Method and device for detecting nicotine escape ability

Abstract

This application relates to a method and apparatus for detecting nicotine escape capacity. The method involves acquiring the headspace peak area of ​​a nicotine sample in a static headspace unit, then introducing it into a gas chromatography-mass spectrometry (GC-MS) unit using headspace injection technology. Based on the headspace peak area and a pre-defined external standard calibration relationship, the mass of nicotine entering the chromatographic column in a single headspace injection is calculated. The partial pressure of nicotine in the gas phase is then calculated based on this mass, and this partial pressure is used as an escape capacity index characterizing nicotine escape capacity. This method establishes an absolute quantitative link from chromatographic response to nicotine gas phase partial pressure, eliminating the need for nicotine standard gas, lowering the detection threshold, and making it suitable for complex matrices. Ultimately, it outputs an escape capacity index with physical dimensions, enabling unified and comparable evaluation across different formulations, equipment, and batches.

Description

Technical Field

[0001] This application relates to the field of analytical chemistry technology, and in particular to a method and apparatus for detecting nicotine escape capacity. Background Technology

[0002] Nicotine escape behavior is one of the core performance indicators of novel vaping products, directly affecting aerosol release efficiency, user experience, and exposure risk. The e-liquid matrix in vaping products typically consists of propylene glycol (PG), glycerin (VG), water, and flavorings, with nicotine in free base or salt forms (such as lactate and benzoate). The partitioning behavior of nicotine between the gas and liquid phases is significantly influenced by factors such as solvation, pH, salinization degree, and temperature, making quantitative characterization of escape ability quite challenging.

[0003] Existing static headspace-GC / MS (Gas Chromatography-Mass Spectrometry) methods for studying nicotine volatility only report headspace peak area or peak area ratio, failing to establish a complete absolute quantitative pathway. Furthermore, the partitioning behavior of nicotine in the gas-liquid phase varies significantly across different matrices, lacking a unified dimensional indicator and exhibiting poor comparability across different equipment and experimental conditions. Therefore, there is an urgent need for a quantitative detection method and apparatus for nicotine escape capacity that is traceable to physical dimensions and applicable to complex matrices. Summary of the Invention

[0004] Therefore, it is necessary to provide a method and apparatus for detecting nicotine escape capacity that can be traced back to physical dimensions and is applicable to the quantitative characterization of nicotine escape capacity in complex matrices, in order to address the above-mentioned technical problems.

[0005] Firstly, this application provides a method for detecting nicotine escape ability, the method comprising:

[0006] The headspace peak area of ​​the nicotine sample to be tested is obtained after it enters the gas chromatography-mass spectrometry unit in the static headspace unit based on headspace injection technology.

[0007] Based on the headspace peak area and the preset external standard calibration correspondence, the mass of nicotine entering the chromatographic column of the chromatography-mass spectrometry unit in a single headspace injection is calculated.

[0008] The partial pressure of nicotine in the gas phase is calculated based on the mass of the nicotine; the partial pressure of nicotine in the gas phase is used as an escape capacity index characterizing the escape capacity of nicotine.

[0009] In one embodiment, the process of determining the external standard calibration correspondence includes:

[0010] After a predetermined volume of liquid is injected into a standard solution of a preset concentration by the gas chromatography-mass spectrometry unit, the peak area of ​​nicotine in the standard solution is obtained.

[0011] The external standard calibration correspondence is determined based on the preset concentration of the standard solution, the predetermined volume, and the peak area of ​​nicotine in the standard solution.

[0012] In one embodiment, the process of detecting the nicotine sample in a static headspace unit by entering a gas chromatography-mass spectrometry unit based on headspace sampling technology includes:

[0013] After transferring the nicotine sample to be tested into the headspace vial of the static headspace unit, the liquid phase volume is recorded.

[0014] The sealed headspace vial is placed in the incubation device of the static headspace unit and incubated at the target temperature until the gas-liquid two phases reach equilibrium.

[0015] By using standard static headspace operation, the gas in the headspace injection quantitative loop of the static headspace unit is injected into the gas chromatography-mass spectrometry unit, and the headspace peak area of ​​nicotine is recorded.

[0016] In one embodiment, calculating the gas phase partial pressure of nicotine based on the mass of the nicotine includes:

[0017] Calculate the molar concentration of nicotine in headspace gas based on the mass of nicotine mentioned above;

[0018] The gas phase partial pressure of nicotine is calculated based on the molar concentration of nicotine in the headspace gas.

[0019] In one embodiment, calculating the gas phase partial pressure of nicotine based on the nicotine molar concentration in the headspace gas includes:

[0020] The gas phase partial pressure of nicotine is calculated based on the nicotine molar concentration in the headspace, the target temperature, and the ideal gas law.

[0021] In one embodiment, calculating the gas phase partial pressure of nicotine based on the nicotine molar concentration in the headspace gas includes:

[0022] The gas phase partial pressure of nicotine is calculated based on the nicotine molar concentration in the headspace, the liquid phase volume, and the target temperature.

[0023] In one embodiment, calculating the molar concentration of nicotine in headspace gas based on the mass of nicotine includes:

[0024] The molar concentration of nicotine in the headspace gas is calculated based on the mass of nicotine, the molar mass of nicotine, and the volume of the headspace sampling quantitative loop.

[0025] In one embodiment, after calculating the gas phase partial pressure of nicotine based on the mass of the nicotine, the method further includes:

[0026] Obtain the escape capacity index of the reference nicotine sample under the same temperature conditions as the nicotine sample to be tested;

[0027] The relative escape capacity index is obtained based on the escape capacity index of the nicotine sample to be tested and the escape capacity index of the reference nicotine sample.

[0028] Secondly, this application also provides a device for detecting nicotine escape capacity, including a static headspace unit, a gas chromatography-mass spectrometry unit, and a data processing unit. The static headspace unit is connected to the gas chromatography-mass spectrometry unit, the gas chromatography-mass spectrometry unit is connected to the data processing unit, and the data processing unit is used to implement the method described in any one of claims 1-8.

[0029] In one embodiment, the static headspace unit is provided with a headspace sampling quantitative loop with a fixed volume.

[0030] In one embodiment, the operating temperature of the headspace transmission line of the static headspace unit is higher than the temperature of the headspace bottle.

[0031] In one embodiment, the gas chromatography column in the gas chromatography-mass spectrometry unit is a capillary column.

[0032] In one embodiment, the gas chromatography-mass spectrometry unit uses ion monitoring for detection.

[0033] The aforementioned method and apparatus for detecting nicotine escape capacity obtains the headspace peak area of ​​the nicotine sample after it enters the gas chromatography-mass spectrometry (GC-MS) unit in a static headspace unit using headspace injection technology. Based on the headspace peak area and a preset external standard calibration correspondence, the mass of nicotine entering the chromatographic column in a single headspace injection is calculated. The partial pressure of nicotine in the gas phase is then calculated based on this mass, and this partial pressure is used as an escape capacity index characterizing nicotine escape capacity. This scheme establishes an absolute quantitative link from chromatographic response to nicotine gas phase partial pressure, eliminating the need for nicotine standard gas, lowering the detection threshold, and making it suitable for complex matrices. Ultimately, it outputs an escape capacity index with physical dimensions, enabling unified and comparable evaluation across different formulations, equipment, and batches. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a flowchart illustrating a method for detecting nicotine escape ability in one embodiment;

[0036] Figure 2 This is a flowchart illustrating the process of determining the correspondence between external standard calibrations in one embodiment;

[0037] Figure 3 This is a schematic flowchart illustrating the process by which a nicotine sample to be tested enters a gas chromatography-mass spectrometry unit in a static headspace unit for detection based on headspace sampling technology, as shown in one embodiment.

[0038] Figure 4 This is a flowchart illustrating the steps for calculating the gas phase partial pressure of nicotine based on the mass of nicotine in one embodiment.

[0039] Figure 5 This is a flowchart illustrating the step of calculating the gas phase partial pressure of nicotine based on the mass of nicotine in another embodiment.

[0040] Figure 6 This is a flowchart illustrating the step of calculating the gas phase partial pressure of nicotine based on the mass of nicotine in another embodiment.

[0041] Figure 7 This is a flowchart illustrating a method for detecting nicotine escape ability in another embodiment;

[0042] Figure 8 This is a schematic diagram of the structure of a nicotine escape detection device in one embodiment;

[0043] Figure 9 This is a schematic diagram of the test results for Example 2;

[0044] Figure 10 This is a schematic diagram of the test results for Example 3;

[0045] Figure 11 This is a schematic diagram of the test results for Example 4. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0047] It should be noted that the terms "first," "second," etc., used in this application can be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from the second element. The terms "comprising" and "having," and any variations thereof, used in this application, are intended to cover non-exclusive inclusion. The term "multiple" used in this application refers to two or more. The term "and / or" used in this application refers to one of the embodiments, or any combination of multiple embodiments.

[0048] The nicotine escape capability detection method provided in this application is used to detect the nicotine escape capability, which can be understood as the ability of nicotine to escape from the liquid phase to the gas phase. Nicotine escape capability is one of the core performance indicators of electronic atomization devices, and the nicotine escape capability detection method can be used to detect the nicotine escape capability in the atomization matrix of the electronic atomization device. It can be understood that the nicotine escape capability detection method provided in this application can be used to detect the nicotine escape capability of the electronic atomization device before it leaves the factory, or it can be used to detect the nicotine escape capability of the electronic atomization device after a period of use.

[0049] For example, the method for detecting nicotine escape capacity can be used to optimize the formulation of e-liquid for e-cigarette devices. E-liquids typically consist of propylene glycol (PG), glycerin (VG), nicotine (free base or salt form), flavoring, and water. Different PG / VG ratios, different types and ratios of organic acids, and different nicotine contents significantly affect the volatilization / escape behavior of nicotine. Quantitative guidance using the escape capacity index obtained from the embodiments of this application can optimize the formulation of e-liquids, enabling the design of nicotine release curves on demand. Alternatively, the method for detecting nicotine escape capacity can also be used to characterize nicotine release in heat-not-burn e-cigarette devices. Heat-not-burn e-cigarette devices release nicotine-containing aerosols by heating the atomizing matrix at low temperatures. The nicotine form (free base / salt), moisture content, pH value, and heating temperature in the atomizing matrix all affect the ability of nicotine to escape from the solid matrix to the gas phase. The quantitative guidance provided by the escape capacity index obtained through the embodiments of this application can provide data support for setting heating programs, enabling effective nicotine release at the target heating temperature while avoiding the generation of harmful substances from excessively high temperatures. Furthermore, the nicotine escape capacity detection method provided through the embodiments of this application can also effectively guide the assessment of the stability and shelf life of nicotine salt products, and the quality control of nicotine release consistency between different batches, which will not be elaborated further here.

[0050] Furthermore, the nicotine escape detection method provided in this application is based on a general-purpose GC / MS and static headspace platform, which includes a gas chromatography-mass spectrometry unit and a static headspace unit. The nicotine escape detection method can be executed by a data processing unit, which is communicatively connected to the general-purpose GC / MS and static headspace platform. The data processing unit includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the nicotine escape detection method.

[0051] In one exemplary embodiment, a method for detecting nicotine escape ability is provided, such as... Figure 1 As shown, the method includes steps 102 to 106. Wherein:

[0052] Step 102: Obtain the headspace peak area of ​​the nicotine sample to be tested in the static headspace unit after it enters the gas chromatography-mass spectrometry unit based on headspace injection technology.

[0053] The nicotine sample to be tested refers to a liquid, semi-solid, or solid matrix containing nicotine, including but not limited to e-cigarette liquids, heated tobacco formulations, nicotine salt solutions, free nicotine solutions, propylene glycol / glycerin / water mixtures containing nicotine, and biological samples containing nicotine. Nicotine in the sample can exist in the form of a free alkali or an organic acid salt.

[0054] A static headspace unit (SHU) is a device used to heat a sample in a sealed container to a target temperature, allowing volatile components to reach equilibrium between the gas-liquid (or gas-solid) phases, and then quantitatively extracting gas from the headspace for injection. Its basic structure includes: a sealable headspace vial, an incubation device, an injection device, a flow path switching valve, and a gas transfer line (headspace transfer line). The static aspect of a static headspace unit is that no gas is purged into the vial during the equilibrium process; gas is only extracted once during sampling.

[0055] Headspace sampling is an analytical technique that, after gas-liquid equilibrium is established, does not directly extract the sample itself. Instead, it uses an injection device to draw a certain volume of gas from the gas space at the top of the headspace vial, which is not in contact with the liquid, and injects it into the gas chromatograph within the gas chromatography-mass spectrometry unit. This technique minimizes the amount of non-volatile matrix entering the chromatograph.

[0056] Gas chromatography-mass spectrometry (GC / MS) is an analytical system consisting of a gas chromatograph and a mass spectrometer detector connected in series. The gas chromatograph is responsible for separating the components in a gas mixture according to their boiling points or differences in polarity; the mass spectrometer detector is responsible for ionizing and fragmenting the separated components and detecting their characteristic ions, thereby achieving qualitative and quantitative analysis.

[0057] The headspace peak area refers to the area obtained by integrating the chromatographic peak corresponding to the nicotine retention time in the chromatogram obtained from GC / MS analysis. This area is proportional to the intensity of the nicotine ion current entering the mass spectrometer detector and is the original measurement signal.

[0058] The processing steps for the nicotine samples to be tested include:

[0059] Accurately weigh or measure a certain amount of the nicotine sample to be tested, place it in a headspace vial, seal it immediately, and record the volume or mass of the nicotine sample. Then, place the sealed headspace vial into the incubation device of the static headspace unit, set the desired target temperature, and maintain it for a sufficient time to allow the nicotine in the gas-liquid two-phase mixture within the headspace vial to reach equilibrium. The equilibrium time can be determined experimentally beforehand: monitor the headspace peak area at different equilibrium times at the same temperature; equilibrium is considered achieved when the peak area no longer changes significantly with time. After equilibrium is achieved, use the automatic or manual operation of the static headspace unit to extract a fixed volume of headspace gas from the headspace via the injection device, and then inject this gas into the injection port of the gas chromatography-mass spectrometry unit using a carrier gas. Under the set GC / MS conditions, separate and detect the injected headspace gas using mass spectrometry to obtain the peak area of ​​nicotine on the chromatogram.

[0060] The data processing unit obtains the peak area of ​​nicotine on the chromatogram from the gas chromatography-mass spectrometry unit to obtain the headspace peak area of ​​nicotine.

[0061] Nicotine is allowed to naturally evaporate into the headspace and reach equilibrium under sealed, isothermal conditions using a static headspace unit. The original signal (headspace peak area) is then obtained using headspace sampling technology, which is proportional to the gas phase concentration. This step avoids errors caused by sample pretreatment and accurately reflects the escape behavior of nicotine in a specified matrix and temperature.

[0062] Step 104: Based on the headspace peak area and the preset external standard calibration correspondence, calculate the mass of nicotine entering the chromatographic column in the chromatography-mass spectrometry unit in a single headspace injection.

[0063] The preset external standard calibration correspondence characterizes the relationship between the peak area detected by GC / MS and the mass of nicotine entering the column. This preset external standard calibration correspondence can be obtained by pre-analyzing a series of nicotine liquid standard solutions of known concentrations. The form of the preset external standard calibration correspondence is not unique; it can be a functional correspondence or a numerical correspondence table, etc.

[0064] The mass of nicotine entering the column of a gas chromatography-mass spectrometry (GC-MS) unit in a single headspace injection refers to the mass of nicotine from the gas sample taken from the headspace vial that actually enters the column of the GC-MS unit and is detected by mass spectrometry. This mass is directly proportional to the concentration of nicotine in the headspace gas phase.

[0065] After establishing the external standard calibration correspondence in advance, the headspace peak area obtained in step 102 is substituted into the external standard calibration correspondence to back-calculate the mass of the unknown sample entering the column, and the mass of nicotine entering the chromatographic column of the chromatography-mass spectrometry unit in a single headspace injection is calculated.

[0066] This step uses the external standard calibration relationship to convert the headspace peak area into the mass of nicotine. This step reduces the impact of factors such as instrument sensitivity fluctuations and response differences on the results, making the obtained nicotine mass value traceable.

[0067] Step 106: Calculate the gas phase partial pressure of nicotine based on the mass of nicotine.

[0068] The partial pressure of nicotine in the gas phase refers to the pressure component contributed solely by nicotine in the gas phase space of the headspace vial.

[0069] The partial pressure of nicotine in the gas phase is used as an escape index to characterize the nicotine's ability to escape. The escape index quantifies the tendency of nicotine to escape from the liquid phase to the gas phase; its value is equal to the partial pressure of nicotine in the headspace phase at that temperature, i.e., the gas phase partial pressure of nicotine. A higher escape index indicates that, under the same temperature and matrix conditions, nicotine is more easily volatilized into the gas phase, meaning it has a stronger escape ability.

[0070] The mass of nicotine is directly proportional to its absolute content in the headspace phase. According to gas physics, at a fixed volume and temperature, the partial pressure of a gaseous component in a closed container is directly proportional to the amount (or mass) of that component within that volume. Therefore, by combining the mass of nicotine, the headspace equilibrium temperature of the static headspace unit, and the sampling volume, and utilizing the fundamental physical relationships between these parameters, the partial pressure of the gaseous component can be uniquely determined, thus yielding the gas-phase partial pressure of nicotine.

[0071] This step calculates the gas phase partial pressure of nicotine based on the mass of nicotine entering the chromatographic column in the chromatography-mass spectrometry unit. Gas phase partial pressure is a thermodynamic intensity quantity, independent of sample volume and headspace vial size; therefore, gas phase partial pressures measured from different samples and different laboratories can be directly compared. Using gas phase partial pressure as an escape velocity index has clear physical significance and engineering value.

[0072] The aforementioned method for detecting nicotine escape capacity establishes a complete quantitative link from chromatographic response to gas phase partial pressure, converting the raw instrument signal (headspace peak area) into an escape capacity index with definite physical dimensions (such as Pascal), filling the gap in existing methods that cannot directly output gas phase partial pressure. The escape capacity index is an intrinsic thermodynamic property of a substance, independent of specific instrument models, column conditions, or detector sensitivity; therefore, data from different sources have a unified basis for comparison. This method is based on conventional GC / MS and a static headspace platform, requiring no additional purchase of dedicated vapor pressure analyzers or real-time mass spectrometry equipment, making it simple to operate and moderately cost-effective. Furthermore, the escape capacity index can quantitatively guide formulation design (e.g., adjusting the PG / VG ratio, selecting suitable organic acids, and controlling nicotine content) to achieve the target nicotine release efficiency.

[0073] In one exemplary embodiment, such as Figure 2 As shown, the process of determining the correspondence between external standard calibrations includes steps 202 to 204. Wherein:

[0074] Step 202: After a predetermined volume of liquid is injected into the standard solution of a preset concentration by a gas chromatography-mass spectrometry unit for analysis, the peak area of ​​nicotine in the standard solution is obtained.

[0075] In this context, a standard solution refers to a liquid solution containing a known and accurate concentration of nicotine. The solvent is typically a volatile organic solvent (such as isopropanol, methanol, ethanol, or acetonitrile). This solvent should be able to vaporize rapidly under GC / MS conditions, not interfere with the chromatographic peak of nicotine, and have no adverse effect on headspace analysis. The concentration of the standard solution must cover the possible response range of the sample being analyzed.

[0076] The preset concentration refers to the mass concentration of nicotine in the standard solution, usually expressed in ng / mL, μg / mL, or mg / mL. A series of standard solutions with different concentrations (e.g., 10 ng / mL, 100 ng / mL, 1000 ng / mL, etc.) are prepared in advance, and 2 to 3 replicates can be prepared for each concentration.

[0077] The predetermined volume refers to the volume of sample accurately measured and injected into the gas chromatograph injection port by an autosampler or manual syringe during liquid injection, typically in μL. This volume is kept constant (e.g., 1.0 μL) for each injection to ensure that the mass of nicotine entering the column varies only with the concentration of the standard solution.

[0078] Unlike headspace sampling, liquid injection involves injecting the standard solution directly into the GC injector in liquid form. In the high-temperature injector, the solvent vaporizes instantly, carrying nicotine into the chromatographic column.

[0079] The peak area of ​​nicotine in a standard solution refers to the chromatographic peak area of ​​nicotine obtained in GC / MS analysis after the standard solution is injected with liquid.

[0080] The specific process of obtaining the headspace peak area of ​​nicotine in a standard solution of a preset concentration by liquid injection analysis using a gas chromatography-mass spectrometry unit with a predetermined volume includes:

[0081] Preparation of standard solutions:

[0082] Accurately weigh an appropriate amount of nicotine reference standard (e.g., 10 mg) into a volumetric flask (e.g., 10 mL), add a volatile organic solvent (e.g., isopropanol) to dilute to volume and mix well to obtain a nicotine standard stock solution (e.g., 1000 μg / mL); accurately transfer an appropriate amount of the stock solution (e.g., 1.0 mL) into a volumetric flask (e.g., 10 mL), dilute to volume with isopropanol and mix well to obtain an intermediate solution of a certain concentration (e.g., 100 μg / mL); prepare a series of standard solutions with concentration gradients using the stock solution and the intermediate solution, for example: 10, 100, 1000, 5000, 10000, 20000 ng / mL.

[0083] GC / MS Analysis and Peak Area Recording:

[0084] Under the same GC / MS conditions as the nicotine sample being tested, a predetermined volume (e.g., 1 μL) of standard solution at each concentration was injected for liquid analysis, and the peak area of ​​nicotine in the standard solution was recorded. Collecting the peak area of ​​nicotine under identical GC / MS conditions ensures that the external standard calibration correspondence is consistent with the conditions of subsequent headspace analysis, reducing systematic errors.

[0085] The data processing unit obtains the peak area of ​​nicotine in the standard solution from the gas chromatography-mass spectrometry unit.

[0086] Step 204: Determine the external standard calibration correspondence based on the preset concentration, predetermined volume, and peak area of ​​nicotine in the standard solution.

[0087] Under the premise that the injection volume and split settings of the static headspace unit are constant, the mass m of nicotine entering the column is... col (Unit: ng) can be calculated equivalently from the standard solution concentration and injection volume, and is the product of the standard solution concentration and injection volume. Its transfer factor is absorbed by the slope of the curve.

[0088] External standard calibration correspondence can be represented by an external standard calibration equation. Let m be the mass of nicotine entering the column. col Using x as the x-axis and the peak area Y of nicotine in the standard solution as the y-axis, a linear or weighted linear fit (e.g., 1 / x) can be performed to obtain the external standard calibration equation: Where a is the slope and b is the intercept. It can be understood that in other embodiments, the external standard calibration correspondence can also be a quadratic curve obtained through nonlinear fitting, etc.

[0089] Taking a specific calibration as an example, the linear range is 0.01–20 ng (corresponding to a solution concentration of 10–20000 ng / mL, 1 μL injection). The fitting result can be: Therefore, the inverse calculation function m for the mass of the column is defined. col =(Yb) / a.

[0090] The external standard calibration equation described above will be used in the static headspace section to back-calculate the headspace peak area into the mass of nicotine entering the column.

[0091] In this embodiment, after a predetermined volume of a standard solution of a preset concentration is injected into the gas chromatography-mass spectrometry unit for liquid analysis, the peak area of ​​nicotine in the standard solution is obtained. Based on the preset concentration, predetermined volume, and peak area of ​​nicotine in the standard solution, the external standard calibration correspondence is determined. Only conventional liquid standard substances are used; these standards are readily available, low in cost, and have good stability, eliminating the need for nicotine standard gas. The liquid injection process is highly automated and easy to operate. Furthermore, by linking the GC / MS response (dimensionless) to the mass (ng) of nicotine entering the column, a traceable quantitative benchmark is established. Thus, the entire quantitative process of the nicotine escape detection method relies solely on the liquid standard solution, avoiding the problems of difficult-to-obtain, expensive, and unstable nicotine standard gas, thereby lowering the barrier to implementation.

[0092] In one exemplary embodiment, such as Figure 3 As shown, the process of detecting nicotine samples in a static headspace unit by headspace sampling technology includes steps 302 to 306, wherein:

[0093] Step 302: After transferring the nicotine sample to be tested into the headspace vial of the static headspace unit, record the liquid phase volume.

[0094] The nicotine sample to be tested refers to a liquid, semi-solid, or solid matrix containing nicotine, including but not limited to e-cigarette liquids, heated tobacco formulations, nicotine salt solutions, free nicotine solutions, propylene glycol / glycerin / water mixtures containing nicotine, and biological samples containing nicotine. Nicotine in the sample can exist in the form of a free alkali or an organic acid salt.

[0095] A static headspace unit is a device used to heat a sample in a sealed container to a target temperature, so that volatile components reach a distribution equilibrium between the gas-liquid (or gas-solid) two phases, and quantitatively extract gas from the headspace for injection.

[0096] A static headspace unit includes headspace vials, which are sealable glass vials used to hold samples and create a closed gas-liquid equilibrium space. Headspace vials typically have a volume of 5–50 mL, for example, 20 mL. They are usually equipped with PTFE / silicone gaskets and metal sealing caps (aluminum or iron) to provide a good seal and prevent leakage under heating and pressurization conditions.

[0097] Liquid volume refers to the volume of liquid sample transferred into the headspace vial, typically expressed in mL. This parameter can be used to calculate the gas volume within the headspace vial (gas volume = nominal headspace vial volume - liquid volume).

[0098] The specific process includes: accurately transferring the nicotine sample to be tested into a headspace vial, and recording the liquid phase volume Vs (unit: mL); the gas phase volume V in the headspace vial... g Calculated by the following formula: V g =V bootle -V s Among them, V bootle The nominal volume of the headspace vial is given (e.g., 20 mL). Immediately afterward, seal the headspace vial to ensure a good seal.

[0099] Step 304: Place the sealed headspace vial in the incubation device of the static headspace unit and incubate at the target temperature until the gas-liquid two phases reach equilibrium.

[0100] The incubation device, a constant-temperature heating unit within the static headspace unit, is typically a headspace incubator or constant-temperature oven. It heats the headspace vials to a set temperature and maintains it precisely (temperature control accuracy is typically ±0.1℃). The incubation device can control the temperature within a range of 25–200℃, for example, within 25–80℃, to perform constant-temperature incubation of the headspace vials, allowing the gas-liquid phases of the sample to reach equilibrium. The incubation device can usually accommodate multiple headspace vials simultaneously and supports overlapping heating to improve analytical throughput.

[0101] The target temperature is the incubation temperature set for the experiment, that is, the temperature at which the sample reaches gas-liquid equilibrium in the headspace vial. This temperature is set according to the research purpose, such as simulating oral temperature, accelerated aging conditions, or product usage temperature.

[0102] Gas-liquid two-phase equilibrium means that in a closed headspace vial, the rate at which nicotine molecules in the liquid phase evaporate into the gas phase is equal to the rate at which nicotine molecules in the gas phase condense back into the liquid phase. At this point, the concentration of nicotine in the gas phase no longer changes with time.

[0103] The specific process of this step may include:

[0104] Place the sealed headspace vial in a headspace incubator and set the temperature to the target temperature T (e.g., 25 ℃, 37 ℃, 55 ℃, 80 ℃, etc.). Maintain constant temperature incubation until the gas-liquid two phases reach equilibrium. The equilibrium time is generally 10–60 min, which can be determined by monitoring whether the headspace peak area tends to stabilize at different equilibrium times.

[0105] Step 306: Using standard static headspace operation, inject the gas in the headspace injection quantitative loop of the static headspace unit into the gas chromatography-mass spectrometry unit and record the headspace peak area of ​​nicotine.

[0106] The static headspace sampler in a static headspace unit can be either automatic or manual, equipped with a headspace sampling metering loop of known volume, and can be periodically calibrated via gas or liquid methods. The headspace sampling metering loop measures a fixed volume of headspace gas and can be a metering loop of known volume (e.g., 0.1–5.0 mL, particularly 1.000 mL), such as a stainless steel tube. The headspace sampling metering loop is typically installed between the two ports of the six-way valve in the static headspace unit, and its volume is calibrated.

[0107] Standard static headspace operation refers to a series of standardized actions automatically performed by the static headspace sampler of the static headspace unit. These actions may include: pressurizing the headspace vial with carrier gas to a pressure slightly higher than atmospheric pressure; opening the valve to allow headspace gas to flow through the headspace sampling metering loop, filling the loop to a known volume; venting excess gas; switching the six-way valve to connect the headspace sampling metering loop to the carrier gas path; and using carrier gas to purge the gas in the headspace sampling metering loop into the headspace transfer line of the static headspace unit, which then enters the GC inlet. These operations can be controlled by the built-in program of the static headspace unit's headspace sampler without manual intervention.

[0108] In the gas chromatography-mass spectrometry (GC-MS) unit, the gas chromatography column is a capillary column. The stationary phase can be selected from weakly polar polydimethylsiloxane (PDMS) stationary phases, moderately polar 5% phenyl-95% dimethylpolysiloxane (PMS) or similar bonded phases, polar polyethylene glycol (PEG) or PEG-modified stationary phases, and polar WAX stationary phases specifically designed for the analysis of glycerol, organic acids, and nicotine. The mass spectrometry section uses electron impact ionization (EI); the ionization energy is typically 50–80 eV, for example, approximately 70 eV. Selected ion monitoring (SIM) is used to improve the sensitivity and selectivity of nicotine detection; the monitored ions include characteristic ion signals of nicotine, such as one or more of m / z 162, 161, 133, and 84.

[0109] The specific process of this step may include:

[0110] Set the headspace sampling quantitative loop volume V loop (e.g., 1.000 mL), this volume is calibrated periodically to ensure accuracy; the gas in the quantitative loop is injected into the GC / MS through standard static headspace operations such as pressurization-backfilling-valve switching; the headspace transfer line temperature is set higher than the bottle temperature to prevent nicotine condensation; the nicotine headspace peak area is recorded.

[0111] Given that the headspace sampling volume is much smaller than the total volume of the gas phase inside the bottle, the disturbance of the gas phase concentration inside the bottle caused by headspace sampling can be approximated as negligible. Therefore, the concentration in the quantitative loop can be regarded as the representative concentration of the gas phase inside the bottle.

[0112] After the above steps, the nicotine sample to be tested enters the gas chromatography-mass spectrometry unit for detection in the static headspace unit based on headspace injection technology. The data processing unit obtains the headspace peak area detected by the gas chromatography-mass spectrometry unit, which is used to calculate the nicotine escape index.

[0113] In this embodiment, after the nicotine sample to be tested is transferred to the headspace vial of the static headspace unit, the liquid volume is recorded. The sealed headspace vial is placed in the incubation device of the static headspace unit and incubated at the target temperature until the gas-liquid two phases reach equilibrium. Through standard static headspace operation, the gas in the headspace injection quantitative loop of the static headspace unit is injected into the gas chromatography-mass spectrometry unit, and the headspace peak area of ​​nicotine is recorded. Using a quantitative loop with a known volume, the injection volume is constant each time, resulting in a small relative standard deviation. Furthermore, only headspace gas is used, without contact with the sample liquid, avoiding the entry of non-volatile substances (such as glycerol, sugar, and salt) into the GC / MS, extending the column life, and reducing ion source contamination.

[0114] In one exemplary embodiment, such as Figure 4 As shown, step 106 includes steps 406 and 408. Wherein:

[0115] Step 406: Calculate the molar concentration of nicotine in headspace gas based on the mass of nicotine.

[0116] The molar concentration of nicotine in headspace gas refers to the amount of nicotine contained per unit volume in the gas phase space of a headspace vial, typically expressed in moles per cubic meter (mol / m³) or moles per liter (mol / L). Molar concentration is an intermediate physical quantity connecting mass and gas phase partial pressure.

[0117] After obtaining the mass of nicotine, the molar concentration of nicotine in the headspace gas can be calculated by combining parameters such as the volume of nicotine.

[0118] For example, in one exemplary embodiment, step 406 includes: calculating the molar concentration of nicotine in the headspace gas based on the mass of nicotine, the molar mass of nicotine, and the volume of the headspace sampling quantitative loop.

[0119] Wherein, the molar mass of nicotine is a known value, and the molar mass of nicotine M Nic = 162.23 g / mol, then the number of moles of nicotine n in a single injection sample can be calculated. inj (mol) is:

[0120]

[0121] Where, m inj This represents the mass of nicotine that enters the column of the chromatography-mass spectrometry unit during a single headspace injection.

[0122] Then, the volume V of the headspace sampling quantitative loop is... loop Converted to m³:

[0123]

[0124] Using the quantitative loop as a representative volume, calculate the molar concentration C of nicotine in headspace gas. g (Unit: mol·m) - ³) is:

[0125]

[0126] Therefore, based on the mass of nicotine, the molar mass of nicotine, and the volume of the headspace sampling quantitative loop, the molar concentration of nicotine in the headspace gas can be calculated. The molar concentration can be obtained using only three parameters, making the calculation process direct and simple.

[0127] Step 408: Calculate the gas phase partial pressure of nicotine based on the molar concentration of nicotine in the headspace gas.

[0128] This step utilizes the fundamental physical relationship between gas pressure and molar concentration to calculate the gas phase partial pressure of nicotine. There is no single method for calculating the gas phase partial pressure of nicotine based on the molar concentration of nicotine in headspace gas; the following two examples illustrate two different implementations.

[0129] In this embodiment, the molar concentration of nicotine in headspace gas is calculated based on the mass of nicotine, and the gas phase partial pressure of nicotine is then calculated based on the molar concentration. Thus, the molar concentration is calculated first, followed by the partial pressure, resulting in a clear logical chain. The mass signal measured by the instrument is converted into a physical quantity with concentration dimensions. Molar concentration is independent of the sampling volume, better reflecting the true density of nicotine in the headspace phase, facilitating subsequent partial pressure calculations. Furthermore, both the molar concentration and the gas phase partial pressure are derived from SI units, ensuring the traceability of the results.

[0130] The method for calculating the gas-phase partial pressure of nicotine based on the molar concentration of nicotine in headspace gas is not unique. In one exemplary embodiment, such as... Figure 5 As shown, step 408 includes step 508: calculating the gas phase partial pressure of nicotine based on the molar concentration of nicotine in the headspace gas, the target temperature, and the ideal gas law.

[0131] The target temperature, denoted as T, is the incubation temperature set for the nicotine sample in the static headspace unit. It is expressed in degrees Celsius (°C). When calculating the partial pressures of the gas phase, these must be converted to absolute temperature (Kelvin, K) because the ideal gas law uses an absolute temperature scale. The ideal gas law describes the relationship between pressure, volume, amount of substance, and temperature (T) of an ideal gas.

[0132] Based on the molar concentration of nicotine in the headspace gas, the target temperature, and the ideal gas law, calculate the gas-phase partial pressure P of nicotine. Nic The specific method can be:

[0133]

[0134] Among them, P Nic The vapor pressure of nicotine in the headspace is Pa; R is the ideal gas constant, the value of which depends on the system of units used. In the International System of Units (SI), R = 8.314 J / (mol·K). This constant relates energy, temperature, and the amount of substance. T is the target temperature, in K.

[0135] In this embodiment, the gas phase partial pressure of nicotine is calculated based on the molar concentration of nicotine in the headspace, the target temperature, and the ideal gas law. The ideal gas law is simple in form and requires only one multiplication operation, making the calculation simple and fast.

[0136] In another exemplary embodiment, such as Figure 6 As shown, step 408 includes step 608: calculating the gas phase partial pressure of nicotine based on the nicotine molar concentration in the headspace, the liquid phase volume, and the target temperature.

[0137] The target temperature, denoted as T, is the incubation temperature set in the static headspace unit for the nicotine sample. It is in degrees Celsius (°C). When calculating the gas phase partial pressure, it must be converted to absolute temperature (Kelvin, K).

[0138] The liquid volume refers to the volume of liquid sample transferred into the headspace vial, denoted as V. s (Unit: mL). Gas volume V in headspace vial g Calculated by the following formula: V g =V bootle -V s Among them, V bootle This refers to the nominal volume of the headspace vial (e.g., 20 mL).

[0139] Based on the nicotine molar concentration in the headspace gas, the liquid phase volume, and the target temperature, the specific method for calculating the gas phase partial pressure of nicotine can be as follows: First, calculate the total amount of nicotine in the gas phase inside the bottle, n. g The calculation method is as follows:

[0140]

[0141] Among them, C g V represents the molar concentration of nicotine in headspace gas. g This represents the volume of the gas phase inside the headspace bottle.

[0142] Next, the partial pressure P of nicotine in the gas phase was calculated. Nic The specific method can be:

[0143]

[0144] Where, n g Let R be the total amount of nicotine in the gaseous phase of the bottle, and V be the ideal gas constant, the value of which depends on the system of units used. In the International System of Units (SI), R = 8.314 J / (mol·K). This constant relates energy, temperature, and amount of substance. T is the target temperature in Kelvin, and V is the volume of nicotine. g This represents the volume of the gas phase inside the headspace bottle.

[0145] In this embodiment, the gas phase partial pressure of nicotine is calculated based on the nicotine molar concentration in the headspace gas, the liquid phase volume, and the target temperature. This provides another way to calculate the gas phase partial pressure, which is applicable to headspace bottles of different volumes and does not require changing the calculation formula.

[0146] When the sampling volume is much smaller than the total gas volume, the two calculation methods mentioned above are almost equivalent.

[0147] In one exemplary embodiment, such as Figure 7As shown, after step 106, the method for detecting nicotine escape ability also includes steps 706 to 708. Wherein:

[0148] Step 706: Obtain the escape capacity index of the reference nicotine sample under the same temperature conditions as the nicotine sample to be tested.

[0149] The escape capacity index, or nicotine vapor phase partial pressure, is measured in Pascals (Pa) or millipascals (mPa). This index directly reflects the thermodynamic driving force that drives nicotine to escape from the sample into the vapor phase.

[0150] A reference nicotine sample refers to a pre-selected standard formulation or standard substance with a fixed composition and stable properties, used as a comparison benchmark. For example, a reference nicotine sample might be a free nicotine system with a PG:VG ratio of 50:50. This reference sample should have the same or similar matrix type as the sample to be tested (e.g., both being e-liquids), but can be selected as needed.

[0151] The same temperature conditions refer to the reference nicotine sample and the analyte nicotine sample being incubated at the exact same temperature (e.g., 37°C) during headspace equilibrium. Temperature is a key factor affecting escape ability. The hardware used in this embodiment is also a static headspace unit, a gas chromatography-mass spectrometry unit, and a data processing unit.

[0152] The specific process of this step may include: obtaining a reference nicotine sample in a static headspace unit, entering a gas chromatography-mass spectrometry unit based on headspace injection technology, and detecting the headspace peak area; calculating the mass of nicotine entering the chromatographic column in a single headspace injection based on the headspace peak area and the preset external standard calibration correspondence; and calculating the gas phase partial pressure of nicotine based on the mass of nicotine, as an escape capacity index characterizing the escape capacity of nicotine.

[0153] Step 708: Obtain the relative escape capacity index based on the escape capacity index of the nicotine sample to be tested and the escape capacity index of the reference nicotine sample.

[0154] The relative escape index is a dimensionless ratio. The specific way to obtain the relative escape index is as follows: the ratio of the escape index of the nicotine sample to that of the reference nicotine sample is used as the relative escape index.

[0155] Relative Escape Capability Index (NEI) rel The specific calculation formula can be:

[0156]

[0157] Among them, PNic (materix,T) represents the escape index of the nicotine sample to be tested, P Nic (ref,T) represents the escape ability index of the reference nicotine sample.

[0158] The relative escape index (NEI) reflects the relative escape ability of the nicotine sample relative to the reference nicotine sample. rel >1 indicates that the nicotine sample being tested has a greater escape capacity than the reference nicotine sample; if NEI rel If the value is less than 1, it is less than the reference nicotine sample; if it is equal to 1, the two are equal.

[0159] In this embodiment, the escape index of a reference nicotine sample under the same temperature conditions as the nicotine sample to be tested is obtained. Based on the escape index of the nicotine sample to be tested and the escape index of the reference nicotine sample, a relative escape index is obtained. Absolute escape indices may deviate between different batches of experiments, different instruments, and different laboratories (e.g., due to differences in the slope of calibration curves). By calculating the relative index, using a reference sample from the same batch as a benchmark, the comparability of results can be significantly improved. During formulation optimization, only the relative index needs to be compared, eliminating the need for complete absolute calibration each time, saving time and standards.

[0160] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps. It is understood that the steps in different embodiments can be freely combined as needed, and all non-contradictory solutions formed by such combinations are within the scope of protection of this application.

[0161] This application also provides a device for detecting nicotine escape ability, such as Figure 8As shown, the system includes a static headspace unit, a gas chromatography-mass spectrometry (GC-MS) unit, and a data processing unit. The static headspace unit is connected to the GC-MS unit, and the GC-MS unit is connected to the data processing unit. The data processing unit is used to implement the method of any of the above embodiments. Exemplarily, the transmission line outlet of the static headspace unit is directly connected to the GC inlet. The GC column outlet is connected to the MS interface. The MS data output port is connected to the data processing unit via a network cable or USB.

[0162] A static headspace unit (SHU) is a device used to heat a sample in a sealed container to a target temperature, allowing volatile components to reach equilibrium between the gas-liquid (or gas-solid) phases, and then quantitatively extracting gas from the headspace for injection. Its basic structure includes: a sealable headspace vial, an incubation device, an injection device, a flow path switching valve, and a gas transfer line (headspace transfer line). The static aspect of a static headspace unit is that no gas is purged into the vial during the equilibrium process; gas is only extracted once during sampling.

[0163] A gas chromatography-mass spectrometry (GC / MS) unit is an analytical system consisting of a gas chromatograph and a mass spectrometer detector connected in series. The gas chromatograph is responsible for separating the components in the gas mixture from the static headspace unit according to their boiling points or polarity differences; the mass spectrometer detector is responsible for ionizing and fragmenting the separated components and detecting their characteristic ions, thereby achieving qualitative and quantitative analysis.

[0164] The data processing unit is connected to the gas chromatography-mass spectrometry (GC-MS) unit and can acquire data from the GC-MS unit. The data processing unit includes a processor and a memory. The memory stores a computer program, and when the processor executes the computer program, it implements the steps of the nicotine escape detection method of each embodiment.

[0165] In one exemplary embodiment, the static headspace unit is equipped with a headspace sampling quantitative loop with a fixed volume. The headspace sampling quantitative loop measures a fixed volume of headspace gas and can be a quantitative loop of known volume (e.g., 0.1–5.0 mL, particularly 1.000 mL), such as a stainless steel tube. The headspace sampling quantitative loop is typically installed between the two ports of the six-way valve of the static headspace unit, and its volume is calibrated.

[0166] In this embodiment, the static headspace unit is equipped with a headspace sampling quantitative loop with a fixed volume. During each sample injection, the headspace sampling quantitative loop is completely filled with headspace gas, thereby ensuring a constant volume of sample entering the GC.

[0167] In one exemplary embodiment, the operating temperature of the headspace transfer line of the static headspace unit is higher than the temperature of the headspace bottle.

[0168] The headspace transfer line can be a heated conduit connecting the outlet of the six-way valve of the static headspace unit to the GC inlet, typically made of stainless steel or quartz capillary tube with inert inner walls. The operating temperature of the headspace transfer line of the static headspace unit is higher than the temperature of the headspace vial, for example, 5-50°C higher, to prevent nicotine from condensing during transport and to ensure quantitative sample transfer.

[0169] In this embodiment, the operating temperature of the headspace transfer line of the static headspace unit is higher than that of the headspace bottle to prevent nicotine from condensing during the transfer process, thereby significantly improving the recovery rate and repeatability of high-boiling-point components.

[0170] In an exemplary embodiment, the gas chromatography-mass spectrometry unit uses a capillary column. Specifically, a capillary column refers to a fused silica column with an inner diameter of 0.1–0.53 mm and a length of 10–60 m, with its inner wall coated with a stationary phase. Capillary columns can provide high separation efficiency, separating nicotine from other volatile components in the sample (such as propylene glycol, glycerol, and fragrances) while avoiding matrix interference.

[0171] In this embodiment, the gas chromatography column in the gas chromatography-mass spectrometry unit is a capillary column, which can improve the specificity of mass spectrometry detection. Especially when using ion monitoring mode, clean chromatographic peaks can improve quantitative accuracy.

[0172] In one exemplary embodiment, the gas chromatography-mass spectrometry unit employs ion monitoring for detection. Ion monitoring means that the mass spectrometer scans only a few preset characteristic mass numbers, rather than scanning the full mass range. This embodiment can monitor four characteristic ions of nicotine: m / z 84 (base peak), 133, 161, and 162. m / z 162 is a molecular ion, commonly used for quantitative analysis. Using ion monitoring improves the sensitivity and selectivity of nicotine detection and reduces background noise.

[0173] To better understand the above embodiments, a specific embodiment is provided below for detailed explanation. In one embodiment, a traceable quantitative chain of "liquid sample injection external standard calibration + static headspace quantification + ideal gas law" is proposed to realize a method for detecting nicotine escape capacity. A general-purpose GC / MS platform is used to directly convert the headspace response into nicotine headspace molar concentration and partial pressure (vapor pressure), and an escape capacity index is defined to achieve a comparable evaluation of nicotine escape capacity under different e-liquid matrices and conditions. This application also provides a device for detecting nicotine escape capacity to implement this method.

[0174] A calibration curve between the nicotine content on the chromatographic column and the instrument response was established using liquid injection technology. The nicotine content entering the chromatographic column in the headspace was determined by headspace injection technology, thereby inferring the nicotine content in the gaseous state in the headspace vial. The amount of nicotine in the gaseous state was then calculated, and the vapor pressure of nicotine in the gaseous state was obtained.

[0175] The device for detecting nicotine escape capacity includes a static headspace unit, a gas chromatography-mass spectrometry unit, and a data processing unit, wherein:

[0176] Static headspace elements include:

[0177] Headspace vials: with a volume of 5–50 mL, preferably about 20 mL;

[0178] Bottle caps and gaskets: PTFE / silicone gaskets are used, along with aluminum or iron caps to ensure good sealing.

[0179] Headspace incubator or constant temperature oven: The temperature can be controlled in the range of 25 to 200 ℃, preferably in the range of 25 to 80 ℃, and is used to incubate headspace vials at a constant temperature to bring the gas-liquid two phases of the sample to equilibrium.

[0180] Static headspace sampler: Can be an automatic or manual static headspace sampler, equipped with a quantitative loop V of known volume. loop (e.g., 0.1 to 5.0 mL, preferably about 1,000 mL), and can be calibrated periodically by gas or liquid methods;

[0181] Headspace transfer line: Used to introduce headspace gas from the quantitative loop into the gas chromatograph injection port. Its operating temperature is set higher than the headspace vial temperature (e.g., 5-30°C higher) to prevent nicotine from condensing during the transfer process.

[0182] Gas chromatography-mass spectrometry (GC / MS) unit includes:

[0183] Gas chromatography section:

[0184] The gas chromatography column is a capillary column, and its stationary phase can be selected from weakly polar polydimethylsiloxane stationary phases, moderately polar 5% phenyl-95% dimethylpolysiloxane or similar bonded phase stationary phases, polar polyethylene glycol (PEG) or polyethylene glycol modified stationary phases, as well as polar WAX stationary phases specifically used for the analysis of glycerol, organic acids and nicotine.

[0185] Mass spectrometry section:

[0186] Ionization method: Electron ionization (EI) is used.

[0187] Ionization energy: generally 50–80 eV, preferably about 70 eV;

[0188] Specific parameters such as GC / MS interface temperature and ion source temperature are described below;

[0189] Detection method: Selected ion monitoring (SIM) is preferred to improve the sensitivity and selectivity of nicotine detection;

[0190] Monitored ions: including characteristic ion signals of nicotine, such as one or more of m / z 162, 161, 133, 84.

[0191] The data processing unit includes a processor and a memory, in which programs for performing the following calculation steps are stored:

[0192] External standard calibration module: Establishing peak area Y and column mass m col Relationship ;

[0193] Headspace inverse calculation module: based on headspace peak area A HS Back-calculation of the mass m entering the column inj = (A HS - b) / a;

[0194] Vapor pressure calculation module: based on m inj V loop Calculate the gas phase molar concentration of nicotine C using the formula T. g and vapor pressure P Nic ;

[0195] NEI indicator module: Output NEI = P Nic and NEI rel ;

[0196] The Quality Control and Uncertainty Assessment module (optional) is used to assess linearity, repeatability, and systematic errors.

[0197] The above units are connected through a data communication interface to form a complete system from sample preparation, headspace equilibration, GC / MS analysis to data processing and index output.

[0198] Instrument and method parameters include:

[0199] Gas chromatography (GC) conditions

[0200] Chromatographic column: The gas chromatography column is a capillary column, and its stationary phase can be selected from one of the following or its equivalents:

[0201] (1) Weakly polar polydimethylsiloxane columns;

[0202] (2) Medium polarity 5% phenyl-95% dimethylpolysiloxane or similar bonded phase column;

[0203] (3) Polar polyethylene glycol (PEG) or polyethylene glycol modified stationary phase column;

[0204] (4) Polar WAX columns specifically designed for the analysis of glycerol, organic acids, nicotine, etc., including but not limited to DB-WAX, DB-Heavy-WAX, or their equivalent column types.

[0205] Inlet temperature: 220~250 ℃;

[0206] Injection volume (liquid injection): 0.2~2.0μL;

[0207] Heating program:

[0208] Initial temperature 30~60 ℃, hold for 3 min;

[0209] Increase the temperature to 220℃ at a rate of 10~30 ℃ / min and hold for 1~5 min;

[0210] Then increase the temperature to 250℃ at a rate of 2~5℃ / min and hold for 1~5 min;

[0211] Carrier gas: Helium (purity > 99.999%), flow rate 1.0~1.5 mL / min;

[0212] Injection method: split injection, split ratio 5:1~50:1.

[0213] Mass spectrometry (MS) conditions include:

[0214] GC / MS interface temperature: 230~280℃;

[0215] Ion source temperature: 200~260℃;

[0216] Ionization method: Electron impact source (EI);

[0217] Ionization energy: 50~80 eV;

[0218] Monitoring methods: full scan (SCAN) and / or selected ion monitoring (SIM);

[0219] Monitoring ions: Characteristic ion peaks containing nicotine, preferably including at least two characteristic ions in the m / z range of 84 to 180.

[0220] Headspace system conditions include:

[0221] Headspace vial volume: 5~50 mL;

[0222] Headspace caps and gaskets: PTFE / silicone gaskets, aluminum caps, or iron caps;

[0223] Headspace incubation temperature: 25–200 ℃ (e.g., 37 ℃, etc.) can be set.

[0224] Headspace equilibration time: 10–60 min (can be determined experimentally to stabilize the headspace peak area);

[0225] Headspace sampling method: automated static headspace, quantitative loop volume V loop (The volume is 0.5~5.0 mL, and it should be calibrated periodically using either gas or liquid methods).

[0226] Headspace transfer line temperature: 5~50°C higher than the headspace bottle temperature to prevent nicotine from condensing during transfer.

[0227] Preparation of standard solutions and external standard calibration (liquid injection):

[0228] Preparation of standard solutions:

[0229] Accurately weigh 10 mg of nicotine reference standard into a 10 mL volumetric flask, add isopropanol to dilute to volume and mix well to obtain a 1000 μg / mL nicotine standard stock solution;

[0230] Accurately transfer 1.0 mL of the stock solution into a 10 mL volumetric flask, dilute to volume with isopropanol and mix well to obtain an intermediate solution of 100 μg / mL;

[0231] Prepare a series of standard solutions with concentration gradients using stock solutions and intermediate solutions, for example: 10, 100, 1000, 5000, 10000, 20000 ng / mL.

[0232] GC / MS Analysis and Peak Area Recording:

[0233] Under the above GC / MS conditions, 1 μL of liquid was injected into each concentration standard solution for analysis.

[0234] Record the SIM peak area Y of nicotine (e.g., based on m / z 162 or the area of ​​the main characteristic ion peak, or the integrated peak area under the total ion chromatogram).

[0235] Linear equation establishment:

[0236] Under the premise of constant injection volume and split settings, the mass m of nicotine entering the column col (Unit: ng) can be calculated equivalently from the standard solution concentration and injection volume, and its transfer factor is absorbed by the curve slope;

[0237] Nicotine enters the column mass m col Using the x-axis as the abscissa and the peak area Y as the y-axis, a linear or weighted linear fit (e.g., 1 / x) is performed to obtain the external standard calibration equation:

[0238] Where a is the slope and b is the intercept;

[0239] Taking a specific calibration as an example, with a linear range of 0.01–20 ng (corresponding to a solution concentration of 10–20000 ng / mL, 1 μL injection), the fitting result can be: Therefore, the inverse function for calculating the mass of a column is defined as: m col =(Yb) / a.

[0240] The aforementioned external standard calibration equation will be used in the static headspace section to back-calculate the headspace peak area into the nicotine mass entering the column.

[0241] Headspace balancing and sample introduction (headspace section):

[0242] Sample bottling:

[0243] Accurately transfer the e-liquid sample (containing nicotine, free or salt form) into a 20 mL headspace vial and record the liquid volume Vs (unit: mL).

[0244] headspace gas volume V g Calculated by the following formula:

[0245] V g =V bootle -Vs. Where V bootle The nominal volume of the headspace vial (e.g., 20 mL);

[0246] Seal immediately to ensure a good seal.

[0247] isothermal equilibrium:

[0248] Place the sealed headspace vial in a headspace incubator and set the temperature to the target temperature T (e.g., 25 ℃, 37 ℃, 55 ℃, 80 ℃, etc.).

[0249] Maintain constant temperature incubation until the gas-liquid two phases reach equilibrium. The equilibrium time is generally 10–60 min, which can be determined by monitoring whether the headspace peak area tends to stabilize at different equilibrium times.

[0250] Headspace injection:

[0251] Set the headspace sampling quantitative loop volume V loop (For example, 1.000 mL), this volume is calibrated regularly to ensure accuracy;

[0252] Gas in the metering loop is injected into the GC / MS through standard static headspace operations such as pressurization, backfilling, and valve switching.

[0253] The headspace transfer line temperature is set higher than the bottle temperature to prevent nicotine condensation.

[0254] Record the area of ​​the nicotine peak A HS (SIM mode).

[0255] Given that the headspace sampling volume is much smaller than the total volume of the gas phase inside the bottle, the disturbance of the gas phase concentration inside the bottle caused by headspace sampling can be approximated as negligible. Therefore, the concentration in the quantitative loop can be regarded as the representative concentration of the gas phase inside the bottle.

[0256] Headspace quantification and vapor pressure (partial pressure) calculation:

[0257] This application establishes a complete quantitative link from chromatographic signal to vapor pressure using external standard calibration equations and headspace peak areas. The specific steps are as follows:

[0258] Calculation of mass of a single headspace injection into the column:

[0259] The calibration equation obtained from the liquid external standard is:

[0260]

[0261] The top-space peak area A HS Substituting the values, we obtain the mass of nicotine entering the column in a single headspace injection:

[0262] m inj =(A HS -b) / a, the unit is ng.

[0263] Nicotine molar number calculation:

[0264] Given the molar mass M of nicotine Nic = 162.23 g / mol, then the number of moles of nicotine in a single injection sample is:

[0265]

[0266] Headspace molar concentration calculation:

[0267] The volume V of the quantitative loop loop Convert to m³: V loop (m 3 )=V loop (mL)×10 -6 .

[0268] Using the quantitative loop as a representative volume, the molar concentration C of nicotine in headspace gas g (Unit: mol·m)- ³) is: C g =n inj / V loop

[0269] Partial pressure / vapor pressure calculation (ideal gas approximation):

[0270] Using the ideal gas law: P Nic =C g R·T. Where: P Nic R is the partial pressure / vapor pressure in the headspace phase (Pa); R = 8.314 J / (mol·K), and T is the absolute temperature (K).

[0271] It can also be calculated using the gas volume Vg inside the bottle:

[0272] n g =C g ·V g (m) 2 ), P Nic =(n g RT) / V g .

[0273] When the sampling volume is much smaller than the total gas volume, the two calculation methods mentioned above are equivalent.

[0274] Definition of Escape Capability Index

[0275] This application defines the partial pressure of nicotine in the vapor phase (Pa or mPa) as the Nicotine Escape Index (NEI): NEI = P Nic

[0276] To facilitate comparisons under different formulations or conditions, the relative escape index (NEI) can be further defined. rel :

[0277]

[0278] Among them, P Nic (materix,T) represents the escape index of the nicotine sample to be tested, P Nic (ref,T) represents the escape capability index of the reference nicotine sample. The escape capability index and the relative escape capability index constitute a unified index system for characterizing nicotine escape capability.

[0279] The following are several embodiments of the detection method and apparatus for nicotine escape ability provided in this application:

[0280] Example 1: NEI calculation example based on PG / VG e-liquid matrix:

[0281] Taking the Agilent 7890B-5977B GC / MS platform and DB-Heavy-WAX column as an example, the preferred parameters are as follows:

[0282] 1) Gas chromatography (GC) conditions

[0283] Column: DB-Heavy-WAX (30 m × 0.25 mm × 0.25 μm);

[0284] Inlet temperature: 250 ℃;

[0285] Injection volume (liquid injection): 1 μL;

[0286] Heating program:

[0287] Initial temperature 40 ℃, hold for 3 min;

[0288] Increase the temperature to 220℃ at a rate of 30℃ / min and hold for 1 min;

[0289] Increase the temperature to 250 °C at a rate of 5 °C / min and hold for 2 min.

[0290] Carrier gas: Helium (purity > 99.999%), flow rate 1.0 mL / min;

[0291] Injection method: split injection, split ratio 20:1.

[0292] 2) Mass Spectrometry (MS) Conditions

[0293] GC / MS interface temperature: 260 ℃;

[0294] Ion source temperature: 230 ℃;

[0295] Ionization method: Electron impact source (EI);

[0296] Ionization energy: 70 eV;

[0297] Monitoring method: SIM;

[0298] Monitoring ions: m / z 162, 161, 133, 84 (characteristic ions of nicotine).

[0299] Instrument platform: Agilent 7890B-5977B GC / MS;

[0300] Column: DB-Heavy-WAX (30 m × 0.25 mm × 0.25 μm);

[0301] 3) Headspace conditions

[0302] Headspace vial volume: 20 mL;

[0303] Headspace caps and gaskets: PTFE / silicone gaskets, metal caps;

[0304] Headspace incubation temperature: T = 310K (37 ℃);

[0305] Headspace equilibration time: 30 min;

[0306] Headspace sampling method: automated static headspace, quantitative loop volume V loop = 1.000mL;

[0307] Headspace transfer line temperature: 80°C higher than the headspace bottle temperature to prevent nicotine from condensing during transport.

[0308] External standard solvent: isopropanol;

[0309] Example of external standard calibration results:

[0310] Liquid injection was performed using nicotine standard solution, and the mass m entering the column was obtained as shown in Table 1. col Correspondence between peak area Y and peak area Y (example data):

[0311] Table 1

[0312]

[0313] The calibration curve equation obtained by linear fitting is: Y = 4772.9 m col + 52.6, R 2 =0.9995.

[0314] Sample headspace analysis:

[0315] Matrix: PG:VG = 50:50 (mass ratio);

[0316] Nicotine content: 3% (mass fraction), free of organic acids and water;

[0317] Headspace incubation temperature: 37 ℃;

[0318] Headspace equilibration time: 30 min;

[0319] The nicotine peak area was obtained by GC / MS SIM analysis after headspace injection.

[0320] A HS =47968

[0321] Enter column mass calculation:

[0322]

[0323] Mole count calculation:

[0324]

[0325] Molar concentration calculation:

[0326]

[0327]

[0328] Voltage divider / NEI calculation:

[0329]

[0330]

[0331] Thus, the nicotine escape index (NEI) was obtained under the conditions of PG:VG = 50:50, 3% nicotine, and 37 ℃.

[0332] Example 2: The effect of different PG / VG ratios on NEI:

[0333] Under the same nicotine content and temperature, change the PG:VG ratio (e.g., 70:30, 50:50, 30:70, etc.) and calculate the NEI using the method described above. Figure 9 As shown, the results indicate that:

[0334] As the proportion of VG increases, the vapor pressure (NEI) of nicotine in the gas phase increases, indicating that VG has a weaker "capture" ability for nicotine than PG, and nicotine is more likely to escape into the gas phase.

[0335] Example 3: Effects of different organic acid systems on NEI:

[0336] Nicotine lactate and nicotine benzoate systems were prepared separately under the same total nicotine content and PG / VG matrix, and the acid-base molar ratio was controlled. The NEI was calculated according to the method described above. Figure 10 As shown, typical observations are as follows:

[0337] The higher the alkali ratio, the higher the proportion of free nicotine in the system, the larger the NEI, and the higher the nicotine vapor pressure;

[0338] Under the same conditions, the nicotine NEI in the lactate system is often higher than that in the benzoate system, indicating that different organic acids have different regulatory effects on nicotine escape ability.

[0339] Example 4: Correlation between nicotine content and NEI:

[0340] Under the same matrix and temperature, change the nicotine content (e.g., 1%, 3%, 5%) and calculate the NEI using the method described above. Figure 11 As shown, the results are as follows:

[0341] Under conditions where free nicotine dominates, the nicotine vapor pressure (NEI) has an approximately linear relationship with the nicotine content.

[0342] The above-mentioned method and apparatus for detecting nicotine escape ability have the following technical effects:

[0343] 1. Construct a traceable, absolutely quantitative link.

[0344] A calibration function of "nicotine mass entering the column - peak area" was established by liquid injection. This function was then used in the static headspace section to back-calculate the headspace peak area into the mass entering the column, and then converted into headspace molar concentration and partial pressure (vapor pressure). This process eliminates the subjectivity and incomparability of inferences based solely on peak area or relative concentration, and solves the core problem of the lack of absolute quantification.

[0345] 2. Perform vapor pressure calculations without using nicotine standard gas, reducing equipment and operational barriers.

[0346] This application is based entirely on external standard calibration using liquid-phase standard solutions. It does not require the preparation and use of nicotine gaseous standard materials, nor does it rely on a dedicated vapor pressure tester or real-time mass spectrometry equipment. The nicotine vapor pressure can be calculated using only a general-purpose GC / MS with a static headspace apparatus.

[0347] Therefore, this application significantly reduces the equipment threshold and methodological complexity for nicotine vapor pressure quantification, making it more suitable for widespread application in R&D and quality control environments.

[0348] 3. Obtain the "Nicole Escape Index (NEI)," which has excellent comparability.

[0349] By defining the gaseous partial pressure of nicotine in the headspace as the escape capacity index (NEI), the relative escape capacity index (NEI) can be further obtained. rel This application provides a unified, quantifiable, and directly comparable index system for nicotine escape behavior under different e-liquid matrices (different PG / VG ratios, water content, different organic acid salt types, different nicotine contents) and different temperature conditions.

[0350] Compared with traditional methods that only compare peak area or nicotine content, the NEI / NEIrel output by this application has stronger comparability across formulations, batches, and devices.

[0351] 4. Reduce costs and methodological complexity

[0352] The method of this application does not rely on a specific Henry constant or a complex thermodynamic model, and can be directly applied to PG, VG, PG / VG mixed systems, aqueous systems, and systems with different nicotine salts (such as lactate, benzoate, etc.).

[0353] Regardless of whether nicotine is in a free alkaline state or a salt form, this application characterizes its escape capacity by actually measuring the headspace partial pressure, thereby achieving a unified characterization method and wide applicability in complex formulations.

[0354] 5. Adaptable to complex substrates and morphologies

[0355] This method does not rely on a specific Henry's constant or a prior activity model, and directly performs headspace quantitative and partial pressure calculations in PG, VG, aqueous mixtures, and nicotine salt systems; it can further establish the isothermal relationship of NEI (pNic) with temperature for mechanism analysis and formulation optimization.

[0356] 6. Provide quantitative tools for formulation design and risk assessment

[0357] By changing the PG / VG ratio, nicotine content, pH ratio and temperature, and using the method of this application to determine NEI, the effects of formulation and process on nicotine escape ability can be systematically studied, guiding the formulation optimization of electronic atomizing liquids and heated non-combustible products.

[0358] Meanwhile, NEI data at multiple temperatures can also be used to fit thermodynamic parameters such as heat of volatilization, providing quantitative basis for user exposure assessment and product safety studies.

[0359] Therefore, this application not only provides an analytical method, but also forms a set of engineering tools that can be directly used for product development and risk assessment.

[0360] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0361] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0362] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for detecting nicotine escape ability, characterized in that, The method includes: The headspace peak area of ​​the nicotine sample to be tested is obtained after it enters the gas chromatography-mass spectrometry unit in the static headspace unit based on headspace injection technology. Based on the headspace peak area and the preset external standard calibration correspondence, the mass of nicotine entering the chromatographic column of the chromatography-mass spectrometry unit in a single headspace injection is calculated. The partial pressure of nicotine in the gas phase is calculated based on the mass of the nicotine; the partial pressure of nicotine in the gas phase is used as an escape capacity index characterizing the escape capacity of nicotine.

2. The method according to claim 1, characterized in that, The process of determining the correspondence between the external standard calibrations includes: After a predetermined volume of liquid is injected into a standard solution of a preset concentration by the gas chromatography-mass spectrometry unit, the peak area of ​​nicotine in the standard solution is obtained. The external standard calibration correspondence is determined based on the preset concentration of the standard solution, the predetermined volume, and the peak area of ​​nicotine in the standard solution.

3. The method according to claim 1, characterized in that, The process by which the nicotine sample to be tested enters the gas chromatography-mass spectrometry unit for detection in the static headspace unit based on headspace sampling technology includes: After transferring the nicotine sample to be tested into the headspace vial of the static headspace unit, the liquid phase volume is recorded. The sealed headspace vial is placed in the incubation device of the static headspace unit and incubated at the target temperature until the gas-liquid two phases reach equilibrium. By using standard static headspace operation, the gas in the headspace injection quantitative loop of the static headspace unit is injected into the gas chromatography-mass spectrometry unit, and the headspace peak area of ​​nicotine is recorded.

4. The method according to claim 3, characterized in that, The calculation of the gas phase partial pressure of nicotine based on the mass of nicotine includes: Calculate the molar concentration of nicotine in headspace gas based on the mass of nicotine mentioned above; The gas phase partial pressure of nicotine is calculated based on the molar concentration of nicotine in the headspace gas.

5. The method according to claim 4, characterized in that, The calculation of the gas phase partial pressure of nicotine based on the nicotine molar concentration in the headspace gas includes: The gas phase partial pressure of nicotine is calculated based on the nicotine molar concentration in the headspace, the target temperature, and the ideal gas law.

6. The method according to claim 4, characterized in that, The calculation of the gas phase partial pressure of nicotine based on the nicotine molar concentration in the headspace gas includes: The gas phase partial pressure of nicotine is calculated based on the nicotine molar concentration in the headspace, the liquid phase volume, and the target temperature.

7. The method according to claim 4, characterized in that, The calculation of the nicotine molar concentration in headspace gas based on the mass of nicotine includes: The molar concentration of nicotine in the headspace gas is calculated based on the mass of nicotine, the molar mass of nicotine, and the volume of the headspace sampling quantitative loop.

8. The method according to claim 1, characterized in that, After calculating the gas phase partial pressure of nicotine based on the mass of nicotine, the method further includes: Obtain the escape capacity index of the reference nicotine sample under the same temperature conditions as the nicotine sample to be tested; The relative escape capacity index is obtained based on the escape capacity index of the nicotine sample to be tested and the escape capacity index of the reference nicotine sample.

9. A device for detecting nicotine escape ability, characterized in that, The device includes a static headspace unit, a gas chromatography-mass spectrometry unit, and a data processing unit. The static headspace unit is connected to the gas chromatography-mass spectrometry unit, and the gas chromatography-mass spectrometry unit is connected to the data processing unit. The data processing unit is used to implement the method described in any one of claims 1-8.

10. The apparatus according to claim 9, characterized in that, The static headspace unit is equipped with a headspace sampling quantitative circuit with a fixed volume.

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