Method for qualitatively and quantitatively analyzing and detecting content of sodium dimethyl dithiocarbamate through high performance liquid chromatography

Abstract

The invention discloses a method for qualitatively and quantitatively analyzing and detecting the content of sodium dimethyl dithiocarbamate through high performance liquid chromatography. The method comprises the detection steps of preparation of a mobile phase, preparation of a standard substance solution, drawing of a calibration curve, detection of the content of a sample, qualitative analysis of the sample and standard recovery verification. Chromatographic conditions are as follows: a chromatographic column is a high-alkali-resistant reversed-phase chromatographic column, and the pH value application range is 1-12; the wavelength is 260 nm; the flow rate is 0.8 to 1 mL / min; the sample injection volume is 10-25 [mu] L; the column temperature is 30 DEG C; and the acquisition time is 25 minutes. The method has the beneficial effects that derivatization and earlier-stage treatment are not needed before detection and analysis of a sample. The mobile phase of the chromatographic instrument is alkaline and is used for dissolving and diluting a standard substance and a sample so as to keep the stability of the property of sodium dimethyl dithiocarbamate. The sodium dimethyl dithiocarbamate standard substance is dried to constant weight, crystal water and free water in the sodium dimethyl dithiocarbamate standard substance are removed on the premise of ensuring that the sodium dimethyl dithiocarbamate standard substance is not thermally decomposed, and the accuracy of calibration curve drawing and the accuracy of a sample calculation result are ensured. Qualitative analysis and standard recovery verification means are added, so that the accuracy of a detection result and the guiding significance of practical application are further improved.

Description

Technical Field

[0001] The invention belongs to the field of environmental analytical chemistry, and in particular relates to a method for qualitatively and quantitatively detecting the content of solid and liquid sodium thiamethoxam by using high performance liquid chromatography. Background Art

[0002] Sodium fumei is also known as dimethoate. Its chemical name is sodium dimethyl dithiocarbamate, and it can also be called N,N-dimethyl dithiocanbamate sodium salt. Sodium fumei is an important chemical product and organic synthesis intermediate with a wide range of uses. The dithiocarbamate group it contains has a strong coordination ability and can react with most heavy metal ions at room temperature and a wide pH range to form heavy metal chelate precipitates. It can be used in the treatment of industrial wastewater, the stabilization of heavy metals in fly ash, and the removal of heavy metals in the production of electrolytic manganese. It is used as a fungicide and algaecide in industrial water treatment, petroleum and papermaking industries. It is generally used to produce pesticides in agriculture. It is used as a mineral processing agent in mining. Sodium fumei is also an intermediate for a variety of fungicides such as fumei, ferrofumei, fumei ammonium, fumei nickel, etc. In rubber production, it is used as a vulcanization accelerator and terminator for emulsion-polymerized styrene-butadiene rubber and styrene-butadiene latex.

[0003] Common sodium fumarate products are available in two types: solid and liquid. Solid sodium fumarate contains two crystal waters and has a molecular formula of C 3 H 6 NS 2 Na·2H 2 O, the content is generally around 95%; liquid sodium fume is colorless or light yellow, and the content is generally around 40%. The commonly used method for determining the content of sodium fume is titration. Under neutral or weakly alkaline conditions, starch is used as an indicator and titrated with an iodine standard solution. This method causes sodium fume to decompose easily, react incompletely, and have large operating errors. Liquid chromatography uses liquid under high pressure as the mobile phase and column chromatography separation technology with extremely fine particles as the stationary phase. It uses retention time for qualitative analysis and peak height or area of ​​the chromatographic peak for quantitative analysis. Liquid chromatography has a wide range of applicability to samples and is not limited by the volatility and thermal stability of the analyzed object. It has fast speed and high sensitivity and is widely used.

[0004] At present, in the reports of methods for detecting and analyzing the content of sodium fumei using liquid chromatography, the Chinese patents "A method for determining the content of sodium dimethyldithiocarbamate in a solution by high performance liquid chromatography" (application number: 201810511373.3) and "A method for determining trace amounts of sodium N,N-dimethyldithiocarbamate in water" (application number: 201210380963.X) disclose methods suitable for detecting and analyzing the content of sodium fumei in liquids. Before performing liquid phase analysis, derivatization treatment is required. The treatment process is cumbersome and it is difficult to avoid inaccurate test results due to incomplete derivatization reaction. The Chinese patent "A method for detecting the purity of solid sodium fume by liquid chromatography" (application number: 201810885398.X) discloses a method for detecting the content of solid sodium fume, which uses sodium dihydrogen phosphate solution as a solvent to dissolve sodium fume solid. The pH value of sodium fume is 9~11, and sodium dihydrogen phosphate is acidic. Experiments have confirmed that the effective ingredients of sodium fume begin to decompose and become ineffective in about 4 hours under an acidic environment, and the content of sodium fume standard products has decreased significantly; and the patent adds alkaline organic amine compounds to the mobile phase, and the Kromstar C18 chromatographic column used is made of silica gel, which will cause the column efficiency of the chromatographic column to decrease during detection, affecting the accuracy of the detection. In addition, when using liquid chromatography to detect the content of sodium fume samples, the purity of the standard directly affects the accuracy of the standard curve drawing, and then affects the calculation accuracy of the sample content. Summary of the invention

[0005] In order to overcome the shortcomings and deficiencies of the existing sodium furam content determination method, such as complexity, large error and low accuracy, the present invention provides a method for detecting the content of sodium furam by high performance liquid chromatography. The method does not require any chemical pretreatment, is simple to operate, has high accuracy and good repeatability, and has a short detection time. After a standard solution curve is drawn using a high performance liquid chromatograph, the content of the detection sample can be qualitatively and quantitatively analyzed according to the chromatogram results of the detection sample, and the accuracy of the result is verified by a spike recovery method. The method is suitable for the detection of solid and liquid sodium furam samples.

[0006] To solve the above problems, the following technical solutions are adopted:

[0007] The method for detecting the content of sodium furam by high performance liquid chromatography adopts a sodium furam standard product, an acetonitrile aqueous solution as a mobile phase, and a high performance liquid chromatograph with an ultraviolet detector for detection, a calibration curve is drawn by peak area, the content of the sodium furam sample is measured, and the accuracy of the result is verified by a spike recovery method, and the specific steps are as follows:

[0008] (1) Preparation of mobile phase: Mix acetonitrile and water in a volume ratio of 55-70:45-30, add an appropriate amount of 300 g / L NaOH solution, adjust the pH value to 11-13, filter through a 0.45 μm membrane, and ultrasonically degas for 15 minutes before use.

[0009] (2) Preparation of standard solution: Dry the sodium fumarate standard at 115-180°C to constant weight to remove the crystal water and free water. Weigh an appropriate amount of the dried standard and dilute it with the mobile phase prepared in step (1) and shake well. Degas by ultrasonic for 15 minutes to obtain a series of standard solutions of different concentrations. Prepare and measure immediately.

[0010] Among them, when the sodium fumei standard is dried at 115~135℃ to constant weight, dimethyl silicone oil is used for oil bath; when it is dried at 135~180℃ to constant weight, it is dried in an oven under nitrogen atmosphere.

[0011] The concentration of the sodium thiamethoxam standard solution series is between 100-200 mg / L.

[0012] (3) Calibration curve drawing: The series of concentrations of the sodium furam standard solution prepared in step (2) are measured under the selected HPLC conditions, and a calibration curve is drawn with the concentration of the sodium furam standard as the abscissa and the measured corresponding peak area as the ordinate. The number of calibration points (including blank) shall not be less than 6, and the correlation coefficient of the linear regression equation shall not be less than 0.99.

[0013] The HPLC conditions are:

[0014] Chromatographic column: high alkali resistant reverse phase chromatography column, model shim-pack Scepter C18, specification 4.6x250mm, filler particle size 5μm, pH value applicable range 1-12.

[0015] Wavelength: 260nm;

[0016] Flow rate: 0.8-1mL / min;

[0017] Injection volume: 10-25 μL;

[0018] Column temperature: 30°C;

[0019] Collection time: 25min.

[0020] (4) Sample content determination: Weigh 1-2 g of solid or 3-4 g of liquid sodium furam sample and place it in a 250 mL volumetric flask, dilute it to the mark with the mobile phase prepared in step (1) and shake well, filter it through a 0.45 μm membrane, and ultrasonically degas for 15 min to obtain a sample solution. Then transfer 2.5 mL of the sample solution to a 100 mL volumetric flask, dilute it to the mark with the mobile phase, shake well, and determine it using the same liquid chromatography conditions as step (3). Substitute the measured peak area into the calibration curve obtained in step (3) to calculate the content of the sodium furam sample.

[0021] (5) Qualitative analysis of samples: Qualitative analysis is performed based on the retention time of the chromatogram of the standard solution. The width of the retention time window used for qualitative analysis is based on the actual retention time change of the standard sample in the current batch. The absolute value of the relative deviation between the retention time of the sample and the retention time of the standard should be less than 2.0%.

[0022] (6) Verification of spike recovery: Weigh 20-25 μL of the sample solution in step (4) and place them in two equal parts, 1# and 2# injection bottles, respectively. Add 1000 μL of the mobile phase prepared in step (1) and 40-50 μL of the standard solution prepared in step (2) to injection bottle 1; add 1000 μL of the mobile phase prepared in step (1) to injection bottle 2. Then, both injection bottles 1# and 2# are measured under the same HPLC conditions as in step (3) and the spike recovery is calculated.

[0023] The spike recovery verification is performed by sampling 10-20% of the test sample quantity, and the spike recovery rate should be between 95-105%. Beneficial effects of the present invention

[0024] The invention is applicable to the detection and analysis of the content of solid and liquid sodium fumarate products, and no derivatization and preliminary treatment are required before the detection and analysis of the sample, the operation is simple, and the detection result is highly accurate.

[0025] The pH of sodium fume is 9-11, which is alkaline. Experiments have confirmed that the active ingredients of sodium fume can be decomposed in a short time (4h) under acidic conditions (4.5-5.5). Therefore, the chromatograph mobile phase of the present invention uses NaOH to adjust the pH to maintain between 11-13, and the chromatograph mobile phase is used to dissolve and dilute the standard and sample to maintain the stability of the properties of sodium fume. At the same time, the pH of the detection solution needs to be around 12, and the ordinary chromatographic column tolerates a pH range of 2.0-7.5. Long-term use will cause the column efficiency of the chromatographic column to decrease, and its tailing factor will gradually increase. The present invention uses a high-alkali resistant chromatographic column, which can reduce the chromatographic peak tailing factor by 10% compared to ordinary chromatographic columns, to about 1.8, and the peak tailing situation is significantly improved.

[0026] Most of the sodium furam standards are dihydrates or monohydrates, and there is a risk of sodium furam standard products losing water or absorbing moisture during storage, resulting in changes in the purity of the standard products. According to the thermogravimetric spectrum of sodium furam, the inventors concluded that the weight loss rate of sodium furam is the largest at 133.77°C, all crystal water is lost at about 200°C, and it begins to decompose at about 275°C. Therefore, the present invention uses a temperature range of 115~180°C to dry the sodium furam standard product to constant weight, which can not only remove the crystal water and free water in the sodium furam standard product, but also ensure that the sodium furam standard product will not be decomposed by heat, so as to ensure the accuracy of the calibration curve drawing and the accuracy of the sample calculation results.

[0027] At the same time, the inventors developed a spike verification method for sodium fumarate liquid chromatography. After analyzing a large amount of experimental data and combining the content range of the substance to be tested, the amount of standard substance added was determined to ensure the accuracy of the spike recovery rate and ensure the accuracy and reliability of the detection method and instrument.

[0028] The present invention provides a method for qualitatively analyzing a substance to be tested by liquid chromatography, wherein the relative deviation of the method is less than 1%, and the detection similarity and accuracy thereof are more than 99%, so that the quantitative detection has directionality and clarity, and the measured content data has more guiding significance in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The standard curve of the relationship between the concentration and peak area of ​​the sodium thiamethoxam standard solution in implementation case 1

[0030] Figure 2 This is the HPLC chromatogram of the solid sample of sodium fumei in implementation case 1

[0031] Figure 3 This is the HPLC chromatogram of the sodium thiamethoxam liquid sample measured in Example 1 DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with implementation cases and drawings, but the implementation methods of the present invention are not limited thereto.

[0033] Example 1

[0034] Detection conditions of HPLC:

[0035] (1) Detection wavelength: 260nm;

[0036] (2) Flow rate: 1 mL / min;

[0037] (3) Injection volume: 10 μL;

[0038] (4) Column temperature: 30°C.

[0039] (5) Collection time: 25 minutes.

[0040] Test steps:

[0041] (1) Preparation of mobile phase: Mix acetonitrile and water in a volume ratio of 60:40, add an appropriate amount of 300 g / L NaOH solution, adjust the pH value to 12.4, filter through a 0.45 μm membrane, and ultrasonically degas for 15 min before use.

[0042] (2) Preparation of standard solution: Dry the sodium thiamethoxam standard in an oven at 150°C to constant weight to remove the crystal water and free water therein. Weigh 1.000 g of the dried standard into a 100 mL volumetric flask and dilute to scale with the mobile phase prepared in step (1). Shake well and degas by ultrasonication for 15 min to obtain a series of standard solutions of different concentrations. Prepare and measure immediately.

[0043] (3) Drawing of standard curve: Use a pipette to transfer 100 μL, 110 μL, 120 μL, 130 μL, 140 μL, 150 μL, 160 μL, 170 μL, 180 μL, 190 μL, and 200 μL of the standard solution prepared in step (2) above into injection bottles, and then add 900 μL, 890 μL, 880 μL, 870 μL, 860 μL, 850 μL, 840 μL, 830 μL, 820 μL, 810 μL, and 800 μL of the mobile phase prepared in step (1) above into the sample vials, respectively. The corresponding injection bottles were sealed and placed in a vortex oscillator for uniform mixing. The mass concentrations of the prepared sodium furam standard solutions were 100 mg / L, 110 mg / L, 120 mg / L, 130 mg / L, 140 mg / L, 150 mg / L, 160 mg / L, 170 mg / L, 180 mg / L, 190 mg / L and 200 mg / L, respectively. High performance liquid chromatography was used for determination to obtain a chromatogram of the sodium furam standard. The concentration of the sodium furam standard was used as the abscissa and the corresponding peak area was used as the ordinate to draw a standard curve. The standard curve is shown in FIG. Figure 1 , linear regression equation: y=47625.7455x-35365.0000, R 2 =0.9915, x is the concentration of the added sodium thiamethoxam standard, mg / L, y is the peak area. The sodium thiamethoxam standard solution has a good linear relationship in the range of 100-200 mg / L, and the method of the present invention is accurate and reliable.

[0044] (4) Determination of samples: Weigh 2.0056 g of solid sample and place it in a 250 mL volumetric flask, dilute it to the mark with the mobile phase in step (1), shake well, filter it through a 0.45 μm membrane, and ultrasonically degas for 15 min to prepare sample solution A. Then transfer 2.5 mL of sample solution A to a 100 mL volumetric flask, dilute it to the mark with the mobile phase, shake well to prepare solution B, and determine it under the same liquid chromatography conditions as step (3). The measured peak area is substituted into the calibration curve obtained in step (3), and the concentration of solution B is calculated to be 149.528 mg / L. Then, based on the dilution factor and the mass of the weighed sample, the mass fraction of the solid sample of sodium thiamethoxam (dihydrate) is calculated to be 95.58%.

[0045] Weigh 4.0053 g of liquid sample and place it in a 250 mL volumetric flask, dilute it to the mark with the mobile phase in step (1), shake well, filter it through a 0.45 μm membrane, and ultrasonically degas for 15 min to obtain sample solution A. Then transfer 2.5 mL of sample solution A to a 100 mL volumetric flask, dilute it to the mark with the mobile phase, shake well to obtain solution B, and measure it under the same liquid chromatography conditions as step (3). The measured peak area is brought into the calibration curve obtained in step (3), and the concentration of solution B is calculated to be 165.699 mg / L. Then, based on the dilution multiple and the mass of the weighed sample, the mass fraction of the sodium thiamethoxam liquid sample is calculated to be 42.40%.

[0046] Example 2

[0047] The qualitative analysis was carried out based on the retention time of the chromatogram of the standard solution. The width of the retention time window used for qualitative analysis was based on the actual retention time change of the standard sample in the batch measurement. The absolute values ​​of the relative deviations between the retention time of the sample and the retention time of the standard were 0.06% and 0.12%, respectively. The similarity exceeded 99%, and it was determined that the sample to be tested was sodium thiamethoxam.

[0048] Table 1 Retention time of standard products

[0049]

[0050] Table 2 Comparison of sample retention time and standard retention time

[0051]

[0052] Example 3

[0053] Verification of spike recovery: Weigh 25 μL of the sample solution in step (4) of Example 1 and place them in two equal parts, respectively, into injection bottles #1 and #2. Add 1000 μL of the mobile phase prepared in step (1) of Example 1 and 50 μL of the standard solution prepared in step (2) of Example 1 into injection bottle #1; add 1000 μL of the mobile phase prepared in step (1) of Example 1 into injection bottle #2. Then, both injection bottles #1 and #2 were measured using the same liquid chromatography conditions as in step (3) of Example 1. The calculated spike recovery rates were between 95% and 105%. The detection data of the sodium thiamethoxam content in Example 1 was reliable.

[0054] Table 3 Sample spike recovery data

[0055]

[0056] The above embodiments are specific descriptions of the present invention and are only used to further illustrate the present invention. They cannot be understood as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the contents of the above invention fall within the scope of protection of the present invention.

Claims

1. A method for qualitative and quantitative analysis of the content of sodium thiram by high performance liquid chromatography, characterized in that: The method comprises: preparation of mobile phase, preparation of standard solution, drawing of calibration curve, sample content detection, sample qualitative analysis, and spike recovery verification. The specific steps are as follows: (1) Preparation of mobile phase: acetonitrile and water were mixed evenly in a volume ratio of 55-70:45-30, and an appropriate amount of 300 g / L NaOH solution was added. The pH value was adjusted to be stable between 11 and 13, and the mobile phase was filtered through a 0.45 μm membrane and ultrasonically degassed for 15 min before use. (2) Preparation of standard solution: Dry the sodium thiamethoxam standard at 115-180°C to constant weight, weigh an appropriate amount of the dried standard, dilute and shake well with the mobile phase prepared in step (1), and ultrasonically degas for 15 minutes to obtain a series of concentrations of standard solutions, which are prepared and measured immediately; Among them, when the sodium fumei standard is dried to constant weight at 115-135°C, dimethyl silicone oil is used for oil bath; when it is dried to constant weight at 135-180°C, it is dried in an oven under a nitrogen atmosphere; (3) Calibration curve drawing: The series of concentrations of the sodium thiamethoxam standard solution prepared in step (2) are measured under the selected HPLC conditions, and a calibration curve is drawn with the concentration of the sodium thiamethoxam standard as the abscissa and the measured corresponding peak area as the ordinate. The number of calibration points (including blank) shall not be less than 6, and the correlation coefficient of the linear regression equation shall not be less than 0.99; The HPLC conditions are: Chromatographic column: high-alkali resistant reverse phase chromatography column, model shim-pack Scepter C18, specification 4.6x250mm, filler particle size 5μm, pH value applicable range 1-12; Wavelength: 260nm; Flow rate: 0.8-1mL / min; Injection volume: 10-25 μL; Column temperature: 30°C; Collection time: 25min; (4) Sample content detection: Weigh 1-2g of solid or 3-4g of liquid sodium furam sample, place it in a 250mL volumetric flask, dilute it to the mark with the mobile phase prepared in step (1), shake well, filter it through a 0.45μm membrane, and ultrasonically degas for 15min to obtain a sample solution. Then, transfer 2.5mL of the sample solution to a 100mL volumetric flask, dilute it to the mark with the mobile phase, shake well, and determine it using the same liquid chromatography conditions as step (3). The measured peak area is substituted into the calibration curve obtained in step (3) to calculate the content of the sodium furam sample; (5) Sample qualitative analysis: qualitative analysis is performed based on the retention time of the chromatogram of the standard solution. The width of the retention time window used for qualitative analysis is based on the actual retention time change of the standard sample in the current batch. The absolute value of the relative deviation between the retention time of the sample and the retention time of the standard should be less than 2.0%; (6) Verification of spike recovery: Weigh 20-25 μL of the sample solution in step (4) and place them in two equal parts, 1# and 2# injection bottles, respectively. Add 1000 μL of the mobile phase prepared in step (1) and 40-50 μL of the standard solution prepared in step (2) to injection bottle 1; add 1000 μL of the mobile phase prepared in step (1) to injection bottle 2. Then, both injection bottles 1# and 2# are measured under the same HPLC conditions as in step (3) and the spike recovery is calculated.

2. The method for qualitative and quantitative analysis of sodium thiram by high performance liquid chromatography according to claim 1, characterized in that: The concentration of the sodium thiamethoxam standard solution series described in step (2) is between 100-200 mg / L.

3. The method for qualitative and quantitative analysis of sodium thiram by high performance liquid chromatography according to claim 1, characterized in that: The spike recovery verification described in step (6) is verified by sampling 10-20% of the test sample quantity, and the spike recovery rate should be between 95-105%.

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