A method for determining water-soluble colorants in cigarette tipping paper using high performance liquid chromatography.

Abstract

This invention discloses a method for determining water-soluble colorants in cigarette tipping paper using high-performance liquid chromatography (HPLC), comprising the following steps: Standard solution preparation: Weigh tartrazine, amaranth, carmine, sunset yellow, allura red, brilliant blue, acid red, erythrosine, indigo, and quinoline yellow to prepare single standard stock solutions; Mix the single standard stock solutions to prepare a mixed standard stock solution; Transfer different amounts of the mixed standard solution to prepare a series of standard working solutions of different concentrations of synthetic colorants; Sample preparation: Place a tipping paper sample in an extraction vessel, add water / methanol / acetonitrile solution, seal the vessel, and perform microwave-assisted extraction. Filter the supernatant to obtain the test solution; Sample analysis: Analyze the test solution using HPLC-PDA and quantify using the external standard method. This method is simple, rapid, and can simultaneously and quickly analyze the content of 10 water-soluble synthetic colorants in cigarette materials, providing technical support for cigarette safety evaluation.

Description

Technical Field

[0001] This invention relates to the field of tobacco technology, and in particular to a method for determining water-soluble colorants in cigarette tipping paper using high performance liquid chromatography. Background Technology

[0002] Color is a crucial factor influencing the sensory properties of a product and forms the first visual impression consumers form. Currently, some cigarette tipping papers utilize coloring and flavoring to establish a relationship with the style characteristics of cigarettes, inducing synesthetic stimulation through sight, smell, and taste in cigarette consumption. The safety of tobacco materials has always been a key concern for the industry and cigarette manufacturers. Currently, there are clear limits on key safety and hygiene indicators such as formaldehyde, solvent residues, and inorganic elements. To effectively control the raw materials used in cigarette materials, it is necessary to analyze the use of colorants in cigarette tipping papers that come into contact with the lips. This paper establishes analytical methods for 10 commonly used food-grade synthetic colorants permitted in cigarette tipping papers, providing technical support for cigarette safety evaluation.

[0003] Currently, there are many analytical methods for synthetic colorants in different substances, and different pretreatment methods are used for different research objects. Commonly used pretreatment methods include solid-phase extraction column adsorption, polyamide adsorption, and ultrasonic extraction. Polyamide adsorption is the colorant pretreatment method recommended by the national standard method GB 5009.35-2016, while ultrasonic extraction is the colorant pretreatment method recommended by SN / T4457-2016. These two pretreatment methods are widely used in the liquid chromatography analysis of synthetic colorants in beverages, each with its own advantages and disadvantages. Yu Hui et al. conducted a comparative study on the sample pretreatment methods of GB 5009.35-2016 and SN / T4457-2016, using polyamide adsorption and ultrasonic extraction to extract colorants from beverages, respectively. Combined with high-performance liquid chromatography analysis, the contents of tartrazine, carmine, and sunset yellow in Mirinda beverages were determined. The results showed no significant difference in the detection results of the two pretreatment methods. Samples treated by polyamide adsorption show fewer interfering peaks and a cleaner chromatographic matrix, but the operation is relatively complex and suitable for quantitative detection of small batches of samples. However, polyamide adsorption is not suitable for erythrosine samples. Erythrosine has a sodium benzoate structure, unlike other synthetic colorants with sodium benzenesulfonate structures. Polyamide adsorbents are highly polar packing materials that utilize intermolecular hydrogen bonds for adsorption. They are suitable for the extraction or chromatographic separation of polar substances in aqueous solutions and can also be used to extract polar substances from non-polar solutions. Therefore, when using polyamide adsorption, erythrosine loss is significant and recovery rate is low. Ultrasonic extraction is simple to operate, low in cost, and greatly shortens the analysis time, making it suitable for quantitative detection of large batches of samples, but it is also susceptible to interference from other impurity peaks.

[0004] Microwave-assisted extraction utilizes electromagnetic fields to effectively separate certain organic components from the matrix in solid or semi-solid substances while preserving the original compound state of the analyte. The strong vibrations, high accelerations, strong cavitation effects, and stirring effects generated by ultrasound can accelerate the entry of active ingredients into the solvent. Furthermore, secondary effects of ultrasound, such as mechanical vibration, emulsification, diffusion, and fragmentation, can also accelerate the diffusion and release of active ingredients. This paper uses microwave-assisted extraction to investigate the extraction of colorants from cigarette tipping paper under different conditions, establishing a universally applicable high-performance liquid chromatography (HPLC) method for the analysis of colorants in paper bases. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for determining water-soluble colorants in cigarette tipping paper using high performance liquid chromatography, which overcomes the above-mentioned defects of the prior art.

[0006] The technical problem to be solved by the present invention is achieved through the following technical solution:

[0007] A method for determining water-soluble colorants in cigarette tipping paper using high-performance liquid chromatography includes the following steps:

[0008] (1) Preparation of standard solutions: Weigh out 10 synthetic colorants, namely tartrazine, amaranth, carmine, sunset yellow, allura red, brilliant blue, acid red, erythrosine, indigo, and quinoline yellow, and dilute to volume with water / methanol / acetonitrile to obtain single standard stock solutions; mix the single standard stock solutions and dilute with water / methanol / acetonitrile to obtain mixed standard stock solutions; transfer different amounts of mixed standard solutions and dilute to volume with water / methanol / acetonitrile to prepare a series of standard working solutions of synthetic colorants with different concentrations.

[0009] (2) Sample preparation: Take the tipped paper sample and place it in the extraction vessel. Add water / methanol / acetonitrile solution, then seal the vessel and use microwave-assisted extraction. Filter the supernatant of the extract to obtain the test solution.

[0010] (3) Sample analysis: The test solution was analyzed by HPLC-PDA and quantified by external standard method. The chromatographic conditions were as follows: Column: Agilent column, mobile phase: 0.02 mol / L ammonium acetate aqueous solution (A) / acetonitrile (B) as the mobile phase for gradient elution, total flow rate of mobile phase: 1.0 mL / min, column temperature: 30℃, injection volume: 10.0 μL, absorption wavelength: the maximum absorption wavelength of each target analyte.

[0011] Preferably, in the above technical solution, step (1) specifically includes:

[0012] (11) Accurately weigh 25 mg of each of the 10 synthetic colorants, namely tartrazine, amaranth, carmine, sunset yellow, allura red, brilliant blue, acid red, erythrosine, indigo and quinoline yellow, into a 25 mL volumetric flask, and make up to volume with water / methanol / acetonitrile to obtain 10 single standard stock solutions with a concentration of 1.0 mg / mL.

[0013] (12) Take 2.5 mL of a single standard stock solution and mix it in a 50 mL volumetric flask. Then dilute it with water / methanol / acetonitrile to obtain a mixed standard stock solution with a concentration of 50.0 μg / mL.

[0014] (13) Transfer 0.1 mL, 0.5 mL, 1.0 mL, 2.0 mL, 3.0 mL and 4.0 mL of the mixed standard solution into a 10 mL volumetric flask, dilute with water / methanol / acetonitrile to obtain a series of standard working solutions of synthetic colorant with concentrations of 0.5 μg / mL, 2.5 μg / mL, 5.0 μg / mL, 10.0 μg / mL, 15.0 μg / mL and 20.0 μg / mL respectively.

[0015] Preferably, in the above technical solution, the volume ratio of the water / methanol / acetonitrile mixture is 3:1:1.

[0016] Preferably, in the above technical solution, step (2) specifically includes:

[0017] Accurately weigh 1.0 g of the tipped paper sample and place it in a 50 mL extraction vessel. Add 20 mL of water / methanol / acetonitrile solution, then seal the vessel and use microwave-assisted extraction. Filter the supernatant of the extract through a 0.45 μm aqueous filter membrane to obtain the test solution.

[0018] Preferably, in the above technical solution, the volume ratio of water / methanol / acetonitrile mixture is 3:1:1, the microwave power is 300W, and the extraction time is 3min.

[0019] Preferably, in the above technical solution, the filtration uses a 0.45μm aqueous phase filter membrane, which is PES, PTFE or PVDF.

[0020] Preferably, in the above technical solution, the chromatographic column in step (3) is: Agilent chromatographic column (HC-C18(2) 4.6x150mm, 5μm).

[0021] The above-described technical solution of the present invention has the following beneficial effects:

[0022] The method described in this application is simple, fast, and easy to use. It can simultaneously and quickly analyze the content of 10 water-soluble synthetic colorants in tobacco materials, providing technical support for cigarette safety evaluation. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0024] Figure 1 The results of thermogravimetric analysis of 10 colorant samples are shown in the figure.

[0025] Figure 2 This is a comparison chart of total colorant extraction results.

[0026] Figure 3 A comparison of peak areas detected by different filtration methods.

[0027] Figure 4 This is a 3D scan outline of the colorant.

[0028] Figure 5 Chromatograms of standard working solutions of 10 colorants. Detailed Implementation

[0029] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0030] Example 1 Materials and Reagents

[0031] Materials: The tipping paper material was taken from colored cigarette samples sold on the market.

[0032] Reagents: Methanol (chromatographic grade, Fisher, USA); Acetonitrile (chromatographic grade, Fisher, USA); Ammonium acetate (analytical grade, Xilong Chemical Plant, Shantou City, Guangdong Province); 10 synthetic colorant standards, all purchased from Dr. Ehrenstorfer GmbH, Germany. Detailed information is shown in Table 1.

[0033] Table 1. Information on 10 synthetic colorant standard samples

[0034]

[0035] Instruments and equipment: Waters Acquity high-performance liquid chromatography system (Waters Corporation, USA), equipped with a diode array detector (wavelength range 200-800nm); Agilent HC-C18(2) (150mm×4.6mm, 5μm); Milli-Q50 ultrapure water system (Millipore Corporation, USA, R>18MΩ); AB204-S electronic analytical balance (accurate to 0.0001g, Mettler-Toledo, Switzerland); microwave-assisted extraction system (CEM Corporation, MARSX); high-speed centrifuge (TDL-5-A, Shanghai Anting Scientific Instrument Factory, maximum speed 10000r / min); PE STA6000 thermogravimetric analyzer (sensitivity 0.001mg, PE Corporation, USA); 0.45μm aqueous phase syringe filter.

[0036] Experimental methods:

[0037] (1) Thermogravimetric analysis experiment

[0038] The thermogravimetric analyzer had a sensitivity of 1 μg, using an empty crucible as a reference. Under normal atmospheric pressure and with high-purity nitrogen as the protective gas, the same mass of sample was weighed into the bottom of a 70 μL alumina crucible and placed on the thermogravimetric analyzer's balance pan. The sample was heated according to the set heating rate. The experiment was repeated three times for different heating rates. The thermogravimetric analyzer's temperature control range was 30–800 °C, the heating rate was 10 °C / min, and the air flow rate was 50 mL / min.

[0039] To understand the thermal stability and thermal behavior of colorants, thermogravimetric analysis (TGA) was used to study the thermogravimetric loss process of 10 colorant samples under air atmosphere with temperature changes. Equal masses of samples were weighed into 70 μL alumina crucibles and placed in a PE STA6000 TGA analyzer. Thermogravimetric analysis was performed at a temperature range of 30–800 °C, a heating rate of 10 °C / min, and an air flow rate of 50 mL / min. The tests were repeated three times for different heating rates.

[0040] (2) Optimization of microwave-assisted extraction conditions

[0041] Microwave-assisted extraction was used to study the effects of different extraction conditions, such as extraction solvent, liquid-to-solid ratio, microwave power, and extraction time, on the extraction rate, with the total content of colorant as the evaluation index. Based on the single-factor experiments, microwave power (A), extraction time (B), solid-to-liquid ratio (C), and organic phase (1:1 methanol / acetonitrile) ratio (D) were used as evaluation factors, and the extraction rate of total colorant content was used as the evaluation index. An orthogonal experimental design using orthogonal table L9(34) was used to determine the optimal process conditions. The levels of the orthogonal experimental factors are shown in Table 2.

[0042] Table 2. Factor Levels in Orthogonal Experiments

[0043]

[0044] (3) Preparation of standard solutions

[0045] First, accurately weigh 25 mg (accurate to 0.1 mg) each of the 10 synthetic colorants—tartrazine, amaranth, carmine, sunset yellow, allura red, brilliant blue, acid red, erythrosine, indigo, and quinoline yellow—into a 25 mL volumetric flask. Dilute to volume with water / methanol / acetonitrile (3:1:1, volume ratio) to obtain 1.0 mg / mL stock solutions of 10 single standard solutions. Take 2.5 mL of each stock solution and mix in a 50 mL volumetric flask. Then dilute with ultrapure water / methanol / acetonitrile (3:1:1, volume ratio) to obtain a concentration of... Prepare a 50.0 μg / mL mixed standard stock solution; transfer 0.1 mL, 0.5 mL, 1.0 mL, 2.0 mL, 3.0 mL, and 4.0 mL of the mixed standard solution into 10 mL volumetric flasks, respectively, and dilute to volume with water / methanol / acetonitrile (3:1:1, volume ratio) to obtain a series of standard working solutions of synthetic colorant with concentrations of 0.5 μg / mL, 2.5 μg / mL, 5.0 μg / mL, 10.0 μg / mL, 15.0 μg / mL, and 20.0 μg / mL.

[0046] (4) Sample preparation

[0047] Accurately weigh 1.0 g (accurate to 0.1 mg) of the tipped paper sample and place it in a 50 mL extraction vessel. Add 20 mL of water / methanol / acetonitrile (3:1:1, volume ratio) solution, then seal the vessel and perform microwave-assisted extraction (microwave power 300 W, extraction time 3 min). Filter the supernatant of the extract through a 0.45 μm aqueous filter membrane to obtain the test solution.

[0048] (5) HPLC analysis of samples

[0049] HPLC-PDA was used to analyze the test solution, and external standard method was used for quantification. The chromatographic column was an Agilent column (HC-C18(2) 4.6 x 150 mm, 5 μm), the column oven temperature was 30℃, the injection volume was 10.0 μL, and the total flow rate of the mobile phase was 1.0 mL / min. The absorption wavelength was the maximum absorption wavelength of each target analyte. Gradient elution was performed using 0.02 mol / L ammonium acetate aqueous solution (A) / acetonitrile (B) as the mobile phase. The gradient elution program is shown in Table 3 below.

[0050] Table 3 Gradient elution program

[0051]

[0052] Example 2

[0053] Thermogravimetric analysis of 10 synthetic colorants

[0054] To understand the thermal stability and thermal behavior of 10 colorants, thermogravimetric analysis was used to study the thermogravimetric process of the 10 colorant samples under air atmosphere as temperature changed. Figure 1 Thermogravimetric analysis results of 10 colorant samples (Figure) Figure 1 The figures show the thermogravimetric curves (TG, red), differential thermogravimetric curves (DTG, green), and heat flow curves (DSC, purple) for samples of Allura Red, Amaranth, Acid Red, Carmine, Erythrosine, Quinoline Yellow, Indigo, Brilliant Blue, Tartrazine, and Sunset Yellow, respectively. The results indicate that:

[0055] (1) The thermal weight loss processes of different samples were significantly different. The TG curves of Allura Red and Amaranth Red were divided into two weight loss stages, with the main weight loss stages occurring at 355.02-520.36℃ and 361.60-548.59℃, respectively. The TG curves of Acid Red and Carmine were divided into three weight loss stages, with the main weight loss stages occurring at 438.36-586.40℃ and 711.97-790.33℃, respectively. The TG curves of Quinoline Yellow, Erythrosine, Indigo, Brilliant Blue, Tartrazine, and Sunset Yellow were divided into four weight loss stages, with the main weight loss stages occurring at 722.85-798.00℃, 341.14-452.21℃, 460.47-555.64℃, 561.87-797.86℃, 385.10-672.72℃, and 453.57-637.54℃, respectively.

[0056] (2) Sunset Yellow, Acid Red and Tartrazine lost the most weight in the third stage, ranging from 27.737% to 43.737%, while Quinoline Yellow lost the most weight in the fourth stage, ranging from 30.982% to 41.282%. The remaining colorants lost the most weight in the second stage, ranging from 33.131% to 58.071%.

[0057] (3) At the end of pyrolysis, the amount of residue remaining for Allura Red, Amaranth, Acid Red, Carmine and Quinoline Yellow was between 17.52% and 28.77%, while the amount of residue remaining for Erythrosine was 1.333%.

[0058] The results showed that all 10 colorants were relatively stable below 300℃. The relatively flat DSC curves in the thermogravimetric analysis (TGA) showed no obvious peaks, indicating no significant change in heat, possibly due to weight loss from water evaporation. The subsequent phase, with greater heat release, likely indicated weight loss from combustion and decomposition.

[0059] Example 3

[0060] (1) Comparison of single-factor experiments

[0061] Single-factor optimization of microwave-assisted extraction conditions was performed, changing individual factors to optimize the extraction solvent, extraction time, microwave power, and solid-liquid ratio. The results for the total colorant content are shown below. Figure 2 As shown in Figure a, the relationship between the total content of the target analytes and different extraction solvents (water, water / methanol (v / v 9:1), water / ethanol (v / v 9:1), and water / methanol / acetonitrile (v / v / v 3:1:1) is illustrated. All 10 target analytes analyzed in the experiment are readily soluble in water and methanol; therefore, water and alcohol solutions were used as extraction solvents. Considering that the mobile phase was acetonitrile, water, water / methanol (v / v 9:1), water / ethanol (v / v 9:1), and water / methanol / acetonitrile (v / v / v 3:1:1) were compared as extraction solvents for the colorant extraction. The results of the total content of the target analytes are shown in Figure a. Figure 2 Figure a shows the results. The results indicate that water / ethanol as the solvent has low extraction efficiency, with the greatest impact on amaranth. The results for water and water / methanol as extraction solvents show little difference, while the extraction rate of erythrosine in both samples significantly increases when water / methanol / acetonitrile is used as the solvent. Erythrosine has a sodium benzoate structure and is relatively less polar than other colorants, making it more soluble in acetonitrile, which is even less polar than water. Therefore, water / methanol / acetonitrile was chosen as the extraction solvent in this experiment. The results for different extraction times (1 min, 3 min, 5 min, 10 min) and the total colorant content are shown in Figure a. Figure 2 As shown in Figure b, it can be seen from the figure that when the extraction time exceeds 3 minutes, the amount of target substance extracted remains basically unchanged. Figure 1 Figure c shows the results of different microwave powers (300W, 400W, 500W, 600W) versus the total colorant content. (See figure) Figure 2 As shown in Figure c, the amount of target analyte extracted remained essentially unchanged after 3 minutes. Based on the optimized conditions, 1.0 g of tipped paper sample was weighed and 10 mL, 20 mL, and 30 mL of extraction solvent were added respectively. The results of different material-to-liquid ratios were investigated. The results were then analyzed. Figure 2 The d-plot shows that when the material-to-liquid ratio is 1:100, the colorant extraction is incomplete.

[0062] (2) Optimal process for microwave-assisted extraction of colorants

[0063] Microwave-assisted extraction was used, via L9(3) 4 An orthogonal experimental design was used to study the effects of different microwave power, extraction time, solid-liquid ratio, and methanol / acetonitrile / water mixture concentration on the extraction efficiency. To investigate these factors, microwave-assisted extraction was employed, and L9(3) was selected as the extraction method. 4The orthogonal design experiments are shown in Table 3, and the extraction process was optimized. A represents microwave power, B represents extraction time, C represents the solid-liquid ratio, and D represents the organic phase ratio (1:1 methanol / acetonitrile). The results are shown in Table 4. Table 4 shows that when using microwave-assisted extraction, the order of factors affecting the extraction effect is: A > D > B > C, with microwave power having the greatest impact on the extraction rate. The optimal process is: A1B2C2D2, i.e., extraction microwave power 300W, time 3min, solid-liquid ratio 1:100, methanol / acetonitrile (1:1) to water ratio 40%, i.e., methanol / acetonitrile / water volume ratio 1:1:3.

[0064] Table 4 Orthogonal L9(3) 4 Experimental results

[0065]

[0066] (3) Filter membrane selection

[0067] The microwave-assisted extraction solution was filtered to investigate the effects of polyethersulfone (PES), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), nylon 6 (domestic), nylon 66 (imported), mixed cellulose (MCM) needle filter membranes, and no filter membrane on the filtration of a standard mixed solution (5 μg / mL) using methanol / acetonitrile / water as the solvent. The results are as follows: Figure 3 As shown.

[0068] from Figure 3 It can be observed that, except for the nylon filter membrane, the results obtained from the other filter membranes are basically the same, with peak area RSD ≤ 0.09%. The peak areas of the samples filtered by organic nylon 6 (domestic) and nylon 66 (imported from the UK) decreased to varying degrees. In particular, nylon 6 showed significant adsorption of Acid Red, Erythrosine, Quinoline Yellow, and Brilliant Blue. This may be because nylon, or polyamide, is a filler material used for the enrichment and purification of colorants in GB 5009.35-2016, and it has varying degrees of adsorption on each target analyte. Therefore, this standard recommends using aqueous PES, PTFE, and PVDF as filter membranes.

[0069] (4) Wavelength scanning

[0070] Using method 1.2.5 as the instrumental analysis method, a diode array detector was employed to perform a full wavelength scan in the range of 190 nm to 800 nm. It was found that 10 colorants exhibited strong absorption at 254 nm. However, in practical operation, this wavelength is susceptible to absorption by various substances, leading to numerous interfering peaks. Therefore, 254 nm is not considered an ideal chromatographic detection wavelength. Different colorants have different maximum absorption wavelengths in the visible light region. Detection at the corresponding maximum absorption wavelengths of different colorants can effectively avoid interference from impurities and increase detection sensitivity. Figure 4Table 5 shows the 3D scanning profiles of 10 colorants and their maximum absorption wavelengths in the visible light region. The corresponding research in this paper uses the maximum absorption wavelengths of each colorant listed in Table 5.

[0071] Table 5. Detection wavelengths of 10 synthetic colorants

[0072]

[0073] (5) Working curve, limit of detection and limit of quantitation

[0074] A mixed standard solution (concentration range 0.5-20.0 μg / mL) of tartrazine, amaranth, carmine, sunset yellow, allura red, brilliant blue, acid red, erythrosine, indigo, and quinoline yellow was prepared. A standard curve was plotted with the concentration (μg / mL) of each synthetic colorant as the x-axis and the corresponding peak area as the y-axis (peak areas of the four isomers of quinoline yellow were combined). The R² values ​​for all 10 synthetic colorants were higher than 0.999, indicating good linearity of the 10 target compounds within the range of 0.5–20.0 μg / mL. The chromatogram of the standard working solutions is shown below. Figure 5 The lowest concentration standard solution was measured 10 times consecutively. The limit of detection (LOD) was 3 times the standard deviation (S / N=3), and the limit of quantitation (LOQ) was 10 times the standard deviation (S / N=10). The specific data are shown in Table 6. The LOD of the 10 synthetic colorants ranged from 0.95 to 3.21 μg / g, and the LOQ ranged from 3.16 to 10.72 μg / g.

[0075] Table 6 Standard Curve and Detection Limit

[0076]

[0077]

[0078] Note: Quinoline Yellow is a standard curve plotted based on the sum of the peak areas of quinoline yellow disodium salts (QYNa2 I, QYNa2 II) and quinoline yellow monosodium salts (QYNa I, QYNaII) at corresponding concentrations.

[0079] (6) Recovery test

[0080] Recovery rate experiments are one method for testing systematic errors. A better recovery rate indicates less sample loss during processing and a result closer to the true value, meaning better accuracy. Using blank spliced ​​paper samples, recovery and precision experiments were conducted using a three-level spiking method. The recovery rate and repeatability results are shown in Table 7. The average recovery rate ranged from 92.6% to 100.3%, and the average RSD ranged from 0.9% to 3.8%, indicating small systematic errors and good accuracy.

[0081] Table 7. Method recovery and repeatability (n=5)

[0082]

[0083]

[0084] (7) Partial Sample Analysis

[0085] Five cigarette tipping paper samples of different colors were collected and processed using this method for colorant detection. Allura Red and Tartrazine were detected in two samples, with levels below the maximum permitted levels for food use specified in GB 2760-2011. These were not detected in the other three samples. Based on previous research, some cigarette tipping paper uses natural colorants such as lycopene, safflower yellow, and red yeast rice for coloring; therefore, no synthetic colorants were detected.

[0086] Conclusion: Ten water-soluble colorants were selected as targets in this experiment. Microwave-assisted extraction was used to extract the colorants from tipping paper. The precision, accuracy, and recovery rate of the method were investigated by optimizing the sample pretreatment method. A liquid chromatography method for the analysis of ten water-soluble synthetic colorants in cigarette tipping paper was established.

[0087] Ten colorants were extracted using methanol / acetonitrile / water (1:1:3) as solvent, with a microwave power of 300W, an extraction time of 3 min, and a solid-liquid ratio of 1:100. Tartrazine, amaranth, carmine, sunset yellow, allura red, brilliant blue, acid red, erythrosine, indigo, and quinoline yellow were separated and analyzed by reversed-phase chromatography. Quantification was performed using a high-performance liquid chromatograph equipped with a diode array and the external standard method. The method showed a linear range of 0.5–20.0 μg / mL, with a linear correlation coefficient greater than 0.999. The method's limits of detection (LOD) were between 0.95 and 3.21 mg / kg, and the LOD was between 3.16 and 10.72 mg / kg. Spike recovery experiments at three levels (5 μg, 200 μg, and 400 μg) showed recoveries ranging from 92.6% to 100.3%. This method provides technical support for the safety evaluation of cigarette tipping paper.

[0088] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various different choices and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention is defined by the claims and their equivalents.

Claims

1. A method for determining water-soluble colorants in cigarette tipping paper using high-performance liquid chromatography, characterized in that, Includes the following steps: (1) Preparation of standard solutions: Weigh out tartrazine, amaranth, carmine, sunset yellow, allura red, brilliant blue, acid red, erythrosine, indigo and quinoline yellow, and dilute to volume with water / methanol / acetonitrile to obtain single standard stock solutions; mix the single standard stock solutions and dilute with water / methanol / acetonitrile to obtain mixed standard stock solutions; transfer different amounts of mixed standard solutions and dilute to volume with water / methanol / acetonitrile to prepare a series of standard working solutions of synthetic colorants of different concentrations; wherein the volume ratio of water / methanol / acetonitrile mixture is 3:1:1; (2) Sample preparation: Take the tipped paper sample and place it in the extraction vessel. Add water / methanol / acetonitrile solution and seal the vessel. Use microwave-assisted extraction. Filter the supernatant of the extract to obtain the test solution. The microwave power is 300W and the extraction time is 3min. (3) Sample analysis: The test solution was analyzed by HPLC-PDA and quantified by external standard method; the chromatographic conditions were as follows: Column: Agilent HC-C18(2) column, 4.6 x 150 mm, 5 µm, mobile phase A: 0.02 mol / L ammonium acetate aqueous solution, mobile phase B: acetonitrile, gradient elution was performed, total flow rate of mobile phase: 1.0 mL / min, column temperature: 30 ℃, injection volume: 10.0 μL, absorption wavelength: the maximum absorption wavelength of each target analyte; the gradient elution program was as follows:

2. The method for determining water-soluble colorants in cigarette tipping paper using high-performance liquid chromatography according to claim 1, characterized in that, The specific steps (1) are as follows: (11) Accurately weigh 25 mg each of tartrazine, amaranth, carmine, sunset yellow, allura red, brilliant blue, acid red, erythrosine, indigo and quinoline yellow into a 25 mL volumetric flask, and make up to volume with water / methanol / acetonitrile to obtain 10 single standard stock solutions with a concentration of 1.0 mg / mL. (12) Take 2.5 mL of a single standard stock solution and mix it in a 50 mL volumetric flask. Then dilute it with water / methanol / acetonitrile to obtain a mixed standard stock solution with a concentration of 50.0 μg / mL. (13) Transfer 0.1 mL, 0.5 mL, 1.0 mL, 2.0 mL, 3.0 mL and 4.0 mL of the mixed standard solution into a 10 mL volumetric flask, dilute with water / methanol / acetonitrile to obtain a series of standard working solutions of synthetic colorant with concentrations of 0.5 μg / mL, 2.5 μg / mL, 5.0 μg / mL, 10.0 μg / mL, 15.0 μg / mL and 20.0 μg / mL respectively.

3. The method for determining water-soluble colorants in cigarette tipping paper using high-performance liquid chromatography according to claim 1, characterized in that, Step (2) specifically involves: Accurately weigh 1.0 g of the tipped paper sample and place it in a 50 mL extraction vessel. Add 20 mL of water / methanol / acetonitrile solution, then seal the vessel and use microwave-assisted extraction. Filter the supernatant of the extract through a 0.45 μm aqueous filter membrane to obtain the test solution.

4. The method for determining water-soluble colorants in cigarette tipping paper using high-performance liquid chromatography according to claim 3, characterized in that, The filtration uses a 0.45 μm aqueous phase filter membrane, which is PES, PTFE or PVDF.

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