Chlorine element standard substance solution in light oil and preparation method of chlorine element standard substance solution

Abstract

The invention relates to the technical field of standard substance preparation, in particular to a light oil chlorine element standard substance solution and a preparation method thereof.The preparation method comprises the specific preparation steps that 1, a composite purifying agent is dispersed in an ethanol water solution, and after ultrasonic dispersion, a composite purifying agent solution is obtained; step 2, mixing the mixed solvent and the composite purifying agent solution, adding ultrapure water until the total volume is 4-6 times of the volume of the original mixed solution, standing, separating out a solvent phase by a separating funnel, transferring into a brown bottle, and storing in a dark place to obtain a purified solvent; and step 3, dispersing hexachlorobenzene in a purification solvent, carrying out ultrasonic dispersion, and standing in a dark place to obtain the chlorine element standard substance solution. The chlorine content standard substance solution has the advantages of high determination accuracy, good uniformity and excellent stability, can keep the stability of the chlorine content for a long time, and is not easy to change due to the influence of environmental factors such as temperature and humidity.

Description

Technical Field

[0001] This application relates to the technical field of preparation of reference materials, and more specifically, to a standard substance solution of chlorine element in light oil and a preparation method thereof. Background Art

[0002] In the petrochemical field, the content of chlorine element in light oil has an important impact on equipment corrosion, catalyst activity, etc. Accurately measuring the content of chlorine element in light oil is crucial for ensuring the safety of the production process and product quality. At present, the detection of chlorine element in light oil usually requires calibration using a standard substance solution of chlorine element. However, for the standard substance of chlorine content in light oil products, its matrix is refined oil, which cannot guarantee the stability of its quality. The prepared standard substance solution of chlorine element has low accuracy of chlorine content, poor homogeneity and stability, and cannot meet the actual detection requirements. Based on the above defects, this application provides a standard substance solution of chlorine element in light oil and a preparation method thereof, which is of great significance for filling the blank in the research and development of petrochemical reference materials. Summary of the Invention

[0003] In order to solve the technical problems mentioned in the background art, this application provides a preparation method and a production method of a standard substance solution of chlorine element in light oil.

[0004] This application provides a preparation method of a standard substance solution of chlorine element in light oil, and adopts the following technical scheme:

[0005] A preparation method of a standard substance solution of chlorine element in light oil includes the following preparation steps:

[0006] Step 1: Disperse the composite purifying agent in an ethanol aqueous solution, after ultrasonic dispersion, transfer it to a volumetric flask, and seal and stand still at a temperature of 20 - 25°C for 12 - 24 h to obtain a composite purifying agent solution;

[0007] Step 2: Mix the mixed solvent and the composite purifying agent solution, place it in a constant temperature oven at 20 - 25°C, avoid light and stand still for 24 - 48 h. Transfer the above mixed solution to a container, add ultrapure water to make the total volume 4 - 6 times the volume of the original mixed solution, stand still for 12 - 24 h, separate the solvent phase with a separatory funnel, transfer it to a brown bottle and store it in the dark to obtain a purified solvent;

[0008] Step 3: Disperse hexachlorobenzene in the purified solvent at a temperature of 20 - 25°C, after ultrasonic dispersion, avoid light and stand still at a temperature of 20 - 25°C for 24 - 36 h to obtain the standard substance solution of chlorine element.

[0009] Preferably, in Step 1, the composite purifying agent is composed of N,N - diethyl - p - phenylenediamine sulfate, tetrabutylammonium bromide and triethanolamine in a mass ratio of 15 - 20:2 - 5:1 - 3.

[0010] Preferably, the volume percentage concentration of the aqueous ethanol solution in step 1 is 70-85%.

[0011] Preferably, the mass ratio of the composite purifying agent to the aqueous ethanol solution in step 1 is 1-1.2:4-5.

[0012] Preferably, the mixed solvent in step 2 is composed of n-hexane and n-octane, and the volume ratio of n-octane in the mixed solvent is 10-15%.

[0013] Preferably, the volume ratio of the mixed solvent to the composite purifying agent solution in step 2 is 100-120:1-3.

[0014] Preferably, the resistivity of the ultrapure water in step 2 is higher than 18 MΩ·cm.

[0015] Preferably, the dosage ratio of hexachlorobenzene to the purifying solvent in step 3 is 32-40 mg:250-280 mL.

[0016] A standard substance solution of chlorine element in light oil is prepared by the above method.

[0017] In summary, the present application has the following beneficial effects:

[0018] In the present application, N,N-diethyl-p-phenylenediamine sulfate, tetrabutylammonium bromide and triethanolamine are selected for compounding to obtain a composite purifying agent. N,N-diethyl-p-phenylenediamine sulfate is used to remove other forms of organic chlorine, and tetrabutylammonium bromide and triethanolamine are compounded. Tetrabutylammonium bromide is used as a phase transfer catalyst and an ion pair reagent, and the quaternary ammonium cation in its structure can form a lipophilic ion pair with chloride ions. The compounding of the three components improves the dispersibility of the purifying agent in the mixed solvent, avoids uneven local concentration, and promotes the uniform dispersion of chlorine element in the non-polar solvent (n-hexane / n-octane) by reducing the liquid-liquid interfacial tension, ensuring the stability of the chlorine element standard substance solution.

[0019] In the present application, by mixing a certain volume of n-octane into n-hexane, the volatility of the mixed solvent can be adjusted, and the long carbon chain structure of n-octane has a higher solubility for certain high molecular weight organic compounds (such as polycyclic aromatic hydrocarbons, long chain alkanes). It can cooperate with n-hexane to cover a wider range of organic pollutants and improve the purification effect. The polarity and density of the mixed solvent are more different from the aqueous phase (ultrapure water), promoting stratification and phase separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the working curve of ICP-MS in the concentration range of 10-200 mg / L. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The following further elaborates on the present application in conjunction with embodiments.

[0022] In the examples and comparative examples of the present application, N,N - diethyl - p - phenylenediamine sulfate (product number: A419426), tetrabutylammonium bromide (product number: T103372), triethanolamine (product number: T108153), hexachlorobenzene (product number: H465468), n - hexane (product number: N431448), and n - octane (product number: O100577) were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0023] Examples 1 - 3 provide a standard substance solution of chlorine element in light oil and its preparation method.

[0024] Example 1

[0025] A preparation method of a standard substance solution of chlorine element in light oil, comprising the following preparation steps:

[0026] Step 1: Disperse the composite purifying agent in an ethanol - water solution with a volume percentage concentration of 70%. Under an ultrasonic power of 100 W, an ultrasonic frequency of 40 KHz, ultrasonic for 10 min. After ultrasonic dispersion, transfer it to a volumetric flask, and seal and leave it standing at 20 °C for 12 h to obtain a composite purifying agent solution. Among them, the composite purifying agent is composed of N,N - diethyl - p - phenylenediamine sulfate, tetrabutylammonium bromide, and triethanolamine with a mass ratio of 15:2:1, and the mass ratio of the composite purifying agent to the ethanol - water solution is 1:4;

[0027] Step 2: Mix the mixed solvent and the composite purifying agent solution in a volume ratio of 100:1, place it in a constant - temperature oven at 20 °C, and leave it standing in the dark for 24 h. Transfer the above - mentioned mixed solution to a container, add ultrapure water until the total volume is 4 times the volume of the original mixed solution, leave it standing for 12 h, separate the solvent phase with a separatory funnel, and transfer it to a brown bottle for storage in the dark to obtain a purified solvent. Among them, the mixed solvent is composed of a mixture of n - hexane and n - octane, and the volume percentage of n - octane in the mixed solvent is 10%, and the resistivity of the ultrapure water is 18.2 MΩ·cm;

[0028] Step 3: At 20 °C, disperse hexachlorobenzene in the purified solvent. Under an ultrasonic power of 120 W, an ultrasonic frequency of 50 KHz, ultrasonic for 10 min. After ultrasonic dispersion, at 20 °C, leave it standing in the dark for 24 h to obtain a standard substance solution of chlorine element. The dosage ratio of hexachlorobenzene to the purified solvent is 33.47 mg:250 mL.

[0029] Example 2

[0030] A preparation method of a standard substance solution of chlorine element in light oil, comprising the following preparation steps:

[0031] Step 1: Disperse the composite purifying agent in an ethanol aqueous solution with a volume percentage concentration of 75%. Under an ultrasonic power of 120 W, an ultrasonic frequency of 50 KHz, ultrasonic treatment for 15 min, after ultrasonic dispersion, transfer it to a volumetric flask, and seal and leave it standing for 18 h at a temperature of 22 °C to obtain a composite purifying agent solution. Among them, the composite purifying agent is composed of N,N - diethyl - p - phenylenediamine sulfate, tetrabutylammonium bromide, and triethanolamine with a mass ratio of 18:3:2, and the mass ratio of the composite purifying agent to the ethanol aqueous solution is 1.1:4.5;

[0032] Step 2: Mix the mixed solvent and the composite purifying agent solution in a volume ratio of 110:2, place them in a constant - temperature incubator at 22 °C, and leave them standing in the dark for 36 h. Transfer the above - mentioned mixed solution to a container, add ultrapure water until the total volume is 5 times the volume of the original mixed solution, leave it standing for 18 h, separate the solvent phase with a separatory funnel, and transfer it to a brown bottle for storage in the dark to obtain a purified solvent. Among them, the mixed solvent is composed of n - hexane and n - octane, and the volume proportion of n - octane in the mixed solvent is 13%, and the resistivity of the ultrapure water is 18.2 MΩ·cm;

[0033] Step 3: At a temperature of 22 °C, disperse hexachlorobenzene in the purified solvent. Under an ultrasonic power of 135 W, an ultrasonic frequency of 55 KHz, ultrasonic treatment for 15 min, after ultrasonic dispersion, at a temperature of 22 °C, leave it standing in the dark for 30 h to obtain a chlorine element reference material solution. The dosage ratio of hexachlorobenzene to the purified solvent is 35 mg:265 mL.

[0034] Example 3

[0035] A preparation method of a chlorine element reference material solution in light oil, including the following preparation steps:

[0036] Step 1: Disperse the composite purifying agent in an ethanol aqueous solution with a volume percentage concentration of 85%. Under an ultrasonic power of 150 W, an ultrasonic frequency of 60 KHz, ultrasonic treatment for 20 min, after ultrasonic dispersion, transfer it to a volumetric flask, and seal and leave it standing for 24 h at a temperature of 25 °C to obtain a composite purifying agent solution. Among them, the composite purifying agent is composed of N,N - diethyl - p - phenylenediamine sulfate, tetrabutylammonium bromide, and triethanolamine with a mass ratio of 20:5:3, and the mass ratio of the composite purifying agent to the ethanol aqueous solution is 1.2:5;

[0037] Step 2: After mixing the mixed solvent and the composite purifying agent solution at a volume ratio of 120:3, place it in a constant temperature oven at 25°C, keep it in the dark and let it stand for 48 hours. Transfer the above mixed solution to a container, add ultrapure water until the total volume is 6 times the volume of the original mixed solution, let it stand for 24 hours, then separate the solvent phase with a separating funnel, transfer it to a brown bottle and store it in the dark to obtain the purified solvent. Among them, the mixed solvent is composed of n-hexane and n-octane, and the volume percentage of n-octane in the mixed solvent is 15%. The resistivity of the ultrapure water is 18.2 MΩ·cm;

[0038] Step 3: At a temperature of 25°C, disperse hexachlorobenzene in the purified solvent, with an ultrasonic power of 150 W, an ultrasonic frequency of 60 KHz, and ultrasonic treatment for 20 minutes. After ultrasonic dispersion, at a temperature of 25°C, keep it in the dark and let it stand for 36 hours to obtain the chlorine element reference material solution. The dosage ratio of hexachlorobenzene to the purified solvent is 40 mg:280 mL.

[0039] Comparative Example 1

[0040] A preparation method of a chlorine element reference material solution in light oil includes the following preparation steps:

[0041] Step 1: Disperse the composite purifying agent in an ethanol aqueous solution with a volume percentage concentration of 70%, with an ultrasonic power of 100 W, an ultrasonic frequency of 40 KHz, and ultrasonic treatment for 10 minutes. After ultrasonic dispersion, transfer it to a volumetric flask, and at a temperature of 20°C, seal it and let it stand for 12 hours to obtain the composite purifying agent solution. Among them, the composite purifying agent is composed of N,N-diethyl-p-phenylenediamine sulfate and triethanolamine with a mass ratio of 15:1, and the mass ratio of the composite purifying agent to the ethanol aqueous solution is 1:4;

[0042] Step 2: After mixing the mixed solvent and the composite purifying agent solution at a volume ratio of 100:1, place it in a constant temperature oven at 20°C, keep it in the dark and let it stand for 24 hours. Transfer the above mixed solution to a container, add ultrapure water until the total volume is 4 times the volume of the original mixed solution, let it stand for 12 hours, then separate the solvent phase with a separating funnel, transfer it to a brown bottle and store it in the dark to obtain the purified solvent. Among them, the mixed solvent is composed of n-hexane and n-octane, and the volume percentage of n-octane in the mixed solvent is 10%. The resistivity of the ultrapure water is 18.2 MΩ·cm;

[0043] Step 3: At a temperature of 20°C, disperse hexachlorobenzene in the purified solvent, with an ultrasonic power of 120 W, an ultrasonic frequency of 50 KHz, and ultrasonic treatment for 10 minutes. After ultrasonic dispersion, at a temperature of 20°C, keep it in the dark and let it stand for 24 hours to obtain the chlorine element reference material solution. The dosage ratio of hexachlorobenzene to the purified solvent is 33.47 mg:250 mL.

[0044] Comparative Example 2

[0045] A preparation method of a chlorine element reference material solution in light oil, comprising the following preparation steps:

[0046] Step 1: Disperse the composite purifying agent in an ethanol aqueous solution with a volume percentage concentration of 70%. Under an ultrasonic power of 100 W, an ultrasonic frequency of 40 KHz, and ultrasonic treatment for 10 min, after ultrasonic dispersion, transfer it to a volumetric flask. At a temperature of 20 °C, seal and let it stand for 12 h to obtain a composite purifying agent solution. Among them, the composite purifying agent is composed of N,N-diethyl-p-phenylenediamine sulfate and tetrabutylammonium bromide with a mass ratio of 15:2, and the mass ratio of the composite purifying agent to the ethanol aqueous solution is 1:4;

[0047] Step 2: Mix the mixed solvent and the composite purifying agent solution in a volume ratio of 100:1, place it in a constant temperature oven at 20 °C, and let it stand in the dark for 24 h. Transfer the above mixed solution to a container, add ultrapure water until the total volume is 4 times the volume of the original mixed solution, let it stand for 12 h, separate the solvent phase with a separatory funnel, and transfer it to a brown bottle for storage in the dark to obtain a purified solvent. Among them, the mixed solvent is composed of n-hexane and n-octane, and the volume fraction of n-octane in the mixed solvent is 10%. The resistivity of the ultrapure water is 18.2 MΩ·cm;

[0048] Step 3: At a temperature of 20 °C, disperse hexachlorobenzene in the purified solvent. Under an ultrasonic power of 120 W, an ultrasonic frequency of 50 KHz, and ultrasonic treatment for 10 min, after ultrasonic dispersion, at a temperature of 20 °C, let it stand in the dark for 24 h to obtain a chlorine element reference material solution. The dosage ratio of hexachlorobenzene to the purified solvent is 33.47 mg:250 mL.

[0049] Comparative Example 3

[0050] A preparation method of a chlorine element reference material solution in light oil, comprising the following preparation steps:

[0051] Step 1: Disperse the composite purifying agent in an ethanol aqueous solution with a volume percentage concentration of 70%. Under an ultrasonic power of 100 W, an ultrasonic frequency of 40 KHz, and ultrasonic treatment for 10 min, after ultrasonic dispersion, transfer it to a volumetric flask. At a temperature of 20 °C, seal and let it stand for 12 h to obtain a composite purifying agent solution. Among them, the composite purifying agent is composed of N,N-diethyl-p-phenylenediamine sulfate, tetrabutylammonium bromide and triethanolamine with a mass ratio of 15:2:1, and the mass ratio of the composite purifying agent to the ethanol aqueous solution is 1:4;

[0052] Step 2: Mix n-hexane and the composite purification agent solution at a volume ratio of 100:1, place it in a constant temperature oven at 20°C, let it stand still in the dark for 24 hours. Transfer the above mixed solution to a container, add ultrapure water until the total volume is 4 times the volume of the original mixed solution. After standing still for 12 hours, separate the solvent phase with a separatory funnel, transfer it to a brown bottle and store it in the dark to obtain the purified solvent, where the resistivity of the ultrapure water is 18.2 MΩ·cm;

[0053] Step 3: At a temperature of 20°C, disperse hexachlorobenzene in the purified solvent. Under an ultrasonic power of 120 W and an ultrasonic frequency of 50 KHz, ultrasonicate for 10 minutes. After ultrasonic dispersion, at a temperature of 20°C, let it stand still in the dark for 24 hours to obtain the chlorine element reference material solution. The dosage ratio of hexachlorobenzene to the purified solvent is 33.47 mg:250 mL.

[0054] Comparative Example 4

[0055] A method for preparing a chlorine element reference material solution in light oil, comprising the following preparation steps:

[0056] Step 1: Disperse the composite purification agent in an ethanol aqueous solution with a volume percentage concentration of 70%. Under an ultrasonic power of 100 W and an ultrasonic frequency of 40 KHz, ultrasonicate for 10 minutes. After ultrasonic dispersion, transfer it to a volumetric flask, and at a temperature of 20°C, seal and let it stand still for 12 hours to obtain the composite purification agent solution, where the composite purification agent is composed of N,N-diethyl-p-phenylenediamine sulfate, tetrabutylammonium bromide, and triethanolamine with a mass ratio of 15:2:1, and the mass ratio of the composite purification agent to the ethanol aqueous solution is 1:4;

[0057] Step 2: Mix the mixed solvent and the composite purification agent solution at a volume ratio of 100:1, place it in a constant temperature oven at 20°C, let it stand still in the dark for 24 hours. Transfer the above mixed solution to a container, add ultrapure water until the total volume is 4 times the volume of the original mixed solution. After standing still for 12 hours, separate the solvent phase with a separatory funnel, transfer it to a brown bottle and store it in the dark to obtain the purified solvent, where the mixed solvent is composed of n-hexane and n-octane, and the volume fraction of n-octane in the mixed solvent is 5%, and the resistivity of the ultrapure water is 18.2 MΩ·cm;

[0058] Step 3: At a temperature of 20°C, disperse hexachlorobenzene in the purified solvent. Under an ultrasonic power of 120 W and an ultrasonic frequency of 50 KHz, ultrasonicate for 10 minutes. After ultrasonic dispersion, at a temperature of 20°C, let it stand still in the dark for 24 hours to obtain the chlorine element reference material solution. The dosage ratio of hexachlorobenzene to the purified solvent is 33.47 mg:250 mL.

[0059] Comparative Example 5

[0060] A method for preparing a chlorine element reference material solution in light oil, comprising the following preparation steps:

[0061] Step 1: Disperse the composite purifying agent in an ethanol aqueous solution with a volume percentage concentration of 70%. Under an ultrasonic power of 100 W, an ultrasonic frequency of 40 KHz, and ultrasonic treatment for 10 min, after ultrasonic dispersion, transfer it to a volumetric flask. At a temperature of 20 °C, seal and let it stand for 12 h to obtain a composite purifying agent solution. Among them, the composite purifying agent is composed of N,N - diethyl - p - phenylenediamine sulfate, tetrabutylammonium bromide, and triethanolamine with a mass ratio of 15:2:1, and the mass ratio of the composite purifying agent to the ethanol aqueous solution is 1:4;

[0062] Step 2: Mix the mixed solvent and the composite purifying agent solution at a volume ratio of 100:1, place it in a constant - temperature oven at 20 °C, and let it stand in the dark for 24 h. Transfer the above - mentioned mixed solution to a container, add ultrapure water until the total volume is 4 times the volume of the original mixed solution, let it stand for 12 h, then separate the solvent phase with a separatory funnel and transfer it to a brown bottle for storage in the dark to obtain a purified solvent. Among them, the mixed solvent is composed of n - hexane and n - octane, and the volume percentage of n - octane in the mixed solvent is 20%. The resistivity of the ultrapure water is 18.2 MΩ·cm;

[0063] Step 3: At a temperature of 20 °C, disperse hexachlorobenzene in the purified solvent. Under an ultrasonic power of 120 W, an ultrasonic frequency of 50 KHz, and ultrasonic treatment for 10 min, after ultrasonic dispersion, at a temperature of 20 °C, let it stand in the dark for 24 h to obtain a chlorine element reference material solution. The dosage ratio of hexachlorobenzene to the purified solvent is 33.47 mg:250 mL.

[0064] Performance test

[0065] Taking the chlorine element reference material solution prepared in Example 1 as an example, use an ICP - MS produced by PE Company for value determination. The carrier gas is argon, and the flow rate is 0.6 L / min; Nebulizer: PFA nebulizer; Nebulizer chamber temperature: - 2 °C; Torch tube: 1.5 mm central channel; Sampling cone, skimmer cone: Platinum cone; Injection volume: 20 μL.

[0066] Instrument linearity: Use standard solutions numbered NIM - RM2124 - NIM - RM2128 produced by the National Institute of Metrology, China to make a response value - concentration curve. As Figure 1 shown, in the range of (10 - 200) mg / L, the linear correlation coefficient R between the response value and the concentration is 0.999426, and the instrument linearity within the concentration range is > 0.999, with good linearity.

[0067] Use an injection system to send the prepared chlorine element reference material solution into the ICP - MS for detection, obtain the solution concentration according to the measured response value, and the measurement result is 100.02 mg / L. Rounding to one decimal place, it is 100.0 mg / L.

[0068] Homogeneity Detection

[0069] Homogeneity detection method: Conduct homogeneity inspection on the standard substance of chlorine content solution. The sampling method and number are carried out according to the regulations of the national standard "JJF1343-2022 Evaluation of Certification and Homogeneity and Stability of Reference Materials". The number of units for homogeneity inspection is less than 200 bottles. Randomly select 11 samples from the developed reference material (generate the extraction numbers using EXCEL random numbers). Measure each of the selected samples by ICP-MS and repeat the measurement 3 times. The sampling amount for homogeneity inspection is 20 μL. Use the one-way analysis of variance method for data analysis. Compare the homogeneity variance analysis result (ubb) with the expected target of the standard uncertainty of this characteristic value. If it is not significant, the reference material is considered homogeneous, and calculate the uncertainty component introduced by the inhomogeneity of the characteristic value to be measured and synthesize it into the total uncertainty of the reference material.

[0070] The specific statistical steps are as follows:

[0071] The average value of the i-th specimen is calculated according to Equation 1:

[0072]

[0073] The average value of n×m measurements of m specimens is calculated according to Equation 2:

[0074]

[0075] The sum of squares between groups (Q1) and the sum of squares within groups (Q2) are calculated according to Equations 3 and 4 respectively:

[0076]

[0077] The degrees of freedom (υ1, υ2) of the F-distribution function are calculated according to Equations 5 and 6 respectively:

[0078] υ1 = m - 1 (5)

[0079] υ2 = m(n - 1) (6)

[0080] The statistic F is calculated according to Equation 7:

[0081]

[0082] Results of homogeneity inspection

[0083] The statistical results of the homogeneity inspection of the chlorine content reference material in Example 1 are listed in Table 1. Taking the significance level α = 0.05, from the F α numerical table, it can be seen that Fα(10, 22) = 2.30.

[0084] As can be seen from Table 1, the statistical quantity F = 1.83 at 100.2 mg / L, which is less than Fα(0.05, 10, 22) = 2.30. Therefore, it can be judged that the prepared reference material is homogeneous, and the uncertainty component introduced by the inhomogeneity of the characteristic value to be measured is calculated and combined into the total uncertainty of the reference material.

[0085] Table 1 Statistical Results of the Homogeneity Test of the Chlorine Content Reference Material in Example 1 (100 mg / L)

[0086]

[0087]

[0088] Stability Test of the Reference Material

[0089] The basic model for stability research can be expressed as:

[0090] Y = β0 + β1X + ε (8)

[0091] Where:

[0092] β0 and β1 - regression coefficients;

[0093] ε - random error component.

[0094] Suppose there is a set of n pairs of observations of Y against X. For each Y i There is Equation 9:

[0095] Y i = β0 + β1X i + ε i (9)

[0096] Due to repeated measurements, using more than one bottle of sample at each time point, etc., for each X i Often more than one Y i value is obtained, and these factors should be included in the model of a specific stability study. However, when performing trend analysis, the average value of the results obtained for each bottle at time X i can be used.

[0097] The regression parameters can be obtained from the following formulas.

[0098] The estimated value of the slope can be calculated according to Equation 10:

[0099]

[0100] The estimated value of the intercept is calculated according to Equation 11:

[0101]

[0102] The standard deviations of β1 and β0 can be calculated through error analysis. Estimate the standard deviation of β1 according to Equation 12:

[0103]

[0104] In Equation 12:

[0105]

[0106] When the degrees of freedom are n - 2 and p = 0.95 (95% confidence level) according to the requirements of the t-test and remain unchanged, the t-factor is fixed. If

[0107] |β1| < t 0.95,n-2 ·s(β1) (14)

[0108] Then the slope is not significant, and thus no instability is observed.

[0109] Results of stability test

[0110] Short-term stability

[0111] To evaluate the stability of the reference material under short-term transportation conditions, a short-term stability test was conducted on the developed reference material. Samples of the chlorine content reference material were randomly selected and stored at 50°C for 7 days (achieved by placing them in an oven). During these 7 days, samples were taken at 0 day, 2 days, 4 days, and 7 days, and were uniformly tested on the 8th day. Since the samples were always stored in a refrigerator environment, no low-temperature short-term stability test was required.

[0112] Each of the selected samples was repeatedly measured 3 times. Before measurement, the reference material was placed at room temperature for a period of time to reach equilibrium. The reference material was measured three times repeatedly each time, and the average value of the three repeated measurements was taken as the measurement result.

[0113] The statistical results of the stability test data of the reference material are listed in Table 2. As can be seen from Table 2, the data of the chlorine content reference material in Example 1 did not change significantly within 7 days. Therefore, the developed chlorine content reference material passed the short-term stability test under the condition of 50°C.

[0114] Table 2 Statistical results of short-term stability test of chlorine content reference material in Example 1 (50°C, 100 mg / L)

[0115]

[0116] Long-term stability

[0117] In order to evaluate the stability of reference materials, it is necessary to regularly sample and measure the reference materials during storage. During each sampling measurement process, ICP-MS is used to measure each of the extracted samples, and various conditions are controlled as much as possible to make them tend to be consistent. The differences between the measurement results mainly reflect the differences caused by the changes in the substance. According to the requirements of JJF1343-2022 "Certification and Evaluation of Homogeneity and Stability of Reference Materials", for the developed chlorine content reference material, in accordance with the principle of being dense first and then sparse, a stability test was carried out for about 12 months. Each time, the measurement was repeated 3 times, and the average value of the 3 repeated measurements was taken as the measurement result. The statistical results of the long-term stability test data of the reference material are listed in Table 3. It can be seen from Table 2 that the data of the chlorine content reference material in Example 1 did not change significantly. Therefore, the characteristic quantity value of the developed chlorine content reference material is stable within 12 months.

[0118] Table 3 Statistical Results of Long-Term Stability Test of Chlorine Content Reference Material in Example 1 (100 mg / L)

[0119]

[0120] Table 4 Test Results of Homogeneity and Stability of Chlorine Element Reference Material Solutions Prepared in Examples 1-3 and Comparative Examples 1-5

[0121]

[0122]

[0123] It can be seen from Table 4 that the chlorine content reference material solution prepared in this application not only performs excellently in terms of measurement accuracy, effectively reducing the detection error and providing a reliable reference basis for the detection of chlorine elements in light oil; but also performs well in terms of homogeneity, with the chlorine content of the entire reference material being evenly distributed, and at the same time having high stability, being able to maintain the stability of the chlorine content for a long time and not being easily affected by environmental factors such as temperature and humidity and changing. Therefore, it can meet the requirements for the use of reference materials under different times and different environmental conditions in the actual detection process, and has high practical value and application prospects.

[0124] This specific embodiment is only an interpretation of the present application and does not limit the present application. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A preparation method of a standard substance solution of chlorine element in light oil, characterized in that, It includes the following preparation steps: Step 1: Disperse the composite purifying agent in an ethanol aqueous solution. After ultrasonic dispersion, transfer it to a volumetric flask, and seal and leave it standing at 20 - 25°C for 12 - 24 h to obtain a composite purifying agent solution; Step 2: Mix the mixed solvent and the composite purifying agent solution, place them in a constant temperature oven at 20 - 25°C, and leave it standing in the dark for 24 - 48 h. Transfer the above mixed solution to a container, add ultrapure water until the total volume is 4 - 6 times the volume of the original mixed solution. After standing for 12 - 24 h, separate the solvent phase with a separatory funnel, transfer it to a brown bottle and store it in the dark to obtain a purified solvent; Step 3: At 20 - 25°C, disperse hexachlorobenzene in the purified solvent. After ultrasonic dispersion, at 20 - 25°C, leave it standing in the dark for 24 - 36 h to obtain a chlorine element reference material solution.

2. The chlorine element reference material solution according to claim 1, wherein In Step 1, the composite purifying agent is composed of N,N - diethyl - p - phenylenediamine sulfate, tetrabutylammonium bromide, and triethanolamine with a mass ratio of 15 - 20:2 - 5:1 - 3.

3. The chlorine element reference material solution according to claim 1, characterized in that, In Step 1, the volume percentage concentration of the ethanol aqueous solution is 70 - 85%.

4. The chlorine element reference material solution according to claim 1, characterized in that, In Step 1, the mass ratio of the composite purifying agent to the ethanol aqueous solution is 1 - 1.2:4 - 5.

5. The chlorine element reference material solution according to claim 1, wherein In Step 2, the mixed solvent is composed of n - hexane and n - octane, and the volume proportion of n - octane in the mixed solvent is 10 - 15%.

6. The chlorine elemental standard substance solution according to claim 1, wherein In Step 2, the volume ratio of the mixed solvent to the composite purifying agent solution is 100 - 120:1 - 3.

7. The chlorine elemental standard substance solution according to claim 1, wherein In Step 2, the resistivity of the ultrapure water is higher than 18 MΩ·cm.

8. The chlorine elemental standard substance solution according to claim 1, wherein In Step 3, the dosage ratio of hexachlorobenzene to the purified solvent is 32 - 40 mg:250 - 280 mL.

9. A chlorine element reference material solution obtained by the preparation method according to any one of claims 1 - 8.

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