Method for detecting ethanol in ambient air and waste gas

Abstract

The invention relates to the field of detection, in particular to a method for detecting ethanol in ambient air and waste gas. The invention provides a method for detecting ethanol in ambient air and waste gas. The method comprises the following steps: S1, solvent adsorption; s2, carrying out headspace-gas chromatography analysis; according to the method, water is creatively adopted as the adsorption liquid for adsorbing and collecting the ethanol, then the headspace-gas chromatograph is adopted for content analysis testing, the separation effect of substances of different components is good, mutual interference is avoided, the detection limit of the testing result is low, repeatability is high, and the content analysis effect is excellent.

Description

Technical Field

[0001] The invention relates to the field of detection, and in particular to a method for detecting ethanol in ambient air and waste gas. Background Art

[0002] Ethanol, also known as alcohol, is a common organic solvent that can dissolve a variety of organic and inorganic substances. Ethanol has a wide range of uses. It can be used to make acetic acid, beverages, flavors, etc. It can also be used as a raw material and energy fuel for industrial production. However, with the widespread use of ethanol, its emissions are also increasing. Industrial production, transportation and other fields are the main sources of ethanol emissions. High concentrations of ethanol emissions will have a negative impact on air quality. It will not only cause harm to human health, such as irritating the respiratory tract and causing poisoning, but will also aggravate air pollution and affect the balance of the ecological environment. Although the emissions and hazards of ethanol can no longer be ignored, there is currently no national standard for the rapid determination of ethanol in the air in my country. Traditional detection methods have problems such as complex operation, time-consuming and labor-intensive, and low sensitivity, and cannot meet the needs of on-site sampling in the workplace and quickly and accurately obtain test results.

[0003] Patent document CN110824061A discloses a method for detecting ethanol content in a working environment, which mainly includes: sampling with an activated carbon sampling tube, followed by sample pretreatment, headspace purification, gas chromatography analysis and measurement calculation; Patent document CN105181853A discloses a method for determining the content of ethanol and isopropanol in air and exhaust gas, which mainly includes activated carbon tube adsorption, desorption and gas chromatography quantitative analysis. The above test methods can effectively test the ethanol content in the air environment, but using an activated carbon tube for ethanol adsorption is difficult because the pore size of the activated carbon surface is mostly The size and polarity of ethanol molecules make it difficult for them to enter these tiny pores completely and effectively; therefore, the adsorption effect of activated carbon on ethanol is relatively limited, and the cost of activated carbon is relatively high, which is not conducive to reducing the cost of ethanol content analysis.

[0004] Therefore, it is of great research value to provide a low-cost, high-sensitivity method for detecting ethanol content in ambient air and exhaust gas. Summary of the invention

[0005] In order to solve the above technical problems, the first aspect of the present invention provides a method for detecting ethanol in ambient air and exhaust gas, comprising:

[0006] S1, solvent adsorption;

[0007] S2, headspace-gas chromatography analysis.

[0008] As an implementable case, the implementation method of the solvent adsorption in step S1 includes: using a porous wave plate filled with an adsorption liquid to adsorb and collect ambient air containing ethanol, organized waste gas containing ethanol, or unorganized waste gas containing ethanol.

[0009] Furthermore, the implementation method of the S1 step includes: using a porous wave plate filled with 10 mL of adsorption liquid to adsorb and collect ambient air containing ethanol, organized waste gas containing ethanol, or unorganized waste gas containing ethanol.

[0010] Among them, organized waste gas refers to the waste gas that is centrally discharged through specific exhaust equipment (such as exhaust pipes) during the industrial production process. The waste gas is usually treated by certain pretreatment or purification facilities to meet the emission standards; while unorganized waste gas refers to the waste gas that is directly discharged into the environment without being treated or passing through specific exhaust equipment due to equipment leakage, improper operation or poor management during the industrial production process.

[0011] As an implementable example, the adsorption liquid includes an organic solvent and / or an inorganic solvent.

[0012] Furthermore, the adsorption liquid is an inorganic solvent.

[0013] Furthermore, the inorganic solvent includes water.

[0014] At present, the most common method for adsorbing ethanol in ambient air in the prior art is activated carbon adsorption. However, due to the large pore size of the activated carbon material, the adsorption capacity is relatively limited, and the procurement cost of the activated carbon is relatively high. Therefore, in the present invention, inorganic solvent water is used as the adsorption liquid to adsorb ethanol. It is well known that water and ethanol can be miscible in any volume ratio, so the efficiency of using water to adsorb ethanol is higher. In addition, water is a non-toxic and environmentally friendly solvent. Using water to dilute ethanol can reduce pollution to the environment. Compared with some organic solvents, water is safer during handling and storage. In addition, water has a wider source and lower cost, which can further reduce the cost of detection without affecting the detection limit of ethanol.

[0015] As an implementable case, the ventilation flow rate of the adsorption collection is 0.5-1.0L / min.

[0016] The inventors further discovered that it is necessary to further limit the ventilation flow rate for adsorption collection. When the sampling ventilation flow rate is too small, the residence time of the sample in the absorption liquid will be correspondingly extended. Although the ethanol will be more fully enriched, the time required for sampling will also be significantly increased. When a large volume of air samples needs to be collected or time is tight, the work efficiency will be seriously reduced. When the sampling ventilation flow rate is too large, the residence time of the sample in the adsorption liquid becomes shorter, and the contact time between the ethanol component and water is reduced, thereby increasing the risk of penetration. Therefore, the ventilation flow rate for adsorption collection in the present invention is preferably 0.5-1.0L / min. This ensures that the ethanol component in the sample is fully enriched by water, avoids the risk of penetration and instrument contamination, and ensures a high content analysis efficiency.

[0017] As an implementable case, the adsorption collection time is 20-60 minutes.

[0018] As an implementable case, the implementation method of the S2 step includes: transferring the adsorbed liquid into a headspace bottle, and placing the headspace bottle on a headspace-gas chromatograph for detection and analysis.

[0019] Furthermore, the implementation method of the S2 step includes: transferring the adsorbed liquid to a 22 mL headspace bottle, if the adsorption liquid is lost, it needs to be replenished to 10 mL, and the headspace bottle is placed on a headspace-gas chromatograph, and detection and analysis are performed using a hydrogen flame ionization detector.

[0020] As an implementable case, the chromatographic column selected in the headspace-gas chromatograph includes a DB-FFAP chromatographic column, and the specification of the DB-FFAP chromatographic column is: 30m×320μm×0.5μm.

[0021] The DB-FFAP column is made of polyethylene glycol modified with nitroterephthalic acid and has strong chemical polarity. Therefore, the DB-FFAP column has high selectivity for alcohol compounds, ethanol. When testing the ethanol content in the air, the strong polarity helps to effectively separate ethanol from other alcohols and non-alcohol compounds, thereby improving the accuracy and sensitivity of the detection. In addition, the DB-FFAP column has excellent separation effect and can clearly separate the ethanol peak from other interference peaks, which helps to accurately determine the concentration of ethanol when testing the ethanol content in the air and reduce the possibility of misjudgment and missed judgment.

[0022] As an implementable case, the chromatographic analysis conditions of the headspace-gas chromatography are:

[0023] Inlet temperature: 240-300℃;

[0024] Split ratio: (4-8): 1;

[0025] Injection volume: 1-2mL;

[0026] Column flow rate: 1-2mL / min;

[0027] Column temperature: Initial temperature is 40°C, maintained for 1 min, then raised to 80°C at a heating rate of 4-8°C / min;

[0028] Detector temperature: 200-300℃;

[0029] Air flow rate: 300-450mL / min;

[0030] Hydrogen flow rate: 40-60mL / min;

[0031] Tail blowing flow rate: 10-25mL / min;

[0032] Headspace heating box temperature: 75-90℃;

[0033] Quantitative loop temperature: 100-120°C;

[0034] Transmission line temperature: 100-120°C;

[0035] Loop volume: 1-2mL.

[0036] Furthermore, the chromatographic analysis conditions of the headspace-gas chromatography instrument are:

[0037] Inlet temperature: 250°C;

[0038] Split ratio: 5:1;

[0039] Injection volume: 1mL;

[0040] Column flow rate: 1.2 mL / min;

[0041] Column temperature: Initial temperature is 40℃, maintained for 1 min, then heated to 80℃ at a heating rate of 5℃ / min;

[0042] Detector temperature: 300°C;

[0043] Air flow rate: 400mL / min;

[0044] Hydrogen flow rate: 50mL / min;

[0045] Tail blowing flow rate: 20mL / min;

[0046] Headspace heating box temperature: 80°C;

[0047] Quantitative loop temperature: 100°C;

[0048] Transmission line temperature: 110°C;

[0049] Loop volume: 1 mL.

[0050] Beneficial Effects

[0051] (1) The present invention creatively uses a solvent to absorb ethanol to adsorb the ethanol content in the air and exhaust gas, which has lower costs than the prior art of using activated carbon to adsorb ethanol, and is more convenient and quick to operate.

[0052] (ii) In the present invention, inorganic solvent water is selected as the adsorption liquid. Since water and ethanol can be miscible in any volume ratio, the detection limit of the detection method provided by the present invention is relatively low, which can reach 0.10 mg / L.

[0053] (III) The present invention further limits the ventilation flow rate of adsorption collection to 0.5-1.0 L / min, thereby ensuring that the ethanol component in the sample is fully enriched by water, avoiding the risk of breakthrough and instrument contamination, and ensuring high work efficiency.

[0054] (IV) When the test method provided by the present invention is used for actual measurement, the response time of ethanol is 5.224 min, the response time of methanol is 4.714 min, and the response time of acetone is 3.829 min. The separation effect of different components is good and there is no interference between them.

[0055] (V) The present invention fully demonstrates the feasibility of this method for testing ambient air, organized waste and unorganized waste gas through determination of blank matrix spike recovery rate, precision, detection limit, etc. DETAILED DESCRIPTION

[0056] Example 1

[0057] This example provides a method for detecting ethanol in ambient air and exhaust gas, which specifically consists of the following steps:

[0058] S1. Solvent adsorption: A porous wave plate filled with 10 mL of water was used to adsorb and collect ambient air containing ethanol. The ventilation flow rate of the adsorption collection was 0.5 L / min, and the adsorption collection time was 60 min.

[0059] S2. Headspace-gas chromatography analysis: The adsorbed liquid was transferred to a 22 mL headspace bottle, and the headspace bottle was placed on a headspace-gas chromatograph for detection and analysis using a hydrogen flame ionization detector.

[0060] The chromatographic column selected in the headspace-gas chromatograph is a DB-FFAP chromatographic column, and the specification of the DB-FFAP chromatographic column is: 30m×320μm×0.5μm.

[0061] The chromatographic analysis conditions of the headspace-gas chromatography instrument are:

[0062] Inlet temperature: 250°C;

[0063] Split ratio: 5:1;

[0064] Injection volume: 1mL;

[0065] Column flow rate: 1.2 mL / min;

[0066] Column temperature: Initial temperature is 40℃, maintained for 1 min, then heated to 80℃ at a heating rate of 5℃ / min;

[0067] Detector temperature: 300°C;

[0068] Air flow rate: 400mL / min;

[0069] Hydrogen flow rate: 50mL / min;

[0070] Tail blowing flow rate: 20mL / min;

[0071] Headspace heating box temperature: 80°C;

[0072] Quantitative loop temperature: 100°C;

[0073] Transmission line temperature: 110°C;

[0074] Loop volume: 1 mL.

[0075] Example 2

[0076] This example provides a method for detecting ethanol in ambient air and exhaust gas, which specifically consists of the following steps:

[0077] S1. Solvent adsorption: The porous wave plate filled with 10 mL of water was used to adsorb and collect the unorganized waste gas containing ethanol. The ventilation flow rate of the adsorption collection was 0.5 L / min, and the adsorption collection time was 60 min.

[0078] S2. Headspace-gas chromatography analysis: The adsorbed liquid was transferred to a 22 mL headspace bottle, and the headspace bottle was placed on a headspace-gas chromatograph for detection and analysis using a hydrogen flame ionization detector.

[0079] The chromatographic column selected in the headspace-gas chromatograph includes a DB-FFAP chromatographic column, and the specification of the DB-FFAP chromatographic column is: 30m×320μm×0.5μm.

[0080] The chromatographic analysis conditions of the headspace-gas chromatography instrument are:

[0081] Inlet temperature: 250°C;

[0082] Split ratio: 5:1;

[0083] Injection volume: 1mL;

[0084] Column flow rate: 1.2 mL / min;

[0085] Column temperature: Initial temperature is 40℃, maintained for 1 min, then heated to 80℃ at a heating rate of 5℃ / min;

[0086] Detector temperature: 300°C;

[0087] Air flow rate: 400mL / min;

[0088] Hydrogen flow rate: 50mL / min;

[0089] Tail blowing flow rate: 20mL / min;

[0090] Headspace heating box temperature: 80°C;

[0091] Quantitative loop temperature: 100°C;

[0092] Transmission line temperature: 110°C;

[0093] Loop volume: 1 mL.

[0094] Example 3

[0095] This example provides a method for detecting ethanol in ambient air and exhaust gas, which specifically consists of the following steps:

[0096] S1. Solvent adsorption: A porous wave plate filled with 10 mL of water was used to adsorb and collect the organized waste gas containing ethanol. The ventilation flow rate of the adsorption collection was 0.5 L / min, and the adsorption collection time was 45 min.

[0097] S2. Headspace-gas chromatography analysis: The adsorbed liquid was transferred to a 22 mL headspace bottle, and the headspace bottle was placed on a headspace-gas chromatograph for detection and analysis using a hydrogen flame ionization detector.

[0098] The chromatographic column selected in the headspace-gas chromatograph includes a DB-FFAP chromatographic column, and the specification of the DB-FFAP chromatographic column is: 30m×320μm×0.5μm.

[0099] The chromatographic analysis conditions of the headspace-gas chromatography instrument are:

[0100] Inlet temperature: 250°C;

[0101] Split ratio: 5:1;

[0102] Injection volume: 1mL;

[0103] Column flow rate: 1.2 mL / min;

[0104] Column temperature: Initial temperature is 40℃, maintained for 1 min, then heated to 80℃ at a heating rate of 5℃ / min;

[0105] Detector temperature: 300°C;

[0106] Air flow rate: 400mL / min;

[0107] Hydrogen flow rate: 50mL / min;

[0108] Tail blowing flow rate: 20mL / min;

[0109] Headspace heating box temperature: 80°C;

[0110] Quantitative loop temperature: 100°C;

[0111] Transmission line temperature: 110°C;

[0112] Loop volume: 1 mL.

[0113] Performance Evaluation

[0114] 1. Ethanol standard curve

[0115] Ambient air containing ethanol at calibration mass concentrations of 0.79 mg / L, 1.58 mg / L, 3.95 mg / L, 6.32 mg / L, and 7.90 mg / L was selected for ethanol standard curve determination. Four groups of samples of each concentration were tested in parallel. The test results are detailed in Tables 1-4.

[0116] Table 1

[0117]

[0118] Table 2

[0119]

[0120] Table 3

[0121]

[0122] Table 4

[0123]

[0124] It can be seen from the test results in Tables 1 to 4 that when the mass concentration of ethanol is in the range of 0.79-7.9 mg / L, the linear correlation between the mass concentration and the response value is high, and the correlation coefficients of the four linear equations are all greater than 0.999, indicating that the mass concentration of ethanol is in the range of 0.79-7.9 mg / L, and the credibility of the test results is high.

[0125] 2. Ethanol precision determination

[0126] Ambient air containing ethanol at mass concentrations of 0.79 mg / L, 3.95 mg / L, and 7.11 mg / L was selected to test the ethanol content according to the technical scheme in Example 1. Six groups were measured in parallel for each concentration. The test results are detailed in Table 5.

[0127] Table 5

[0128]

[0129] From the standard deviation and coefficient of variation in Table 5, the dispersion of the test results is relatively small. For example, the standard deviation of the 0.79 mg / L sample is 0.008 and the coefficient of variation is 0.9%, indicating that the consistency between the measured values ​​is good.

[0130] 3. Ethanol blank matrix spike determination

[0131] 15.8 μg and 63.2 μg of ethanol standard were added to 1 L of blank water sample, respectively, and the headspace-gas chromatograph was used to repeat the measurement 3 times. The chromatographic conditions were the same as those in Example 1. The recovery results of the ethanol standard were tested. The test results are detailed in Table 6.

[0132] Table 6

[0133]

[0134] From the experimental test results in Table 6, it can be seen that the recovery rate of ethanol standards is relatively high, ranging from 98.1% to 103%, indicating that the experimental method has high accuracy and good repeatability, and can be used for subsequent experiments or analyses.

[0135] 4. Determination of actual ethanol samples

[0136] According to the technical scheme in Examples 1-3, ambient air containing ethanol, unorganized waste gas containing ethanol and organized waste gas containing ethanol were tested respectively. The test results are detailed in Table 7.

[0137] Table 7

[0138]

[0139] The experimental results in Table 7 indicate that the test method provided by the present invention is applicable to the determination of ethanol content in ambient air containing ethanol, unorganized waste gas containing ethanol, and organized waste gas containing ethanol, and the experimental repeatability is high.

[0140] 5. Detection limit determination

[0141] The detection limit of ethanol was tested according to the test method of Example 1, and the detection limit was determined using t distribution. The formula is as follows: LOD = t (n-1,0.99)×3.143(SD, standard deviation), t (n-1,0.99) It is the critical value of t distribution when the degree of freedom is n-1 and the confidence level is 99%. The standard deviation SD of the blank sample test value is 3.143. Seven groups were tested. The test results are shown in Table 8.

[0142] Table 8

[0143]

[0144] It can be seen from the experimental test results in Table 8 that the detection limit of the ethanol content test method provided by the present invention is relatively low, which can reach 0.10 mg / L, indicating that the test method provided by the present invention has high sensitivity and can be applied to the determination of ethanol content in ambient air and exhaust gas.

Claims

1. A method for detecting ethanol in ambient air and exhaust gas, characterized in that: include: S1, solvent adsorption; S2, headspace-gas chromatography analysis.

2. The method for detecting ethanol in ambient air and exhaust gas according to claim 1, characterized in that: The implementation method of the solvent adsorption in step S1 includes: using a porous wave plate filled with an adsorption liquid to adsorb and collect ambient air containing ethanol, organized waste gas containing ethanol, or unorganized waste gas containing ethanol.

3. The method for detecting ethanol in ambient air and exhaust gas according to claim 2, characterized in that: A porous wave plate filled with 10 mL of adsorption liquid is used to adsorb and collect ambient air containing ethanol, organized waste gas containing ethanol, or unorganized waste gas containing ethanol.

4. The method for detecting ethanol in ambient air and exhaust gas according to claim 2, characterized in that: The adsorption liquid includes an organic solvent and / or an inorganic solvent.

5. The method for detecting ethanol in ambient air and exhaust gas according to claim 4, characterized in that: The inorganic solvent includes water.

6. The method for detecting ethanol in ambient air and exhaust gas according to claim 2, characterized in that: The adsorption collection time is 20-60min.

7. The method for detecting ethanol in ambient air and exhaust gas according to claim 2, characterized in that: The ventilation flow rate of the adsorption collection is 0.5-1.0L / min.

8. The method for detecting ethanol in ambient air and exhaust gas according to any one of claims 1 to 7, characterized in that: The implementation method of the step S2 includes: transferring the adsorbed liquid into a headspace bottle, placing the headspace bottle on a headspace-gas chromatograph, and performing headspace-gas chromatography detection and analysis.

9. The method for detecting ethanol in ambient air and exhaust gas according to claim 8, characterized in that: The chromatographic column selected in the headspace-gas chromatograph includes a DB-FFAP chromatographic column.

10. The method for detecting ethanol in ambient air and exhaust gas according to claim 8, characterized in that: The chromatographic analysis conditions of the headspace-gas chromatography are: Inlet temperature: 240-300℃; Split ratio: (4-8): 1; Injection volume: 1-2mL; Column flow rate: 1-2mL / min; Column temperature: Initial temperature is 40°C, maintained for 1 min, then raised to 80°C at a heating rate of 4-8°C / min; Detector temperature: 200-300℃; Air flow rate: 300-450mL / min; hydrogen Flow rate: 40-60mL / min; Tail blowing flow rate: 10-25mL / min; Headspace heating box temperature: 75-90℃; Quantitative loop temperature: 100-120°C; Transmission line temperature: 100-120°C; Quantitative loop volume: 1-2mL.

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