Method for determining chromium acid mist in exhaust gas

Abstract

The present application relates to the technical field of environmental monitoring, and provides a method for determining chromic acid mist in waste gas, comprising: collecting a chromic acid mist sample in waste gas to obtain a sample carrier; extracting and treating the sample carrier by using an aqueous solvent to obtain a sample solution; determining the chromium content in the sample solution by using atomic absorption spectrophotometry; and calculating the concentration of the chromic acid mist in waste gas based on the chromium content. The present application discards unstable color reaction steps, effectively shields the interference of coexisting ions by using the high selectivity of atomic absorption spectroscopy, significantly improves the accuracy, stability and operation simplicity of determination, and reduces the detection cost.

Description

Technical Field

[0001] This invention relates to the field of environmental monitoring technology, and in particular to a method for measuring chromic acid mist in exhaust gas. Background Technology

[0002] Currently, the legally mandated method for determining chromic acid mist in exhaust gas from stationary sources in China is primarily based on the national environmental protection standard "Determination of Chromic Acid Mist in Exhaust Gas from Stationary Sources - Diphenylcarbazide Spectrophotometric Method" (HJ / T 29-1999). The core principle of this method is the colorimetric reaction between diphenylcarbazide and hexavalent chromium under acidic conditions, forming a purplish-red complex, which is then quantified by measuring absorbance. However, this method has several shortcomings in practical applications: First, the complex formed by the colorimetric reaction has poor stability, and its color easily decays over time, requiring a strict measurement time window and affecting the repeatability of the results; second, the complex matrix of the exhaust gas sample, with coexisting ions such as iron and mercury ions, can significantly interfere with the colorimetric reaction, leading to deviations in the measurement results; third, the diphenylcarbazide solution, the colorimetric reagent, needs to be stored at low temperature and protected from light, has a short shelf life, and is cumbersome to prepare; finally, the entire colorimetric process has stringent operating conditions, and differences in operator technique can significantly affect the results. Summary of the Invention

[0003] To address the problems of unstable colorimetric reactions and poor accuracy of measurement results caused by numerous interfering factors in existing technologies, this application proposes a method for determining chromic acid mist in exhaust gas. This method abandons the traditional colorimetric reaction steps and uses aqueous solvent extraction combined with atomic absorption spectrophotometry to directly determine the chromium content, achieving a stable measurement process, strong anti-interference ability, and simple operation.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for determining chromic acid mist in exhaust gas includes the following steps: collecting a chromic acid mist sample from the exhaust gas to obtain a sample carrier; extracting the sample carrier with an aqueous solvent to obtain a sample solution; determining the chromium content in the sample solution using atomic absorption spectrophotometry; and calculating the concentration of chromic acid mist in the exhaust gas based on the chromium content.

[0005] The above method, by employing aqueous solvent extraction and atomic absorption spectrophotometry, completely eliminates the unstable colorimetric reaction step and effectively shields the interference of coexisting ions by utilizing the high selectivity of atomic absorption spectroscopy, thus significantly improving the accuracy and stability of the determination.

[0006] In one embodiment, the aqueous solvent is water.

[0007] The above-described method avoids the introduction of additional chemical reagents by using water as the extraction solvent, reducing reagent costs and background interference, while simplifying the pretreatment process. Furthermore, since hexavalent chromium exists in water as chromate or dichromate ions and has good water solubility, while trivalent chromium readily forms hydroxide precipitates in water and is poorly soluble, using water as the extraction solvent allows for the selective extraction of hexavalent chromium, effectively eliminating interference from trivalent chromium.

[0008] In one embodiment, the extraction process includes extracting the sample carrier using water at a temperature of 90–100°C.

[0009] The above-mentioned method, through hot water extraction, improves the dissolution efficiency of chromic acid mist from the sample carrier, ensuring sufficient extraction and further guaranteeing the accuracy of the measurement results. Simultaneously, hot water extraction further promotes the dissolution of hexavalent chromium, while trivalent chromium remains in the filter residue as insoluble hydroxides, thus achieving selective extraction of hexavalent chromium. Experiments show that at 90–100℃, the extraction rate of hexavalent chromium can reach over 98%, while the extraction rate of trivalent chromium is less than 5%, effectively eliminating interference from trivalent chromium.

[0010] In one embodiment, the atomic absorption spectrophotometry is flame atomic absorption spectrophotometry.

[0011] The above method utilizes flame atomic absorption spectrophotometry, which has the advantages of fast analysis speed, simple operation and low cost, and is suitable for rapid analysis of large batches of samples.

[0012] In one embodiment, the wavelength of the measured characteristic spectral line is 357.9 nm.

[0013] The above method ensures the sensitivity and accuracy of the measurement by selecting the most sensitive characteristic spectral line of chromium.

[0014] In one embodiment, in the determination step, a standard curve is plotted using a series of chromium standard solutions, wherein the solvent for the series of chromium standard solutions is water.

[0015] The above method uses water-based solvents to prepare a series of standard solutions, which makes the matrix of the standard solutions match that of the sample solutions. This eliminates the need to add matrix modifiers, simplifies the operation, and reduces the influence of matrix effects.

[0016] In one embodiment, the extraction process does not involve the addition of acids, alkalis, or color developers.

[0017] The above scheme further simplifies the types of reagents, avoids the corrosion or interference that acid and alkali reagents may cause, and avoids the errors caused by the instability of colorimetric reagents, thereby reducing detection costs and risks.

[0018] In one embodiment, the sample carrier is a glass fiber filter cartridge.

[0019] The above scheme uses a glass fiber filter cartridge as a sampling carrier, which can effectively capture chromic acid mist in the exhaust gas and has good compatibility with the subsequent aqueous solvent extraction step.

[0020] As one implementation, the extraction process further includes a step of crushing the glass fiber filter cartridge.

[0021] The above method increases the contact area between the sample and the extraction solvent by breaking the filter cartridge, thus significantly improving the extraction efficiency.

[0022] In one embodiment, the flame type for the flame atomic absorption spectrophotometry is an air-acetylene flame.

[0023] The above method uses an air-acetylene flame, which can provide a suitable atomization temperature and reducing atmosphere, which is conducive to the atomization of chromium and ensures the stability of the determination.

[0024] The beneficial effects of this invention are as follows: By employing aqueous solvent extraction and atomic absorption spectrophotometry, the unstable colorimetric reaction step in traditional methods is completely eliminated, fundamentally removing measurement errors caused by the colorimetric time window and significantly improving the stability of the measurement results. Simultaneously, the high selectivity of atomic absorption spectrometry effectively shields the spectral interference of common coexisting metal ions in exhaust gases, improving the accuracy of measurements on complex matrix samples. Furthermore, this method eliminates the need for complex colorimetric reagents, simplifies the operation process, reduces reliance on operator skills, and requires fewer reagents, resulting in lower costs and easier standardization and promotion. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method for measuring chromic acid mist in exhaust gas provided in an embodiment of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0028] Example 1: like Figure 1 As shown, this embodiment provides a method for determining chromic acid mist in exhaust gas. The method includes steps S100 to S400, which combine aqueous solvent extraction with atomic absorption spectrophotometry to achieve stable and accurate determination of chromic acid mist in exhaust gas.

[0029] Step S100: Collect chromic acid mist samples from the exhaust gas to obtain a sample carrier.

[0030] Specifically, this step can employ existing isokinetic sampling technology, using a sampling probe inserted deep into the exhaust stack of a fixed pollution source to extract a certain volume of waste gas at a set flow rate. Chromic acid mist particles in the waste gas are captured on a sample carrier. It should be understood that the sample carrier material must possess characteristics such as high temperature resistance, corrosion resistance, and high adsorption efficiency for chromic acid mist, such as glass fiber or quartz fiber filter cartridges or membranes, as long as they can effectively capture gaseous or aerosol chromic acid mist.

[0031] Step S200: Extract the sample carrier using an aqueous solvent to obtain a sample solution.

[0032] Specifically, an aqueous solvent refers to a liquid system with water as the base solvent. In this embodiment, the aqueous solvent is preferably water, such as distilled water or deionized water. As a polar solvent, water can effectively dissolve chromic acid mist in the form of chromates or dichromates without introducing interfering ions or corrosive media. Compared with the use of strongly alkaline solutions for extraction in the prior art, this embodiment uses water as the extraction solvent, which not only simplifies the reagent preparation process but also reduces the risk of matrix interference and equipment corrosion in subsequent detection processes.

[0033] Step S300: The chromium content in the sample solution is determined by atomic absorption spectrophotometry.

[0034] Specifically, atomic absorption spectrophotometry is a method for quantitative analysis based on the absorption of characteristic spectral lines by ground-state atoms. This step abandons the principle of relying on colorimetric reactions in traditional diphenylcarbazide spectrophotometry, directly utilizing the absorption characteristics of chromium atoms at specific wavelengths of light for measurement. During the measurement process, the sample solution is atomized and atomized, and the concentration of chromium in the sample solution is directly calculated by measuring the absorbance at a specific wavelength. Because atomic absorption spectrometry has extremely high selectivity and its characteristic spectral lines are element-specific, it can effectively shield against interference from common coexisting ions (such as iron ions and mercury ions) in waste gas samples, eliminating the need for complex masking agents or separation steps. Furthermore, since it does not involve unstable colorimetric reactions, the sample solution has a longer shelf life and better stability after preparation, fundamentally solving the measurement error problem caused by the decay of colorimetric complexes over time.

[0035] Step S400: Calculate the concentration of chromic acid mist in the exhaust gas based on the chromium content.

[0036] Specifically, based on the chromium content in the sample solution measured in step S300, and combined with the standard gas sampling volume recorded during sampling, the mass concentration of chromic acid mist in the exhaust gas can be obtained through mathematical conversion. For example, the measured chromium mass concentration can be multiplied by a conversion factor (such as the molecular weight ratio of CrO3 to Cr) to obtain the emission concentration in terms of chromic acid mist.

[0037] Through the above steps, this embodiment constructs a measurement system that requires no colorimetric reaction and has strong anti-interference capabilities. Aqueous solvent extraction simplifies the pretreatment process and reduces background interference, while atomic absorption spectrophotometry provides a highly selective detection method. The synergistic effect of both significantly improves the accuracy and ease of operation in the determination of chromic acid mist in exhaust gas.

[0038] Example 2: Based on Example 1, this embodiment optimizes the sample carrier, extraction solvent, and extraction process in the pretreatment step to further improve the accuracy of the determination and the extraction efficiency.

[0039] In step S100, the sample carrier is preferably a glass fiber filter cartridge. Specifically, glass fiber filter cartridges have the characteristics of high porosity, high collection efficiency, and high temperature resistance, and can effectively adsorb chromic acid mist particles in the exhaust gas. It should be understood that in other embodiments, depending on the temperature or humidity of the exhaust gas, quartz fiber filter cartridges or corundum filter cartridges may also be selected, as long as they do not chemically react with chromic acid mist and can be wetted by the subsequent extraction solvent.

[0040] In step S200, the aqueous solvent is preferably water. Specifically, the water here can be laboratory-prepared deionized water or distilled water. Pure water is chosen as the extraction solvent because chromic acid mist (mainly existing in the form of chromic acid or dichromic acid) is readily soluble in water, and pure water has an extremely low background value, avoiding potential interference from impurity ions in subsequent atomic absorption measurements, while also reducing reagent costs. Compared to acid-base extraction solutions that may be used in existing technologies, the pure water system is less corrosive to the instrument and is safer and more environmentally friendly to operate. It should be understood that hexavalent chromium exists in water as chromate (CrO4²⁻) or dichromate (Cr2O7²⁻), exhibiting good water solubility; while trivalent chromium easily forms hydroxide precipitates in water and is poorly soluble. Therefore, this embodiment uses water as the extraction solvent, which can selectively extract hexavalent chromium from the waste gas, effectively eliminating interference from trivalent chromium, and ensuring that the measurement results accurately reflect the actual content of chromic acid mist (hexavalent chromium).

[0041] Furthermore, before using water for extraction, the process includes a step of breaking down the glass fiber filter cartridge. Specifically, the glass fiber filter cartridge containing the sample is placed in a container and broken into small pieces using a glass rod or a specialized crushing tool. The key function of this step is to disrupt the dense fiber structure of the filter cartridge, significantly increasing the contact surface area between the sample and the extraction solvent. This allows the chromic acid mist particles encapsulated in the fibers to be fully exposed and rapidly dissolved in the solvent, thereby significantly improving extraction efficiency.

[0042] Furthermore, the extraction process involves heating the mixture of water and the sample carrier at a temperature of 90–100°C. Specifically, a container holding a broken filter cartridge and water is placed on a hot plate and boiled. This heating process utilizes thermodynamic principles to accelerate the transfer of chromic acid mist from the solid-phase carrier to the liquid-phase solvent by increasing the velocity of solvent molecules and the diffusion coefficient of the solute. Compared to room-temperature immersion, heating extraction significantly shortens the extraction time and effectively avoids sample adsorption or volatilization losses caused by prolonged immersion. Experiments show that boiling extraction at 90–100°C achieves a chromic acid mist dissolution rate of over 98% in the filter cartridge, ensuring the reliability of the measurement results.

[0043] Through the above optimizations, this embodiment constructs an efficient and thorough pretreatment scheme. The combination of glass fiber filter cartridge crushing and heating extraction processes creates a synergistic effect, ensuring that the target pollutants in the sample are completely transferred to the solution, laying a solid foundation for subsequent accurate determination.

[0044] Example 3: This embodiment further optimizes the detection steps based on Embodiment 1. Specifically, in step S300, the chromium content in the sample solution is determined by atomic absorption spectrophotometry, specifically by flame atomic absorption spectrophotometry.

[0045] Compared with graphite furnace atomic absorption spectrophotometry, the flame atomic absorption spectrophotometry method preferred in this embodiment has significant advantages. While the graphite furnace method offers high sensitivity, it is expensive, has a long analysis cycle, and is extremely sensitive to the sample matrix, easily affected by background absorption, often requiring complex matrix modifiers. In contrast, the pretreatment step of this invention uses aqueous solvent extraction, resulting in a sample solution with chromium content typically at constant levels (mg / L), and the matrix is ​​simple and low in salinity. The flame method not only fully meets the determination requirements for this concentration range but also features fast analysis speed, low operating costs, and strong anti-interference capabilities, making it particularly suitable for rapid screening and determination of large batches of environmental samples.

[0046] Furthermore, in the specific parameter settings for flame atomic absorption spectrophotometry, this embodiment selects an air-acetylene flame. The air-acetylene flame is a widely used chemical flame with a maximum temperature of approximately 2300℃, providing sufficient energy for the effective atomization of chromium. More importantly, since the sample solution of this invention is an aqueous sample using water as a solvent, it does not contain organic solvents or high-concentration acids or alkalis. When combined with air-acetylene flame combustion, the flame state is stable, the background absorption is extremely low, and salt accumulation or crystallization is less likely to occur at the burner slit, thus ensuring the stability and reproducibility of long-term continuous sample injection measurements. This demonstrates the high compatibility between the pretreatment process and the detection method: aqueous extraction avoids the introduction of strong oxidants or complex matrices, allowing the air-acetylene flame to perform at its optimal level.

[0047] In the specific measurement process, this embodiment sets the characteristic spectral line wavelength to 357.9 nm. This wavelength is the characteristic resonance line of chromium. At this wavelength, ground-state chromium atoms absorb the light source radiation most strongly, resulting in the highest measurement sensitivity and effectively ensuring the accuracy of the detection results, meeting the requirements for quantitative analysis of low concentrations of pollutants in environmental monitoring. In actual operation, the instrument parameters can be set to a lamp current of 4.0 mA, a spectral passband of 0.2 nm, a burner height of 8 mm, an acetylene flow rate of 2.0 L / min, and an air flow rate of 8.0 L / min to obtain the optimal absorbance signal. It should be understood that these specific parameters are only illustrative examples, and operators can make fine adjustments according to the instrument model and actual response, as long as the measurement is performed below the 357.9 nm characteristic spectral line.

[0048] Through the optimization of the above detection steps, this embodiment constructs a highly efficient, stable, and low-cost detection scheme. The combination of flame atomic absorption spectrophotometry with air-acetylene flame and characteristic spectral line determination, along with the aqueous solvent extraction process described in the previous embodiment, creates a synergistic effect, significantly reducing analytical costs and improving analytical efficiency while ensuring accuracy.

[0049] Example 4: Based on Example 1, this embodiment further optimizes and limits the preparation method and reagent system of the standard curve.

[0050] In step S300, the determination step further includes preparing a series of chromium standard solutions for plotting a standard curve, wherein the solvent for the chromium standard solutions is water. Specifically, in this embodiment, water is used as the solvent to dilute the chromium standard stock solution and prepare a series of standard solutions of known concentrations. This design closely complements the process of extracting samples using aqueous solvents in the aforementioned embodiments. Since the sample extract is an aqueous solution, if the standard series solutions are prepared using traditional acidic media (such as nitric acid solution), significant differences in viscosity, surface tension, and matrix composition will occur between the standard solutions and the sample solutions, leading to physical interference during atomic absorption sampling, resulting in inconsistent atomization efficiency and ultimately affecting the accuracy of the determination results. This embodiment achieves "matrix matching" between the standard solutions and the sample solutions by limiting the solvent of the standard series solutions to water, effectively eliminating systematic errors caused by matrix effects and further improving the accuracy of quantitative analysis.

[0051] Furthermore, this embodiment explicitly specifies that no acid, alkali, or colorimetric reagent is added during the extraction process. This feature reflects the minimalist, environmentally friendly, and stable design philosophy of this invention. Specifically, traditional methods for determining chromic acid mist (such as diphenylcarbazide spectrophotometry) must rely on a strong acid environment to adjust the pH value and add a colorimetric reagent for the colorimetric reaction. Colorimetric reagents are not only cumbersome to prepare and have a short shelf life, but the stability of the complexes after color development is also poor, requiring measurement within a specific time window. This embodiment completely eliminates these complex reagents. Adding acid during extraction may increase the solubility of certain metals, but it is not necessary for chromic acid mist, and the strong acid matrix easily generates background absorption interference in flame atomic absorption spectrometry, while also corroding the instrument's atomizer and burner head. Adding alkali may introduce a large amount of sodium or potassium ions, leading to salt accumulation and blockage at the burner opening, affecting flame stability. As for the colorimetric reagent, this invention uses atomic absorption spectrometry to directly determine the total elemental amount, eliminating the need for a colorimetric reaction, thus completely avoiding problems such as the instability of the colorimetric reagent and the sensitivity to color development time. By not adding any acid, alkali or colorimetric reagent, this embodiment not only significantly reduces reagent costs and waste liquid treatment costs, but also simplifies the operation process, making the entire determination process more green and environmentally friendly. In addition, the sample solution remains stable for a longer period of time, which is convenient for batch processing and retesting.

[0052] Example 5: This embodiment is an application example used to verify the accuracy and reliability of the measurement method provided by the present invention in actual stationary pollution source exhaust gas monitoring.

[0053] Step S100: Collect chromic acid mist samples from the exhaust gas to obtain a sample carrier. Specifically, the exhaust stack of a chemical plant emitting chromic acid mist was selected as the monitoring point. A dust sampler was used, equipped with a glass fiber filter cartridge as the sample carrier. Following the isokinetic sampling principle, the sampling flow rate was set to 15 L / min, and continuous sampling was conducted for 30 minutes, recording a standard gas volume of approximately 450 L. After sampling, the filter cartridge was carefully removed with tweezers and placed in a clean sample box for storage.

[0054] Step S200 involves extracting the sample carrier using an aqueous solvent to obtain a sample solution. Specifically, a glass fiber filter containing the sample is placed in a 250 mL Erlenmeyer flask. 40 mL of deionized water is measured and boiled. The boiled deionized water is poured into the Erlenmeyer flask containing the filter, and the filter is broken into flocculent pieces with a glass rod to increase the contact area. The mixture is shaken for 5 minutes without additional heating. The solution is filtered, and the filtrate is collected in a 100 mL volumetric flask. The residue is washed 3–5 times with a small amount of hot, boiled deionized water, and the washings are added to the volumetric flask. After cooling, the solution is diluted to the mark with room temperature water and shaken well before use. During this process, no acids, alkalis, or colorimetric reagents are added, greatly simplifying the procedure.

[0055] Step S300: The chromium content in the sample solution is determined by atomic absorption spectrophotometry. Specifically, in this embodiment, a flame atomic absorption spectrophotometer is used for the determination. The instrument parameters are set as follows: chromium hollow cathode lamp, lamp current 4.0 mA; characteristic spectral line wavelength 357.9 nm; spectral passband 0.2 nm; burner height 8 mm; flame type air-acetylene flame, acetylene flow rate 2.0 L / min, air flow rate 8.0 L / min. After ignition, preheating, and stabilization, deionized water is used for zeroing, and standard series solutions and sample solutions are sequentially drawn in for measurement.

[0056] Before the determination, a standard curve needs to be plotted. A series of chromium standard solutions are prepared for plotting the standard curve using water as the solvent. Specifically, 1000 mg / L of hexavalent chromium standard stock solution is pipetted and serially diluted with deionized water to prepare a series of standard solutions with concentrations of 0.0, 0.1, 0.2, 0.5, 1.0, and 2.0 mg / L. A standard curve is plotted with concentration on the x-axis and absorbance on the y-axis. The linear regression equation is y = 0.0268x + 0.0007, and the correlation coefficient R² = 0.9994, indicating a good linear relationship.

[0057] Step S400: Calculate the concentration of chromic acid mist in the exhaust gas based on the chromium content. The chromium concentration is calculated by substituting the measured absorbance of the sample solution into the standard curve, and then, combined with the standard sampling gas volume, the final concentration of chromic acid mist in the exhaust gas is calculated.

[0058] To verify the accuracy of the method, spiked recovery and precision experiments were conducted in this embodiment. A known amount of chromium standard solution was added to the same actual sample, and the entire process was determined according to the above steps. The results showed that the spiked recovery rate of six parallel determinations was between 90% and 110%, and the relative standard deviation (RSD) was less than 5%. This data strongly demonstrates that the method provided by this invention has extremely high accuracy and precision, fully meeting the quality control requirements for environmental monitoring. Compared with the traditional diphenylcarbazide spectrophotometric method, this method does not require a colorimetric reaction, the sample solution has good stability, and the retest results after 24 hours show no significant change. Furthermore, the operation is not affected by common coexisting ions such as iron ions.

[0059] To verify the selective extraction capability of this method for hexavalent chromium, an interference experiment was conducted in this embodiment. A mixed solution containing 10 mg / L of trivalent chromium (Cr(III)) was prepared to simulate potential interference from trivalent chromium in the exhaust gas. Extraction and determination were performed according to the method of this invention. The results showed that the extraction rate of trivalent chromium was less than 5%, while the extraction rate of hexavalent chromium remained above 98%. This data strongly demonstrates that pure hydrothermal extraction can selectively extract hexavalent chromium and effectively eliminate interference from trivalent chromium.

[0060] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention, such as using other types of atomizers, replacing extraction solvents with equivalent functions, or adjusting specific process parameters, should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for determining chromic acid mist in exhaust gas, characterized in that, Includes the following steps: A sample of chromic acid mist in the exhaust gas was collected to obtain a sample carrier; The sample carrier was extracted using an aqueous solvent to obtain a sample solution; The chromium content in the sample solution was determined by atomic absorption spectrophotometry. The concentration of chromic acid mist in the exhaust gas is calculated based on the chromium content.

2. The method for determining chromic acid mist in exhaust gas according to claim 1, characterized in that, The aqueous solvent is water.

3. The method for determining chromic acid mist in exhaust gas according to claim 2, characterized in that, The extraction process includes extracting the sample carrier using water at a temperature of 90–100°C.

4. The method for determining chromic acid mist in exhaust gas according to claim 1, characterized in that, The atomic absorption spectrophotometry method is flame atomic absorption spectrophotometry.

5. The method for determining chromic acid mist in exhaust gas according to claim 4, characterized in that, The wavelength of the characteristic spectral line measured was 357.9 nm.

6. The method for determining chromic acid mist in exhaust gas according to claim 1, characterized in that, In the determination step, a standard curve is plotted using a series of chromium standard solutions, wherein the solvent for the series of chromium standard solutions is water.

7. The method for determining chromic acid mist in exhaust gas according to claim 1, characterized in that, The extraction process does not involve the addition of acids, alkalis, or color developers.

8. The method for determining chromic acid mist in exhaust gas according to claim 1, characterized in that, The sample carrier is a glass fiber filter cartridge.

9. The method for determining chromic acid mist in exhaust gas according to claim 8, characterized in that, Before the extraction process, the method further includes a step of crushing the glass fiber filter cartridge.

10. The method for determining chromic acid mist in exhaust gas according to claim 4, characterized in that, The flame type used in the flame atomic absorption spectrophotometry is an air-acetylene flame.

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