acid, valeric acid, hexanoic acid, benzyl alcohol, phenethyl alcohol, and anisaldehyde, all with a concentration of 5.0 mg / mL;

[0092] In the strong polar VOCs standard gas in tobacco of Examples 5-8 and Comparative Example 2, methyl heptenone, nonanal, furfural, benzaldehyde, propionic acid, 5-methyl furfural, butyric acid, acetophenone, 2-methyl butyric acid, valeric acid, hexanoic acid, benzyl alcohol, phenethyl alcohol, and anisaldehyde are included, all with a concentration of 1.0 x 10 4 ng / L.

[0093] Examples 9-12 and Comparative Example 3

[0094] Examples 9-12 and Comparative Example 3 provide different quantitative analysis methods of strong polar VOCs in tobacco, which are different from Example 1 only in that the temperature of the secondary enrichment with a cold trap in step S2, the strong polar VOCs standard solution in tobacco, and the strong polar VOCs standard gas in tobacco are different, and the rest are consistent with Example 1, as shown in Table 4:

[0095] Table 4 Temperature of secondary enrichment with a cold trap in step S2 of Examples 9-12 and Comparative Example 3

[0096] Temperature of secondary enrichment with cold trap (°C) Example 9 -20 Example 10 -40 Example 11 -60 Example 12 -80 Comparative Example 3 -100

[0097] In addition, the tobacco strong polar VOCs standard solution of Examples 9 to 12 and Comparative Example 3 includes pentanol, methyl heptenone, nonanal, furfural, benzaldehyde, propionic acid, 5-methyl furfural, 2-methyl butyric acid, valeric acid, benzyl alcohol, phenethyl alcohol, and anisaldehyde each at a concentration of 5.0 mg / mL;

[0098] In the tobacco strong polar VOCs standard gas of Examples 9 to 12 and Comparative Example 3, pentanol, methyl heptenone, nonanal, furfural, benzaldehyde, propionic acid, 5-methyl furfural, 2-methyl butyric acid, valeric acid, benzyl alcohol, phenethyl alcohol, and anisaldehyde are included each at a concentration of 1.0 x 10 4 ng / L.

[0099] Examples 13 to 16

[0100] Examples 13 to 16 provide different quantitative analysis methods of tobacco strong polar VOCs, and differ from Example 1 only in that the temperature of the secondary analysis in step S2, the tobacco strong polar VOCs standard solution, and the tobacco strong polar VOCs standard gas are different, and the rest are consistent with Example 1, as shown in Table 5:

[0101] Table 5 Temperature of secondary analysis in step S2 of Examples 13 to 16

[0102] Temperature of secondary desorption (°C) Example 13 150 Example 14 200 Example 15 250 Example 16 300

[0103] In addition, the tobacco strong polar VOCs standard solution of Examples 13 to 16 includes pentanol, methyl heptenone, nonanal, acetic acid, furfural, benzaldehyde, propionic acid, 5-methyl furfural, acetophenone, furfuryl alcohol, benzyl alcohol, phenethyl alcohol, and anisaldehyde each at a concentration of 5.0 mg / mL;

[0104] In the tobacco strong polar VOCs standard gas of Examples 13 to 16, pentanol, methyl heptenone, nonanal, acetic acid, furfural, benzaldehyde, propionic acid, 5-methyl furfural, acetophenone, furfuryl alcohol, benzyl alcohol, phenethyl alcohol, and anisaldehyde are included each at a concentration of 1.0 x 10 4 ng / L.

[0105] Examples 17 to 21

[0106] Examples 17 to 21 provide different quantitative analysis methods of tobacco strong polar VOCs, and differ from Example 1 only in that the time of thermal desorption in step S2, the tobacco strong polar VOCs standard solution, and the tobacco strong polar VOCs standard gas are different, and the rest are consistent with Example 1, as shown in Table 6:

[0107] Table 6 Time of thermal desorption in step S2 of Examples 17 to 21

[0108] Time of thermal desorption (min) Example 17 8 Example 18 12 Example 19 16 Example 20 20 Example 21 24

[0109] In addition, the tobacco strong polar VOCs standard solution of embodiments 17-21 comprises: nonanal, benzaldehyde, propionic acid, 2-methylbutyric acid, valeric acid, hexanoic acid, benzyl alcohol, phenethyl alcohol, and anisaldehyde, each at a concentration of 5.0 mg / mL;

[0110] In the tobacco strong polar VOCs standard gas of embodiments 17-21, there are included: nonanal, benzaldehyde, propionic acid, 2-methylbutyric acid, valeric acid, hexanoic acid, benzyl alcohol, phenethyl alcohol, and anisaldehyde, each at a concentration of 1.0 x 10 4 ng / L.

[0111] Embodiments 22-26

[0112] Embodiments 22-26 provide different quantitative analysis methods for tobacco strong polar VOCs, which differ from embodiment 1 only in that the flow rate of inert gas blowing during enrichment of tobacco strong polar VOCs in step S2, the tobacco strong polar VOCs standard solution, and the tobacco strong polar VOCs standard gas are different, and the rest are consistent with embodiment 1, as shown in Table 7:

[0113] Table 7 Flow rate of inert gas blowing during enrichment of tobacco strong polar VOCs in step S2 of embodiments 22-26

[0114] Flow rate of inert gas purge (L / min) Example 22 0.1 Example 23 0.3 Example 24 0.5 Example 25 0.7 Example 26 0.9

[0115] In addition, the tobacco strong polar VOCs standard solution of embodiments 22-26 comprises: hexanal, amyl alcohol, methyl heptenone, nonanal, furfural, benzaldehyde, propionic acid, 5-methyl furfural, butyric acid, acetophenone, 2-methyl butyric acid, valeric acid, hexanoic acid, benzyl alcohol, phenethyl alcohol, and anisaldehyde, each at a concentration of 5.0 mg / mL;

[0116] In the tobacco strong polar VOCs standard gas of embodiments 22-26, there are included: hexanal, amyl alcohol, methyl heptenone, nonanal, furfural, benzaldehyde, propionic acid, 5-methyl furfural, butyric acid, acetophenone, 2-methyl butyric acid, valeric acid, hexanoic acid, benzyl alcohol, phenethyl alcohol, and anisaldehyde, each at a concentration of 1.0 x 10 4 ng / L.

[0117] Embodiments 27-31

[0118] Embodiments 27-31 provide different quantitative analysis methods for tobacco strong polar VOCs, which differ from embodiment 1 only in that the time of inert gas blowing during enrichment of tobacco strong polar VOCs in step S2, the tobacco strong polar VOCs standard solution, and the tobacco strong polar VOCs standard gas are different, and the rest are consistent with embodiment 1, as shown in Table 8:

[0119] Table 8 shows the inert gas purging time during step S2 of Examples 27-31 for enriching tobacco-based highly polar VOCs.

[0120]

[0121]

[0122] In addition, the tobacco strong polar VOCs standard solutions in Examples 27-31 include: methyl heptenone, nonanal, furfural, benzaldehyde, 5-methylfurfural, butyric acid, acetophenone, 2-methylbutyric acid, valeric acid, hexanoic acid, benzyl alcohol, phenethyl alcohol and anisaldehyde, all with a concentration of 5.0 mg / mL.

[0123] The tobacco-based highly polar VOCs standard gases in Examples 27–31 all contained a concentration of 1.0 × 10⁻⁶. 4 ng / L of methylheptenone, nonanal, furfural, benzaldehyde, 5-methylfurfural, butyric acid, acetophenone, 2-methylbutyric acid, valeric acid, hexanoic acid, benzyl alcohol, phenethyl alcohol, and anisaldehyde.

[0124] Example 32

[0125] This embodiment provides a quantitative analysis method for highly polar VOCs in tobacco, including the following steps:

[0126] S1. Specifically as follows:

[0127] (1) Pulverize the tobacco (i.e. tobacco shreds) through a 20-mesh sieve, freeze dry for 12 hours, thaw to room temperature, take 5g and put it into a 250mL sample bottle, and plug a small amount of deactivated glass wool at the outlet end of the sample bottle airflow, and quickly seal the device for later use.

[0128] (2) Figure 3 This is a schematic diagram of a tobacco strong polar VOCs purge and trap sampling device, which includes an inert gas source 1, a first gas delivery tube 2, a sample bottle 3, a vacuum valve 11, a second gas delivery tube 4, a diaphragm pump 5, and a gas sampling bag 6 connected in sequence. It also includes a water bath heating tank 7 and a magnetic stirrer 10. The sample bottle 3 is located inside the water bath heating tank 7. The magnetic stirrer 10 includes a stir bar 1001 and a magnetic stirrer base 1002. The water bath heating tank 7 is located on the magnetic stirrer base 1002, and the stir bar 1001 is located inside the sample bottle 3.

[0129] based on Figure 3 The assembled tobacco strong polar VOCs purge and trap sampling device is shown. Using a diaphragm pump, tobacco in the sample vial is purged with inert gas at a flow rate of 5 L / min for 6 min, while simultaneously magnetically stirred and heated to 30°C. The gas stream containing tobacco strong polar VOCs is collected in a container pre-injected with 40 μL of 1.0 × 10⁻⁶ molten silica gel.3 Place the ng / L strongly polar VOCs internal standard in a Tedlar gas sampling bag, let stand for 15 minutes, and then shake the Tedlar gas sampling bag to make the gas distribution inside the bag uniform.

[0130] S2. Specifically as follows:

[0131] (1) 0.04g of reduced graphene oxide (rGO) was loaded into a thermal desorption tube, and deactivated glass wool was filled at both ends of the thermal desorption tube. The tube was heated and aged at 250°C for 5 hours in a thermal desorption device. During the entire aging process, 100mL / min of inert gas was passed through to obtain the rGO thermal desorption tube for later use.

[0132] (2) Figure 2 As shown, a Tedlar gas sampling bag, an rGO thermal desorption tube, and a sampling pump were connected in sequence. The tobacco's highly polar VOCs were enriched by purging with inert gas at a flow rate of 0.5 L / min for 8 min. Then, the thermal desorption chamber was inserted, and thermal desorption was performed for 16 min at an inert gas purging flow rate of 30 mL / min and 325 °C. A second enrichment was then performed using a cold trap at -40 °C, followed by a second desorption at 250 °C. Finally, GC-MS quantitative analysis was performed.

[0133] Examples 33-35

[0134] Examples 33-35 provide different quantitative analysis methods for highly polar tobacco VOCs. The only difference between these methods and Example 32 is the heating temperature in step S1; all other methods are the same as in Example 32, as shown in Table 9.

[0135] Table 9 shows the heating temperatures in step S1 of Examples 32-35.

[0136] Temperature of heating (°C) Example 32 30 Example 33 10 Example 34 20 Example 35 50

[0137] Example 36

[0138] This embodiment provides a quantitative analysis method for highly polar tobacco VOCs. Two batches of a series of highly polar tobacco VOCs standard gases with concentrations ranging from 0.1 to 300.0 ng / L were used to measure the linear range and detection limit of different highly polar tobacco VOCs (2,3,5-trimethylpyrazine, furfural, benzaldehyde, propionic acid, 5-methylfurfural, butyric acid, 2-methylbutyric acid, valeric acid, hexanoic acid, benzyl alcohol, phenethyl alcohol, and anisaldehyde) in the quantitative analysis method of this invention. Each batch of a series of highly polar tobacco VOCs standard gases was repeated three times (n=3), including the following steps:

[0139] S1. A series of different concentrations of tobacco strong polar VOCs standard solution was prepared with dichloromethane as a solvent, 40 μL of tobacco strong polar VOCs standard solution was taken by a microsyringe and injected into a Tedlar gas sampling bag pre-injected with 40 μL of 1.0×10 4 ng / L strong polar VOCs internal standard, and N2 was filled, and the volatile was balanced at room temperature for 15 min, and the Tedlar gas sampling bag was shaken to make the gas in the bag evenly distributed, thereby obtaining a series of Tedlar gas sampling bags containing tobacco strong polar VOCs standard gas with concentrations in the range of 0.1-300.0 ng / L;

[0140] S2. Specifically as follows:

[0141] (1) 0.04 g of reduced graphene oxide (rGO) was loaded into a thermal desorption tube, and deactivated glass wool was filled at both ends of the thermal desorption tube, and the thermal desorption tube was heated and aged at 250℃ for 5 h in the thermal desorption device, and 100 mL / min of inert gas was passed through during the whole aging process, thereby obtaining the rGO thermal desorption tube, which was ready for use;

[0142] (2) As shown in Figure 2 , the Tedlar gas sampling bag containing tobacco strong polar VOCs standard gas, the rGO thermal desorption tube and the sampling pump were connected in sequence, and the tobacco strong polar VOCs was enriched by blowing 0.5 L / min of inert gas for 8 min, then inserted into the thermal desorption chamber, and the thermal desorption was carried out at an inert gas blowing flow rate of 30 mL / min and 325℃ for 16 min, and then the cold trap was used to carry out secondary enrichment at-40℃ and secondary analysis at 250℃, and finally GC-MS quantitative analysis was carried out;

[0143] Among any one of the tobacco strong polar VOCs standard gas, the concentrations of 2,3,5-trimethylpyrazine, furfural, benzaldehyde, propionic acid, 5-methylfurfural, butyric acid, 2-methylbutyric acid, valeric acid, hexanoic acid, benzyl alcohol, phenethyl alcohol and anisaldehyde were the same and in the range of 0.1-300.0 ng / L.

[0144] Performance test

[0145] 1. The enrichment capacity of reduced graphene oxide (rGO) of the application to tobacco strong polar VOCs

[0146] The enrichment capacity of rGO prepared according to the scheme 7 described in Table 1 and the commercial polymer adsorption medium Tenax TA to tobacco strong polar VOCs was studied, and butyric acid was taken as a representative of tobacco strong polar VOCs, and specifically as follows:

[0147] (1) 40 μL of 5×10 3 -2.25×106 μg / L of butyric acid, and the Tedlar gas sampling bag was used to collect a series of butyric acid gas with concentrations ranging from 10.0 to 4.5 x 10 3 ng / L at room temperature for 15 min;

[0148] (2) 0.001 g of reduced graphene oxide (rGO) or commercial polymer adsorption medium Tenax TA was loaded into a thermal desorption tube, and deactivated glass wool was filled at both ends of the thermal desorption tube, and the thermal desorption tube was heated and aged at 250°C for 5 h in the thermal desorption device, and 100 mL / min of inert gas was passed through the thermal desorption tube during the entire aging process, thereby obtaining an rGO thermal desorption tube or a Tenax TA thermal desorption tube;

[0149] (3) The Tedlar gas sampling bag loaded with butyric acid gas with different concentrations, the rGO thermal desorption tube or the Tenax TA thermal desorption tube, and the sampling pump were connected in sequence, 0.5 L / min of inert gas was used for sampling for 8 min to enrich butyric acid, then the thermal desorption tube was inserted into the thermal desorption chamber, and thermal desorption was performed at 325°C for 16 min under the inert gas blowing flow rate of 30 mL / min, and then the cold trap was used for secondary enrichment at -40°C and secondary analysis at 250°C, and finally, GC-MS quantitative analysis was performed.

[0150] Figure 4 The figure is the enrichment capacity of rGO and Tenax TA for butyric acid with different concentrations. As can be seen from the figure, Figure 4 under the condition of the same concentration of butyric acid, compared with the commercial polymer adsorption medium Tenax TA, the rGO prepared in the present application has a higher enrichment capacity for tobacco strong polar VOCs butyric acid, which indicates that when the rGO is used as the adsorption medium of the thermal desorption of the present application, the rGO can absorb more tobacco strong polar VOCs, thereby improving the accuracy of the quantitative analysis method of tobacco strong polar VOCs in the present application.

[0151] 2, Experimental results of the quantitative analysis method of tobacco strong polar VOCs in each example and comparative example

[0152] Figure 5 The figure is the peak area of tobacco strong polar VOCs in Examples 1-4 and Comparative Example 1. As can be seen from the figure, Figure 5It can be seen that when the inert gas purging flow rate of the thermal desorption in step S2 is in the range of 10-70 mL / min, the peak area of each tobacco strong polar VOCs in the tobacco strong polar VOCs quantitative analysis method is large, which is conducive to improving the accuracy of the tobacco strong polar VOCs quantitative analysis method of the present application; while when the inert gas purging flow rate of the thermal desorption in step S2 is too high (90 mL / min), the effect of the subsequent cold trap secondary enrichment will be reduced, resulting in an increased loss of tobacco strong polar VOCs, which is not conducive to improving the accuracy of the tobacco strong polar VOCs quantitative analysis method of the present application.

[0153] Figure 6 The tobacco strong polar VOCs peak area statistical diagram of Examples 5-8 and Comparative Example 2 is shown in Figure 1. Figure 6 It can be seen that when the temperature of the thermal desorption in step S2 is in the range of 250-325℃, the peak area of each tobacco strong polar VOCs in the tobacco strong polar VOCs quantitative analysis method is large, which is conducive to improving the accuracy of the tobacco strong polar VOCs quantitative analysis method of the present application; while when the temperature of the thermal desorption in step S2 is too high (350℃), the tobacco strong polar VOCs is prone to decomposition, which is not conducive to improving the accuracy of the tobacco strong polar VOCs quantitative analysis method of the present application.

[0154] Figure 7 The tobacco strong polar VOCs peak area statistical diagram of Examples 9-12 and Comparative Example 3 is shown in Figure 2. Figure 7 It can be seen that when the temperature of the secondary enrichment with the cold trap in step S2 is in the range of -20--80℃, the peak area of each tobacco strong polar VOCs in the tobacco strong polar VOCs quantitative analysis method is large, which is conducive to improving the accuracy of the tobacco strong polar VOCs quantitative analysis method of the present application; while when the temperature of the secondary enrichment with the cold trap in step S2 is too low (-100℃), the tobacco strong polar VOCs will be hindered from being cold-focused and enriched on the cold trap, which is not conducive to improving the accuracy of the tobacco strong polar VOCs quantitative analysis method of the present application.

[0155] Figure 8 The tobacco strong polar VOCs peak area statistical diagram of Examples 13-16 is shown in Figure 3. Figure 8 It can be seen that when the temperature of the secondary analysis in step S2 is in the range of 150-300℃, the peak area of each tobacco strong polar VOCs in the tobacco strong polar VOCs quantitative analysis method is large, which is conducive to improving the accuracy of the tobacco strong polar VOCs quantitative analysis method of the present application, and the accuracy is the highest when the temperature of the secondary analysis is 250℃.

[0156] Figure 9 The tobacco strong polar VOCs peak area statistical diagram of Examples 17-21 is shown in Figure 4. Figure 9It can be seen that when the time of thermal desorption in step S2 is in the range of 8-24 min, the peak area of various tobacco strong polar VOCs in the quantitative analysis method of tobacco strong polar VOCs is larger, which is beneficial to improve the accuracy of the quantitative analysis method of tobacco strong polar VOCs, and the accuracy is the highest when the time of thermal desorption is 16 min.

[0157] Figure 10 The figure is the peak area of tobacco strong polar VOCs in examples 22-26. From Figure 10 It can be seen that when the flow rate of inert gas blowing in the enrichment of tobacco strong polar VOCs in step S2 is in the range of 0.1-0.9 L / min, the peak area of various tobacco strong polar VOCs in the quantitative analysis method of tobacco strong polar VOCs is larger, which is beneficial to improve the accuracy of the quantitative analysis method of tobacco strong polar VOCs.

[0158] Figure 11 The figure is the peak area of tobacco strong polar VOCs in examples 27-31. From Figure 11 It can be seen that when the time of inert gas blowing in the enrichment of tobacco strong polar VOCs in step S2 is in the range of 2-10 min, the peak area of various tobacco strong polar VOCs in the quantitative analysis method of tobacco strong polar VOCs is larger, which is beneficial to improve the accuracy of the quantitative analysis method of tobacco strong polar VOCs, and the accuracy is the highest when the time of inert gas blowing is 8 min.

[0159] Figure 12 The figure is the chromatogram of tobacco strong polar VOCs in examples 32-35. From Figure 12 It can be seen that when the temperature of heating in step S1 is in the range of 30-50℃, the peak area of various tobacco strong polar VOCs in the quantitative analysis method of tobacco strong polar VOCs is larger, which is beneficial to improve the accuracy of the quantitative analysis method of tobacco strong polar VOCs, and the accuracy is the highest when the temperature of heating is 30℃.

[0160] 3. Sensitivity and accuracy of the quantitative analysis method of tobacco strong polar VOCs

[0161] (1) Sensitivity of the quantitative analysis method of tobacco strong polar VOCs

[0162] Example 36 was carried out on two batches of a series of tobacco strong polar VOCs standard gas with a concentration in the range of 0.1-300.0 ng / L, in order to measure the linear range and detection limit of different tobacco strong polar VOCs in the quantitative analysis method, and the experiment was repeated 3 times (n=3), and the experimental results are shown in the following table:

[0163] Table 10 Experimental results of the quantitative analysis method in example 36 on different tobacco strong polar VOCs

[0164]

[0165] From Table 10, it can be seen that the quantitative analysis method of the tobacco strong polar VOCs of the present application has a linear range of 0.1-300.0 ng / L for different tobacco strong polar VOCs, a detection limit of 0.03-0.37 ng / L, and when repeated for 3 times, the RSD is 0.3-20.1%, indicating that the quantitative analysis method of the present application meets the quantitative analysis of the tobacco strong polar VOCs and has high sensitivity.

[0166] (2) Accuracy of the quantitative analysis method of the tobacco strong polar VOCs

[0167] The tobacco sample of Example 32 was subjected to quantitative analysis of different tobacco strong polar VOCs, and a standard addition experiment was performed by referring to the quantitative analysis method of Example 32; in the standard addition experiment, the corresponding standard addition solution should be injected into the Tedlar gas sampling bag together with the strong polar VOCs internal standard; the experiment was repeated for 3 times (n=3), and the experimental results are shown in the following table:

[0168] Table 11 Determination of the content of the tobacco strong polar VOCs of Example 32 and the results of the standard addition experiment

[0169]

[0170]

[0171] From Table 11, it can be seen that the content of 12 kinds of tobacco strong polar VOCs in the tobacco sample measured by the quantitative analysis method of the tobacco strong polar VOCs of the present application is 24.0-504.0 ng / g; the recovery rate of the standard addition experiment is 72.9-128.3%, and when repeated for 3 times, the RSD is 1.8-19.9%; it is indicated that the quantitative analysis method of the tobacco strong polar VOCs of the present application has high accuracy.

[0172] Obviously, the above examples of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, it is not necessary and impossible to exhaust all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A quantitative analysis method for highly polar VOCs in tobacco, characterized in that, Includes the following steps: S1. Purge tobacco with inert gas while heating and sampling to collect highly polar VOCs from the tobacco; S2. Strongly polar VOCs from tobacco were enriched with reduced graphene oxide, and thermal desorption was performed at 325℃ and an inert gas purging flow rate of 30-50 mL / min. Then, secondary enrichment was performed in a cold trap at -40 to -60℃, followed by secondary desorption, and finally quantitative analysis by GC-MS. In step S2, when reducing graphene oxide to enrich highly polar VOCs in tobacco, an inert gas is used for purging, and the flow rate of the inert gas purging is 0.5~0.9 L / min. The inert gas purging time for enriching highly polar VOCs in tobacco as described in step S2 is 6-10 min; The highly polar tobacco VOCs include 2,3,5-trimethylpyrazine, furfural, benzaldehyde, propionic acid, 5-methylfurfural, butyric acid, 2-methylbutyric acid, valeric acid, hexanoic acid, benzyl alcohol, phenethyl alcohol, anisaldehyde, pentanol, methylheptenone, nonanal, acetophenone, acetic acid, furfuryl alcohol, and hexanal. The method for preparing reduced graphene oxide in step S2 is as follows: graphene oxide, iron powder and hydrochloric acid are heated and reacted in water. After the reaction, excess iron powder is removed to obtain reduced graphene oxide. The mass ratio of graphene oxide to iron powder is 1:60, the mass of iron powder is 3g, the hydrochloric acid is 36% HCl with a mass fraction of 10mL, and the heating temperature is 50℃.

2. The quantitative analysis method according to claim 1, characterized in that, The thermal desorption time in step S2 is 8~24 min.

3. The quantitative analysis method according to claim 1, characterized in that, The temperature for the secondary analysis in step S2 is 150~300℃.

4. The quantitative analysis method according to claim 1, characterized in that, The heating temperature in step S1 is 10~50℃.

5. The quantitative analysis method according to claim 1, characterized in that, The sampling device used in step S1 has the following structure: it includes an inert gas source (1), a first gas guide tube (2), a sample bottle (3), a vacuum valve (11), a second gas guide tube (4), a diaphragm pump (5), and a gas sampling bag (6) connected in sequence. It also includes a water bath heating tank (7) and a magnetic stirrer (10). The sample bottle (3) is located in the water bath heating tank (7). The magnetic stirrer (10) includes a stir bar (1001) and a base (1002) of the magnetic stirrer. The water bath heating tank (7) is located on the base (1002) of the magnetic stirrer, and the stir bar (1001) is located in the inner cavity of the sample bottle (3).

6. The quantitative analysis method according to claim 1, characterized in that, The specific operation of step S1 is as follows: (1) Crush the tobacco, freeze-dry it, put it into a sample bottle, and seal it for later use; (2) Purge the tobacco in the sample bottle with inert gas while stirring and heating. Collect the gas flow containing strong polar VOCs from tobacco in a gas sampling bag that has been pre-injected with strong polar VOCs internal standard, let stand, and shake well.

7. The quantitative analysis method according to claim 6, characterized in that, The ratio of the volume of the sample bottle to the maximum mass of the tobacco is (30 mL: 1 g) to (50 mL: 1 g).

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