Pretreatment method of chlorine content detection sample in dibromohydantoin

Abstract

The invention relates to the technical field of medicine and chemical engineering, in particular to a pretreatment method for a chlorine content detection sample in dibromohydantoin. According to the chemical characteristics of dibromohydantoin, a rapid pretreatment process is designed and comprises the following steps: adding dibromohydantoin into an alkali solution to completely dissolve dibromohydantoin in water, adding an oxidizing agent for oxidation, adding concentrated oxidizing strong acid to adjust the pH value, converting bromine in a sample into a bromine simple substance, and releasing the element chlorine to be detected in an ion form to adapt to subsequent testing. The method comprises the following steps: extracting elemental bromine by using a non-polar solvent, separating a water layer to obtain a water sample, and further measuring the content of chlorine in dibromohydantoin by adopting an ion chromatography; according to the method for detecting the chloride ions in the dibromohydantoin, pretreatment of the dibromohydantoin and determination of the chlorine content can be rapidly completed, and the method is low in cost, easy to operate, good in repeatability and wide in application range.

Description

Technical Field

[0001] The present invention relates to the technical fields of medicine and chemical engineering. Specifically, it particularly relates to a method for sample pretreatment for detecting the chlorine content in dibromohydantoin. Background Art

[0002] Dibromohydantoin, with the chemical name of 1,3-dibromo-5,5-dimethylhydantoin, abbreviated as DBDMH. Structurally, dibromohydantoin belongs to N-halogen substituted hydantoin organic compounds and has oxidizing properties. Among them, the N-Br bond is easily broken, and it is a very useful brominating agent. Compared with brominating agents such as N-bromoacetamide and N-bromosuccinimide, it has the advantages of high active bromine content, good storage stability, and economic use. It is widely used in the bromination of allyl and benzyl compounds and active aromatic rings in the chemical and pharmaceutical industries, the addition of bromine or hydrogen bromide to double bonds, and the selective oxidation reaction of secondary alcohols; compared with brominating agents such as NBS, it has the advantages of high active bromine content, stable storage, and economic price, and has been widely used in the construction of bioactive molecules. It is also a new type of highly efficient disinfectant, with the advantages of a broad bactericidal spectrum, strong bactericidal effect, mild performance, low toxicity, and small corrosiveness; as a bactericidal and algaecidal agent, it can effectively kill various bacteria, fungi, viruses, algae, hepatitis viruses, Escherichia coli, Staphylococcus aureus, gonorrhea, cholera, Salmonella typhimurium, etc., and can be widely used for disinfection in public places, disinfection of environmental object surfaces and sanitary wares, and preservation of food; in aquaculture, it can effectively prevent and control various bacterial and fungal diseases of fish, turtles, crabs, shrimps, frogs, shellfish, etc., and is a disinfectant with significant advantages. As an impurity in dibromohydantoin, chlorine, as an active brominating agent and disinfectant, has a great impact on the purity, quality, and subsequent applications of dibromohydantoin.

[0003] In recent years, the country has also begun to pay attention to the promotion of bromine-containing disinfectants, which are included in the "Disinfection Technical Specifications" (2002 edition) of the Ministry of Health of the People's Republic of China and are approved for disinfection in hospitals, epidemic areas, public places, and household health prevention and control. They are also included in the "List of Raw Materials (Ingredients) for Food Disinfectants" (2009 edition) of the Ministry of Health of the People's Republic of China. According to the national standard GB / T23849-2009, it is required that the mass fraction of chloride in dibromohydantoin (calculated as Cl) ≤ 0.08%. There are few reports on the detection methods of chlorine in dibromohydantoin and the detection methods disclosed in the prior art, and it cannot provide a good solution for the determination of the chlorine content in dibromohydantoin. When detecting chlorine in dibromohydantoin, the quality of the pretreatment process will also directly affect the accuracy of the determination result. Therefore, combined with the chemical properties of dibromohydantoin, developing an efficient pretreatment method is of great significance for the detection of impurities in dibromohydantoin. In order to better and more accurately control the impurities in the product and ensure the quality, it is necessary to study an analytical method suitable for the chlorine content in dibromohydantoin.

[0004] Upon retrieval, a Chinese invention patent application with the application number "CN201010161670.3" discloses a method for quantitatively determining the bromine and chlorine contents in nitrogen bromochloride or a mixture. A reducing metal or a reducing metal compound is used as a reducing agent to reduce the bromine and chlorine with a valence of +1 in the analyte to bromine and chlorine inorganic compounds with a valence of -1. The reducing agent is in sufficient excess, and water and sulfuric acid are added to fully reduce the higher-valent bromine and chlorine. An excess precipitating agent is added to the fully-reduced bromide and chloride ion solution to fully precipitate the bromide and chloride ions. Finally, the excess precipitating agent is back-titrated to calculate the bromine and chlorine contents. The purpose of the present invention is simple, fast, highly sensitive, and has a small measurement error.

[0005] However, the above method for quantitatively determining the bromine and chlorine contents in nitrogen bromochloride or a mixture can achieve the determination of the bromine and chlorine contents, but it cannot accurately determine the chlorine content in dibromohydantoin and cannot meet the quality control requirements of dibromohydantoin. Therefore, there is an urgent need for a sample pretreatment method for detecting the chlorine content in dibromohydantoin to solve the above problems. Summary of the Invention

[0006] In view of the problems in the prior art that the chlorine content in dibromohydantoin cannot be accurately determined and the quality control requirements of dibromohydantoin cannot be met, the present application proposes a sample pretreatment method for detecting the chlorine content in dibromohydantoin, so as to realize that through the method for detecting chloride ions in dibromohydantoin described in the present invention, the pretreatment and determination of the chlorine content in dibromohydantoin can be quickly completed. This method has low cost, simple operation, good repeatability, and a wide application range, and can be used for the quality control of dibromohydantoin.

[0007] To achieve the purpose of the present invention, the present invention provides the following technical solutions:

[0008] A sample pretreatment method for detecting the chlorine content in dibromohydantoin, the specific steps of which are as follows:

[0009] Step S1: Weigh an alkaline substance into a beaker, add an appropriate amount of ultrapure water, and stir until completely dissolved;

[0010] Step S2: Accurately weigh the dibromohydantoin product into the beaker in Step 1 and stir well until the dibromohydantoin is completely dissolved;

[0011] Step S3: Add an appropriate amount of hydrogen peroxide to the solution obtained in Step S2, stir, add an appropriate amount of strong acid until the dibromohydantoin is completely decomposed and bromine is completely precipitated, extract with a non-polar solvent, and take the aqueous layer for determination;

[0012] Step S4: Use ion chromatography to determine the chlorine content;

[0013] As a preferred embodiment, the ICS-6000 Thermo Fisher ion chromatograph is used in step S4, and the reagents used are Cl- standard solution (1000 mg / L, Shanghai Institute of Measurement and Testing Technology), methanol (chromatographic pure, Merck), and the experimental water is secondary deionized water with a resistivity greater than 18.2 MΩ.cm;

[0014] Chromatographic conditions: Eluent: 30 mM KOH isocratic elution, flow rate is 1.2 mL / min; ASRS300 (4 mm) cyclic regeneration electro-inhibition mode: injection volume is 30 μL; AXP auxiliary pump flow rate: 0.65 mL / h·min, column temperature is 30 °C.

[0015] Step S5, Sample determination: The sample test is carried out under the same conditions as the standard curve.

[0016] Specifically, the diluted sample is filtered through a microporous membrane and then analyzed and detected by an ion chromatograph, and the chloride ion concentration is obtained from the working curve.

[0017] As a preferred embodiment, in step 1, the weighed amount of the alkaline substance is 0.001 g - 1.0 g;

[0018] As a preferred embodiment, in step 1, the alkaline substance is preferably one of sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium acetate;

[0019] As a preferred embodiment, in step 1, the added amount of ultrapure water is 5 mL - 50 mL;

[0020] As a preferred embodiment, in step 2, the weighed amount of the dibromohydantoin product is 0.001 g - 1.0 g;

[0021] As a preferred embodiment, in step 3, the mass fraction of hydrogen peroxide is 30 - 50%;

[0022] As a preferred embodiment, in step 3, the mass fraction of concentrated sulfuric acid is 80 - 98%, and the mass fraction of concentrated nitric acid is 60 - 70%;

[0023] As a preferred embodiment, in step 3, the non-polar solvent is preferably one or more of carbon tetrachloride, petroleum ether, and chloroform, the extraction times are 1 - 6 times, and the extraction time is 1 - 20 minutes;

[0024] As a preferred embodiment, in step 3, the alkaline substance, strong acid, and non-polar solvent are all of analytical grade;

[0025] As a preferred embodiment, in step 3, the amount of hydrogen peroxide added is 0.1ml-2ml, and the amount of strong acid added is controlled at 0.1ml-1.5ml;

[0026] As a preferred embodiment, in step 3, the amount of the non-polar solvent added is controlled to be 1 mL-20 mL.

[0027] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0028] 1. The present application provides a fast and effective pretreatment method for dibromohydantoin. Combining the chemical properties of dibromohydantoin, a fast pretreatment process is designed: dibromohydantoin is added to an alkaline solution to completely dissolve the dibromohydantoin in water, an oxidizing agent is added for oxidation, and a concentrated oxidizing strong acid is added to adjust the pH, and the bromine in the sample is converted into a single bromine substance, so that the element chlorine to be tested is released in the form of ions to adapt to subsequent tests. The single bromine is extracted with a non-polar solvent, and the water layer is separated to obtain a water sample. Further, the chlorine content in dibromohydantoin is determined by ion chromatography; the chloride ion detection method in dibromohydantoin described in the present invention can quickly complete the pretreatment and chlorine content determination in dibromohydantoin, and the method has low cost, simple operation, good repeatability, and a wide range of applications. At the same time, the present method is a low-cost, accurate, and repeatable method for detecting the chlorine content in dibromohydantoin, which provides strong support for the quality control of dibromohydantoin. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A standard series concentration distribution diagram of a sample pretreatment method for detecting chlorine content in dibromohydantoin according to the present invention;

[0030] Figure 2 The concentration peak area and C1 - Linear distribution graph of concentration;

[0031] Figure 3 The infrared spectrum of the solution after being treated with hydrogen peroxide in a sample pretreatment method for detecting the chlorine content in dibromohydantoin of the present invention. DETAILED DESCRIPTION

[0032] Unless otherwise specified, the reagents and instruments used in the following examples are commercially available conventional products.

[0033] Embodiment 1:

[0034] Glassware and reagents:

[0035] 100mL beaker, electronic analytical balance, ion chromatograph, pipette, 50mL volumetric flask;

[0036] Dibromohydantoin, 98% concentrated sulfuric acid, carbon tetrachloride, sodium hydroxide, 35% hydrogen peroxide.

[0037] Sample pretreatment includes:

[0038] Step S1: Accurately weigh 0.1998 g of sodium hydroxide into a beaker, add 20 mL of ultrapure water, and stir until completely dissolved;

[0039] Step S2: Accurately weigh 0.5000 g of dibromohydantoin product into the beaker in Step 1, and stir thoroughly until the dibromohydantoin is completely dissolved;

[0040] Step S3: Add 0.4 ml of 35% hydrogen peroxide to the solution obtained in Step S2. After stirring the reaction completely, add 0.3 ml of 98% concentrated sulfuric acid until the dibromohydantoin is completely decomposed and bromine is completely precipitated. Extract with carbon tetrachloride for 3 minutes, repeat the extraction 4 times, and take the water layer for determination;

[0041] Step S4: Determine the chlorine content using ion chromatography;

[0042] The specific implementation method is: an ICS-6000 Thermo Fisher ion chromatograph is used. The reagents used are Cl- standard solution (1000 mg / L, Shanghai Institute of Measurement and Testing Technology), methanol (chromatographically pure, Merck), and the experimental water is all secondary deionized water with a resistivity greater than 18.2 MΩ.cm;

[0043] Chromatographic conditions: Eluent: 30 mM KOH isocratic elution, flow rate is 1.2 mL / min; ASRS300 (4 mm) cyclic regenerative electro-inhibition mode: injection volume is 30 μL; AXP auxiliary pump flow rate: 0.65 mL / h·min, column temperature is 30 °C.

[0044] Step S5: Sample determination: The sample test is carried out under the same conditions as the standard curve;

[0045] Standard series preparation: (Cl - The standard solution (1000 mg / L, Shanghai Institute of Measurement and Testing Technology) is diluted step by step. As shown in Table 1, according to Figure 1 the different Cl - concentration standard solutions, the standard series concentration distribution table is obtained:

[0046]

[0047] Table 1 Standard series concentration distribution table

[0048] As Figure 2 shown, the determination coefficient r of the standard series concentration peak area and Cl - concentration 2is 0.9991 and shows a linear distribution. Then, the peak area of the standard series concentration and C1 - The calculation formula for the concentration is y = 0.2173x;

[0049] The specific implementation method is as follows: Sample testing: Add 2 mL of acetic acid - sodium acetate buffer solution, 2 mL of chloramine T solution and color reagent, and 5 mL of sodium thiosulfate solution to the solution obtained in step 3. Measure the absorbance at 590 nm, which is 1.030. Substitute it into the formula to calculate that the chlorine content in dibromohydantoin is 0.05238%.

[0050] Perform a multi - group standard addition recovery experiment on the solution obtained in step 3

[0051] It is achieved by adding different volumes of sodium chloride standard sample solution to the sample solution and examining the influence of the addition amount on the measurement result. It is required that the recovery rate of bromine should be between 95.0% and 105.0% before and after adding the sample.

[0052]

[0053] Table 2 Recovery rate of the sample after adding standard

[0054] Through simple extraction and measurement, the pretreatment and determination of chlorine content in dibromohydantoin are realized.

[0055] The technical principle of this application lies in:

[0056] Dibromohydantoin is insoluble in water and contains an amide bond in its structure. The amide bond can undergo hydrolysis reaction under strong alkaline conditions. Therefore, adding sodium hydroxide can catalyze and accelerate the rapid hydrolysis of dibromohydantoin, and the chloride ions in the sample can be transferred to water. Through experimental observation, the mass ratio of dichlorohydantoin to sodium hydroxide used in this experiment is 2.5:1, and dibromohydantoin can be completely hydrolyzed, finally showing a transparent yellow solution. The reaction formula is:

[0057]

[0058] Adding hydrogen peroxide will cause the yellow color to fade to a transparent colorless solution, indicating that sodium hypobromite reacts with hydrogen peroxide, further accelerating the decomposition of dibromohydantoin. The reaction formula is:

[0059] NaBrO + H 2 O 2 =O 2 +H 2 O + NaBr

[0060] Concentrate the solution obtained in this process by a rotary evaporator, dry it and perform infrared structure analysis. The results are as Figure 3 shown. The absorption peak at 1630 cm -1 can be attributed to the stretching vibration of the C=O group; at 3150 cm-1 New broad absorption peaks appear on the left and right, which can be attributed to the stretching vibration peaks of N-H;

[0061] Concentrated sulfuric acid is added. As the pH of the solution changes, bromide ions are oxidized to elemental bromine, and the solution turns reddish-brown. At this time, dibromohydantoin is completely decomposed. All chloride ions in the sample dissolve in water.

[0062] Extract with carbon tetrachloride to separate the elemental bromine in the solution, and make the volume of the aqueous layer constant. Take samples and determine the chloride ion content by ion chromatography. This method is repeated three times, and the measurement results are shown in Table 3

[0063] Mass of dibromohydantoin (g) Sodium hydroxide (g) Chloride ion content (%) 0.5004g 0.2001 0.0723 0.5004g 0.2000 0.0713 0.5004g 0.2003 0.0739

[0064] Table 3 Total chloride ions measured in alkali-treated dibromohydantoin

[0065] Through the chloride ion detection method for dibromohydantoin described in the present invention, the pretreatment and the determination of chlorine content in dibromohydantoin can be quickly completed. This method has low cost, simple operation, good repeatability and wide application range.

[0066] The above are only the preferred embodiments of the present invention and do not limit the present invention. Those skilled in the art should understand that various modifications and changes can be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined by the claims.

Claims

1. A method for pre-treating samples for detecting chlorine content in dibromohydantoin, characterized in that: Specifically include the following steps: Step S1, weigh an alkaline substance into a beaker, add an appropriate amount of ultrapure water, and stir until it is completely dissolved; Step S2, accurately weighing the dibromohydantoin product into the beaker of step 1, and stirring thoroughly until the dibromohydantoin is completely dissolved; Step S3, adding an appropriate amount of hydrogen peroxide to the solution obtained in step S2, stirring, adding an appropriate amount of strong acid until dibromohydantoin is completely decomposed and the bromine element is completely precipitated, extracting with a non-polar solvent, and taking the water layer for determination; Step S4, measuring the chlorine content by ion chromatography; Step S5, sample determination: the sample test and the standard curve are carried out under the same conditions.

2. A method for pre-treating samples for detecting chlorine content in dibromohydantoin according to claim 1, characterized in that: In the step 1, the amount of the alkaline substance weighed is 0.001g-1.0g.

3. A method for pre-treating samples for detecting chlorine content in dibromohydantoin according to claim 2, characterized in that: In step 1, the alkaline substance is preferably one of sodium hydroxide, potassium hydroxide, sodium carbonate and sodium acetate.

4. A method for pre-treating samples for detecting chlorine content in dibromohydantoin according to claim 3, characterized in that: In the step 1, the amount of ultrapure water added is 5 mL-50 mL.

5. A method for pre-treating samples for detecting chlorine content in dibromohydantoin according to claim 1, characterized in that: In the step 2, the weighed amount of dibromohydantoin product is 0.001g-1.0g.

6. A method for pre-treating samples for detecting chlorine content in dibromohydantoin according to claim 1, characterized in that: In step 3, the non-polar solvent is preferably one or more of carbon tetrachloride, petroleum ether, and chloroform, the number of extractions is 1-6 times, and the extraction time is 1-20 minutes.

7. A method for pre-treating samples for detecting chlorine content in dibromohydantoin according to claim 6, characterized in that: In step 3, the amount of hydrogen peroxide added is 0.1 ml-2 ml, and the amount of strong acid added is controlled to be 0.1 ml-1.5 ml.

8. A method for pre-treating samples for detecting chlorine content in dibromohydantoin according to claim 7, characterized in that: In the step 3, the amount of the non-polar solvent added is controlled to be 1 mL-20 mL.

9. A method for pre-treating samples for detecting chlorine content in dibromohydantoin according to claim 8, characterized in that: In step 3, the mass fraction of concentrated sulfuric acid is 80-98%, and the mass fraction of concentrated nitric acid is 60-70%.

10. A method for pre-treating samples for detecting chlorine content in dibromohydantoin according to claim 9, characterized in that: In the step 3, the mass fraction of hydrogen peroxide is 30-50%.

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