Method for detecting hexavalent chromium in tipping paper for cigarettes by adopting HPLC-ICP-MS

Abstract

The invention belongs to the technical field of hexavalent chromium detection, and particularly relates to a method for detecting hexavalent chromium in tipping paper for cigarettes by adopting HPLC-ICP-MS. The method comprises the steps of sample pretreatment, HPLC-ICP-MS measurement and obtaining of the hexavalent chromium content of a sample. The analysis and test method disclosed by the invention is simple and convenient in pretreatment operation, efficient, high in precision and high in result accuracy, and meets the test requirements of a target object. The target object shows a good linear relationship (r2gt; 0.999) in a concentration range of 0.00 [mu] g / L-5. 0 [mu] g / L; the detection limit and the quantitative limit value are relatively low and are 0.61 mu g / kg and 2.02 mu g / kg respectively; in a precision test, the relative standard deviation is less than 5%; in an accuracy test, the adding standard recovery rate of the sample is 90.0%-94.6%, and the method is relatively high in accuracy and can meet test requirements.

Description

Technical Field

[0001] This invention belongs to the field of hexavalent chromium detection technology, specifically relating to a method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS. Background Technology

[0002] Cigarette tipping paper, as a packaging material for cigarette filters, is one of the important materials in cigarette production. It is a special type of paper that uses cigarette tipping base paper as a substrate and undergoes pre-press design, printing, processing, and post-press treatment to connect the filter to the cigarette. The processing of cigarette tipping paper involves many raw materials, dyes, and auxiliaries, and environmental factors contribute to the presence of trace amounts of chromium in the paper. Prolonged direct oral contact with chromium may allow it to enter the body. Chromium exists in nature primarily in the forms of trivalent and hexavalent chromium. Studies have shown that trivalent chromium is a trace element needed by humans, while hexavalent chromium readily enters cells through anion channels in the cell membrane and is eventually reduced to trivalent chromium. However, this reduction process produces many byproducts that irritate the respiratory and digestive tracts, causing diseases such as nephritis, anemia, and neuritis, and is highly carcinogenic. With increasing global demands for tobacco product safety, establishing accurate and sensitive methods for detecting hexavalent chromium has become a crucial issue in tobacco quality control.

[0003] Currently, although there are reports in the literature on the detection methods of hexavalent chromium in cigarette tipping paper, different methods have drawbacks such as expensive detection equipment, complicated operation procedures, long time consumption, and high detection limits. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems and propose a method for pretreatment that is simple, efficient, precise, accurate, and practical, for determining the hexavalent chromium content in cigarette tipping paper. This invention aims to provide a new solution for the accurate determination of hexavalent chromium content in cigarette tipping paper.

[0005] Therefore, the present invention provides a method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS, the method comprising: (1) Preparation of standard solutions: Standard working solutions with different chromium concentrations were obtained and measured using HPLC-ICP-MS. The linear regression equation for the content of hexavalent chromium and the mass spectrometric response signal of hexavalent chromium was obtained; the linear regression equation can be automatically generated by HPLC-ICP-MS. (2) Sample pretreatment: The cigarette tipping paper sample was extracted, the extract was filtered and added to the mobile phase, and the resulting solution was analyzed by HPLC-ICP-MS to obtain the mass spectrometry response signal of the cigarette tipping paper sample. (3) Obtain the content of the sample: Substitute the mass spectrometry response signal of the cigarette tipping paper sample from step (2) into the linear regression equation from step (1) to obtain the content of hexavalent chromium in the cigarette tipping paper sample. Optionally perform step (1); The extraction reagent was a degassed dipotassium hydrogen phosphate solution with a pH of 8.0 ± 0.1. The mobile phase was a 75 mM nitric acid solution, with its pH adjusted to 7.5 using ammonia. In step (2), if the pH of the obtained solution is not in the range of 7.5-8.0, nitric acid solution or ammonia water is used to adjust the pH.

[0006] The above-described method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS employs 75 mM nitric acid as the mobile phase, with ammonia water adjusted to pH 7.5. The technical principle is as follows: Ammonium nitrate, as the mobile phase in anion exchange chromatography, has moderate ionic strength, effectively suppressing background conductivity and allowing the separated solution to be directly introduced into the mass spectrometer for detection, reducing interference. Hexavalent chromium readily converts to dichromate (Cr₂O₇) under acidic conditions. 2- ), while under neutral or weakly alkaline conditions (pH 7-8), it is more likely to form chromate (CrO4). 2- Ammonium nitrate exists in the form of ) and its buffering capacity helps maintain a stable pH environment and improve separation efficiency.

[0007] As a preferred embodiment, the above-mentioned method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS requires a sample size of (4-6) mm × (4-6) mm, preferably 5 mm × 5 mm. The sample in step (2) is cut to a size within a specified range to increase the contact area between the sample and the extraction reagent, thereby achieving a better extraction effect.

[0008] As a preferred option, in the above-mentioned method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS, the extraction temperature in step (2) is 36.5~37.5℃, which is a temperature that simulates human body temperature. Technical principle: This temperature range simulates human body temperature (approximately 37℃), which is consistent with the actual usage scenario of cigarette tipping paper (oral contact). Beneficial effects: Realistic simulation: Reflects the leaching behavior of hexavalent chromium under real contact conditions, improving the actual reference value of the detection data; Stability assurance: Avoids the degradation of hexavalent chromium caused by high temperature, ensuring the reliability of the recovery rate.

[0009] As a preferred embodiment, in the above-mentioned method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS, the extraction method in step (2) is water bath oscillation at 140-160 r / min, and the extraction time is 25-120 min, more preferably 29-31 min. Technical principle: Water bath oscillation enhances solid-liquid mass transfer through mechanical shear force, which is gentler and more controllable than static immersion or ultrasonic extraction. Too short an extraction time may lead to incomplete extraction, while too long an extraction time increases the risk of hexavalent chromium reduction. Beneficial effects: High-efficiency mass transfer: The oscillation frequency of 140-160 r / min ensures that the extractant fully penetrates the fiber structure of the tipping paper, shortening the equilibrium time; Prevention of valence state conversion: The extraction amount of hexavalent chromium reaches its peak at about 30 minutes, and the recovery rate decreases due to the reduction reaction after being extended to 60 minutes.

[0010] As a preferred specific method, when using dipotassium hydrogen phosphate solution (degassed) and water bath shaking extraction at 37°C, the target chromium hexavalent can obtain symmetrical chromatographic peaks within 3 minutes. Technical principle: A weakly alkaline environment (pH=8.0) allows hexavalent chromium to exist as stable CrO4. 2- The chromium exists in its original form, and phosphate ions can complex trivalent chromium in the sample, reducing competitive adsorption. Degassing treatment avoids bubble interference with chromatographic injection. Beneficial effects: Selective extraction: preferentially dissolves hexavalent chromium and inhibits its reduction, increasing the recovery rate to 90.0%~94.6%; Chromatographic compatibility: matched with weak anion exchange columns, obtaining symmetrical chromatographic peaks within 3 minutes, avoiding peak bifurcation.

[0011] As a preferred embodiment, in the above-mentioned method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS, the chromium concentration range of the standard working solution in step (2) is 0 μg / L to 5.0 μg / L, exhibiting good linearity within this range. Technical principle: This concentration covers common contamination levels (trace to moderate contamination) of hexavalent chromium in cigarette tipping paper. Beneficial effects: Wide dynamic range: Meets the precise quantitative requirements from the detection limit to the quantitation limit; Reduced dilution error: Avoids operational errors introduced by multiple dilutions of high-concentration samples.

[0012] As a preferred embodiment, the above-mentioned method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS requires HPLC conditions that satisfy at least one of the following characteristics: Flow rate: 1.0 mL / min, balancing chromatographic separation rate and column efficiency to achieve optimal resolution; Chromatographic column: Weak anion exchange HPLC guard column, such as Agilent Bio WAX, NP5, 4.6x50mm, guard, PEEK; Injection volume: 100 μL; Total analysis time: 3 min.

[0013] Under these chromatographic conditions, characteristic peaks with ideal elution times and shapes can be obtained.

[0014] As a preferred embodiment, the above-mentioned method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS requires that the ICP-MS conditions satisfy at least one of the following characteristics: Collision response mode; Mass number selection Cr 52 ; RF power: 1550W; Carrier gas flow rate: 1.0 L / min; Auxiliary gas flow rate: 0.9 L / min; Helium flow rate: 3.6 mL / min; Atomization chamber temperature: 2℃.

[0015] The above-mentioned method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS showed a sample spike recovery rate of 90.0% to 94.6%.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: The analytical testing method of this invention features simple, efficient, precise, and accurate pretreatment procedures, meeting the testing requirements of the target analyte. The target analyte exhibits good linearity (r0) within the concentration range of 0.00 μg / L to 5.0 μg / L. 2 The detection limit and quantitation limit are both low, at 0.61 μg / kg and 2.02 μg / kg, respectively; in the precision test, the relative standard deviation is less than 5%; in the accuracy test, the sample spike recovery rate is 90.0%~94.6%. This method has high accuracy and can meet the testing requirements.

[0017] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0018] Figure 1 Recovery rates of hexavalent chromium using different extraction methods; Figure 2 Recovery rate of hexavalent chromium at different extraction times; Figure 3 The instrument tests the solution to adjust the chromatographic peaks at different pH values. Detailed Implementation

[0019] The following description provides numerous specific details to offer a more thorough understanding of the technical solutions provided by this invention. However, it will be apparent to those skilled in the art that the technical solutions provided by this invention can be implemented without one or more of these details.

[0020] Example 1 This embodiment provides a method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS.

[0021] Sample pretreatment: Accurately weigh 0.5 g of cigarette tipping paper containing hexavalent chromium and place it in a 50 mL Erlenmeyer flask with a stopper. Accurately add 25 mL of dipotassium hydrogen phosphate solution (pH 8.0 ± 0.1, degassed), and extract by shaking in a water bath (150 rpm) for 30 min. Filter the solution using filter paper. Transfer 5 mL of the extract and add 5 mL of mobile phase (75 mM nitric acid, adjusted to pH 7.5 with ammonia) and mix thoroughly. Check the pH of the resulting solution; if it is not between 7.5 and 8.0, adjust the pH with nitric acid. Analyze the solution using HPLC-ICP-MS.

[0022] Preparation of standard solutions: A series of standard working solutions with concentrations of 0.0 μg / L (undiluted), 0.2 μg / L, 0.5 μg / L, 1.0 μg / L, 2.0 μg / L, and 5.0 μg / L were obtained by serial dilution with 1000 mg / L hexavalent chromium standard solution. The concentrations were determined by HPLC-ICP-MS.

[0023] Instrument and method conditions: HPLC conditions: Mobile phase: 75 mM nitric acid, adjusted to pH 7.5; Flow rate: 1.0 mL / min; Column: Weak anion exchange HPLC guard column, Agilent Bio WAX, NP5, 4.6 x 50 mm, guard, PEEK; Column temperature: Ambient temperature; Injection volume: 100 μL; Total analysis time: 3 min.

[0024] ICP-MS conditions: collision response mode; mass number selection Cr 52 Radio frequency power: 1550W; Carrier gas flow rate: 1.0L / min; Auxiliary gas flow rate: 0.9L / min; Helium flow rate: 3.6mL / min; Atomization chamber temperature: 2℃.

[0025] Experimental results: 1) Linear equations and correlation coefficients Linearity range and limit of detection (LOD) tests were conducted for hexavalent chromium. Standard solutions were serially diluted with mobile phase to prepare a series of standard working curve solutions with concentrations of 0.0 μg / L (undiluted), 0.2 μg / L, 0.5 μg / L, 1.0 μg / L, 2.0 μg / L, and 5.0 μg / L. A standard curve was plotted with the hexavalent chromium concentration (X) on the x-axis and the hexavalent chromium mass spectrometry response signal (Y) on the y-axis. The linear regression equation and other parameters for hexavalent chromium are shown in Table 1. The data in the table show that hexavalent chromium exhibits good linearity within the concentration range of 0.00 μg / L to 5.0 μg / L, with low LOD and LQ.

[0026] Table 1 Linear equation, detection limit and quantitation limit

[0027] 2) Accuracy and precision Recovery experiments were conducted using a blank matrix spiking test. A sample without the analyte was used as the blank matrix, and three different spiking concentration levels were set (0.2 μg / L, 1.0 μg / L, and 5.0 μg / L). Each spiking level was tested in parallel six times (n=6) to perform precision experiments. The results are shown in Table 2. At the three spiking levels, the recovery rate of the target analyte was within the range of 90.0%–94.6%, indicating that the method has high accuracy. The relative standard deviation of the recovery rate was no greater than 5.0%, indicating that the test method has high precision and meets the testing requirements.

[0028] Table 2 Recovery and Precision Results

[0029] Comparative Example 1 The other pretreatment and detection methods in Comparative Example 1 were the same as those in Example 1, except that the extraction reagent was replaced with primary water in the pretreatment, and the sample recovery rate was 42.0%.

[0030] Comparative Example 2 In Comparative Example 2, the other pretreatment and detection methods were the same as in Example 1, except that the pH of the pretreatment extraction reagent, dipotassium hydrogen phosphate solution (degassed), was changed to 6.0 and 7.0, and the sample recovery rates were 74.3% and 78.3%, respectively.

[0031] Test Example 1: Selection of Extraction Method Positive samples were extracted with dipotassium hydrogen phosphate solution (degassed) at 37°C using three different extraction methods: water bath immersion (x-axis 1), water bath shaking (x-axis 2, Example 1), and ultrasound (x-axis 3), each for 30 min. The extraction effects of the three methods were compared using HPLC-ICP-MS, and the results are shown below. Figure 1 As shown, through result comparison, the preferred extraction method is water bath shaking.

[0032] Test Example 2: Selection of Extraction Time Hexavalent chromium is easily reduced to trivalent chromium during prolonged extraction in the extractant, resulting in low recovery rates; while short extraction times may lead to incomplete extraction. Therefore, optimizing the extraction time is crucial to ensure complete extraction of the target analyte. Under controlled conditions, extraction experiments were conducted using positive samples at different extraction times of 10 min, 30 min (Example 1), 60 min, and 120 min. The results are as follows: Figure 2 As shown, the extraction efficiency of hexavalent chromium reached its peak when the extraction time was increased from 10 min to 30 min. After the extraction time increased from 30 min to 60 min, the extraction efficiency decreased and then stabilized. Considering the overall extraction efficiency of hexavalent chromium, the optimal extraction time is 30 min.

[0033] Test Example 3: Adjustment of pH of the solution after extraction Considering the potential conversion between trivalent and hexavalent chromium in the sample solution, the pH of the sample solution was adjusted using nitric acid or ammonia (pH = 6.0, 7.0, 7.5, 8.0). With other conditions kept constant, positive samples were used to determine the optimal stable pH for hexavalent chromium. The results are as follows: Figure 3 As shown in the figure. Through comparison, when the pH of the post-extraction solution is ≤7, hexavalent chromium is easily reduced to trivalent chromium, resulting in a trivalent chromium peak. When the pH is 8, hexavalent chromium tends to stabilize. Since hexavalent chromium mainly exists as CrO4 at pH >7.0... 2- It exists in various forms, with trivalent chromium primarily existing as Cr(OH). 2+ The presence of Cr(OH)3 and other forms of precipitates in the system increases the alkalinity of the solution, making it easier for the sample to precipitate and clog the chromatographic column. Considering all factors, the experiment selected a pH setting of 7.5-8.0 after extraction.

[0034] In Test Examples 1-3, all parameters were the same as in Example 1, except for the changed parameters.

[0035] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for detecting hexavalent chromium content in cigarette tipping paper using HPLC-ICP-MS, characterized in that, The method includes: (1) Preparation of standard solutions: Standard working solutions with different concentrations of hexavalent chromium were obtained and determined by HPLC-ICP-MS. The linear regression equation for the content of hexavalent chromium and the mass spectrometry response signal of hexavalent chromium was obtained. (2) Sample pretreatment: The cigarette tipping paper sample was extracted, the extract was filtered and added to the mobile phase, and the resulting solution was analyzed by HPLC-ICP-MS to obtain the mass spectrometry response signal of the cigarette tipping paper sample. (3) Obtain the content of the sample: Substitute the mass spectrometry response signal of the cigarette tipping paper sample from step (2) into the linear regression equation from step (1) to obtain the content of hexavalent chromium in the cigarette tipping paper sample. Among them, step (1) can be performed arbitrarily. The extraction reagent was a degassed dipotassium hydrogen phosphate solution with a pH of 8.0 ± 0.

1. The mobile phase was a 75 mM nitric acid solution, with its pH adjusted to 7.5 using ammonia. In step (2), if the pH of the obtained solution is not in the range of 7.5-8.0, nitric acid solution or ammonia water is used to adjust the pH.

2. The method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS according to claim 1, characterized in that, The dimensions of the sample to be tested are (4-6) mm × (4-6) mm.

3. The method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS according to claim 1, characterized in that, In step (2), the extraction temperature is 36.5~37.5℃.

4. The method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS according to claim 1, characterized in that, In step (2), the extraction method is water bath shaking at 140-160 r / min, and the extraction time is 25-120 min.

5. The method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS according to claim 4, characterized in that, The extraction time is 29-31 min.

6. The method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS according to claim 1, characterized in that, In step (1), the chromium concentration range of the standard working solution is 0 μg / L to 5.0 μg / L.

7. The method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS according to claim 1, characterized in that, HPLC conditions must satisfy at least one of the following characteristics: Flow rate: 1.0 mL / min; Chromatographic column: Weak anion exchange HPLC guard column; Injection volume: 100 μL; Total analysis time: 3 min.

8. The method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS according to claim 7, characterized in that, The weak anion exchange HPLC guard column was an Agilent Bio WAX, NP5, 4.6x50mm, guard, PEEK.

9. The method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS according to claim 1, characterized in that, ICP-MS conditions satisfy at least one of the following characteristics: Collision response mode; Mass number selection Cr 52 ; RF power: 1550W; Carrier gas flow rate: 1.0 L / min; Auxiliary gas flow rate: 0.9 L / min; Helium flow rate: 3.6 mL / min; Atomization chamber temperature: 2℃.

10. The method for detecting hexavalent chromium in cigarette tipping paper using HPLC-ICP-MS according to claim 1, characterized in that, The recoveries of spiked samples ranged from 90.0% to 94.6%.

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