SEM-EDS-based method for quantitatively detecting content of silicon dioxide in nicotine bag

Abstract

The invention relates to the technical field of quality control of novel buccal products, in particular to a method for quantitatively detecting the content of silicon dioxide in a nicotine bag based on SEM-EDS. The method provided by the invention comprises the following steps: firstly, pretreating nicotine bag powder, and separating to obtain an insoluble phase; grinding and mixing the insoluble phase and a specific internal standard substance in proportion; the method comprises the following steps: establishing a standard curve between the mass ratio of SiO2 to an internal standard substance and the Si / Mg element signal ratio measured by EDS by preparing a series of standard samples; and finally, measuring a to-be-measured sample by using SEM-EDS, substituting the obtained Si / Mg ratio average value into the standard curve, and accurately calculating the mass percent of silicon dioxide in the nicotine bag by combining a calculation formula. The method effectively overcomes the problems of interference and physical separation of complex matrixes, has the advantages of being simple in pretreatment, rapid in analysis, low in cost, high in precision, high in accuracy and the like, and is suitable for quality control and compliance verification of nicotine bag products.

Description

Technical Field

[0001] This invention relates to the field of quality control technology for novel oral products, and in particular to a method for quantitatively detecting the silica content in nicotine bags based on SEM-EDS. Background Technology

[0002] Nicotine pouches are a novel type of oral product with a complex composition, primarily consisting of over ten components including nicotine tartrate, microcrystalline cellulose, potassium sorbate, sodium alginate, sodium chloride, silicon dioxide, xylitol, flavoring, WS-23, glycerin, water, sodium carbonate, and sucralose. Among these components, silicon dioxide acts as an anti-caking agent and flow aid, playing a crucial role in maintaining the product's texture and processing properties. Therefore, accurate and rapid content analysis of key inorganic components (such as sodium chloride and silicon dioxide) in nicotine pouches is of great significance for product quality control, compliance assessment, and new product development.

[0003] Currently, the detection of inorganic components in nicotine bags faces three main technical challenges: (1) Severe matrix interference: The product contains a large number of organic components (such as microcrystalline cellulose, sodium alginate, fragrance, etc.) and various inorganic salts (such as sodium carbonate, potassium sorbate). Traditional chemical analysis methods (such as chloride ion titration and silicomolybdenum blue colorimetric method) are easily interfered with by coexisting ions (such as carbonate, organic acid, etc.), resulting in low selectivity and accumulation of systematic errors; (2) Difficult physical separation: Silica and microcrystalline cellulose and other excipients have similar physical properties, and conventional filtration methods are difficult to separate them effectively, affecting the accuracy of subsequent quantification; (3) Existing instrument methods have obvious limitations: For example, ICP-MS / AES requires complex acid digestion pretreatment and has high equipment costs; XRF has low sensitivity to light elements (Na, Si) and cannot distinguish between inorganic chlorine and organic chlorine; Gravimetric methods are prone to overestimation of results due to the presence of organic matter (such as sodium alginate) or residual microcrystalline cellulose in the precipitate.

[0004] While existing analytical techniques such as ion chromatography (IC), high-performance liquid chromatography (HPLC), near-infrared spectroscopy (NIR), and thermogravimetric analysis (TG) are widely used in tobacco component analysis, they still have significant limitations. For example, thermogravimetric analysis has limited detection capabilities for inorganic components such as silica; chromatographic methods involve complex and time-consuming pretreatment and are easily affected by interference in complex matrices; and while near-infrared spectroscopy offers advantages such as speed and non-destructive testing, its quantitative accuracy for specific components is relatively low, making it difficult to meet the detection requirements of multi-component systems in nicotine pouches.

[0005] Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), as an elemental analysis technique based on characteristic X-rays, has been widely applied in materials science, environmental science, and food science, offering advantages such as micro-area analysis capabilities and minimal sample pretreatment. In tobacco-related research, SEM-EDS has been used to analyze inorganic components (such as aluminosilicates, silicon, and calcium compounds) in smoke particles and leaf surfaces. However, current work is mostly limited to qualitative characterization, and quantitative methods for specific components in nicotine pouches (such as sodium chloride, silica, and potassium sorbate) have not yet been established. Furthermore, the complexity of the matrix, sample homogeneity, and inter-element interference effects also limit the further development of SEM-EDS's quantitative applications in this field.

[0006] Therefore, the industry urgently needs to develop an efficient and integrated detection method that can adapt to the complex matrix of nicotine bags. This method should have core capabilities such as high selectivity (able to distinguish target components from interfering substances), accuracy verification mechanism (correcting errors introduced by co-precipitation or encapsulation), and integrated process (avoiding repeated sample processing).

[0007] Based on the aforementioned challenges and requirements, this invention proposes using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) as the core analytical technique. The aim is to establish a multi-parameter coupled quantitative method based on micro-area analysis, focusing on solving the following key problems: how to achieve the separation and accurate quantification of silica in highly interfering matrices, effectively eliminating the influence of insoluble coexisting substances such as microcrystalline cellulose; and how to construct a low-cost, high-efficiency integrated analytical scheme to achieve silica detection and data cross-validation, thereby improving the reliability and efficiency of analytical results. Summary of the Invention

[0008] In view of the above challenges and needs, this invention proposes an analytical method based on scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) to quantitatively detect the content of silica using an internal standard method (e.g., magnesium stearate as an internal standard). This method combines chemical precipitation and elemental analysis, is simple to operate, and has high accuracy, overcoming the shortcomings of traditional methods (such as ion chromatography, liquid chromatography, and inductively coupled plasma mass spectrometry) which have complex pretreatment and are time-consuming.

[0009] The first aspect of this invention provides a method for quantitatively detecting the silica content in nicotine bags based on SEM-EDS, comprising the following steps: (1) Sample pretreatment: Weigh the nicotine bag contents powder sample, add anhydrous ethanol for ultrasonic treatment, centrifuge to separate and collect the insoluble phase, wash and dry and weigh; (2) Addition and mixing of internal standard: The dried insoluble phase is mixed with the selected internal standard in a predetermined mass ratio and ground until the particles are evenly distributed; the internal standard is a compound that is stable under EDS detection conditions and whose characteristic X-ray peaks do not overlap with the characteristic peaks of silicon. (3) Standard curve plotting: Prepare a series of standard samples containing silicon dioxide and the internal standard, wherein the mass ratio of silicon dioxide to the internal standard changes in a gradient; after grinding and mixing each standard sample, use SEM-EDS to measure the mass percentage ratio of Si element to characteristic element of internal standard, and use this ratio to perform linear fitting on the mass ratio of silicon dioxide to internal standard to obtain the standard curve equation. (4) Sample testing and calculation: The sample prepared in step (2) is placed under SEM-EDS for detection. Multiple areas are randomly selected for surface scanning. The average value of the mass percentage ratio of Si element to the characteristic element of the internal standard is calculated. The average value is substituted into the standard curve equation to calculate the mass ratio of silicon dioxide to the internal standard in the sample, and then the content of silicon dioxide in the nicotine bag is calculated.

[0010] In some embodiments of the present invention, in step (1), the temperature of the ultrasonic treatment is 20~40°C and the time is 30~40 minutes.

[0011] In some embodiments of the present invention, in step (1), the centrifugation speed is 5000~10000 rpm and the centrifugation time is 2~5 minutes.

[0012] In some embodiments of the present invention, in step (1), the washing involves washing the insoluble phase with anhydrous ethanol 2 to 3 times.

[0013] In some embodiments of the present invention, in step (2), the internal standard is selected from any one of magnesium stearate, magnesium oxide, magnesium phosphate or titanium dioxide.

[0014] In some embodiments of the present invention, in step (2), the particle size of the internal standard is not greater than 5 μm.

[0015] In some embodiments of the present invention, in step (2), the mass mixing ratio of the dried insoluble phase to the internal standard is 5~15:1.

[0016] In some embodiments of the present invention, in step (2), the evaluation criteria for the uniformity of grinding is: at least 5 points are randomly selected on the mixed sample for scanning using SEM-EDS, and the relative standard deviation (RSD) of the Si / Mg element mass ratio is less than 5%.

[0017] In some embodiments of the present invention, in step (3), the standard sample further comprises microcrystalline cellulose.

[0018] In some embodiments of the present invention, in step (3), the standard sample is prepared by mixing microcrystalline cellulose, silica and internal standard in a predetermined mass ratio.

[0019] In some embodiments of the present invention, in step (4), the randomly selected detection areas are no less than three, and the average value of their elemental mass percentage ratios is calculated.

[0020] In some embodiments of the present invention, in step (4), the formula for calculating the silica content (ω) in the final nicotine bag is: ω=[m1×(y×m3 / m2) / m]×100% (Ⅰ) Where m is the mass of nicotine bag powder weighed in step (1); m1 is the total mass of the insoluble phase after drying in step (1); m2 is the mass of the insoluble phase taken from m1 in step (2) for mixing with the internal standard; m3 is the mass of the internal standard added in step (2); and y is the mass ratio of silicon dioxide to the internal standard calculated by the standard curve equation.

[0021] In some embodiments of the present invention, the precision of the method is expressed as a relative standard deviation (RSD), which is no greater than 5.0% for the determination of silica content.

[0022] In some embodiments of the present invention, the accuracy of the method is expressed as spike recovery rate, which is between 90.0% and 110.0% for the determination of silica content.

[0023] The second aspect of this invention provides the application of the above-mentioned method for quantitative detection of silica content in nicotine bags based on SEM-EDS in the quality control of nicotine bag products and the verification of silica content compliance.

[0024] Compared with the prior art, the present invention has the following advantages: 1. Compared with traditional detection methods, the SEM-EDS technology used in this invention has significant economic advantages. Currently, instruments commonly used for silica analysis, such as ICP-MS or XRF, are not only expensive to purchase but also require sophisticated laboratory environments and skilled operators, resulting in relatively limited instrument adoption. In contrast, SEM-EDS, as a commonly used microscopic analysis device, is already equipped in most materials and quality control laboratories, requiring no significant additional investment and effectively reducing hardware barriers and operating costs.

[0025] 2. In the sample pretreatment stage, the method of this invention avoids the complex digestion process required by ICP-MS, such as the use of large amounts of strong acid, high temperature and high pressure digestion, etc., which not only shortens the processing time, but also reduces the consumption of high-purity reagents and the cost of potential hazardous waste disposal. The method of this invention only requires simple pretreatment such as sample separation and drying before SEM-EDS measurement can be performed directly, which greatly improves the detection efficiency.

[0026] 3. Regarding method reliability, this invention establishes a standardized calibration curve, enabling rapid and stable quantitative elemental analysis. This standard curve possesses excellent reusability and verifiability, facilitating inter-laboratory comparisons and data traceability, while also reducing the time and material consumption associated with frequent calibrations, significantly improving the overall economic efficiency of the analytical process.

[0027] 4. This invention achieves high-precision, rapid, and stable detection of silica content with low operating costs and equipment requirements, providing a more user-friendly, economical, and reliable analytical solution for the quality control and R&D of nicotine bag manufacturers. Attached Figure Description

[0028] Figure 1 This is the Si-Mg standard curve of an embodiment of the present invention. Detailed Implementation

[0029] The following specific embodiments further illustrate a method for quantitatively detecting the silica content in nicotine bags based on SEM-EDS.

[0030] The first aspect of this invention provides a method for quantitatively detecting the silica content in nicotine bags based on SEM-EDS, comprising the following steps: (1) Sample pretreatment: Weigh the nicotine bag contents powder sample, add anhydrous ethanol for ultrasonic treatment, centrifuge to separate and collect the insoluble phase, wash and dry and weigh; (2) Addition and mixing of internal standard: The dried insoluble phase is mixed with the selected internal standard in a predetermined mass ratio and ground until the particles are evenly distributed; the internal standard is a compound that is stable under EDS detection conditions and whose characteristic X-ray peaks do not overlap with the characteristic peaks of silicon. (3) Standard curve plotting: Prepare a series of standard samples containing silicon dioxide and the internal standard, wherein the mass ratio of silicon dioxide to the internal standard changes in a gradient; after grinding and mixing each standard sample, use SEM-EDS to measure the mass percentage ratio of Si element to characteristic element of internal standard, and use this ratio to perform linear fitting on the mass ratio of silicon dioxide to internal standard to obtain the standard curve equation. (4) Sample testing and calculation: The sample prepared in step (2) is placed under SEM-EDS for detection. Multiple areas are randomly selected for surface scanning. The average value of the mass percentage ratio of Si element to the characteristic element of the internal standard is calculated. The average value is substituted into the standard curve equation to calculate the mass ratio of silicon dioxide to the internal standard in the sample, and then the content of silicon dioxide in the nicotine bag is calculated.

[0031] In step (1) of this invention, the pretreatment operations such as ultrasonic treatment with ethanol and centrifugation can dissolve and remove a large amount of water-soluble salts (such as sodium chloride) in the sample, effectively avoiding the interference that sodium chloride may cause in subsequent SEM-EDS analysis, and laying the foundation for accurate detection of silica in the insoluble phase.

[0032] In some embodiments of the present invention, in step (1), the temperature of the ultrasonic treatment is 20~40℃, which can be 20~25℃, 25~30℃, 30~35℃, or 35~40℃, and the time is 30~40 minutes, which can be 30~35 minutes or 35~40 minutes.

[0033] In some embodiments of the present invention, in step (1), the centrifugation speed is 5000~10000 rpm, which can be 5000~6000 rpm, 6000~7000 rpm, 7000~8000 rpm, 8000~9000 rpm, or 9000~10000 rpm, and the centrifugation time is 2~5 minutes, which can be 2~3 minutes, 3~4 minutes, or 4~5 minutes.

[0034] In some embodiments of the present invention, in step (1), the washing involves washing the insoluble phase with anhydrous ethanol 2 to 3 times.

[0035] In some embodiments of the present invention, in step (2), the internal standard is selected from any one of magnesium stearate, magnesium oxide, magnesium phosphate, or titanium dioxide. Preferably, the internal standard is magnesium stearate. The internal standard is dried before use to remove moisture. The selection of the internal standard in the present invention is based on the following principles: ① Element specificity: The characteristic elements (such as magnesium and titanium) contained in the internal standard are not present in the original components of the nicotine bag to avoid background interference; ② Detection compatibility: In EDS detection, the X-ray peak intensity of the characteristic elements of the internal standard is high and does not overlap with the characteristic peaks of the elements to be measured in the sample (such as Si, Na, Cl, etc.). For example, the Mg-Kα peak (1.25 keV) can be effectively distinguished from the Na-K peak (1.04 keV) and Si-Kα (1.74 keV), while the Ti-Kα peak (~4.51 keV) has higher energy and less interference; ③ Physicochemical stability: During the mixing and preparation of samples and the detection process, the internal standard needs to be stable, non-volatile, non-decomposing, and non-reactive with the sample; ④ Dispersibility and representativeness: The internal standard should be able to be fully and uniformly mixed with the dried insoluble phase residue, and be easy to grind and disperse, thereby ensuring the representativeness of the measurement points during EDS micro-area analysis and improving the quantitative accuracy.

[0036] In some embodiments of the present invention, in step (2), the particle size of the internal standard is no greater than 5 μm, to ensure the uniformity of mixing and the representativeness of the measurement points, reduce the shadowing effect and local charge accumulation in EDS analysis, and improve the consistency and comparability between the standard curve and the sample to be tested.

[0037] In some embodiments of the present invention, in step (2), the mass mixing ratio of the dried insoluble phase to the internal standard is 5~15:1, preferably 8~12:1, and more preferably 10:1.

[0038] In some embodiments of the present invention, in step (2), the evaluation criteria for the uniformity of grinding is: at least 5 points are randomly selected on the mixed sample for scanning using SEM-EDS, and the relative standard deviation (RSD) of the Si / Mg element mass ratio is less than 5%.

[0039] In some embodiments of the present invention, in step (3), the standard sample further comprises microcrystalline cellulose. In some embodiments of the present invention, the mass ratio of microcrystalline cellulose to internal standard in the standard sample is 1~2.5:1. The microcrystalline cellulose has a particle size of no more than 50 μm and is dried before use.

[0040] In some embodiments of the present invention, in step (3), the standard sample is prepared by mixing microcrystalline cellulose, silica, and an internal standard in a predetermined mass ratio. The purpose is to construct an analytical system similar to the matrix of the test sample (the insoluble phase after treatment in step (1)), wherein the mass of the internal standard remains constant in all standard samples. These standard samples do not contain the water-soluble organic components found in the contents of the nicotine pouch, and are used to establish a quantitative relationship between the response signals of silica and the internal standard.

[0041] In some embodiments of the present invention, in step (4), at least three randomly selected detection areas are used, and the average value of their elemental mass percentage ratios is calculated. The relative standard deviation (RSD) of the mass percentage ratios of Si and the characteristic elements of the internal standard measured in the at least three random detection areas should not be greater than 5%.

[0042] In some embodiments of the present invention, in step (4), the formula for calculating the silica content (ω) in the final nicotine bag is as follows: ω=[m1×(y×m3 / m2) / m]×100% (Ⅰ) Where m is the mass of nicotine bag powder weighed in step (1); m1 is the total mass of the insoluble phase after drying in step (1); m2 is the mass of the insoluble phase taken from m1 in step (2) for mixing with the internal standard; m3 is the mass of the internal standard added in step (2); and y is the mass ratio of silicon dioxide to the internal standard calculated by the standard curve equation.

[0043] Specifically, the masses m, m1, m2, and m3 in the calculation formula are all in grams, and the weighing accuracy is not less than 0.0001 g; the y value in the calculation formula is calculated by the standard curve equation y=kx, where x is the average value of the mass percentage ratio of Si element to the characteristic element of the internal standard measured by SEM-EDS, and k is the slope obtained by linear fitting.

[0044] The precision of the method described in this invention is expressed as relative standard deviation (RSD). For the determination of silica content, the RSD is no greater than 5.0%.

[0045] The accuracy of the method described in this invention is expressed as spike recovery rate. For the determination of silica content, the spike recovery rate is between 90.0% and 110.0%.

[0046] The second aspect of this invention provides the application of the above-mentioned method for quantitative detection of silica content in nicotine bags based on SEM-EDS in the quality control of nicotine bag products and the verification of silica content compliance.

[0047] In this invention, the quality control includes sampling inspection of batches of nicotine bag products. The compliance verification verifies whether the silica content in the product meets the requirements of national or industry regulations and product labeling.

[0048] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention.

[0049] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, this invention can be implemented using any prior art methods, apparatus, and materials similar to or equivalent to those described in the embodiments of this invention, based on the knowledge of those skilled in the art and the description of this invention.

[0050] Example 1: Quantitative determination of silica content in nicotine bags based on SEM-EDS and magnesium stearate internal standard method The instruments and parameters used in this embodiment are shown in Table 1 below.

[0051] Table 1. Instruments and parameters used in this embodiment.

[0052] Magnesium stearate was selected as the internal standard in this embodiment to meet the following requirements: magnesium was not present in the nicotine bag to avoid background interference; the Mg-Kα peak (1.25 keV) in the EDS spectrum did not overlap with the Si-Kα peak (1.74 keV) and the Na-K peak (1.04 keV), making them easy to distinguish; it was stable, non-volatile, non-decomposing, and did not participate in the reaction; and the particles were small (particle size ≤ 5 μm) to facilitate uniform mixing with insoluble residues and ensure representative sampling.

[0053] Sample preparation and testing process (1) Accurately weigh 0.5089 g of the nicotine bag contents powder and place it in a centrifuge tube. Add 10 mL of anhydrous ethanol and sonicate at room temperature for 30 min. Control the water temperature within the range of 25±5℃ to prevent the decomposition of heat-sensitive components.

[0054] (2) Centrifuge the centrifuge tube at 8000 rpm for 2 min to separate the supernatant from the insoluble solid. Collect the insoluble phase and wash it three times with anhydrous ethanol to remove residual soluble components.

[0055] (3) Transfer the washed insoluble phase to a weighing dish, place it in a 60℃ oven to dry for 2 hours, take it out and place it in a desiccator to cool to room temperature, and accurately weigh its mass.

[0056] (4) Take 0.1722g of the dried insoluble phase and weigh 0.0170g of magnesium stearate as an internal standard at a mass ratio of about 10:1. Place them together in an agate mortar and grind them thoroughly until the powder particles are uniform and fine.

[0057] (5) Preparation of standard curve samples: Microcrystalline cellulose (MCC), silica (SiO2) and magnesium stearate (MgSt) were accurately weighed according to the mass ratio shown in Table 2 to prepare five standard samples ST1~ST5. Each sample was thoroughly ground and mixed to ensure that the particle size and uniformity met the requirements of SEM-EDS analysis.

[0058] Table 2. Mass ratio of microcrystalline cellulose, silica, and magnesium stearate in standard samples

[0059] (6) Spread the sample and standard sample evenly on the sample stage covered with carbon conductive adhesive, avoiding stacking and gaps. For each sample, randomly select 3 different regions for surface scanning under SEM-EDS and collect the normalized mass percentage of Si and Mg elements. After each batch is turned on, use at least two standard samples from ST2, ST3, and ST4 to verify the stability of the curve. All tests must be completed under the same instrument conditions.

[0060] 2. Data Processing and Result Calculation (1) Calculate the average value of the normalized mass ratio of Si / Mg at the three measuring points in each standard sample (as shown in Table 3 below), and plot the standard curve based on its known m(SiO2) / m(MgSt) mass ratio.

[0061] Table 3. Average Si / Mg normalized mass ratio and m(SiO2) / m(MgSt) mass ratio at three measurement points in the standard sample

[0062] (2) Use Origin software to perform linear fitting on the above data, such as... Figure 1 As shown, the equation of the standard curve is obtained: y = 0.1735x (R² = 0.9963) Where x represents the normalized Si-Mg mass ratio measured by SEM-EDS, and y represents the mass ratio of silicon dioxide to magnesium stearate m(SiO2) / m(MgSt).

[0063] (3) Calculation of silica content in the sample: The mass of nicotine bag powder weighed is m = 0.5089 g. The total mass of the dried insoluble phase obtained after pretreatment is m1 = 0.2831 g. 0.1722 g of m2 (m2 = 0.1722 g, taken from the insoluble phase mass of m1 used for mixing with the internal standard) is mixed with magnesium stearate m3 = 0.0170 g. The Si% / Mg% ratio measured by SEM-EDS is 4.133. The standard curve equation is known as y = 0.1735x, where x represents the normalized mass ratio of Si-Mg measured by SEM-EDS, and y represents the mass ratio of silica to magnesium stearate m(SiO2) / m(MgSt).

[0064] 1) Substitute the values ​​into the standard curve equation to calculate the mass ratio of silica to the internal standard: y = 0.1735x × 4.133 = 0.7170; 2) Calculate the mass of silica in the mixed sample (i.e., the mass of silica contained in the insoluble phase m2): m (SiO2)_in_m2 =y×m3=0.7170×0.0170g=0.0122g; 3) Calculate the total amount of silica in the total insoluble phase m1: m (SiO2,总) =(m (SiO2)_in_m2 (m2)×m1=(0.0122g / 0.1722g)×0.2831g=0.0201g; 4) Calculate the silica content ω (wt%) in the nicotine bag: ω=[m (SiO2,总) / m]×100%=[m1×(y×m3 / m2) / m]×100%=(0.0201g / 0.5089g)×100%=3.94%.

[0065] It is known that the actual amount of silica added in this sample is 3.99%, and the measured value matches the reference value well.

[0066] Example 2: Precision Verification Following the preparation method of the test sample (insoluble phase after drying) in Example 1, standard samples of known concentrations were prepared. The precision of the standard samples of known concentrations was determined by measuring them 6 times. The measurement results are shown in Table 4 below.

[0067] Table 4 Precision Measurement Results

[0068] As shown in Table 4, the relative standard deviation (RSD) of the six parallel determinations was 2.01%, indicating that the method has high repeatability and that the detection method of this application has good precision, which can meet the quantitative analysis requirements for detecting the silica content in nicotine bag powder.

[0069] Example 3: Accuracy Verification The accuracy of the method was examined by spiked recovery. A sample S1 was spiked with the standard curve at low, medium and high concentration levels, with two replicates for each concentration level, and the recovery rate was calculated according to formula (II).

[0070] Validation criteria: Recovery rates should all be between 90.0% and 110.0%.

[0071] Recovery=[(C test -C0) / C spiked ×100% (II) Among them, C test C0: Content of sample after spiking (mg / kg); C0: Content of sample before spiking (mg / kg); C spiked : Dosage (mg).

[0072] The results are shown in Table 5 below.

[0073] Table 5 Accuracy Measurement Results

[0074] As shown in Table 5, the recovery rate of silica ranged from 90.16% to 94.74%, meeting the requirement of 90% to 110%. This indicates that the detection method of this application has good accuracy and can be used for the quantitative determination of silica content in nicotine bag powder.

[0075] Comparative Example 1 Except for the ultrasonic treatment time of 20 min in step (1), which is 10 min shorter than that in Example 1, the rest is the same as in Example 1.

[0076] The results are shown in Table 6 below.

[0077] Table 6 Results of Comparative Example 1

[0078] As shown in Table 6, the average measurement value of Comparative Example 1 (3.12%) is significantly lower than the actual amount of silica added in the nicotine bag (3.99%), and the RSD is higher than that of Example 1. This indicates that the shorter ultrasonic time may lead to incomplete extraction or uneven mixing of silica in the nicotine bag, resulting in significantly lower detection results and reduced precision.

[0079] Comparative Example 2 Except for replacing the ultrasonic treatment in step (1) with vortex dispersion (the treatment time is the same, 30 min), the rest is the same as in Example 1.

[0080] The results are shown in Table 7 below.

[0081] Table 7 Results of Comparative Example 2

[0082] As shown in Table 7, the measured values ​​of Comparative Example 2 (1.91% and 3.22%) are significantly lower than the actual amount of silica added in the nicotine bag (3.99%), and the difference between parallel samples is large. This indicates that vortex dispersion cannot effectively replace ultrasonic treatment to achieve complete dispersion of silica, resulting in lower results and poor parallelism.

[0083] Comparative Example 3 Except for replacing anhydrous ethanol with an equal amount of pure water in step (1), the rest is the same as in Example 1.

[0084] The results are shown in Table 8 below.

[0085] Table 8 Results of Comparative Example 3

[0086] As shown in Table 8, the measured value of Comparative Example 3 (3.63%) differs significantly from the actual amount of silica added in the nicotine bag (3.99%). This indicates that using pure water instead of ethanol for ultrasonic treatment cannot effectively remove or destroy certain components, which may lead to the formation of gel or cause silica to be encapsulated, preventing it from being fully dispersed and resulting in a lower test result.

[0087] Comparative Example 4 Except for steps (1) to (3) (i.e., directly weighing 0.5g of the nicotine bag contents powder, without processing, and directly mixing and grinding with an appropriate amount of magnesium stearate), the rest is the same as in Example 1.

[0088] The results are shown in Table 9 below.

[0089] Table 9. Results of Comparative Example 4

[0090] As shown in Table 9, the measured value of Comparative Example 4 differs significantly from the actual amount of silica added in the nicotine bag (3.99%), and the difference between parallel samples is also large. This indicates that without pretreatment, water-soluble components cannot be removed and the microcrystalline cellulose cannot be broken to encapsulate the silica, resulting in severely low and non-reproducible results, thus proving the necessity of the pretreatment step.

[0091] Comparative Example 5 Except for the ultrasonic treatment time of 1 hour in step (1), which is the same as in Example 1 (compared to Example 1, the ultrasonic time is extended to 1 hour), the rest is the same as in Example 1.

[0092] The results are shown in Table 10 below.

[0093] Table 10 Results of Comparative Example 5

[0094] As shown in Table 10, the two parallel measurements of Comparative Example 5 differed greatly (5.41% and 7.05%), and the spiked recovery rate was only 51.18%, indicating that the excessively long ultrasonic time seriously damaged the accuracy and precision of the method. This may be due to the change in the physical properties of the powder caused by prolonged ultrasonication, which interfered with the quantitative analysis of SEM-EDS.

[0095] Comparative Example 6 Except for reducing the centrifugation speed to 3000 rpm in sample preparation and pretreatment step (2), the rest is the same as in Example 1.

[0096] The results showed that because the silica powder was very fine (1-10 μm), the low centrifugation speed could not effectively collect the silica, resulting in its loss during the removal of the liquid phase and causing the detection results to be significantly lower.

[0097] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. In the above embodiments, the descriptions of each embodiment have different emphases; parts not described in detail in a certain embodiment can be referred to in the relevant descriptions of other embodiments. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for quantitative determination of the content of silicon dioxide in a nicotine bag based on SEM-EDS, characterized by, It comprises the following steps: (1) sample pretreatment: weigh the nicotine bag content powder sample, add anhydrous ethanol for ultrasonic treatment, centrifugal separation and collection of insoluble phase, washing, drying and weighing; (2) internal standard addition and mixing: mix the dried insoluble phase with the selected internal standard according to the predetermined mass ratio, and grind to uniform particle distribution; the internal standard is a compound that is stable under EDS detection conditions and has no overlap with the characteristic peak of silicon element; (3) standard curve drawing: prepare a series of standard samples containing silicon dioxide and the internal standard, wherein the mass ratio of silicon dioxide to internal standard changes in gradient; after grinding and mixing each standard sample, the mass percentage ratio of Si element to internal standard characteristic element is measured by SEM-EDS, and the mass ratio of silicon dioxide to internal standard is linearly fitted to obtain the standard curve equation; (4) sample testing and calculation: the sample prepared in step (2) is detected under SEM-EDS, multiple areas are randomly selected for area scanning, the average value of the mass percentage ratio of Si element to internal standard characteristic element is calculated, and the mass ratio of silicon dioxide to internal standard in the sample is calculated by substituting the average value into the standard curve equation, and then the content of silicon dioxide in the nicotine bag is calculated.

2. The method for quantitatively detecting the content of silicon dioxide in a nicotine bag based on SEM-EDS according to claim 1, wherein, In step (1), one or more of the following features are included: (a) the ultrasonic treatment temperature is 20-40℃, and the time is 30-40 minutes; (b) the centrifugal separation speed is 5000-10000 rpm, and the centrifugal time is 2-5 minutes; (c) the washing is washing the insoluble phase with anhydrous ethanol for 2-3 times.

3. The method for quantitatively detecting the content of silicon dioxide in a nicotine bag based on SEM-EDS according to claim 1, wherein, In step (2), one or more of the following features are included: (a) the internal standard is selected from any one of magnesium stearate, magnesium oxide, magnesium phosphate or titanium dioxide; (b) the particle size of the internal standard is not greater than 5μm; (c) the mass mixing ratio of the dried insoluble phase to the internal standard is 5-15:1; (d) the evaluation standard of uniformity of grinding is that at least 5 points on the mixed sample are randomly selected for scanning by SEM-EDS, and the relative standard deviation (RSD) of Si / Mg element mass ratio is less than 5%.

4. The method for quantitatively detecting the content of silicon dioxide in a nicotine pouch based on SEM-EDS according to claim 3, characterized in that, One or more of the following features are included: (a1) the internal standard is magnesium stearate; (a2) the internal standard is dried before use to remove moisture; (c1) the mass mixing ratio of the dried insoluble phase to the internal standard is 8-12:

1.

5. The method for quantitatively detecting the content of silicon dioxide in a nicotine bag based on SEM-EDS according to claim 1, wherein, In step (3), one or more of the following features are included: (a) the standard sample further comprises microcrystalline cellulose; (b) the standard sample is mixed by microcrystalline cellulose, silicon dioxide and internal standard according to the predetermined mass ratio.

6. The method for quantitatively detecting the content of silicon dioxide in a nicotine pouch based on SEM-EDS according to claim 5, wherein, One or more of the following features are included: (a1) the mass ratio of microcrystalline cellulose to internal standard in the standard sample is 1-2.5:1; (a2) the particle size of the microcrystalline cellulose is not greater than 50μm, and it is dried before use; (b1) the standard sample does not contain water-soluble organic components in the nicotine bag content.

7. The method for quantitatively detecting the content of silicon dioxide in a nicotine pouch based on SEM-EDS according to claim 1, wherein, In step (4), one or more of the following features are included: (a) the randomly selected detection areas are not less than 3, and the average of the mass percentage ratio of the elements is calculated; (b) the calculation formula of the silicon dioxide content (ω) in the final nicotine bag is: ω = [m1 × (y × m3 / m2) / m] × 100% (I) wherein m is the mass of the nicotine bag powder weighed in step (1); m1 is the total mass of the insoluble phase after drying in step (1); m2 is the mass of the part of the insoluble phase taken from m1 for mixing with the internal standard in step (2); m3 is the mass of the internal standard added in step (2); y is the mass ratio of silicon dioxide to the internal standard calculated from the standard curve equation.

8. The method for quantitatively detecting the content of silicon dioxide in a nicotine pouch based on SEM-EDS according to claim 7, wherein, One or more of the following features are included: (a1) the relative standard deviation (RSD) of the mass percentage ratio of Si element to internal standard characteristic element measured by the not less than 3 random detection areas should be not more than 5%; (b1) the masses m, m1, m2, and m3 in the calculation formula are in grams, and the weighing precision is not less than 0.0001 g; (b2) the value y in the calculation formula is calculated by the standard curve equation y = kx, wherein x is the average of the mass percentage ratio of Si element to internal standard characteristic element measured by SEM-EDS, and k is the slope obtained by linear fitting.

9. The method for quantitatively detecting the content of silicon dioxide in a nicotine pouch based on SEM-EDS according to claim 1, wherein, One or more of the following features are included: (a) the precision of the method is represented by the relative standard deviation RSD, and for the determination of the silicon dioxide content, the RSD is not more than 5.0%; (b) the accuracy of the method is represented by the standard addition recovery rate, and for the determination of the silicon dioxide content, the standard addition recovery rate is between 90.0% and 110.0%.

10. The application of the method for quantitatively detecting the silicon dioxide content in nicotine bags based on SEM-EDS according to any one of claims 1-9 in the quality control and silicon dioxide content compliance verification of nicotine bag products.

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