CN105675740A - Carbon isotope method for tracing aldehyde ketone pollutants - Google Patents

Abstract

The invention discloses a carbon isotope method for tracing aldehyde and ketone pollutants. The method judges the source of aldehyde and ketone pollutants in the atmospheric environment according to whether isotope fractionation occurs and the difference in carbon isotope ratio (δ ¹³ C value). The experimental results show that the present invention has good reproducibility and high precision, can effectively overcome the existing defects of the traditional concentration measurement method (EPA? TO-11A), and can be used to measure the carbon isotope composition (δ ¹³ C value) can directly and accurately determine the source of atmospheric aldehyde and ketone pollutants, and can be used as an effective means to trace the source of atmospheric aldehyde and ketone pollutants, which is helpful for the study of the formation mechanism of atmospheric organic pollution and contributes to the development of atmospheric organic environmental pollution. Research work provides a scientific basis.

Description

Carbon Isotope Method for Tracing Aldehyde and Ketone Contaminants

technical field

The invention belongs to the field of detection and analysis of aldehyde and ketone pollutants in the atmospheric environment, and in particular relates to a carbon isotope method for tracing aldehyde and ketone pollutants.

Background technique

At present, the United States EPATO-11A method is widely used in the world to detect the concentration of aldehyde and ketone pollutants in the atmosphere, and methods such as concentration ratio and correlation analysis, namely formaldehyde/acetaldehyde or acetaldehyde/acetone, etc. are used to determine the concentration of formaldehyde and ketone in the atmosphere. Different sources of aldehyde and ketone pollutants such as aldehydes and acetone. However, the interpretation of the source by this method of analysis is indirect, and because the ratio varies widely and is unstable, the conclusions drawn are rather vague. Nowadays, the frequent occurrence of atmospheric compound pollution incidents has drawn widespread attention to atmospheric aldehyde and ketone pollutants, and it is urgent to solve the problem of determining the source of volatile organic compounds such as atmospheric aldehyde and ketone pollutants. With the rapid development of gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) analysis technology, it has laid a foundation for using carbon isotope ratio to trace the source of atmospheric aldehydes and ketones.

Contents of the invention

The technical problem to be solved by the present invention is to provide an accurate and reliable carbon isotope method for tracing aldehyde and ketone pollutants, which is convenient for directly judging the source of the pollution, and provides a scientific basis for the research work of atmospheric organic environmental pollution.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical scheme: trace the carbon isotope method of aldehyde and ketone pollutants, first collect samples _of aldehyde and ketone pollutants in the air through a silica gel sampling tube coated with NaHSO3, and then use cysteamine derivatization React aldehydes and ketones pollutants, and then use gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) to measure the δ ¹³ C value of cysteamine and aldehydes, ketones-cysteamine derivatives, and finally calculate according to the isotope effect theory δ ¹³ C values of aldehyde and ketone pollutants in the atmosphere.

The carbon isotope method of the above-mentioned tracer aldehydes and ketones pollutants, comprises the following steps:

(1) Prepare standard samples of aldehydes, ketones and aldehydes, ketones-cysteamine derivatives

Take 1mL of aldehyde and ketone solution and add it to a 5mL sample bottle to equilibrate for at least 1h, and then seal it with a perforated cap that can hold a chromatographic sampling pad; After reacting in the aqueous solution of ～9 for 24 hours, extract with CHCl ₃ , dry the extract with anhydrous Na ₂ SO ₄ and filter, and the filtrate can be concentrated by rotary evaporation at room temperature until it is completely concentrated;

(2) Simulated response or sampling of atmospheric environment

Simulated reaction: After flushing the Teflon reaction bag with high-purity N ₂ , use the sampling pump to evacuate the reaction bag; inject the volatilized aldehyde and ketone gas sample into the reaction bag, and connect the Sep-Pak silica gel sampling tube coated with NaHSO ₃ to the sampling pump For collection, the flow rate is 2L/min;

Atmospheric environment sampling: Connect the sampling pump to the Sep-Pak silica gel sampling tube coated with NaHSO ₃ for atmospheric sample collection;

(3) Processing of samples

After the simulated reaction, the sampling tube sample was eluted with 2 mL of HCl solution with a pH of 2 in a 5 mL graduated test tube, heated in a water bath at 60°C for 20 minutes, then added 20 μL of 150 μg/μL cysteamine solution, and adjusted the pH value to 8-9 with 200 μg/μL NaOH solution; at room temperature After reacting for 24 hours, extract 3 times with 2 mL of CHCl ₃ , dry the extract with anhydrous Na ₂ SO ₄ and filter, concentrate the filtrate to 200 μL with high-purity N ₂ at room temperature and seal it for analysis;

(4) Determination of δ ¹³ C values of cysteamine hydrochloride, aldehydes, ketones and their derivatives

The δ ¹³ C value of cysteamine hydrochloride was determined by DELTA ^plus XL isotope ratio mass spectrometer (EA-IRMS);

The determination of the δ ¹³ C value of aldehydes, ketones and aldehydes, ketones-cysteamine derivatives uses gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS);

(5) Calculate the theoretical value of aldehydes and ketones

By comparing the δ ¹³ C values of the derivatives measured by GC-C-IRMS with the calculated theoretical values, it was judged whether isotope fractionation occurred during the reaction.

The theoretical value in step (5) is calculated by the following equation:

δ ¹³ C _{aldehyde and ketone} = δ ¹³ C _{aldehyde and ketone-NaHSO3} (1)

δ ¹³ C _{aldehyde ketone-cysteamine derivative} = f _{aldehyde ketone} δ ¹³ C _{aldehyde ketone} + f _cysteamine δ ¹³ C _cysteamine (2)

S ² _{aldehydes and ketones} =(f _cysteamine /f _{aldehydes and ketones} ) ² S ² _cysteamines +(1/f _{aldehydes and ketones} ) ² S ² _{aldehydes and ketones-cysteamine derivatives} (3)

Wherein, f _{aldehyde ketone} and f _{cysteamine are} respectively the fractions of carbon atoms of the substance in the derivative, and f _{aldehyde ketone} +f _cysteamine =1, (as for acetaldehyde, f _acetaldehyde = 1/2); In addition, the standard deviation of the atmospheric aldehyde and ketone pollutant δ ¹³ C value is calculated by equation (3).

In view of the problems existing in the identification method of the source of aldehyde and ketone pollutants in the existing atmospheric environment, the inventors used the gas chromatography/combustion/isotope ratio (GC-C-IRMS) technology to establish a carbon isotope method for tracing aldehyde and ketone pollutants , this method judges the source of aldehyde and ketone pollutants in the atmospheric environment according to whether there is isotope fractionation and the difference of carbon isotope ratio (δ ¹³ C value). Experimental results show that in the present invention, cysteamine hydrochloride, aldehydes and ketones and aldehydes and ketones-cysteamine derivatives have a deviation range of 0.09 to 0.21%, and the reproducibility is good; use this method to measure atmospheric aldehydes and ketones When the δ ¹³ C of the pollutant is measured, the deviation between the theoretical value and the measured value is less than 0.50‰, which is within the allowable range of the accuracy of the instrument (±0.50‰) ^. No isotopic fractionation occurs during the derivatization reaction, and the theoretical value of aldehydes and ketones calculated by the formula can represent the δ ¹³ C value of aldehydes and ketones in the actual atmosphere. It can be seen that the determination results of the present invention have good reproducibility and high precision, can effectively overcome the defects of the traditional concentration measurement method (EPATO-11A), and can be used to determine the carbon isotope composition (δ ¹³ C value) of atmospheric aldehyde and ketone pollutants It can directly and accurately determine the source of atmospheric aldehyde and ketone pollutants, and can be used as an effective means to trace the source of atmospheric aldehyde and ketone pollutants, which is helpful for the study of the formation mechanism of atmospheric organic pollution and provides a scientific basis for the research of atmospheric organic environmental pollution. in accordance with.

Description of drawings

Fig. 1 is a technical roadmap for applying the present invention to carry out carbon isotope analysis.

detailed description

What Fig. 1 shows is the technical roadmap of applying the present invention to carry out carbon isotope analysis, the present invention will be further described below in conjunction with embodiment 1.

Example 1

In this example, aldehydes and ketones (acetaldehyde, other aldehydes and ketone pollutants are similar to this example) are chosen to simulate known concentrations for sampling and real atmospheric environment samples are collected for experiments to determine their carbon isotope composition.

Main analytical instruments: German Finnigan DELTA ^plus XL isotope ratio mass spectrometer (EA-IRMS); British GV company gas chromatography-combustion-isotope ratio mass spectrometer (GC-C-IRMS)

(1) Preparation of standard samples of acetaldehyde and acetaldehyde-cysteamine derivatives

Add 1mL of acetaldehyde solution into a 5mL sample bottle and equilibrate for at least 1h, then seal it with a perforated cap that can hold a chromatographic sampling pad and wait for analysis; mix acetaldehyde and cysteamine hydrochloride (purity 97%) was reacted in an aqueous solution with a pH of 8 to 9 for 24 hours, extracted with CHCl ₃ (analytical pure, used after double distillation), the extract was dried with anhydrous Na ₂ SO ₄ and filtered, and the filtrate was rotated at room temperature Concentrated by evaporation until complete to be analyzed;

(2) Simulation experiment sampling and atmospheric environment sampling

(a) Simulation experiment sampling: After flushing the Teflon reaction bag with high-purity N ₂ (99.99%), use a gas sampling pump to evacuate the reaction bag to make it free of other gas impurities; A certain volume concentration of acetaldehyde solution (analytically pure, A1 and A2 manufacturers), open the _N2 valve, acetaldehyde volatilizes under the action of _N2 and enters the reaction bag, when the reaction bag is completely filled with _N2 , close the _N2 valve , use the Sep _- Pak silica gel sampling tube coated with NaHSO3 to connect to the sampling pump for collection, the flow rate is 2L/min;

(b) Atmospheric environment sampling: Connect the sampling pump to the Sep-Pak silica gel sampling tube coated with NaHSO ₃ to collect atmospheric samples. The sampling points are Guangzhou Institute of Geochemistry and Dinghushan, Zhaoqing City.

(3) Processing of samples

After sampling, the sample tubes were wrapped in tinfoil paper and filter paper soaked in NaHSO ₃ in turn, sealed with Teflon bags and stored in a refrigerator at 4°C. After sampling, a field blank and a laboratory blank were tested, and the test results showed that there was no blank interference. The sampling tube sample was eluted with 2 mL of HCl solution (pH 2) in a 5 mL graduated test tube, heated in a water bath at 60°C for 20 minutes, then added 20 μL of cysteamine solution (150 μg/μL), and finally added about 100 μL of NaOH solution (200 μg/μL) Adjust the pH value to 8-9; after reacting at room temperature for 24 hours, extract it three times with 2 mL of CHCl ₃ , dry the extract with anhydrous Na ₂ SO ₄ and filter it, and concentrate the filtrate to 200 μL with high-purity N ₂ at room temperature, then seal it and store in Refrigerator at 4°C for analysis;

(4) Determination of δ ¹³ C values of cysteamine hydrochloride, acetaldehyde and its derivatives

The δ ¹³ C value of cysteamine hydrochloride was determined by DELTA ^plus XL isotope ratio mass spectrometer (EA-IRMS), and the following operations were carried out: after the sample was put into the automatic sampler, it entered the CEEA1112CN/S analyzer, and under the action of O ₂ Combustion in a combustion furnace at 960°C, using CuO as a catalyst, the gas after combustion is loaded into the reduction furnace by high-purity He, and using Cu as a catalyst to reduce at 650°C, enter the chromatographic column for separation, and the separated gas (CO ₂ ) into the DELTA ^plus XL isotope ratio mass spectrometer through the ConfloⅢ connector (Finnigan); the precision and stability of the instrument were evaluated with δ ¹³ C=–36.91‰ carbon black provided by the laboratory before each sample analysis.

The determination of the δ ¹³ C value of the acetaldehyde standard sample is carried out as follows: use GC/C/IRMS, use a 5mL Hamilton gas sampling needle to take 20 μL of the headspace gas of the acetaldehyde solution, and inject it with the known δ ¹³ C = -26.65‰ The CO ₂ gas is used as the internal standard, and the CH ₄ standard sample with the isotopic composition of –36.30‰ is used to detect the accuracy and stability of the instrument. The specific detection conditions are: CuO combustion furnace temperature: 880°C, Cu reduction furnace temperature: 580°C, GC and Furnace junction temperature: 300°C, split ratio: 50:1, chromatographic column HP-PLOTQ (30m×0.32mm×20μm), carrier gas (He) flow rate: 1.5mL/min, inlet temperature: 200°C, Column temperature: 180°C constant temperature.

The determination of the δ ¹³ C value of acetaldehyde-cysteamine derivatives is carried out as follows: GC-C-IRMS is used, and CO ₂ with a known isotope ratio δ ¹³ C = -26.65‰ is used as a reference gas, and the carbon isotope ratio is respectively -28.60‰, -26.70‰, -28.60‰ containing C ₁₀ , C ₁₁ , C ₁₂ n-alkanes and C ₁₃ compound GV-mix standard sample with carbon isotope ratio of -30.50‰ (methyl-deaconate, by GVInstruments, UK) to evaluate the accuracy and stability of the instrument. The detection conditions are: temperature of combustion furnace (oxidation furnace) filled with CuO/Ni/Pt: 850°C, temperature of Cu reduction furnace: 580°C, temperature setting at the connection between GC and combustion furnace: 300°C, splitless injection, chromatographic column It is HP-5MS (30m×0.32mm×0.25μm), carrier gas (He) flow rate: 1.5mL/min, injection port temperature: 200°C, column temperature program is 50°C for 2min, and then 3°C/ min rises to 85°C.

(5) Calculate the theoretical value of aldehydes and ketones

According to the isotope effect theory, isotope fractionation in chemical reactions depends on the first-order reaction that determines the reaction rate. If there is no formation and breakage of chemical bonds connected to carbon atoms at this level, no obvious isotope fractionation will occur; the derivative reaction The carbon atom of cysteamine does not participate in the reaction process, so the isotope effect of this reaction is only related to the carbon atom of aldehyde and ketone, as long as the excess cysteamine is allowed to allow all aldehyde and ketone to participate in the reaction, no obvious isotope fractionation will occur; The isotope effect before and after the reaction under this condition conforms to equation (1-2):

δ ¹³ C _{aldehyde and ketone} = δ ¹³ C _{aldehyde and ketone-NaHSO3} (1)

δ ¹³ C _{aldehyde ketone-cysteamine derivative} = f _{aldehyde ketone} δ ¹³ C _{aldehyde ketone} + f _cysteamine δ ¹³ C _cysteamine (2)

Wherein, f _{aldehyde ketone} and f _{cysteamine are} respectively the fractions of carbon atoms of the substance in the derivative, and f _{aldehyde ketone} +f _cysteamine =1, (as for acetaldehyde, f _acetaldehyde = 1/2); In addition, the standard deviation of the atmospheric aldehyde and ketone pollutant δ ¹³ C value is calculated by equation (3).

S ² _{aldehydes and ketones} =(f _cysteamine /f _{aldehydes and ketones} ) ² S ² _cysteamines +(1/f _{aldehydes and ketones} ) ² S ² _{aldehydes and ketones-cysteamine derivatives} (3)

By comparing the δ ¹³ C value of the derivative measured by GC-C-IRMS with the theoretical value calculated by equation (1-3), it is judged whether isotope fractionation occurred during the reaction.

The carbon isotope effect results of the acetaldehyde simulation experiments of different manufacturers are listed in Table 1.

Table 1 Carbon isotope effect results (δ ¹³ C value) in the reaction process of acetaldehyde simulation experiment

Each sample is analyzed multiple times, and their standard deviation range is less than 0.50%, and the standard deviation range of the corresponding derivative measurement value is less than 0.50‰; the deviation range between the δ ¹³ C measurement value and the theoretical value of the derivative is also less than 0.50% ‰, the above results are all within the range of instrument accuracy (±0.50 ‰), and the multiple measured values all have good reproducibility, indicating that the inventive method does not have carbon isotope fractionation.

The carbon isotope composition (δ ¹³ C value) of acetaldehyde in the atmospheric environment samples collected in this example is shown in Table 2.

Table 2 Carbon isotope effect results (δ ¹³ C value) during atmospheric environment sampling

Known from Table 2, in the air samples collected with different emission sources, the range of variation of acetaldehyde δ ¹³ C values in the atmospheric environment is different, such as forest atmosphere and urban atmosphere in this example, illustrating that the carbon isotope composition analysis method of the present invention can As an effective means to identify the source of atmospheric aldehyde and ketone pollutants.

The experimental results of GC-C-IRMS analysis and determination of the isotope effect of aldehydes and ketones (such as acetaldehyde) show that there will be no carbon isotopes when NaHSO ₃ silica gel sampling tubes are used to collect and derivatize aldehydes and ketones in the atmosphere with cysteamine. Fractional distillation, good reproducibility of experimental data, high measurement accuracy, carbon isotope composition of atmospheric aldehyde and ketone pollutants can be calculated by mass balance equation. The result of measuring the carbon isotope composition of the atmospheric aldehyde and ketone pollutants by the method of the invention shows that the carbon isotope composition of the aldehyde and ketone pollutants in the atmospheric environment with different emission sources is different. Therefore, the present invention can be used as an effective means for identifying sources of aldehyde and ketone pollutants in the atmosphere, and provides technical support for the research of atmospheric aldehyde and ketone pollutants.

Claims (3)

1. the carbon isotope method of spike aldehyde ketone pollutant, it is characterised in that: first pass through coating NaHSO₃Silica gel sampling tube gather aldehyde ketone pollutant sample in air, then adopt cysteamine derivative reaction aldehyde ketone pollutant, recycling gas chromatogram-burning-isotopic ratio mass spectrum measures cysteamine and the δ of aldehyde ketone-Cysteamine derivatives¹³C value, obtains the δ of aldehyde ketone pollutant in air finally according to isotope effect Theoretical Calculation¹³C value.

2. the carbon isotope method of spike aldehyde ketone pollutant according to claim 1, it is characterised in that comprise the following steps:

(1) preparation aldehyde ketone and aldehyde ketone-Cysteamine derivatives standard sample

Take after 1mL aldehyde ketone solution joins and at least balance 1h in 5mL sample bottle, with the screw capping good seal with holes that can fill chromatography column feed materials pad; After the aldehyde ketone waiting amount of substance is reacted 24h with Mercaptamine in the aqueous solution that pH is 8～9, use CHCl₃Extract, extract anhydrous Na₂SO₄Dried filtration, filtrate rotary evaporation at normal temperatures is concentrated into after completely;

(2) simulation reaction or atmospheric environment sampling

Simulation reaction: with high-purity N₂After rinsing Teflon reaction bag, evacuate reaction bag with sampling pump; After aldehyde ketone gaseous sample after volatilization is injected reaction bag, with coating NaHSO₃Sep-Pak silica gel sampling tube be connected with sampling pump and be acquired, flow 2L/min;

Atmospheric environment is sampled: by sampling pump and coating NaHSO₃Sep-Pak silica gel sampling tube be connected carry out atmospheric sample collection; (3) process of sample

After simulation reaction, sampling tube sample adds 20 μ L150 μ g/ μ L cysteamine solution with the 2mLpH HCl solution eluting being 2 after 5mL scale test tube, 60 DEG C of heating in water bath 20min, regulates pH value 8～9 with 200 μ g/ μ LNaOH solution; With the CHCl of 2mL after normal-temperature reaction 24h₃Extract 3 times, extract anhydrous Na₂SO₄Dried filtration, filtrate is at normal temperatures with high-purity N₂Seal to be analyzed after being concentrated into 200 μ L;

(4) δ of Mercaptamine, aldehyde ketone and derivant thereof is measured¹³C value

Mercaptamine δ¹³C value adopts DELTA^plusXL isotope-ratio mass spectrometer measures;

Aldehyde ketone and aldehyde ketone-Cysteamine derivatives δ¹³The mensuration of C value adopts gas chromatogram-burning-isotopic ratio mass spectrum;

(5) aldehyde ketone theoretical value is calculated

By comparing the derivant δ being measured out by GC-C-IRMS¹³C value and the theoretical value calculated, judge whether there occurs isotope fractionation in course of reaction.

3. the carbon isotope method of spike aldehyde ketone pollutant according to claim 2, it is characterised in that the theoretical value in step (5) calculates by below equation:

δ¹³C_{Aldehyde ketone}=δ¹³C_{Aldehyde ketone-NaHSO3}(1)

δ¹³C_{Aldehyde ketone-Cysteamine derivatives}=f_{Aldehyde ketone}δ¹³C_{Aldehyde ketone}+f_Cysteamineδ¹³C_Cysteamine(2)

S² _{Aldehyde ketone}=(f_Cysteamine/f_{Aldehyde ketone})²S² _Cysteamine+(1/f_{Aldehyde ketone})²S² _{Aldehyde ketone-Cysteamine derivatives}(3)

Wherein, f_{Aldehyde ketone}With f_CysteamineThe respectively mark shared by this material carbon atom in derivant, and f_{Aldehyde ketone}+f_Cysteamine=1; It addition, air aldehyde ketone pollutant δ¹³The standard deviation of C value is calculated by equation (3).