CN109580798B - Method for detecting residual expanding medium in cut tobacco - Google Patents

Abstract

The invention provides a method for detecting the residual expansion medium in shredded tobacco, comprising: mixing the shredded tobacco sample with cyclohexane, performing static headspace-gas chromatography-mass spectrometry combined detection, and analyzing the content of KC-2A in the shredded tobacco sample content. The present invention is based on the low boiling point of the KC-2A medium, the volatile chemical characteristics and the characteristics of the static headspace-gas chromatography (static headspace gas chromatography, SHS-GC) technology, and establishes a fast and accurate static headspace-gas chromatography-mass spectrometry This method is used to determine the residue of expansion medium in shredded tobacco, which provides technical support for improving the application technology of the new expansion medium KC-2A and improving the smoking quality of cigarettes.

Description

A method for detecting residual expansion medium in tobacco shreds

Technical Field

The invention relates to the technical field of detection and analysis, and in particular to a method for detecting expansion medium remaining in tobacco shreds.

Background Art

In recent years, with the advancement of the tobacco industry's "reducing tar and reducing harm" and "reducing costs and increasing efficiency" work, the use of expanded tobacco and stem cuts has also increased. This is mainly because expanded tobacco or stem cuts have the advantages of strong filling capacity, good combustion performance, and obvious tar reduction and harm reduction effects. Their use in cigarette formulas can not only reduce the consumption of tobacco in a single box of cigarettes, but also reduce the tar release of cigarettes. Therefore, tobacco expansion technology has always been one of the important research areas in the tobacco industry. Researchers at home and abroad have conducted in-depth research on tobacco expansion process technology and equipment. New technologies and new processes are constantly emerging, making it an important part of the cigarette manufacturing process.

The traditional CFCs tobacco expansion method has been eliminated, and the dry ice expansion method is the most mature. There are also many new expansion technologies such as steam expansion technology and microwave expansion technology. The tobacco expansion methods used at home and abroad mainly include: steam, dry ice, liquid nitrogen and SP series tobacco expansion agent KC-2A. The tobacco expanded by the expansion medium KC-2A has bright color and full body, and is a good tobacco expansion agent. Studies have found that if the new expansion medium KC-2A is used in actual production, if the process is not perfect, there will be problems with medium residue. Since the medium residue will directly affect the smoking quality of cigarettes, it is particularly important to establish a rapid and accurate analytical method for detecting the residue of expansion medium in tobacco, so as to guide process improvement and reduce the residue of tobacco medium after expansion. At present, there has been no report on the detection of residues using KC-2A as a new expansion medium for tobacco.

Summary of the invention

In view of this, an object of the present invention is to provide a method for detecting expansion medium remaining in tobacco shreds.

The present invention provides a method for detecting residual expansion medium in tobacco shreds, comprising:

Mixing the expanded cut tobacco sample and cyclohexane to obtain a mixed liquid;

The mixed liquid was subjected to static headspace-gas chromatography-mass spectrometry detection to analyze the content of KC-2A in the expanded tobacco sample.

In the present invention, the preparation method of the expanded shredded tobacco sample is:

The unexpanded cut tobacco sample was immersed in an expansion medium KC-2A and expanded by microwave heating to obtain an expanded cut tobacco sample.

The present invention has no special limitation on the source of the unexpanded tobacco shreds. The unexpanded tobacco shreds well known to those skilled in the art can be used, and can be purchased from the market.

The present invention adopts static headspace-gas chromatography-mass spectrometry to detect the obtained mixed liquid. The specific method is to first pass the mixed liquid into an automatic headspace instrument for sampling, and then detect the obtained headspace gas by using a gas chromatography-mass spectrometer.

The content of each component in the headspace gas is related to its own volatility and the sample matrix, especially those components with large solubility (large distribution coefficient) in the sample matrix. The matrix effect is more obvious, that is, the composition of the headspace gas is different from that in the original sample, which is particularly serious for the adverse effect of quantitative analysis. The inventor has found through research on the basis of a large number of experiments that in order to accurately carry out quantitative analysis, the matrix effect of the sample can be effectively eliminated by selecting the quantitative analysis sample to have the same matrix as the standard solution.

The present invention uses cyclohexane as a matrix calibrant, and the expanded tobacco sample and cyclohexane are mixed to obtain a mixed solution. The inventors have found through research that the boiling points of methanol, n-hexane, and ethyl acetate are 64.5°C, 68.7°C, and 77.0°C, respectively. The peak times of these solvents are close to those of the medium KC-2A, which affects the accurate integral quantification of the medium and is not suitable as a matrix calibrant for the medium KC-2A. The boiling point of cyclohexane is 80.0°C, and it is a good hydrophilic reagent that can dissolve the KC-2A medium, so that the sample is evenly dispersed in the matrix solvent, thereby making the quantitative result more accurate. Therefore, cyclohexane is selected as a matrix calibrant.

In the present invention, the concentration of the expanded cut tobacco sample in the mixed liquid is preferably 0.3-0.7 g/mL, more preferably 0.4-0.6 g/mL, and most preferably 0.5 g/mL.

Based on a large number of experiments and studies, the inventors determined that according to the characteristics of the headspace and the physicochemical properties of the target compound, the equilibrium temperature of the static headspace in the process of static headspace-gas chromatography-mass spectrometry is preferably 40-80°C, more preferably 50-70°C, most preferably 55-65°C, and most preferably 60°C; the equilibrium time of the static headspace is preferably 10-30 min, more preferably 15-25 min, and most preferably 15 min.

In the present invention, the detection conditions of static headspace in the static headspace-gas chromatography-mass spectrometry process are:

The sample loop temperature is preferably 110-130°C, more preferably 115-125°C, and most preferably 120°C;

The transfer line temperature is preferably 130-150°C, more preferably 135-145°C, and most preferably 140°C;

The pressurization pressure is preferably 30-40 psi, more preferably 34-36 psi, and most preferably 35 psi;

The pressurization time is preferably 1.8 to 2.5 min, more preferably 1.8 to 2.2 min, and most preferably 2 min;

The carrier gas pressure is preferably 35 to 45 psi, more preferably 38 to 42 psi, and most preferably 40 psi;

The inflation time is preferably 0.15 to 0.25 min, more preferably 0.18 to 0.22 min, and most preferably 0.2 min;

The sample loop equilibration time is preferably 0.04 to 0.06 min, more preferably 0.05 min.

In the present invention, a static headspace-gas chromatography-mass spectrometry coupling process is performed. When performing gas chromatography detection, the inventors find that based on the physical and chemical properties of the target object to be analyzed, based on a large number of experiments, it is preferred to select a HP-PONA (50m×0.2mm×0.5μm) capillary column as a chromatographic separation column, which can enable the target object to obtain better baseline separation. In the present invention, the column flow rate of the chromatographic column during gas chromatography detection is preferably 0.6 to 1mL/min, more preferably 0.7 to 0.9mL/min, and most preferably 0.8mL/min.

When performing gas chromatography detection, the inventors conducted research based on a large number of experiments and optimized the furnace temperature and program heating so that the entire separation process can be completed within 21.5 minutes. In the present invention, the furnace temperature control during gas chromatography detection is preferably:

The initial furnace temperature is 30-50°C and maintained for 3-5 minutes, then increased to 70-90°C at 2-6°C/min, and then increased to 140-160°C at 15-25°C/min and maintained for 4-6 minutes.

More preferably:

The initial furnace temperature is 35-45°C and maintained for 3.5-4.5 min, then increased to 75-85°C at 3-5°C/min, and then increased to 145-155°C at 18-22°C/min and maintained for 4.5-5.5 min.

Most preferably:

The initial furnace temperature was 40°C for 4 min, increased to 80°C at 4°C/min, and then increased to 150°C at 20°C/min and maintained for 5 min.

In the present invention, the temperature rise program during gas chromatography detection is preferably:

The initial temperature is 140-160°C, which is increased to 275-285°C at a heating rate of 4-8°C/min, maintained for 3-7 minutes, and then increased to 290-310°C at a heating rate of 8-12°C/min, and maintained for 13-17 minutes.

More preferably:

The initial temperature is 145-155°C, which is increased to 278-282°C at a heating rate of 5-7°C/min, maintained for 4-6 minutes, and then increased to 295-305°C at a heating rate of 9-11°C/min, and maintained for 14-16 minutes.

Most preferably:

The initial temperature was 150°C, which was increased to 280°C at a heating rate of 6°C/min and maintained for 5 min. Then, the temperature was increased to 300°C at a heating rate of 10°C/min and maintained for 15 min.

In the present invention, the detection conditions of gas chromatography during the static headspace-gas chromatography-mass spectrometry are:

The injection port temperature is preferably 140-160°C, more preferably 145-155°C, and most preferably 150°C;

The constant flow mode is preferred for sample injection, and the split ratio during the sample injection process is preferably (40-60):1, more preferably (45-55):1, and most preferably 50:1;

The carrier gas is preferably argon, more preferably high-purity argon, and the purity of the argon is preferably ≥ 99.999%.

In the present invention, during mass spectrometry detection in the static headspace-gas chromatography-mass spectrometry coupling process, the inventors used mass spectrometry to obtain the identification information of the medium KC-2A by selected ion scanning. The identification information of KC-2A is shown in Table 1. Based on a large number of experiments, it was found that when the medium KC-2A selected to monitor the characteristic ion 81, the target compound could obtain a better chromatogram, as shown in Figure 3.

Table 1 Identification information of medium KC-2A

In the present invention, the detection conditions of mass spectrometry in the static headspace-gas chromatography-mass spectrometry process are:

The EI ionization energy is preferably 60 to 80 eV, more preferably 65 to 75 eV, and most preferably 70 eV;

The ion source temperature is preferably 220-240°C, more preferably 225-235°C, and most preferably 230°C;

The transfer line temperature is preferably 240-260°C, more preferably 245-255°C, and most preferably 250°C;

The solvent delay time is preferably 0.1 to 0.3 min, more preferably 0.15 to 0.25 min, and most preferably 0.2 min;

The scanning mode is preferably full scanning, and the scanning range is preferably 29-400 aeu;

The selected monitoring ions are preferably 81, and more preferably 61 and 81.

The important technical problems solved by the present invention are: 1) optimization of equilibrium time and equilibrium temperature in the detection method and selection of matrix corrector; 2) using SHS-GC/MS to perform external standard quantitative analysis on the medium KC-2A in the sample, determine the regression equation and correlation coefficient of the expansion medium KC-2A, the detection limit and quantitative limit of the detection method; 3) determine the recovery rate and precision of the detection method.

Through extensive research, the inventors have established a fast and accurate static headspace gas chromatography-mass spectrometry method for determining the residues of expansion medium in tobacco shreds by optimizing experimental conditions based on the low boiling point and volatile chemical properties of the KC-2A medium and the characteristics of static headspace gas chromatography (SHS-GC) technology, providing technical support for improving the process technology of using the new expansion medium KC-2A and improving the smoking quality of cigarettes.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

FIG1 is a graph showing the effect of headspace equilibrium time on peak area tested in Example 1 of the present invention;

FIG2 is the effect of headspace equilibrium temperature on peak area tested in Example 2 of the present invention;

FIG. 3 is a selected ion chromatogram of the medium KC-2A (a) and the expanded tobacco sample (b) in the present invention.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

The KC-2A used in the following examples of the present invention is a product provided by Beijing Institute of Spaceflight Experimental Technology 101.

The unexpanded tobacco samples used were products provided by the Tongren Cigarette Factory of Guizhou China Tobacco Industry Co., Ltd.

The method for obtaining the expanded tobacco sample used is:

The unexpanded cut tobacco sample was soaked in the expansion medium KC-2A and then expanded by microwave heating to obtain the expanded cut tobacco sample.

The equipment used for SHS-GC/MS (static headspace-gas chromatography-mass spectrometry) detection is gas chromatography-mass spectrometry and automatic headspace analyzer.

Example 1

Weigh 0.5 g (accurate to 0.001 g) of expanded tobacco sample into a 20 mL headspace bottle, add 1 mL of cyclohexane, quickly tighten the bottle cap, put it into the headspace injector of the automatic headspace instrument, and then measure the obtained headspace gas by gas chromatography-mass spectrometry.

The expansion medium KC-2A in the tobacco shreds was quantitatively analyzed by external standard method using SHS-GC/MS (static headspace-gas chromatography-mass spectrometry). The detection conditions are as follows:

Static headspace detection:

Sample balancing temperature: 60℃; sample loop temperature: 120℃; transfer line temperature: 140℃; sample balancing time: 15min; sample bottle pressurization pressure: 35psi; carrier gas pressure: 40psi; pressurization time: 2.0min; filling time: 0.20min; sample loop balancing time: 0.05min; injection time: 0.1min.

Gas chromatography detection:

Chromatographic column: HP-PONA capillary column (50m×0.2mm×0.5μm); Oven temperature: initially 40°C for 4 min, then increased to 80°C at 4°C/min, then increased to 150°C at 20°C/min for 5 min; Inlet temperature: 150°C, split ratio: 50:1; Carrier gas: high-purity helium, purity ≥99.999%; Constant flow mode, column flow rate: 0.8mL/min.

Detection heating program: initial temperature 150℃, increase to 280℃ at a heating rate of 6℃/min, hold for 5min, then increase to 300℃ at a heating rate of 10℃/min, hold for 15min.

Mass spectrometry detection:

EI ionization energy: 70 eV; ion source temperature: 230°C, transfer line temperature: 250°C, solvent delay: 0.2 min, scanning mode: full scan, scanning range 29-400 aeu; selected ion monitoring (SIM), monitored ions are 61 and 81.

The detection result obtained by the method provided in Example 1 of the present invention is that the residual amount of KC-2A is 5.28 μg/g. The method provided by the present invention is suitable for detecting the residue of tobacco expansion medium KC-2.

Example 2

70 μg/mL of KC-2A medium standard solution was added to unexpanded tobacco shreds, and the equilibrium temperature was 60°C, and the equilibrium time was measured for 10 min, 15 min, 20 min and 30 min, respectively. Other detection conditions were the same as in Example 1. The measurement results are shown in Figure 1. As can be seen from Figure 1, the peak area equilibrium time of the response chromatogram of medium KC-2A increased slightly from 10 min to 15 min, decreased slightly from 15 min to 20 min, and basically had no difference from 20 min to 30 min. Since the boiling point of medium KC-2A is low and volatile, the relative equilibrium time has little effect. In order to fully balance the sample to be tested, a 15 min equilibrium time is selected as the best.

Example 3

70 μg/mL of KC-2A medium standard solution was added to unexpanded tobacco shreds, and the test was performed at equilibrium temperatures of 40°C, 50°C, 60°C and 80°C respectively under an equilibrium time of 15 min, and other test conditions were the same as those in Example 1. The test results are shown in FIG2 , and it can be seen from FIG2 that with the increase of the equilibrium temperature, the peak area of KC-2A medium gradually increases, the growth rate is slightly lower at 40 to 60°C, and the growth rate is obvious at 60 to 80°C. Usually, the residual amount of the expansion medium KC-2A in the expanded tobacco shreds at room temperature is tested, and the medium KC-2A has a low boiling point, taking into account the full volatilization of the sample medium KC-2A, as well as the requirements of improving the method sensitivity and reducing the interference of the sample matrix, the equilibrium temperature of 60°C is selected as the best.

Example 4 Working curve and determination of detection limit

Preparation of KC-2A medium standard solution:

10 μL of KC-2A medium was measured and added to 10 mL of cyclohexane solvent. The medium weighed 7.0 mg and its concentration was 0.7 mg/mL.

KC-2A medium working curve:

5 μL, 10 μL, 20 μL, 50 μL, 100 μL and 150 μL of KC-2A medium standard solution were respectively measured and added to 1 mL of cyclohexane solvent to prepare a series of standard solutions with mass concentrations of 3.5 μg/mL, 7.0 μg/mL, 14 μg/mL, 35 μg/mL, 70 μg/mL and 105 μg/mL, and 0.5 g of unexpanded tobacco was added to each of them.

The seven standard solutions of different concentrations were analyzed and tested according to the method described in Example 1, and regression analysis was performed with the chromatographic peak area of KC-2A medium as the ordinate and its corresponding mass concentration X (μg/mL) as the abscissa, and the regression equation was obtained as Y=1741.89X (r ² ＝0.9999). The detection limit was calculated to be 0.03μg/mL using a 3-fold signal-to-noise ratio (S/N≥3).

Example 5 Recovery and Repeatability of Detection Method

Weigh 0.5 g of unexpanded tobacco (medium KC-2A content is 0.0 μg), add 1 mL of standard solution containing KC-2A with concentrations of 5.0 μg/mL, 10.0 μg/mL, and 20.0 μg/mL, respectively, and perform analysis and detection according to the method of Example 1. Perform parallel tests 6 times for each concentration, and calculate the recovery rate based on the measured amount, spiked amount, and original content.

The test results are shown in Table 2, which shows the recovery rate and repeatability of KC-2A obtained by the method provided in the embodiment of the present invention.

Table 2 Recovery and repeatability of KC-2A obtained by the method provided in the embodiment of the present invention (n=6)

As shown in Table 2, the sample pretreatment operation of the detection method provided by the present invention is simple, fast, reproducible and accurate. The method provided by the present invention can accurately detect the residue of tobacco expansion medium KC-2, and is simple and fast.

As can be seen from the above embodiments, the present invention provides a method for detecting the residual expansion medium in tobacco shreds, comprising: mixing the expanded tobacco shreds sample with cyclohexane and then conducting static headspace-gas chromatography-mass spectrometry detection to analyze the content of KC-2A in the expanded tobacco shreds sample. Based on the low boiling point and volatile chemical properties of the KC-2A medium and the characteristics of static headspace gas chromatography (SHS-GC) technology, the present invention establishes a fast and accurate static headspace-gas chromatography-mass spectrometry to determine the residual expansion medium in tobacco shreds, providing technical support for improving the use process technology of the new expansion medium KC-2A and improving the smoking quality of cigarettes.

Claims (5)

1. A method for detecting residual expansion medium in tobacco shreds, comprising: Mixing the expanded cut tobacco sample and cyclohexane to obtain a mixed liquid; The mixed liquid was subjected to static headspace-gas chromatography-mass spectrometry to analyze the content of KC-2A in the expanded tobacco sample; The detection conditions of static headspace in the static headspace-gas chromatography-mass spectrometry process are: The equilibrium temperature is 40-80°C; The equilibrium time is 10 to 30 minutes; The detection conditions of gas chromatography in the static headspace-gas chromatography-mass spectrometry process are: The chromatographic column was a HP-PONA capillary column with a column flow rate of 0.6 to 1 mL/min; The furnace temperature is controlled as follows: initially at 35-45°C for 3-5 minutes, then heated to 70-90°C at 3-5°C/min, then heated to 140-160°C at 15-25°C/min and heated for 4-6 minutes; The injection temperature is 140-160°C; The detection conditions of mass spectrometry in the static headspace-gas chromatography-mass spectrometry coupling process are: EI ionization energy is 65-75 eV; The ion source temperature is 220～240℃, The transmission line temperature is 240-260°C; The solvent delay time is 0.1 to 0.3 min; The scanning mode is full scan, and the scanning range is 29～400aeu; The ions selected for monitoring were 61 and 81. 2. The method according to claim 1, characterized in that the preparation method of the expanded shredded tobacco sample is: The unexpanded cut tobacco sample was immersed in an expansion medium KC-2A and expanded by microwave heating to obtain an expanded cut tobacco sample. 3 . The method according to claim 1 , wherein the concentration of the expanded shredded tobacco sample in the mixed solution is 0.3 to 0.7 g/mL. 4. The method according to claim 1, characterized in that the detection conditions of static headspace in the static headspace-gas chromatography-mass spectrometry process are: The transmission line temperature is 130～150℃; The pressurization pressure is 30-40 psi; The pressurization time is 1.5 to 2.5 minutes. 5. The method according to claim 1, characterized in that the detection conditions of static headspace in the static headspace-gas chromatography-mass spectrometry process are: The carrier gas pressure is 35-45 psi; The inflation time is 0.15 to 0.25 minutes; Injection time: 0.05～0.15min.

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