A method for simultaneously determining contents of nicotine salts and alcohol compounds in electronic cigarette liquid by gas chromatography-mass spectrometry

Abstract

The present application relates to a kind of gas chromatography-mass spectrometry simultaneously determining the method for the content of nicotine salt and alcohol compound in electronic cigarette liquid, the method includes the following steps: (1) electronic cigarette liquid is taken in centrifugal tube, add internal standard extraction solution, vortex oscillation, pass organic phase filter membrane, obtain extract; (2) the extract in step (1) is taken to carry out gas chromatography-mass spectrometry (GC-MS) analysis;(3) the content of target in sample is calculated using internal standard standard curve method.This method does not need derivatization, realizes the simultaneous separation and analysis of nicotine, 15 kinds of organic acids, 5 kinds of alcohol compounds and 21 kinds of compounds, with the advantages of high flux, good peak shape, high separation degree, high sensitivity, good recovery rate, etc., suitable for the analysis and determination of main nicotine salt and alcohol compound in electronic cigarette liquid.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical analysis, and particularly relates to a method for simultaneously determining contents of nicotine salts and alcohol compounds in electronic cigarette liquid by gas chromatography-mass spectrometry. BACKGROUND

[0002] Electronic cigarette liquid, often referred to as tobacco tar, is a mixture composed of 1,2-propanediol, glycerol (commonly used atomizing agent, Nicotine Tob. Res. 2016, 18 (5), 708-714.), nicotine salt (nicotine + organic acid, Nicotine Tob. Res. 2019, 22 (7), 1239-1243.), various flavoring substances (such as menthol, Nicotine Tob. Res. 2016, 18 (5), 708-714.), and in addition, it has been reported that micro-toxic impurities such as ethylene glycol and diethylene glycol have been detected in electronic cigarettes (Cell, 2008, 8: 1-28; Nicotine Tob Res, 2016, 18 (5): 708-714.). At present, the national standard of electronic cigarette has been promulgated (GB41700-2022), and the maximum use amount of nicotine and additives in electronic cigarette liquid is limited, such as nicotine, benzoic acid, acetic acid, propionic acid, butyric acid, 2-methyl butyric acid, menthol, etc., therefore, it is necessary to establish a method for simultaneously detecting and accurately quantifying nicotine salt and alcohol compounds. At present, there are many methods for detecting nicotine, organic acid and alcohol compound, mainly including liquid chromatography, ion chromatography and gas chromatography, but all of them are classified detection, and there are significant deficiencies in throughput and efficiency. SUMMARY

[0003] The purpose of the present application is to improve the detection throughput, improve the analysis efficiency and simplify the pretreatment process. Based on gas chromatography-mass spectrometry (GC-MS), a method for simultaneously determining the contents of nicotine salt and alcohol compounds in electronic cigarette liquid is established. This method does not require derivatization, and realizes the simultaneous separation and analysis of 21 compounds such as nicotine, 15 kinds of organic acids and 5 kinds of alcohol compounds, has the advantages of high throughput, good peak shape, high separation degree, high sensitivity and good recovery rate, and is suitable for the analysis and determination of main nicotine salt and alcohol compounds in electronic cigarette liquid.

[0004] The purpose of the present application is achieved by the following technical solutions:

[0005] A method for simultaneously determining the contents of nicotine salt and alcohol compounds in electronic cigarette liquid by gas chromatography-mass spectrometry, which comprises the following steps:

[0006] (1) Take electronic cigarette liquid and place it in a centrifuge tube, add an internal standard extraction solution, vortex oscillate, pass through an organic phase filter membrane, and obtain an extraction solution;

[0007] (2) taking the extraction solution in step (1) to perform gas chromatography-mass spectrometry (GC-MS) analysis;

[0008] (3) calculating the content of the target compound in the sample by an internal standard curve method.

[0009] Preferably, in step (1), the internal standard extraction solution is a methanol solution of valeric acid-d9, 1,4-butanediol and 2-methylquinoline, with concentrations of 20 μg / mL, 200 μg / mL and 50 μg / mL, respectively.

[0010] Preferably, in step (1), the vortex oscillation time is 5-20 min, preferably 10 min.

[0011] Preferably, in step (1), the mass-to-volume ratio between the e-liquid and the internal standard extraction solution is 20 mg:10 mL.

[0012] Preferably, in step (1), the organic phase filter membrane is a hydrophobic PTFE needle filter membrane with a pore size of 0.22 μm.

[0013] Preferably, in step (2), the chromatographic conditions used in the gas chromatography-mass spectrometry analysis are as follows: the chromatographic column is an Agilent DB-624UI chromatographic column (30 m x 0.32 mm x 1.8 μm).

[0014] Preferably, in step (2), the chromatographic conditions used in the gas chromatography-mass spectrometry analysis further include: the temperature rising program is initial temperature 80℃, holding for 1 min, rising to 120℃ at 5℃ / min, holding for 1 min, rising to 230℃ at 8℃ / min, holding for 1 min, total running time 24.75 min, running for 5 min after 250℃.

[0015] Preferably, in step (2), the chromatographic conditions of the gas chromatography-mass spectrometry analysis further include: injection port temperature: 250℃; transfer line temperature: 230℃; carrier gas: helium (≥99.999%); carrier gas flow rate 1.5 mL / min; constant flow mode; split ratio 20:1; injection volume 1 μL; solvent delay: 1.8 min.

[0016] Preferably, in step (2), the mass spectrometry conditions of the gas chromatography-mass spectrometry analysis include: ionization mode: Extractor EI ion source; ionization energy: 70 eV; ion source temperature (TEM): 230℃; quadrupole temperature: 150℃; scanning mode: full scan (Scan) and selected ion monitoring (SIM).

[0017] Preferably, in step (2), the mass spectrometry detection parameters of the target compound and the internal standard are as follows:

[0018]

[0019]

[0020] Preferably, in step (3), the internal standard standard curve method is as follows: a series of standard working solutions containing the target substance are prepared, and an internal standard (valeric acid-d9, 1,4 butanediol and 2-methylquinoline) is added, a standard working curve is prepared with the quantitative ion peak area ratio of the target substance to the internal standard in each standard working solution as the ordinate and the content of the target substance in each standard working solution as the abscissa; the analysis result of step (2) is substituted into the standard curve to obtain the content of the target substance in the solution to be tested, and the content of the target substance in the sample is further calculated.

[0021] Preferably, the concentration range of each target substance in the series of standard working solutions is as follows: benzoic acid and formic acid are 5-200 μg / mL, acetic acid is 2-200 μg / mL, 1,2 propanediol and glycerol are 5-2000 μg / mL, the rest of the organic acids and alcohol compounds are 1-200 μg / mL, and nicotine is 1-200 μg / mL.

[0022] Preferably, the nicotine salt includes nicotine salts formed by nicotine and formic acid, acetic acid, propionic acid, butyric acid, 2-methyl butyric acid, valeric acid, 3-methyl valeric acid, 4-methyl valeric acid, n-hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, benzoic acid, sorbic acid, and the alcohol compound includes 1,2-propanediol, glycerol, ethylene glycol, diethylene glycol and menthol.

[0023] Preferably, in a specific embodiment, the method comprises the following steps:

[0024] (1) 20 mg of electronic cigarette liquid is taken into a 15 mL centrifuge tube, 10 mL of internal standard extraction solution is added, vortexed for 10 min, and filtered through an organic phase filter membrane to obtain an extraction solution;

[0025] (2) The extraction solution in step (1) is subjected to gas chromatography-mass spectrometry (GC-MS) analysis,

[0026] The chromatographic conditions used in the gas chromatography-mass spectrometry analysis are as follows:

[0027] Chromatographic column: Agilent DB-624UI chromatographic column (30 m x 0.32 mm x 1.8 μm);

[0028] Temperature rising program: initial temperature 80℃, hold for 1 min, rise to 120℃ at 5℃ / min, hold for 1 min, rise to 230℃ at 8℃ / min, hold for 1 min, total running time 24.75 min, run for 5 min after 250℃;

[0029] Injection port temperature: 250℃; transfer line temperature: 230℃; carrier gas: helium (>99.999%); carrier gas flow rate 1.5 mL / min; constant flow mode; split ratio 20:1; injection volume 1 μL; solvent delay: 1.8 min.

[0030] The mass spectrometry conditions used in the gas chromatography-mass spectrometry analysis are as follows: ion source temperature (TEM): 230℃; quadrupole temperature: 150℃; ionization energy: 70 eV; scanning mode: full scan (Scan) and selected ion monitoring (SIM).

[0031] The mass spectrometry detection parameters of the target compounds and the internal standard are as follows:

[0032]

[0033]

[0034] Note: "2-methylquinoline" is the internal standard of nicotine, "1,4-butanediol" is the internal standard of 1,2-propanediol and glycerol, and "valeric acid-d9" is the internal standard of other compounds.

[0035] (3) The content of the target compound in the sample is quantitatively calculated by the internal standard standard curve method.

[0036] The internal standard standard curve method is as follows: a series of standard working solutions containing the target compound are prepared, and the internal standard (valeric acid-d9, 1,4-butanediol and 2-methylquinoline) is added. The quantitative ion peak area of the target compound and the internal standard in each standard working solution is used as the ordinate, and the content of the target compound in each standard working solution is used as the abscissa to prepare a standard working curve. The analysis results of step (2) are substituted into the standard curve to obtain the content of the target compound in the test solution, and the content of each target compound in the sample is further calculated.

[0037] The concentration range of each target compound in the series of standard working solutions is as follows: benzoic acid and formic acid are 5-200 μg / mL, acetic acid is 2-200 μg / mL, 1,2-propanediol and glycerol are 5-2000 μg / mL, the remaining organic acids and alcohol compounds are 1-200 μg / mL, and nicotine is 1-200 μg / mL.

[0038] Compared with the prior art, the present application has at least the following beneficial technical effects:

[0039] The application is based on GC-MS technology, and chromatographic column, carrier gas flow rate and temperature program are investigated, a method for simultaneously determining the contents of 15 nicotine salts and 5 alcohol compounds in electronic cigarette liquid is established, the simultaneous analysis of nicotine, 15 organic acids, 5 alcohol compounds and 21 compounds is realized, the method has the advantages of good resolution, high flux, simple operation, high sensitivity, good recovery rate and repeatability, and is suitable for content analysis of main nicotine salts and alcohol compounds in electronic cigarette liquid. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 Figure 1 shows the chromatographic separation diagrams of four chromatographic columns in the gas chromatography-mass spectrometry (GC-MS) analysis method (1. formic acid; 2. acetic acid; 3. propionic acid; 4. ethylene glycol; 5. 1,2-propanediol; 6. butyric acid; 7. 2-methyl butyric acid; 8. pentanoic acid-d9 (internal standard); 9. pentanoic acid; 10. 3-methyl pentanoic acid; 11. 4-methyl pentanoic acid; 12. 1,4-butanediol (internal standard); 13. n-hexanoic acid; 14. diethylene glycol; 15. glycerol; 16. heptanoic acid; 17. sorbic acid; 18. menthol; 19. octanoic acid; 20. benzoic acid; 21. nonanoic acid; 22. 2-methylquinoline (internal standard); 23. nicotine; 24. decanoic acid), wherein A: DB-WAX chromatographic column; B: DB-FFAP chromatographic column; C: TG-WAXMS A chromatographic column; D: DB-624UI chromatographic column. DETAILED DESCRIPTION

[0041] The technical solutions of the application will be further described below in combination with the specific embodiments.

[0042] Example 1: A method for simultaneously determining the contents of 15 nicotine salts and 5 alcohol compounds in electronic cigarette liquid

[0043] (1) Instruments and reagents

[0044] Instruments: GC-MS system (Agilent 8890-5977B, USA), qualitative analysis and quantitative processing software (Qualitative Analysis 10.0 and Quant-My-Way); electronic balance (AE163, Mettler, Switzerland, sensitivity: 0.0001g); Talboys digital multi-tube vortex mixer.

[0045] Reagents and consumables: formic acid, acetic acid, propionic acid, butyric acid, 2-methyl butyric acid, pentanoic acid, 3-methyl pentanoic acid, 4-methyl pentanoic acid, n-hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, sorbic acid, benzoic acid, ethylene glycol, diethylene glycol, 1,2-propanediol, glycerol, menthol, nicotine, pentanoic acid-d9, 1,4-butanediol, 2-methylquinoline, all purchased from TRC company, and methanol (DUKSAN, chromatographic pure).

[0046] (2) Instrument operating conditions

[0047] Chromatographic conditions: The chromatographic column was Agilent DB-624UI chromatographic column (30 m x 0.32 mm x 1.8 μm); the injection port temperature was 250 °C; the transfer line temperature was 230 °C; the carrier gas was helium (≥ 99.999 %); the carrier gas flow rate was 1.5 mL / min; the constant flow mode; the split ratio was 20:1; the injection volume was 1 μL; the solvent delay was 1.8 min; the temperature program was as follows: the initial temperature was 80 °C, maintained for 1 min, increased to 120 °C at a rate of 5 °C / min, maintained for 1 min, increased to 230 °C at a rate of 8 °C / min, maintained for 1 min, the total running time was 24.75 min, and the running after 250 °C was 5 min.

[0048] Mass spectrometric conditions: the ion source temperature (TEM) was 230 °C; the quadrupole temperature was 150 °C; the ionization energy was 70 eV; the scanning mode was full scan (Scan) and selected ion monitoring (SIM).

[0049] The mass spectrometric detection parameters of the target compound and the internal standard were as follows:

[0050] No. Compound Qual. ion (m / z) Quant. ion (m / z) 1 Formic acid 45 46 2 Acetic acid 45 60 3 Propionic acid 57 74 4 Butyric acid 73 60 5 2-Methylbutyric acid 57 74 6 Valeric acid 73 60 7 3-Methylvaleric acid 87 60 8 4-Methylvaleric acid 73 57 9 n-Hexanoic acid 73 60 10 Heptanoic acid 73 60 11 Octanoic acid 73 60 12 Nonanoic acid 73 60 13 Decanoic acid 73 60 14 Sorbic acid 112 97 15 Benzoic acid 122 105 16 1,2-Propanediol 43 45 17 Glycerol 43 61 18 Ethylene glycol 31 33 19 Diethylene glycol 75 45 20 Menthol 95 81 21 Nicotine 84 162 22 Valeric acid-d9 (internal standard) 77 63 23 2-Methylquinoline (internal standard) 128 143 24 1,4-Butanediol (internal standard) 44 42

[0051] (3) Sample pretreatment

[0052] 20 mg of the e-cigarette liquid sample was weighed in a 15 mL centrifuge tube, 10 mL of the internal standard extraction solution (valeric acid-d9, 1,4-butanediol and 2-methylquinoline, the concentrations were 20 μg / mL, 200 μg / mL and 50 μg / mL, respectively) was added, and the extraction was oscillated for 10 min. After filtration with a 0.22 μm hydrophobic PTFE needle filter, it was placed in a chromatographic bottle for testing.

[0053] (4) Preparation of standard working solutions

[0054] ① Preparation of internal standard stock solution: 0.2 g of valeric acid-d9, 2.0 g of 1,4-butanediol and 0.5 g of 2-methylquinoline were accurately weighed into a 100 mL brown volumetric flask, and then methanol was added to constant volume to prepare internal standard stock solutions with different concentrations.

[0055] ② Preparation of mixed standard stock solution

[0056] Accurately weigh 0.1 g of formic acid, acetic acid, propionic acid, butyric acid, 2-methyl butyric acid, pentanoic acid, 3-methyl pentanoic acid, 4-methyl pentanoic acid, n-hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, sorbic acid, benzoic acid, ethylene glycol, diethylene glycol, menthol, 1.0 g of 1,2-propanediol, glycerol and 0.2 g of nicotine into a 100 mL brown volumetric flask, and dilute to the mark with methanol to prepare a mixed standard stock solution with a concentration of 1-10 mg / mL. The solution should be stored at 4-8°C in the dark.

[0057] ③ Preparation of standard working solution

[0058] Accurately pipette 5 μL, 10 μL, 20 μL, 50 μL, 100 μL, 200 μL, 500 μL, 1000 μL and 2000 μL of the mixed standard stock solution into different 10 mL brown volumetric flasks, respectively, and then accurately add 100 μL of the internal standard solution. Dilute to the mark with methanol to obtain nine series of standard working solutions with different concentrations.

[0059] (5) Sample determination

[0060] Perform GC-MS analysis on the standard working solution obtained in step (4) and the sample solution obtained in step (3), respectively. The chromatograms of the target substances and the internal standard in the standard working solution are shown in FIG. 1. Figure 1 Take the ratio of the quantitative ion peak area of the target substance to the internal standard in each standard working solution as the vertical coordinate, and take the content of the target substance in each standard working solution as the vertical coordinate to prepare a standard working curve. Substitute the analysis results of step (3) into the standard curve to obtain the content of the target substance in the test solution, and further calculate the content of each target substance in the sample.

[0061] (6) Method validation

[0062] According to the lowest standard working solution, calculate the detection limit of the method according to 3 times the signal-to-noise ratio, calculate the spiked recovery rate according to low, medium and high three addition levels, add 6 parallel samples at each level, and calculate the test precision according to the parallel test results. The linear range, linear coefficient, detection limit, limit of quantification, average spiked recovery rate and average precision of the method are shown in Table 1.

[0063] Table 1. Linear range, linear coefficient, detection limit, limit of quantification, average spiked recovery rate and average precision of each target substance

[0064]

[0065]

[0066] (7) Analysis of actual samples

[0067] According to the above determination method, 5 electronic cigarette liquid samples were selected, and the target content was measured as shown in Table 2:

[0068] Table 2: Determination results of nicotine, organic acid and alcohol content in typical electronic cigarette liquid samples (mg / g)

[0069]

[0070]

[0071] Example 2: Selection experiment of chromatographic column

[0072] Considering the chemical properties of the target, the chromatographic column is mainly selected for medium polarity and strong polarity chromatographic column for research, which are DB-FFAP (60m x 0.25mm x 0.25μm), DB-WAX (30m x 0.25mm x 0.25μm) of Agilent Company, TG-WAXMS A (30m x 0.25mm x 0.25μm) and DB-624UI (30m x 0.32mm x 1.8μm) of Thermo Company. The specific implementation process is shown in Example 1.

[0073] Research findings:

[0074] ① DB-WAX chromatographic column can achieve baseline separation of 21 compounds such as organic acids, alcohol compounds and nicotine, but there are two problems, one is that the response to formic acid is not high enough, and the other is that the column repeatability is poor, and the peak shape is easy to tail (as shown in Figure 1 A).

[0075] ② DB-FFAP chromatographic column can achieve baseline separation of organic acids and nicotine, but the response to glycerol is poor, the detection limit is high and the peak shape is tailing (as shown in Figure 1 B).

[0076] ③ TG-WAXMS A chromatographic column has poor response to formic acid, and cannot achieve baseline separation of formic acid and propionic acid (as shown in Figure 1 C).

[0077] ④ The separation degree of DB-624UI chromatographic column to 21 compounds can reach more than 1.5, the peak shape is good, the stability is good, and the response to formic acid is higher than other chromatographic columns (as shown in Figure 1 D).

[0078] Therefore, the final selected chromatographic column is DB-624UI chromatographic column.

[0079] Example 3: Selection experiment of carrier gas flow rate

[0080] In order to investigate the influence of carrier gas flow rate on the detection method, the flow rate of carrier gas was selected as 1.0 mL / min, 1.5 mL / min and 2 mL / min. It was found that the response and separation effect of the compound were the best when the flow rate was 1.5 mL / min, so the final flow rate was determined as 1.5 mL / min.

[0081] Example 4: Selection experiment of temperature program

[0082] In order to investigate the influence of temperature program on the detection method, the influence of three temperature programs on the separation degree and peak shape was investigated respectively. Three initial temperatures were set, which were 50℃, 80℃ and 100℃ respectively.

[0083] It was found that:

[0084] The initial temperature was 50℃, maintained for 1 min, and the target compound appeared late.

[0085] The initial temperature was 80℃, maintained for 1 min, and the target compound appeared late.

[0086] The initial temperature was 100℃, maintained for 1 min, and the peak shape of 2-methylbutyric acid was not good.

[0087] Therefore, the final initial temperature was determined as 80℃.

Claims

1. A method for simultaneously determining contents of nicotine salts and alcohol compounds in e-liquid of electronic cigarettes by gas chromatography-mass spectrometry, the method comprising the following steps: (1) taking the e-liquid of electronic cigarettes into a centrifuge tube, adding an internal standard extraction solution, vortexing, and passing through an organic phase filter membrane to obtain an extraction solution; (2) taking the extraction solution in step (1) for gas chromatography-mass spectrometry analysis; (3) calculating the content of the target substance in the sample by an internal standard standard curve method; wherein, in step (2), the chromatographic conditions used in the gas chromatography-mass spectrometry analysis are as follows: the chromatographic column is an Agilent DB-624UI chromatographic column, 30 m × 0.32 mm × 1.8 μm; the temperature rising program is initial temperature 80℃, holding for 1 min, rising to 120℃ at 5℃ / min, holding for 1 min, rising to 230℃ at 8℃ / min, holding for 1 min, total running time 24.75 min, running for 5 min after 250℃; the inlet temperature is 250℃; the transfer line temperature is 230℃; the carrier gas is helium; the carrier gas flow rate is 1.5 mL / min; the constant flow mode is used; the split ratio is 20:1; the sample injection volume is 1 μL; and the solvent delay is 1.8 min; the nicotine salts comprise nicotine salts formed by formic acid, acetic acid, propionic acid, butyric acid, 2-methylbutyric acid, pentanoic acid, 3-methylpentanoic acid, 4-methylpentanoic acid, n-hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, benzoic acid, and sorbic acid and nicotine; and the alcohol compounds comprise 1,2-propanediol, glycerol, ethylene glycol, diethylene glycol, and menthol. In step (1), the internal standard extraction solution is a methanol solution of pentanoic acid-d9, 1,4-butanediol, and 2-methylquinoline, and the concentrations thereof are 20 μg / mL, 200 μg / mL, and 50 μg / mL, respectively. In step (1), the vortexing time is 5-20 min. In step (1), the vortexing time is 10 min. In step (1), the mass-to-volume ratio between the e-liquid of electronic cigarettes and the internal standard extraction solution is 20 mg:10 mL. In step (1), the organic phase filter membrane is a hydrophobic PTFE needle filter membrane, and the pore size thereof is 0.22 μm. In step (2), the mass spectrometry conditions of the gas chromatography-mass spectrometry analysis comprise: ionization mode: Extractor EI ion source; ionization energy: 70 eV; ion source temperature: 230℃; quadrupole temperature: 150℃; and scanning mode: full scan and selected ion monitoring. In step (2), the mass spectrometry detection parameters of the target compounds and the internal standard are as follows: In step (3), the internal standard standard curve method is as follows: a series of working solutions containing the target substance are prepared, the internal standard pentanoic acid-d9, 1,4-butanediol, and 2-methylquinoline are added, the quantitative ion peak area ratio of the target substance to the internal standard in each standard working solution is taken as the ordinate, and the content of the target substance in each standard working solution is taken as the abscissa to prepare a standard working curve; the analysis results of step (2) are substituted into the standard curve to obtain the content of the target substance in the solution to be measured, and the content of the target substance in the sample is further calculated. ​ ​ ​ ​ ​ ​ ​ ​ 2. The method of claim 1, wherein, ​ 3. The method of claim 1, wherein, ​ 4. The method of claim 1, wherein, ​ 5. The method according to claim 1 or 2, characterized in that, ​ 6. The method of claim 1 or 2, wherein, ​ 7. The method according to claim 1 or 2, characterized in that, ​ 8. The method of claim 1 or 2, wherein, ​ 9. The method of claim 1 or 2, wherein, ​ 10. The method of claim 1 or 2, wherein, In step (3), the concentration range of each target in the series of standard working solutions is: benzoic acid and formic acid is 5-200ug / mL, 1,2 propanediol and glycerol is 5-2000ug / mL, the rest of the organic acids and alcohols is 1-200ug / mL, nicotine is 1-200ug / mL.

11. The method of claim 1 or 2, wherein, The method comprises the following steps: (1) Take 20mg of electronic cigarette liquid and place it in a 15mL centrifuge tube with a plug, add 10mL of internal standard extraction solution, vortex for 10min, pass through an organic filter membrane to obtain an extract; (2) Take the extract in step (1) for gas chromatography-mass spectrometry analysis, The chromatographic conditions used in the gas chromatography-mass spectrometry analysis are as follows: Chromatographic column: Agilent DB-624 UI chromatographic column, 30m x 0.32mm x 1.8um; Temperature program: initial temperature 80℃, hold for 1min, increase to 120℃ at 5℃ / min, hold for 1min, increase to 230℃ at 8℃ / min, hold for 1min, total running time 24.75min, run for 5min after 250℃; Injection port temperature: 250℃; Transfer line temperature: 230℃; Carrier gas: helium; Carrier gas flow rate 1.5mL / min; Constant flow mode; Split ratio 20:1; Injection volume 1uL; Solvent delay: 1.8min; The mass spectrometry conditions used in the gas chromatography-mass spectrometry analysis are as follows: Ion source temperature: 230℃; Quadrupole temperature: 150℃; Ionization energy: 70eV; Scan mode: full scan and selected ion monitoring; The mass spectrometry detection parameters of the target compounds and internal standards are as follows: Note: "2-methylquinoline" is the internal standard for nicotine, "1,4 butanediol" is the internal standard for 1,2-propanediol and glycerol, and "valeric acid-d9" is the internal standard for other compounds; (3) The internal standard standard curve method is used to quantitatively calculate the content of the target in the sample; The internal standard standard curve method is as follows: a series of standard working solutions containing the target are prepared, and the internal standards valeric acid-d9, 1,4-butandiol and 2-methylquinoline are added, the quantitative ion peak area of the target and the internal standard in each standard working solution is taken as the ordinate, and the content of the target in each standard working solution is taken as the abscissa to prepare a standard working curve: the analysis results of step (2) are substituted into the standard curve to obtain the content of the target in the test solution, and the content of each target in the sample is further calculated; The concentration range of each target in the series of standard working solutions is: benzoic acid and formic acid is 5-200ug / mL, acetic acid is 2-200ug / mL, 1,2 propanediol and glycerol is 5-2000ug / mL, the rest of the organic acids and alcohol compounds is 1-200ug / mL, nicotine is 1-200ug / mL.

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