CN1121158C - Microwave spectrophotometric process for the fast detection of nitrosamine and nitroxide content in tobacco - Google Patents

Abstract

A microwave-spectrophotometric method for quickly determining the content of nitrosamines and nitrogen oxides (NO _x ) in tobacco, which is to place tobacco leaves in a container for microwave radiation, and use N ₂ to convert NO _x and volatilized nitrosamines Blow off, the nitrosamines blown off are absorbed with citric acid-sodium dihydrogen phosphate buffer solution, and then the nitrosamines are determined by "micro-analysis of the apparent total amount of N-nitroso compounds" (patent application number 97107228.0) Content, the unabsorbed NO _x is absorbed with quantitative sulfonamide and naphthalene ethylenediamine hydrochloride solution, converted into NO ₂ ^- and developed color, then measured by spectrophotometry and calculated nitrogen oxides (NO _x ).

Description

Microwave-spectrophotometric method for rapid detection of nitrosamines and nitrogen oxides in tobacco

1. Technical field

The invention relates to a method for detecting the contents of nitrosamines and nitrogen oxides (NO _x ) in tobacco in combination with microwave radiation and improved spectrophotometry.

2. Background technology

Nitrosamines contained in tobacco and cigarette smoke have aroused people's high vigilance due to their strong carcinogenicity. Nitrosamines are strong chemical carcinogens, and about 90% of more than 300 kinds of nitrosamine compounds have been proved to be carcinogenic: all organs and tissues of animals can be induced tumors, and the main target organs are liver, esophagus, lung, Stomach and kidney; can also be inherited through the placenta, resulting in distortion in offspring. Chinese adult males consume an average of 10 cigarettes per day per person, and the average annual consumption of cigarettes has reached 1.8 trillion, accounting for one-third of the world's total consumption. The people affected by cigarette smoke amount to hundreds of millions in China. Slightly different from benzo(a)pyrene (ie 3,4-benzopyrene) and dioxins, nitrosamines have a lower boiling point, so they are more likely to volatilize into cigarette smoke, pollute the environment and harm people's health . More and more experts believe that the content of nitrosamines in cigarettes will be the third parameter that should be marked on cigarette packs after tar and nicotine, and should be reduced as much as possible.

In order to reduce the pollution of nitrosamines from the source, it is necessary to know the content of nitrosamines in raw tobacco leaves in time when purchasing tobacco and making cigarettes. The usual methods for detecting the content of nitrosamines in tobacco and tobacco smoke: (1) Chromatography-thermal energy analyzer (GC-TEA) method is mainly used abroad, but these methods all involve complicated operations such as expensive instruments and column separation It is difficult to popularize and apply the program at the grassroots units; moreover, manufacturers only need to roughly know the total amount of nitrosamines in tobacco, and do not need to separate the nitrosamines one by one to accurately measure their respective concentrations. (2) Leach tobacco with chemical solution to extract nitrosamines, and then extract-concentrate for determination, which takes at least 2 days. (3) The applicant disclosed in the patent application (publication number: CN1193741A) an improved spectrophotometric method for determining the content of nitrosamines in tobacco smoke, but it is mainly used for the determination of finished cigarettes. This just requires tobacco leaves to be made into cigarettes at first; However, after making cigarettes and then lighting the measurement, each cigarette needs about 20 minutes to burn in the air flow, which is not only time-consuming and labor-intensive, but also cannot guide production to reduce the Nitrosamine content. Obviously, there is an urgent need for a quick and simple method for determining the content of nitrosamines in raw tobacco leaves. The nitrogen oxides (NO _x ) produced by the decomposition of nitrite and nitrate in tobacco at high temperature can thermally synthesize nitrosamines with nicotine or amines again, so they are regarded as the precursor compounds for the production of nitrosamines. In addition, microwave radiation on tobacco leaves can also decompose certain nitrosamines to generate NO _x , so the content of nitrogen oxides (NO _x ) in tobacco leaves has an important relationship with the content of nitrosamines. However, if the solution extraction method is used to determine the nitrosamines in tobacco, the content of nitrogen oxides (NO _x ) cannot be measured at the same time. When lighting cigarettes to collect flue gas, it is also difficult to measure the content in the flue gas due to the interference of impurities such as tar; obviously, there is also an urgent need for new methods to quickly and simply measure the content of nitrogen oxides (NO _x ) in raw tobacco leaves.

3. Contents of the invention

The purpose of the present invention is to provide a new method for simple and rapid determination of nitrosamine and nitrogen oxide (NO _x ) content in tobacco.

Aliphatic nitrosamines are strong polar organic substances, and the N-NO bonds in the functional groups are weaker than the C-H, C-C, and C-N bonds. They can be broken during the pyrolysis reaction at 300°C to produce NOx. Jonny R. Williams discloses in its patent application WO9805226 and WO98 58555 and CN97198261 the technology that microwave radiation is used for drying treatment after harvesting of tobacco and marijuana, reduces its tobacco-specific nitrosamine content, and it is to the nitrosamine content in tobacco leaf Nitamines are destructive. But we found that a large proportion of nitrosamines are volatilized under microwave irradiation and based on this new finding the method of the present invention was established.

Therefore technical scheme of the present invention is as follows:

A microwave-spectrometry method for rapid detection of nitrosamines and nitrogen oxides (NO _x ) content in tobacco, which is:

1. Put the shredded tobacco or tobacco leaves in the container for microwave radiation;

2. Use an inert carrier gas to blow off the decomposition product NOx and volatilized nitrosamines;

3. Absorb the blown nitrosamines with citric acid-sodium dihydrogen phosphate buffer solution;

4. The unabsorbed NOx is oxidized to NO ₂ with CrO ₃ oxidation tube;

5. Absorb NO ₂ with a quantitative solution of sulfonamide and naphthaleneethylenediamine hydrochloride, convert it into NO ₂ ^- and develop color;

6. Measure its absorbance with light with a wavelength of 540nm, and calculate the content Y ₁ of nitrogen oxides,

7. The absorption liquid of step 3 is extracted with dichloromethane;

8. Dry the extracted dichloromethane solution with anhydrous Na ₂ SO ₄ ;

9. Concentrating the dried dichloromethane solution under _N2 gas protection;

10. Use the concentrated dichloromethane solution to crack the N-N bond in the N-NO functional group of the N-nitroso compound with HBr-HOAc solution;

11. Use an inert carrier gas to blow off the NOx produced by the decomposition;

12. The blown out gas is purified by alkaline washing cylinder;

13. Oxidize the purified NOx into _NO2 with _CrO3 oxidation tube;

14. Absorb NO ₂ with a quantitative solution of sulfonamide and naphthaleneethylenediamine hydrochloride, convert it into NO ₂ ^- and develop color;

15. Measure the absorbance with light with a wavelength of 540nm, and calculate the content Y ₂ of nitrogen oxides.

Microwave-spectrophotometry of the present invention, used microwave can be the microwave that frequency is 2450MHz or 915MHz, and the power of microwave radiation is 500-2000W, and preferred power is 800-1000W, and radiation time is 30-400 seconds, preferred radiation The time is 60-220 seconds. The inert carrier gas can be high-purity nitrogen, helium or argon. The flow rate of the carrier gas is 10-500mL/min, preferably 100-140mL/min. The nitrosamine absorption solution used is a citric acid-sodium dihydrogen phosphate buffer solution with a pH of 4.5, and the CrCO ₃ oxidation tube used is an oxidation tube filled with CrO ₃ -sea sand.

By measuring these nitrosamines and nitrogen oxides NOx by the method of the present invention, the content of nitrosamines in raw tobacco leaves can be roughly understood. The method of the present invention has the advantages that: (1) tobacco and tobacco smoke contain volatile, non-volatile and tobacco-specific nitrosamines, the main hazards to the environment are those nitrosamines that can volatilize into the smoke, and microwave The method detects precisely those nitrosamines that can be volatilized. (2) Nitrates in tobacco will decompose to produce nitrogen oxides (NO _x ) when cigarettes are burned, and thermally synthesize some nitrosamines with nicotine and amines. Extraction of nitrosamines in tobacco with a solution cannot reflect this high temperature change because it is carried out at room temperature. Microwave radiation will locally heat the shredded tobacco, so the obtained data is closer to the content in cigarette gas. (3) The microwave method can detect shredded tobacco and tobacco leaves, and is not limited by the shape of the sample, nor does it require rolling into cigarettes. Compared with the method of collecting smoke by lighting a cigarette, the microwave method takes less time, and only takes about 3 minutes to collect nitrosamines into the solution for determination. (4) The raw tobacco is directly processed by microwave, which requires less investment, simple process and is suitable for popularization and application in grassroots units.

4. Specific implementation

The present invention is further illustrated by the following examples.

[Example 1] Put the shredded tobacco (16 cigarettes) of cigarette A (flue-cured tobacco type, produced in Yunnan Province, with a tar content of 15 mg/stick and a smoke nicotine content of 1.2 mg/stick) in a container and put it in a WP850D′ microwave oven , connect 4 gas scrubbers in series behind the container, each of which contains 15mL of citric acid-sodium dihydrogen phosphate buffer solution with a pH value of 4.5, to absorb volatilized nitrosamines, and then connect a gas scrubber Double-ball oxidation tube, filled with about 8 grams of CrO ₃ -sea sand (mass ratio 1:20) in the oxidation tube, connected with an absorption bottle after the oxidation tube, and 50.0 mL of chromogenic solution (5 grams of sulfonamide and 0.05 grams of Naphthaleneethylenediamine hydrochloride is dissolved in 1000mL of distilled water containing 50mL of glacial acetic acid), and the carrier gas _N2 flows through the container at a flow rate of 100mL/min, and the microwave oven is started for radiation _, the power is 850W, and the radiation time is 70 seconds. The NO _x and volatilized nitrosamines produced by the decomposition of shredded tobacco in the container are blown out by the carrier gas, the volatilized nitrosamines are absorbed by the gas washing bottle, and the NO _x produced by the decomposition is oxidized into NO ₂ by the oxidation tube and enters the color development bottle. After the radiation is finished, use colorimetric method to measure (at 540mn), calculate the NO ₂ ^- content Y ₁ , and combine the buffer solutions in the four gas washing bottles, extract the nitrosamines with dichloromethane, and then use the improved spectroscopic Photometric method (see CN97107228.0A) detects NO ₂ ^-content Y ₂ , and the content of nitrosamine in cut tobacco is Y ₂ . The content of nitrosamines in cigarette A was measured to be 2.50 nmol/cigarette, and the content of nitrogen oxides (NO _x ) to be 10.01 nmol/cigarette. The experiment was repeated twice, and the measured nitrosamine contents were 2.48 and 2.63 nmol/cartridge, and the (NO _x ) contents were 9.80 and 10.11 nmol/cartridge respectively. The errors between the three data and the mean were 1.6%, 2.4% and 3.5% for nitrosamines and 0.4%, 1.7% and 1.4% for _NOx , respectively.

[Example 2] shredded tobacco (12) cigarettes of cigarette B (cured tobacco type, produced in Jiangsu Province, tar content is 18mg/, smoke nicotine content is 1.4mg/) is put into the container and measured as in Example 1 The method was used to determine the content of nitrosamines, but the irradiation time was changed to 210 seconds, and the flow rate of N ₂ was changed to 120mL/min. The two determination results showed that the total content of nitrosamines was 3.17nmol/cartridge and 3.13nmol/cartridge respectively. The error of the two data is 1.3%.

[Example 3] Cigarette C (cured tobacco type, produced in Jiangsu Province, tar content is 17mg/stick, smoke nicotine content is 1.1mg/stick), after adding 3% m/m porous purification material in shredded tobacco, sideways The content of nitrosamines in the flue gas is reduced from 4.57nmol/branch to 2.31nmol/branch, which is a reduction of 49.5%. Get shredded tobacco (20 cigarettes) and measure the content of nitrosamines in shredded tobacco by the method of embodiment 1, radiation time is 210 seconds, _N The flow velocity is 120mL/min, measure the nitrosamine content of shredded tobacco not containing additive and containing additive respectively are 4.88 and 2.74nmol/branch, and the reduction range is 43.9%, which accurately reflects the effect of additives.

[Example 4] The nitrosamine content in the sidestream smoke of cigarette D (flue-cured tobacco type, produced in the United States, with a tar content of 15 mg/cigarette and a smoke nicotine content of 1.3 mg) is 6.65 nmol/cigarette. The nitrosamine content in sidestream smoke of cigarette E (flue-cured tobacco type, produced in the UK, with a tar content of 12 mg/cigarette and smoke nicotine content of 1.0 mg/cigarette) was 3.65 nmol/cigarette, which was 54.9% of that of cigarette D. The nitrosamine contents measured by the microwave-spectrophotometric method of the present invention (radiation for 210 seconds under 850W power) of the shredded tobacco of the two are 3.00 and 1.85nmol/support respectively, and cigarette E is 61.7% of cigarette D, reflecting that both difference.

[Example 5] The sidestream smoke nitrosamine content of cigarette F (mixed type, produced in the United States, with a tar content of 12 mg/cigarette and a smoke nicotine content of 1.0 mg) is 4.17 nmol/cigarette. Cigarette G (mixed type, produced in Yunnan Province, with a tar content of 11 mg/cigarette and smoke nicotine of 1.0 mg) had a sidestream smoke nitrosamine content of 3.00 nmol/cigarette, which was 71.9% of that of cigarette F. The nitrosamine contents measured by the microwave-spectrophotometric method of the present invention (radiation for 210 seconds under 850W power) of the shredded tobacco of the two are 3.45 and 2.65nmol/support respectively, and cigarette G is 75.9% of cigarette F, which is measured by the ignition method. The difference between the two is close.

It can be seen from the above that the content of nitrosamines and nitrogen oxides (NO _x ) in tobacco can be quickly determined by using microwave radiation combined with improved spectrophotometry, which not only has good repeatability, but also reflects the differences between different tobaccos. The technology of the present invention has strong practicality, less required equipment, low cost, simple and convenient measurement, and short time consumption, and is suitable for popularization and application in cigarette factories and other tobacco departments to grasp the content of nitrosamines in tobacco, develop new types of cigarettes, and then gradually reduce Smoking pollutes the environment.

Claims (4)

1, a kind of microwave-spectrophotometry of fast detection nitrosamine and nitrogen oxide ( _NOx ) content in tobacco, it is characterized in that: (1) Place shredded tobacco or tobacco leaves in a container for microwave radiation, (2) blow off NO _x and volatilized nitrosamines with an inert carrier gas, (3) Absorb the nitrosamine blown out with citric acid-sodium dihydrogen phosphate buffer solution, (4) The unabsorbed NO _x is oxidized to NO ₂ with CrO ₃ oxidation tube, (5) NO ₂ is absorbed with quantitative sulfonamide and naphthalene ethylenediamine hydrochloride solution, converted into NO ₂ ^- and develops color, (6) Measure its absorbance with light with a wavelength of 540nm, and calculate the content Y ₁ of nitrogen oxides, (7) the absorption liquid of step 3 is extracted with dichloromethane, (8) The dichloromethane solution after the extraction is dried with anhydrous Na ₂ SO ₄ , (9) the dried dichloromethane solution is concentrated under N _gas protection, (10) The N-N bond in the N-NO functional group of the N-nitroso compound is cracked with the HBr-HOAc solution of the concentrated dichloromethane solution, (11) Use an inert carrier gas to blow off the NO _x produced by the decomposition, (12) The blown-off gas is purified by an alkaline washing bottle, (13) Oxidize the purified NO _x into NO ₂ with a CrO ₃ oxidation tube, (14) NO ₂ is absorbed with quantitative sulfonamide and naphthalene ethylenediamine hydrochloride solution, converted into NO ₂ ^- and develops color, (15) Measure the absorbance with light with a wavelength of 540nm, and calculate the content Y ₂ of nitrosamine. 2. The microwave-spectrophotometry method according to claim 1, characterized in that the frequency of the microwave used is 2450MHz or 915MHz, and the power is 850W. 3. The microwave-spectrophotometric method according to claim 1, characterized in that the irradiation time is 70-210 seconds. 4. The microwave-spectrophotometry method according to claim 1, characterized in that the inert carrier gas used is nitrogen, and the gas flow rate is 100-120 mL/min.