Application of sulfoxide compound in detection of free chlorine in water body

Abstract

The invention belongs to the technical field of detection, and provides application of a sulfoxide compound in detection of free chlorine in a water body. The method comprises the following steps: by taking a sulfoxide compound as a detection probe of free chlorine, adding the sulfoxide compound and a phosphate buffer solution into a chlorine-containing water body to be detected, carrying out balanced reaction for a period of time, and then detecting the generation amount of a characteristic product, so as to quantitatively evaluate the concentration of the free chlorine in the water body. Compared with the prior art, the novel free chlorine detection probe provided by the invention has a longer shelf life under the same storage condition, is stable in performance and is not easy to deteriorate; high-corrosivity reagents such as sulfuric acid and complex masking agents do not need to be used; the interference of a complex water matrix can be overcome. In addition, the novel free chlorine detection method provided by the invention has a lower detection limit, and the sensitivity and convenience of free chlorine detection are remarkably improved. The novel free chlorine detection method provided by the invention is wide in application range and has relatively high practical value in practical application.

Description

Technical Field

[0001] The invention belongs to the field of detection technology, and particularly relates to the application of sulfoxide compounds in the detection of free chlorine in water bodies. Background Art

[0002] Drinking water disinfection is a key process in water treatment. Its main purpose is to remove pathogenic microorganisms in water and prevent water-borne diseases. − As a strong oxidant with broad spectrum bactericidal and algaecidal properties, HOCl / OCl has broad application prospects. − It can be miscible with water in any proportion, avoiding the technical difficulties of chlorine, chlorine dioxide, ozone and other gaseous disinfectants being difficult to dissolve in water and difficult to accurately add, while effectively reducing the potential safety hazards such as leakage and high toxicity of liquid chlorine, chlorine dioxide and other agents. − It is easy to store, easy to decompose, and has no residue, so it is an ideal disinfectant. Based on its safety and ease of operation, domestic water plants have gradually adopted HOCl / OCl in recent years. − As a method of disinfection.

[0003] At present, the detection of free chlorine concentration in water bodies is mainly based on the "Standard Test Method for Drinking Water" (GB / T5750.11-2023). This method uses DPD reagent as a colorimetric agent and phosphate solution as a buffer reagent, combined with a spectrophotometer to quantitatively determine the free chlorine concentration. The preparation method of DPD solution is: take 1.0 g N,N' -Diethyl-p-phenylenediamine hydrochloride or 1.5 g N,N' -Diethyl-p-phenylenediamine sulfate was dissolved in chlorine-free pure water containing 8 mL of sulfuric acid solution (1+3) and 0.2 g of disodium ethylenediaminetetraacetate (masking agent), and diluted to 1000 mL and stored in the dark. However, DPD solution is easily degraded in light and air and is not suitable for long-term storage. The use of highly corrosive reagents such as sulfuric acid makes this method a safety risk. In addition, the sensitivity of this detection method is low, and the minimum detection limit of free chlorine is 10 μg / L. Therefore, it is urgent to find new probes for free chlorine detection and develop safer, more stable and sensitive analytical methods to accurately detect the free chlorine content in water bodies. Summary of the invention

[0004] The present invention aims to overcome the shortcomings of traditional free chlorine detection reagents (such as DPD reagents) that are easy to fail, have a short storage time, are complicated to operate, and have low detection sensitivity, and to provide the application of sulfoxide compounds in the detection of free chlorine in water bodies. Using sulfoxide compounds as probes, the probe has a longer shelf life under the same storage conditions, stable performance, and is not easy to deteriorate; there is no need to use highly corrosive reagents such as sulfuric acid and complex masking agents; and it can overcome the interference of complex water matrices. In addition, in the detection of free chlorine, the probe has a lower detection limit, which significantly improves the sensitivity and convenience of free chlorine detection.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: The application of sulfoxide compounds in the detection of free chlorine in water bodies, using sulfoxide compounds as detection probes for free chlorine, adding sulfoxide compounds and phosphate buffer to the chlorine-containing water to be tested, after equilibrium reaction, detecting the amount of characteristic product generated, so as to quantitatively evaluate the free chlorine concentration in the water body.

[0006] Preferably, the chlorine in the chlorine-containing water body to be tested is at least one of HOCl, OCl−, chlorine gas, sodium dichloroisocyanurate, and trichloroisocyanuric acid.

[0007] Preferably, the sulfoxide compound is any one of methyl phenyl sulfoxide, dimethyl sulfoxide, diethyl sulfoxide and diphenyl sulfoxide.

[0008] Preferably, the characteristic product is any one of methyl phenyl sulfone, dimethyl sulfone, diethyl sulfone and diphenyl sulfone.

[0009] Preferably, the detection limit of free chlorine in water using sulfoxide compounds is 2 μg / L.

[0010] Preferably, the molar concentration of the sulfoxide compound is higher than the total chlorine concentration in the chlorine-containing water body to be tested; More preferably, the molar concentration of the sulfoxide compound is 10 μM to 100 μM.

[0011] Preferably, the pH value of the phosphate buffer is 3.0 to 11.0.

[0012] Preferably, the equilibrium reaction time is 0 to 48 h.

[0013] Preferably, the chlorine-containing water contains 0 to 10 mg / L of cations; More preferably, the cations include at least one of iron ions, copper ions, magnesium ions, chromium ions, calcium ions, cobalt ions, and the like.

[0014] Preferably, the chlorine-containing water contains 0 to 10 mg / L of anions; More preferably, the anion comprises at least one of chloride ion, sulfate ion, nitrate ion, carbonate ion and the like.

[0015] Preferably, the chlorine-containing water body to be tested is chlorine-containing surface water, drinking water, sewage, industrial waste water, groundwater, recycled water or rainwater.

[0016] Preferably, the method for detecting the amount of characteristic product generated is selected from any one of an ultraviolet spectrophotometer, a fluorescence spectrometer, a liquid chromatography, and a high-resolution mass spectrometer.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses sulfoxide compounds as free chlorine detection probes, which saves the complicated reagent preparation process and avoids the use of highly corrosive sulfuric acid compared to traditional DPD detection reagents. Moreover, the sulfoxide compound reagent can be stored stably for a long time.

[0018] Second, sulfoxide compounds can react chemically with free chlorine in water to generate stable specific products, while sulfoxide compounds cannot generate such specific products with combined chlorine in water (such as monochloramine, dichloramine, trichlorammonium, etc.). Therefore, the free chlorine concentration in the water can be quantitatively fed back by measuring the amount of specific product generated. In addition, compared with the DPD method, the free chlorine detection method based on sulfoxide compounds can measure a wider range of free chlorine (the minimum detection mass concentration can reach 2 μg / L) with higher sensitivity.

[0019] 3. The free chlorine detection method using sulfoxide compounds as detection probes has a wide range of applications, is less affected by matrix ions in water, and has high practical value in actual applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a standard curve of low-level free chlorine concentration (2 ~ 80 μg / L) based on the methyl phenyl sulfoxide detection probe; Figure 2 It is a high-concentration free chlorine concentration standard curve (80 μg / L ~ 2mg / L) based on the methyl phenyl sulfoxide detection probe; Figure 3 The effects of different concentrations and types of cations (iron ions, copper ions, magnesium ions, chromium ions, calcium ions, and cobalt ions) on the free chlorine detection method based on the methyl phenyl sulfoxide detection probe; Figure 4 The study is about the influence of different concentrations and types of anions (chloride ion, sulfate ion, nitrate ion, carbonate ion) on the free chlorine detection method based on methyl phenyl sulfoxide detection probe. DETAILED DESCRIPTION

[0021] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0022] The embodiment of the present invention provides the application of sulfoxide compounds in the detection of free chlorine in water bodies. The sulfoxide compounds are used as detection probes for free chlorine, and the sulfoxide compounds and phosphate buffer are added to the chlorine-containing water body to be tested. After the equilibrium reaction, the amount of characteristic product generated is detected to quantitatively evaluate the free chlorine concentration in the water body.

[0023] The principles of the embodiments of the present invention are: Free chlorine + methyl phenyl sulfoxide → methyl phenyl sulfone + Cl − ; Free chlorine + dimethyl sulfoxide → dimethyl sulfone + Cl − ; Free chlorine + diethyl sulfoxide → diethyl sulfone + Cl − ; Free chlorine + diphenyl sulfoxide → diphenyl sulfone + Cl − ; Sulfoxide compounds can react chemically with free chlorine in water to generate stable specific products (methyl phenyl sulfone, dimethyl sulfone, diethyl sulfone, diphenyl sulfone), while sulfoxide compounds cannot generate such specific products with combined chlorine in water (such as monochloramine, dichloramine, trichlorammonium, etc.). Therefore, the free chlorine concentration in the water can be quantitatively fed back by measuring the amount of specific product generated. In addition, compared with the DPD method, the free chlorine detection method based on sulfoxide compounds can measure a wider range of free chlorine (the minimum detection mass concentration can reach 2 μg / L) and has higher sensitivity.

[0024] The chlorine in the chlorine-containing water to be tested is HOCl, OCl − At least one of chlorine, sodium dichloroisocyanurate, and trichloroisocyanuric acid. It should be noted that although sodium dichloroisocyanurate and trichloroisocyanuric acid are not free chlorine, both of them will continuously release free chlorine.

[0025] The sulfoxide compound can be any one of methyl phenyl sulfoxide, dimethyl sulfoxide, diethyl sulfoxide, and diphenyl sulfoxide. When performing detection, each detection probe can generate different characteristic products with free chlorine, namely methyl phenyl sulfone, dimethyl sulfone, diethyl sulfone, and diphenyl sulfone.

[0026] The detection limit of free chlorine in water using sulfoxide compounds in the embodiment of the present invention is 2 μg / L.

[0027] As for the dosage of the sulfoxide compound, the effect of the present invention can be achieved as long as its molar concentration is higher than the total chlorine concentration in the water body, so its specific dosage does not need to be limited and can be selected by those skilled in the art according to actual conditions. For example, the molar concentration of the sulfoxide compound can be 10 μM to 100 μM.

[0028] In some preferred embodiments, the phosphate buffer is a commonly used buffer in the art, and its pH value can be selected by those skilled in the art based on experience. For example, the pH value of the phosphate buffer is 3.0 to 11.0. After the addition of the phosphate buffer, the equilibrium reaction time does not need to be specifically limited and can be selected by those skilled in the art based on actual conditions. For example, it can be 0 to 48 hours.

[0029] The embodiments of the present invention can shield the interference of anions, and when the chlorine-containing water to be tested contains 0 to 10 mg / L of cations, the detection accuracy is not affected, and the experimental detection error of cations is less than 3%, such as iron ions, copper ions, magnesium ions, chromium ions, calcium ions, cobalt ions, etc.

[0030] The embodiments of the present invention can shield the interference of anions, and when the chlorine-containing water to be tested contains 0 to 10 mg / L of anions, the detection accuracy is not affected, and the experimental detection error of cations is less than 3%, such as chloride ions, sulfate ions, nitrate ions, carbonate ions, etc.

[0031] The embodiments of the present invention are suitable for detecting common chlorine-containing water bodies, such as chlorine-containing surface water, drinking water, sewage, industrial waste water, groundwater, recycled water or rainwater.

[0032] It should be noted that, when detecting the characteristic product generation amount, use the detection method commonly used in the prior art, such as ultraviolet spectrophotometer, fluorescence spectrometer, liquid chromatography, high resolution mass spectrometry, etc. When quantitatively detecting free chlorine content, it is necessary to first establish a standard curve of characteristic product generation amount and free chlorine content, substitute the characteristic product generation amount of determination into the standard curve when actually detecting, and calculate the corresponding free chlorine concentration. For using different sulfoxide compounds, the corresponding standard curve establishment method is the same. In order to make the test result more accurate, standard curves can be established for low concentration free chlorine content and high concentration free chlorine content, respectively.

[0033] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0034] Example 1: Using methyl phenyl sulfoxide as the detection probe, construct low concentration (2μg / L ~ 80μg / L) and high concentration (80μg / L~ 2 mg / L) Two sets of free chlorine standard curves : Select HOCl / OCl −As a typical free chlorine, a free chlorine standard curve was constructed. The purchased HOCl / OCl was accurately determined using the iodine titration method. − The free chlorine content in the solution (solution 1). The specific method is: take 1 mL of sample from solution 1, add it to a 250 mL volumetric flask, dilute it to the mark with pure water, mix it evenly, and obtain the diluted solution 2. In a 250 mL iodine volumetric flask, add 1 g of potassium iodide crystals and 75 mL of pure water, stir until the potassium iodide is completely dissolved, and then add 2 mL of glacial acetic acid. Take 25 mL of sample from solution 2, inject it into the above iodine volumetric flask, seal the bottle mouth and seal it with water, and place it in a dark place for 5 minutes. Titrate with sodium thiosulfate standard solution until the solution is light yellow, then add 1 mL of starch solution, continue to titrate until the blue color just disappears, and record the amount of sodium thiosulfate solution V.

[0035] The free chlorine concentration in solution 1 was calculated according to the following formula: ; The free chlorine concentration in solution 2 was calculated according to the following formula: ; Where: Refers to the free chlorine content in the solution, %; V refers to the amount of sodium thiosulfate standard solution, mL; c refers to the concentration of sodium thiosulfate standard solution, mol / L; 0.03545 refers to the mass of available chlorine in grams equivalent to 1 mL of 1 mol / L sodium thiosulfate standard solution; m refers to the amount of chlorine disinfectant, g.

[0036] In a 50 mL brown volumetric flask, prepare different concentration gradients of free chlorine solutions using pH 7 phosphate buffer as the solvent as follows: 1. Prepare the buffer: First add approximately 40 mL of pH 7 phosphate buffer to a 50 mL brown volumetric flask to ensure that the final solution maintains the desired pH conditions during preparation.

[0037] 2. Add free chlorine standard solution: According to the required concentration, accurately measure the appropriate volume of free chlorine solution from the quantified free chlorine standard solution (solution 1 and solution 2), add it to the brown volumetric flask, and dilute it to the scale with pure water. The target concentration includes the following gradients: Low concentration free chlorine solution: 2, 5, 10, 15, 30, 80 μg / L; High concentration free chlorine solution: 80, 150, 350, 700, 1000, 1500, 2000 μg / L.

[0038] Subsequently, methyl phenyl sulfoxide solution was added to free chlorine solutions of different concentrations and the amount of characteristic product generated was detected by the following steps to construct two sets of standard curves of low concentration and high concentration: 1. Add methyl phenyl sulfoxide solution: Add methyl phenyl sulfoxide solution to the prepared free chlorine solutions of different concentrations (low concentration group and high concentration group) and mix thoroughly.

[0039] 2. Balance reaction: Let the mixture stand to ensure that methyl phenyl sulfoxide reacts completely with free chlorine to form the target product methyl phenyl sulfone.

[0040] 3. Sample processing and characteristic product (methyl phenyl sulfone) detection: Take 1 mL of sample from the balanced mixed solution and filter it through a 0.22 μm filter membrane to remove impurities to ensure the purity of the sample and the accuracy of the detection. Inject the filtered sample into a high performance liquid chromatograph to detect the amount of characteristic product generated.

[0041] 4. Data recording and standard curve drawing: Determine the amount of methyl phenyl sulfone generated in the free chlorine samples of various concentrations and record the data. With the free chlorine concentration as the horizontal axis and the methyl phenyl sulfone determination amount as the vertical axis, draw the low concentration ( Figure 1 ), high concentration ( Figure 2 ) Two sets of standard curves.

[0042] Example 2: Investigating the interference of anions and cations in different water bodies on the free chlorine detection method In a 50 mL brown volumetric flask, prepare 50 μg / L free chlorine solutions containing different types and concentrations of anions and cations as follows, using pH 7 phosphate buffer as the solvent: 1. Prepare the buffer: Add approximately 40 mL of pH 7 phosphate buffer to a 50 mL brown volumetric flask to ensure that the final solution maintains the desired pH conditions during preparation.

[0043] 2. Add free chlorine standard solution: Accurately measure an appropriate volume of free chlorine solution from the quantified free chlorine standard solution (solution 1 or solution 2), add it to a brown volumetric flask, and dilute it to the scale with pure water to prepare a 50 μg / L free chlorine solution. Prepare 50 sets of the same free chlorine solution in total.

[0044] 3. Add different types and concentrations of anions and cations: In the above free chlorine solution, add one type of anion and cation of different concentrations (1, 2, 5, 10 mg / L): including iron ion, copper ion, magnesium ion, chromium ion, calcium ion, cobalt ion, chloride ion, sulfate ion, nitrate ion, and carbonate ion solution, and dilute with pure water to the 50 mL mark.

[0045] Subsequently, in the free chlorine solution containing different types and concentrations of anions and cations, the methyl phenyl sulfoxide solution was added and the amount of characteristic product generated was detected by the following steps: 1. Add methyl phenyl sulfoxide solution: Add 50 μM methyl phenyl sulfoxide solution to the prepared 50 μg / L free chlorine solution containing different types and concentrations of anions and cations, and mix thoroughly.

[0046] 2. Balance reaction: Let the mixture stand to ensure that methyl phenyl sulfoxide reacts completely with free chlorine to form the target product methyl phenyl sulfone.

[0047] 3. Sample processing and characteristic product detection: Take out 1 mL of sample from the balanced mixed solution and filter it through a 0.22 μm filter membrane to remove impurities to ensure the purity of the sample and the accuracy of the detection. Inject the filtered sample into a high performance liquid chromatograph to detect the amount of characteristic product generated.

[0048] 4. Data recording: Determine the amount of methyl phenyl sulfone generated in each sample, record the data, and substitute it into the standard curve to calculate the corresponding free chlorine concentration.

[0049] The effects of different concentrations and types of cations (iron, copper, magnesium, chromium, calcium, cobalt) on the free chlorine detection method are shown in Figure 3 ,because Figure 3 The free chlorine detection concentrations in each group were higher than 48.5 μg / L. The interference value calculation formula (free chlorine detection value of the sample to be tested – 50) / 50) showed that the interference value was less than 3%, indicating that the free chlorine detection method could shield the cation interference.

[0050] The effects of different concentrations and types of anions (chloride, sulfate, nitrate, carbonate) on the free chlorine detection method are shown in Figure 4 , Figure 4 The free chlorine detection concentrations in each group were higher than 48.5 μg / L, and the calculated interference value was less than 3%, indicating that the free chlorine detection method can shield the anion interference.

[0051] Example 3: Investigation of the application of the free chlorine detection method in actual water bodies 1. Water sample preparation and addition of detection probe: Take 50 mL of actual water sample (such as surface water, drinking water, sewage, industrial wastewater, groundwater, recycled water or rainwater), add pH 7 phosphate buffer and 50 μM methyl phenyl sulfoxide solution, and mix thoroughly.

[0052] 2. Reaction equilibrium: Allow the mixture to stand to ensure that methyl phenyl sulfoxide reacts completely with free chlorine to form the target product methyl phenyl sulfone.

[0053] 3. Sample processing and detection: Take out 1 mL of sample from the balanced mixed solution, filter it through a 0.22 μm filter membrane to remove impurities to ensure the purity of the sample and the accuracy of the detection, and inject it into the high performance liquid chromatography for detection.

[0054] 4. Data recording: Determine the amount of methyl phenyl sulfone generated in the actual water sample, record the data, and substitute it into the standard curve to calculate the corresponding free chlorine concentration. The calculated interference values ​​are all less than 5%, indicating that the free chlorine detection method can be applied to actual water bodies.

[0055] The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. The application of sulfoxide compounds in the detection of free chlorine in water is characterized in that: Sulfoxide compounds are used as detection probes for free chlorine. Sulfoxide compounds and phosphate buffer are added to the chlorine-containing water to be tested. After equilibrium reaction, the amount of characteristic products generated is detected to quantitatively evaluate the free chlorine concentration in the water.

2. The use of the sulfoxide compound according to claim 1 in detecting free chlorine in water, characterized in that: The chlorine in the chlorine-containing water to be tested is HOCl, OCl − , chlorine, sodium dichloroisocyanurate, and trichloroisocyanuric acid.

3. The use of sulfoxide compounds according to claim 1 in detecting free chlorine in water, characterized in that: The sulfoxide compound is any one of methyl phenyl sulfoxide, dimethyl sulfoxide, diethyl sulfoxide and diphenyl sulfoxide.

4. The use of sulfoxide compounds according to claim 1 in detecting free chlorine in water, characterized in that: The characteristic product is any one of methyl phenyl sulfone, dimethyl sulfone, diethyl sulfone and diphenyl sulfone.

5. The use of sulfoxide compounds according to claim 1 in detecting free chlorine in water, characterized in that: The detection limit of free chlorine in water using sulfoxide compounds is 2 μg / L.

6. The use of sulfoxide compounds according to claim 1 in detecting free chlorine in water, characterized in that: The molar concentration of the sulfoxide compound is higher than the total chlorine concentration in the chlorine-containing water body to be tested; Preferably, the molar concentration of the sulfoxide compound is 10 μM to 100 μM.

7. The use of sulfoxide compounds according to claim 1 in detecting free chlorine in water, characterized in that: The pH value of the phosphate buffer is 3.0 to 11.

0.

8. The use of sulfoxide compounds according to claim 1 in detecting free chlorine in water, characterized in that: The chlorine-containing water to be tested contains 0-10 mg / L of cations; Preferably, the cations include at least one of iron ions, copper ions, magnesium ions, chromium ions, calcium ions, and cobalt ions.

9. The use of sulfoxide compounds according to claim 1 in detecting free chlorine in water, characterized in that: The chlorine-containing water to be tested contains 0-10 mg / L of anions; Preferably, the anion comprises at least one of chloride ion, sulfate ion, nitrate ion and carbonate ion.

10. The use of sulfoxide compounds according to claim 1 in detecting free chlorine in water, characterized in that: The method for detecting the amount of characteristic product generated is selected from any one of ultraviolet spectrophotometer, fluorescence spectrometer, liquid chromatography, and high-resolution mass spectrometry.

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