CN112730668A - Method for measuring chloromethane in cigarette mainstream smoke - Google Patents

Abstract

The invention discloses a method for measuring chloromethane in mainstream smoke of a cigarette, which is characterized by comprising the steps of collecting chloromethane in mainstream smoke, performing blank experiments, processing smoke samples, preparing standard working solution, selecting instrument measuring conditions, and performing qualitative and quantitative measurement. The invention adopts N, N-dimethylformamide of polar aprotic compound as absorption liquid, and two absorption bottles which are respectively filled with the absorption liquid and are placed in cold hydrazine and are connected in series can realize effective capture of methyl chloride in mainstream smoke, and the capture rate can reach more than 99%. As the polar aprotic solvent N, N-dimethylformamide with higher boiling point and weaker volatility is used as the absorption liquid, the retention time of the polar aprotic solvent N, N-dimethylformamide on a chromatographic column is longer than that of methyl chloride, no solvent interference and no background interference exist, and the absorption liquid migration caused by air flow is avoided. Because cold solution absorption and GC/MS liquid sample injection are adopted, the content of the chloromethane in the mainstream smoke of the cigarette can be simply and conveniently trapped and quickly measured, the detection limit of the chloromethane is 0.26 mu g/cig, and the method has the advantages of high sensitivity, good repeatability, accurate qualitative and quantitative determination and strong operability.

Description

Method for measuring chloromethane in cigarette mainstream smoke

Technical Field

The invention belongs to the technical field of physicochemical inspection, and particularly relates to a method for trapping and measuring chloromethane in cigarette mainstream smoke.

Background

Methyl chloride, also known as methyl chloride, is a colorless gas with a slightly sweet smell like ether, has a boiling point of-23.7 ℃, belongs to a polar aprotic compound, is slightly soluble in water, and is easily soluble in ethanol, acetone and the like. Chloromethane is a slow-acting poison, and low-concentration short-time inhalation can cause symptoms such as drowsiness, somnolence, headache, emotional instability, visual disturbance and tremor, and has great damage to the central nervous system, liver and kidney after long-term inhalation.

Related research shows that various harmful pollutants are generated in the biomass combustion process, wherein methyl chloride is VOC emission_SOne of the identifying components of (1). The cigarette is a cigarette with incomplete combustion of tobacco shredsThe mainstream smoke produced during the firing may contain methyl chloride. Therefore, the method for accurately measuring and researching the content of the chloromethane in the mainstream smoke of the cigarette has important practical significance for evaluating the safety of the cigarette and protecting the health of consumers.

At present, the quantitative determination method of methyl chloride has chemical industry standards HG/T3674-2018, U.S. EPA524.2 and partial literature reports, but the cut tobacco of the cigarette consists of tobacco leaves and added endogenous components, and the cigarette smoking belongs to the periodic cycle of 2s smoking and 58s static combustion; in the pumping process of 2s, the pumping flow rate and the time are distributed in a sine function curve (see figure 1), and the peak flow rate can reach 27.5 mL/s; along with the periodic change of the suction flow (0-27.5-0 mL/s) within 2s, the temperature of a tobacco combustion cone (250-850-250 ℃) and the combustion-supporting oxygen content (oxygen enrichment-oxygen depletion-oxygen enrichment) are changed, so that the cigarette smoke composition is more complicated and becomes aerosol consisting of more than 5000 chemical components. The high instantaneous flow rate and the complex composition of the aerosol state cause that the adsorbent trapping method can not meet the requirements of trapping and measuring the chloromethane in the cigarette smoke. Therefore, the existing method is not suitable for trapping and measuring the chloromethane in the mainstream smoke of the cigarette.

Disclosure of Invention

The invention provides a method for measuring chloromethane in cigarette mainstream smoke, which aims to solve the problems in the prior art.

In order to realize the aim of the invention, the method for measuring the chloromethane in the mainstream smoke of the cigarette is characterized by comprising the following steps:

a. and (3) capturing methyl chloride in the mainstream smoke: in the process of quantitatively smoking cigarettes by using a smoking machine, after a glass fiber filter disc is used for capturing particulate matters in main stream smoke, introducing the particulate matters into cold hydrazine at the temperature of less than or equal to 70 ℃, and then capturing gas-phase matters in the main stream smoke by using two serially connected absorption bottles respectively filled with 15-30 mL of N, N-dimethylformamide absorption liquid;

b. blank experiment: taking the same cigarette without lighting, performing air suction on each cigarette according to the steps to obtain a blank sample in a non-lighting state, and deducting a measurement result after treatment to counteract background pollution existing in a suction channel and the environment;

c. treating a flue gas sample: after pumping, combining absorption liquid and shaking uniformly, and performing GC/MS analysis;

d. preparing a standard working solution: preparing a chloromethane standard solution into standard working solutions with chloromethane mass concentrations of 0.2, 0.5, 1.5, 5.0, 10.0 and 25.0 mu g/mL respectively by using N, N-dimethylformamide;

e. the instrument measurement conditions are as follows:

GC/MS analysis determination conditions:

a chromatographic column: HP-POLT Q chromatographic column 30m × 0.32 mm × 20 μm; carrier gas: helium with purity more than or equal to 99.999%; constant flow rate: 2.0 mL/min; sample inlet temperature: 250 ℃; the split ratio is as follows: 5: 1; sample introduction amount: 1.0 μ L;

column box temperature program: the initial temperature is 45 ℃, the temperature is kept for 2min, the temperature is increased to 120 ℃ at the speed of 5 ℃/min, then the temperature is increased to 250 ℃ at the speed of 20 ℃/min, and the temperature is kept for 10 min; transmission line temperature: 250 ℃; an ionization mode: an EI source; ion source temperature: 230 ℃; quadrupole temperature: 150 ℃; the collection type is as follows: a SIM mode; collecting ions: m/z50, 52;

f. qualitative and quantitative:

and (3) qualitative ion m/z50 and qualitative ion m/z52 are quantitatively determined by adopting a standard sample adding method and an abundance ratio of 100:31 +/-20%, and quantitatively determined by adopting an external standard curve method.

The invention achieves the technical progress that:

1. according to the invention, N-dimethylformamide has larger dipole moment and good hydrogen bond donor-acceptor property, and N, N-dimethylformamide which is a polar aprotic compound is taken as an absorption liquid according to the similar intermiscibility principle, and two serially connected absorption bottles which are respectively filled with the absorption liquid and placed in cold hydrazine are adopted, so that the effective capture of methyl chloride in mainstream smoke can be realized; the trapping rate of the methyl chloride in the method is represented by the ratio of the sum of the content of the methyl chloride in the absorption liquid of the first two stages to the sum of the content of the methyl chloride in the whole absorption liquid, and the trapping rate can reach more than 99 percent.

2. Because the polar aprotic solvent N, N-dimethylformamide with higher boiling point and weaker volatility is used as the absorption liquid, the retention time of the polar aprotic solvent N, N-dimethylformamide on the chromatographic column is longer than that of methyl chloride, the method has no solvent interference and background interference, and the absorption liquid migration caused by airflow is avoided.

3. The method adopts cold solution absorption and GC/MS liquid sample introduction to carry out methodology research and quantitative analysis on the determination of the methyl chloride in the cigarette mainstream smoke, can simply, conveniently and quickly determine the content of the methyl chloride in the cigarette mainstream smoke, has the detection limit of the methyl chloride of 0.26 mu g/cig, and has high sensitivity, good repeatability, accurate qualitative and quantitative determination and strong operability.

Drawings

Figure 1 smoking machine standard smoking profile.

FIG. 2 is an ion flow diagram of a cigarette mainstream smoke sample.

FIG. 3 is an ion flow diagram of a chloromethane standard sample.

Detailed Description

The present invention is further illustrated by the following specific examples.

(1) The main apparatus is as follows: SM450 straight-line smoking machine and Qtm cigarette comprehensive test bench of Cerulean corporation, UK; agilent 7890B/5973 gas chromatography-mass spectrometer; 0.0001g of a sensory AB204-S balance from Mettler, Switzerland; 70mL gas absorption bottle.

(2) The main reagents are as follows: methyl chloride standard solution (2000. mu.g/mL in methanol, national standard, stored at-10 ℃); pure N, N-dimethylformamide was analyzed.

(3) Samples of cigarettes available commercially in 2020 on the local market, of which 6 cured tobacco types and 2 blended types were obtained.

The steps of capturing chloromethane in the mainstream smoke of the cigarette and measuring the content are as follows:

a. preparing a standard working solution: preparing a chloromethane standard solution into standard working solutions with chloromethane mass concentrations of 0.2, 0.5, 1.5, 5.0, 10.0 and 25.0 mu g/mL by using N, N-dimethylformamide, performing GC/MS analysis respectively, performing linear regression analysis on the mass concentration (X) by using the chromatographic peak area (Y) of a chloromethane quantitative ion (m/z 50) to obtain a chloromethane standard curve linear regression equation Y of 20486.82X + 19757.16 and a correlation coefficient R²0.9996. Performing GC/MS separation on the standard working solution with the lowest concentrationAnd (4) analyzing, repeating the measurement for 10 times, calculating the standard deviation, taking the 3-time standard deviation as a detection limit, taking the 10-time standard deviation as a quantification limit, and obtaining the chloromethane with the detection limit of 0.026 mu g/mL and the quantification limit of 0.085 mu g/mL.

b. Capture, treatment and analysis of methyl chloride in mainstream smoke: screening cigarettes by using a cigarette comprehensive test bench according to the mass (average value +/-50) mg and the smoking resistance (average value +/-50) Pa to obtain relatively consistent samples to be tested, smoking by using a smoking machine according to the method specified in GB/T19609-2004, wherein 4 cigarettes are smoked in each channel, and 2 cigarettes are smoked after each round of smoking; the particulate matter in the mainstream smoke is collected by a phi 44mm glass fiber filter disc, and the gaseous matter in the mainstream smoke is collected by two serially connected absorption bottles which are placed in cold hydrazine (less than or equal to-70 ℃) consisting of ethanol/dry ice and are respectively filled with 20.0mL of absorption liquid. And simultaneously, performing blank experiments, namely, the same cigarettes are not ignited, and each cigarette is sucked according to the corresponding amount of the steps to obtain a blank sample in the cigarette non-ignited state. After pumping, combining the absorption liquid in the two absorption bottles and shaking uniformly to obtain the liquid to be detected, then filling a brown chromatographic bottle with a proper amount of the liquid to be detected, immediately carrying out GC/MS analysis, and carrying out blank deduction on the determination result.

c. GC/MS analysis determination conditions:

a chromatographic column: HP-POLT Q column (30 m.times.0.32 mm. times.20 μm); carrier gas: helium with purity more than or equal to 99.999%; constant flow rate: 2.0 mL/min; sample inlet temperature: at 250 ℃, the split ratio: 5: 1; sample introduction amount: 1.0 μ L; column box temperature program: the initial temperature is 45 ℃, the temperature is kept for 2min, the temperature is increased to 120 ℃ at the speed of 5 ℃/min, then the temperature is increased to 250 ℃ at the speed of 20 ℃/min, and the temperature is kept for 10 min; transmission line temperature: 250 ℃; an ionization mode: an EI source; ion source temperature: 230 ℃; quadrupole temperature: 150 ℃; the collection type is as follows: a SIM mode; collecting ions: m/z50, 52;

d. qualitative and quantitative:

and (3) qualitative ion m/z50 and qualitative ion m/z52 are quantitatively determined by adopting a standard sample adding method and an abundance ratio of 100:31 +/-20%, and quantitatively determined by adopting an external standard curve method.

The invention discloses a condition analysis for capturing chloromethane and measuring content in cigarette mainstream smoke, which comprises the following steps:

a. trapping method and selection of absorption liquid

Early tests show that the methyl chloride only exists in the gas phase of the mainstream smoke of the cigarette, so that the total release amount of the methyl chloride in the mainstream smoke can be represented by examining the content of the methyl chloride in the gas phase. The boiling point of the chloromethane is-23.7 ℃, the chloromethane is difficult to be completely trapped by a solvent at normal temperature, and the cold solvent trapping method can overcome the defect, so a cold hydrazine trapping mode is selected. Methyl chloride is a polar aprotic compound, and a polar aprotic inert solvent N, N-dimethylformamide which has a high boiling point (153 ℃), a large dipole moment and good hydrogen bond donor-acceptor properties is selected as an absorption liquid according to the principle of similarity and compatibility, so that the absorption liquid can be effectively prevented from migrating while high absorption rate is obtained.

b. Selection of number of absorption bottles and volume of absorption liquid

The method comprises the steps of connecting 3 absorption bottles containing 20.0mL of absorption liquid in series behind a smoking machine to form three-stage trapping, and inspecting the trapping rate of each stage of absorption bottle. In the measured total amount of the methyl chloride, the first-stage absorption liquid accounts for 91.3%, the second-stage absorption liquid accounts for 8.7%, and no detection is detected in the third-stage absorption liquid, which indicates that the two-stage absorption can reach 99% of the trapping rate. Thus, two absorber bottles in series were selected to trap methyl chloride in the mainstream smoke.

The influence of different volumes of 15, 20, 25 and 30mL of absorption liquid on the capture rate of the chloromethane under optimized conditions was examined. The measurement results showed that the measurement results did not change significantly with the increase in the volume of the absorbent solution, and the volume of the absorbent solution was selected to be 20 mL in general.

c. Selection of chromatography columns

Chloromethane is a polar organic compound with small molecules and low boiling point, and is weakly retained and rapidly appears on a common chromatographic column, while a POLT Q column is a special column for gas analysis, which is widely applied and has stronger retention on volatile small molecule components. Cigarette smoke is an aerosol composed of thousands of chemical constituents, relatively complex, and difficult to separate. Therefore, the separation effect of methyl chloride in the main stream smoke capture liquid of cigarettes of different types and brands on the HP-POLT Q chromatographic column is mainly considered. As can be seen from FIG. 2, under the optimized measurement conditions, the chloromethane and the interferent can realize baseline separation, the separation degree R is more than 1.5, the peak shapes are symmetrical (see FIG. 2 and FIG. 3), and the requirement of accurate quantification is met. Therefore, HP-POLT Q (30 m.times.0.32 mm.times.20 μm) was selected as the separation column.

d. Stability of sample solutions

And respectively filling brown chromatographic bottles with the same liquid to be detected, standing at room temperature for 0, 2, 4, 8, 16, 24, 32 and 40 hours, and then measuring the release amount of methyl chloride in the liquid to be detected at room temperature. The result shows that the content of the chloromethane of the liquid to be detected which is densely stored at room temperature and is protected from light is in a descending trend along with the prolonging of the standing time, the measurement result is reduced by 1.83 percent when the liquid to be detected is placed for 24 hours, and the measurement result is reduced by 3.07 percent when the liquid to be detected is placed for 32 hours, so the measurement of the liquid to be detected is finished within 24 hours after the liquid to be detected is treated.

e. Recovery and precision of the process

20.0mL of absorbing liquid with chloromethane mass concentration of 0, 0.5, 2.5 and 10.0 mug/mL is respectively added into the first-stage absorption bottles connected in series, and the cigarette sample with the number C is subjected to suction treatment and measurement according to the method described in the embodiment. The average recovery rate of the sample at high, middle and low standard adding levels is 93.8-99.4%, and the Relative Standard Deviation (RSD) of the results of 6 times of parallel measurement is 1.7-3.9%.

f. Determination of actual samples

The results of the determination of 6 flue-cured tobacco type and 2 mixed type cigarette samples by using the method of the embodiment are shown in table 1, which indicates that methyl chloride is detected in the mainstream smoke of the selected cigarette samples, the detected amount is 37-104 mug/cig, which indicates that the methyl chloride generated by cigarette combustion is consistent with the conclusion that "methyl chloride is one of the biomass combustion emission marker components" reported in the text of civil biomass combustion volatile organic compound emission characteristics of Lixing and the like.

TABLE 1 determination of methyl chloride in cigarette mainstream smoke

Sample numbering	Cigarette type	Amount of tar (mg/cig)	Content of methyl chloride (μ g/cig)
				A	Hybrid type	9	47.98
B	Hybrid type		8					36.67
				C	Flue-cured tobacco type	10	61.83
D	Flue-cured tobacco type	11	78.35
				E	Flue-cured tobacco type	11	80.41
F	Flue-cured tobacco type	11	91.02
				G	Flue-cured tobacco type	11	104.38
H	Flue-cured tobacco type	9	65.91

Claims (1)

1. A method for measuring chloromethane in cigarette mainstream smoke is characterized by comprising the following steps:

a. and (3) capturing methyl chloride in the mainstream smoke: in the process of quantitatively smoking cigarettes by using a smoking machine, after a glass fiber filter disc is used for capturing particulate matters in main stream smoke, introducing the particulate matters into cold hydrazine at the temperature of less than or equal to 70 ℃, and then capturing gas-phase matters in the main stream smoke by using two serially connected absorption bottles respectively filled with 15-30 mL of N, N-dimethylformamide absorption liquid;

b. blank experiment: taking the same cigarette without lighting, performing air suction on each cigarette according to the steps to obtain a blank sample in a non-lighting state, and deducting a measurement result after treatment to counteract background pollution existing in a suction channel and the environment;

c. treating a flue gas sample: after pumping, combining absorption liquid and shaking uniformly, and performing GC/MS analysis;

d. preparing a standard working solution: preparing a chloromethane standard solution into standard working solutions with chloromethane mass concentrations of 0.2, 0.5, 1.5, 5.0, 10.0 and 25.0 mu g/mL respectively by using N, N-dimethylformamide;

e. the instrument measurement conditions are as follows:

GC/MS analysis determination conditions:

a chromatographic column: HP-POLT Q chromatographic column 30m × 0.32 mm × 20 μm; carrier gas: helium with purity more than or equal to 99.999%; constant flow rate: 2.0 mL/min; sample inlet temperature: 250 ℃; the split ratio is as follows: 5: 1; sample introduction amount: 1.0 μ L;

column box temperature program: the initial temperature is 45 ℃, the temperature is kept for 2min, the temperature is increased to 120 ℃ at the speed of 5 ℃/min, then the temperature is increased to 250 ℃ at the speed of 20 ℃/min, and the temperature is kept for 10 min; transmission line temperature: 250 ℃; an ionization mode: an EI source; ion source temperature: 230 ℃; quadrupole temperature: 150 ℃; the collection type is as follows: a SIM mode; collecting ions: m/z50, 52;

f. qualitative and quantitative:

and (3) qualitative ion m/z50 and qualitative ion m/z52 are quantitatively determined by adopting a standard sample adding method and an abundance ratio of 100:31 +/-20%, and quantitatively determined by adopting an external standard curve method.

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