Preparation method of a standard substance for trace total organic carbon solution

Abstract

The invention discloses a preparation method of a trace total organic carbon solution reference material, belonging to the technical field of reference materials. The preparation method is to dissolve, make up the volume, dilute and encapsulate the GBW10067 sucrose purity reference material in an operating box with a nitrogen atmosphere. The invention can prepare ultrapure water with a total organic carbon content of less than 1 ppb. By treating the vessels used and the bottle body, bottle cap and inner gasket of the encapsulation bottle through the method provided by the invention, the total organic carbon content dissolved from the encapsulation bottle is less than 20 ppb within 6 months; by using the outer packaging methods of filling with nitrogen and vacuum pumping, the prepared trace total organic carbon solution reference material can be stored for 6 months under the conditions of light avoidance and refrigeration; the method provided by the invention can be used to prepare a blank total organic carbon solution reference material with a content of less than 20 μg / L and a total organic carbon solution reference material with a content of 200 μg / L; the method is stable, reliable and has strong repeatability.

Description

Technical Field

[0001] The present invention belongs to the technical field of reference materials, and particularly relates to a preparation method of a trace total organic carbon solution reference material. Background Art

[0002] Total organic carbon refers to the total amount of carbon contained in dissolved and suspended organic matter in water. There are many types of organic matter in water. Besides carbon, it also contains elements such as hydrogen, nitrogen, and sulfur, and not all of them can be separated and identified. It is often represented by "TOC". TOC is a comprehensive index for rapid detection, which represents the total amount of organic matter in water in terms of the amount of carbon. It is usually used as an important basis for evaluating the degree of organic matter pollution in water bodies. The total organic carbon index is determined by the combustion oxidation - non-dispersive infrared method, and the oxidation of organic matter is relatively complete, with an oxidation rate of more than 80%. Therefore, the total organic carbon index can better reflect the degree of organic pollution in water bodies. Many foreign countries place total organic carbon on-line automatic monitors at the total sewage outlets of factories to monitor the sewage discharge situation at any time. Total organic carbon analysis has become the main means of water treatment and quality control in many countries in the world. The determination of total organic carbon is required in drinking water supply, pharmaceuticals, food, semiconductor industry, analysis of the degree of humification of waste, analysis of carbon flux in aquatic systems, determination of soil carbon content, and carbon cycle in soil.

[0003] The trace total organic carbon solution reference material is an important guarantee for ensuring the detection results of water quality TOC. At present, there are 3 kinds of national secondary liquid reference materials for total organic carbon in water, with concentrations of 1000 mg / L (GBW(E)081239, GBW(E)082053) and 100 mg / L (GBW(E)081239) respectively. The concentrations of other commercially available total organic carbon solution reference materials in water are all in ppm level, that is, greater than 1 mg / L. There is no traceable trace total organic carbon solution reference material in the domestic market. For the use demand of trace total organic carbon solution reference materials, it needs to be solved by purchasing imported reference materials. However, the procurement cycle of imported reference materials is long and the price is expensive, and testing institutions have to bear a great economic burden.

[0004] The main difficulty in the production process of trace total organic carbon solution reference materials is that the matrix background requirements for solution reference materials are very high, including that the water quality used must contain extremely low total organic carbon, and at the same time, no external carbon-containing pollutants can be introduced during the preparation and packaging of solution reference materials. However, due to the large number of carbon-containing impurities in the environment, including impurities in the air, impurities attached to glassware, impurities attached to packaging bottles, and trace carbon-containing impurities dissolved from the bottle body, plastic inner pads and plastic bottle caps during the long-term contact between the solution and the packaging bottle, they will all affect the accuracy of the value of trace total organic carbon solution reference materials.

[0005] Therefore, in order to meet the requirement of ensuring the traceability of the amount value of trace total organic carbon at the ppb level, and to ensure the comparability, reliability, and traceability of the detection results in different regions and at different times, it is very necessary to develop a preparation process for the solution reference material of trace total organic carbon, so as to provide a solution reference material with accurate amount value, good homogeneity and stability for the field of trace total organic carbon detection. Summary of the Invention

[0006] The object of the present invention is to overcome the shortcomings of the prior art and provide a preparation method for a solution reference material of trace total organic carbon with accurate amount value, good homogeneity and stability.

[0007] The object of the present invention is achieved by the following technical solutions: A preparation method for a solution reference material of trace total organic carbon, comprising the following steps:

[0008] S1. Dissolution: Accurately weigh the GBW10067 sucrose purity reference material, and then dissolve it in an ultra-high purity water with a total organic carbon content not exceeding 1 ppb in an operating box under a nitrogen atmosphere.

[0009] S2. Volume fixing: Fill the volumetric flask with nitrogen, then pour the dissolved sucrose into the volumetric flask. After maintaining a constant temperature of 20.0 °C ± 0.5 °C in a constant temperature bath for 20 minutes, fix the volume with ultra-high purity water with a total organic carbon content not exceeding 1 ppb.

[0010] S3. Dilution: Gradually dilute the volume-fixed sucrose solution to 200 μg / L, and the dilution water is ultra-high purity water with a total organic carbon content not exceeding 1 ppb.

[0011] S4. Sub-packaging: First fill the packaging bottle with nitrogen in an operating box under a nitrogen atmosphere, then sub-package the diluted sucrose solution into the packaging bottle. Finally, fill the packaging bottle containing the solution with nitrogen, tighten the bottle cap, and store it refrigerated at 2 - 10 °C under a vacuum state.

[0012] As a preferred technical solution, a preparation method for a solution reference material of trace total organic carbon, comprising the following steps:

[0013] S1. Dissolution: Accurately weigh 50 mg of the GBW10067 sucrose purity reference material, and then dissolve it in 50 ml of ultra-high purity water with a total organic carbon content not exceeding 1 ppb in an operating box under a nitrogen atmosphere.

[0014] S2. Volume fixing: Fill the 5 L volumetric flask with nitrogen, then pour the dissolved sucrose into the volumetric flask. After maintaining a constant temperature of 20.0 °C ± 0.5 °C in a constant temperature bath for 20 minutes, fix the volume with ultra-high purity water with a total organic carbon content not exceeding 1 ppb.

[0015] S3. Dilution: Gradually dilute the volumetric sucrose solution to 200 μg / L. The water used for dilution is ultrapure water with a total organic carbon content not exceeding 1 ppb.

[0016] S4. Sub-packaging: First, fill the encapsulation bottle with nitrogen in an operating box under a nitrogen atmosphere. Then, sub-package the diluted sucrose solution into the encapsulation bottle. Finally, fill the encapsulation bottle with the solution above with nitrogen, tighten the bottle cap, and store it refrigerated at 2 - 10 °C under vacuum.

[0017] Furthermore, the vessels in contact with the sucrose solution and ultrapure water are pretreated by the following method: Wash with tap water at least 5 times, then wash with pure water at least 5 times, then ultrasonically wash with ultrapure water with an organic carbon content not exceeding 5 ppb for at least 5 times, with each ultrasonic washing time being 5 - 7 min. Finally, soak with ultrapure water with an organic carbon content not exceeding 1 ppb for 45 - 52 h. After soaking, wash with ultrapure water with a total organic carbon content not exceeding 1 ppb at least 5 times, and use it immediately after drying with nitrogen.

[0018] Furthermore, the ultrapure water with a total organic carbon content not exceeding 5 ppb is prepared by the following method: Ultrapure water is irradiated successively by ultraviolet lamps with wavelengths of 10 nm, 185 nm, and 254 nm, and the irradiation time for each is 4 - 7 min.

[0019] Furthermore, the ultrapure water with a total organic carbon content not exceeding 1 ppb is prepared by the following method: Ultrapure water is irradiated successively by ultraviolet lamps with wavelengths of 10 nm, 185 nm, and 254 nm for 4 - 7 min each, and then filtered through a micro total organic carbon filter.

[0020] Furthermore, the time for filling the volumetric flask with nitrogen in step S2 is 50 - 70 s.

[0021] Furthermore, the time for filling the sub-packaging bottle with nitrogen before sub-packaging in step S4 is 50 - 70 s, and the time for filling the sub-packaging bottle with nitrogen after sub-packaging the solution is 25 - 35 s.

[0022] Furthermore, in step S4, the encapsulation bottle is a screw-cap bottle, and the total organic carbon dissolution after sub-packaging the solution is less than 20 ppb. The present invention has the following advantages:

[0023] (1) The method provided by the present invention can prepare ultrapure water with a total organic carbon content less than 1 ppb, which can be used for the preparation of trace total organic carbon solutions.

[0024] (2) Treat the utensils used, the bottle body, bottle cap, and inner gasket of the encapsulation bottle by the method provided by the present invention. The total organic carbon content dissolved in the encapsulation bottle is less than 20 ppb within 6 months. Using the outer packaging method of filling with nitrogen and vacuum pumping, the prepared trace total organic carbon solution reference material can be stored for 6 months under the conditions of avoiding light and refrigeration, and the packaging permeation water loss rate can be ignored.

[0025] (3) The method provided by the present invention can be used to prepare a blank total organic carbon solution reference material with a content less than 20 μg / L and a total organic carbon solution reference material with a content of 200 μg / L, and the validity period can reach 6 months.

[0026] (4) The method for preparing the trace total organic carbon solution reference material provided by the present invention is stable, reliable, and has strong repeatability. Description of the Drawings

[0027] Figure 1 It is the flow chart of the experiment of the present invention.

[0028] Figure 2 It is the trend chart of the water loss rate of the packaging container. Detailed Embodiments

[0029] The following further describes the present invention in conjunction with the drawings and embodiments. The protection scope of the present invention is not limited to the following:

[0030] Embodiment 1: A method for preparing a trace total organic carbon solution reference material, comprising the following steps:

[0031] S1. Dissolution: Accurately weigh 25 mg of the sucrose purity reference material GBW10067, and dissolve it in 50 ml of ultra-high pure water with a total organic carbon content not greater than 1 ppb in an operating box under a nitrogen atmosphere;

[0032] S2. Volume fixation: Fill nitrogen into a 2.5 L volumetric flask for 50 s, then pour the dissolved sucrose into the volumetric flask. After maintaining a constant temperature of 20.0 °C ± 0.5 °C in a constant temperature bath for 20 min, fix the volume with ultra-high pure water with a total organic carbon content not greater than 1 ppb;

[0033] S3. Dilution: Gradually dilute the fixed-volume sucrose solution to 200 μg / L, and the dilution water used is ultra-high pure water with a total organic carbon content not greater than 1 ppb;

[0034] S4. Sub-packaging: First fill the encapsulation bottle with nitrogen in an operating box under a nitrogen atmosphere for 50 s, then sub-package the diluted sucrose solution into the encapsulation bottle. Finally, fill nitrogen above the encapsulation bottle containing the solution for 25 s, tighten the bottle cap, and store it refrigerated at 2 - 10 °C under vacuum.

[0035] Among them, the ultra-high purity water with a total organic carbon content not exceeding 5 ppb is prepared by the following method: The ultra-high purity water is successively irradiated by ultraviolet lamps with wavelengths of 10 nm, 185 nm, and 254 nm, and the irradiation times are 4 min, 4 min, and 7 min respectively; The ultra-high purity water with a total organic carbon content not exceeding 1 ppb is prepared by the following method: After the ultra-high purity water is successively irradiated by ultraviolet lamps with wavelengths of 10 nm, 185 nm, and 254 nm for 4 min, 4 min, and 7 min respectively, it is then filtered using a Merck LC-Pak trace total organic carbon terminal filter. The total carbon content of the effluent of this terminal filter is less than 1 ppb, and the light absorptions at 200 nm, 205 nm, 210 nm, and 254 nm are <0.05 AU, <0.01 AU, <0.01 AU, and <0.005 AU respectively, and the evaporation residue is <0.0001% (ω / ω).

[0036] The vessels in contact with the sucrose solution and ultra-high purity water during the above operation process are pretreated by the following method: After being washed 5 times with tap water, they are first washed 5 times with pure water, then ultrasonically washed 5 times with ultra-high purity water with a total organic carbon content not exceeding 5 ppb, with each ultrasonic washing time being 5 min. Finally, they are soaked in ultra-high purity water with a total organic carbon content not exceeding 1 ppb for 45 h. After soaking, they are washed 5 times with ultra-high purity water with a total organic carbon content not exceeding 1 ppb, and then immediately used after being dried with nitrogen.

[0037] Example 2: A preparation method for a trace total organic carbon solution reference material, comprising the following steps:

[0038] S1. Dissolution: After accurately weighing 50 mg of the GBW10067 sucrose purity reference material, it is dissolved in 50 ml of ultra-high purity water with a total organic carbon content not exceeding 1 ppb in an operating box under a nitrogen atmosphere;

[0039] S2. Volume fixation: Nitrogen is filled into a 5 L volumetric flask for 70 s. Then the dissolved sucrose is poured into the volumetric flask. After being kept at a constant temperature of 20.0 °C ± 0.5 °C in a constant temperature bath for 20 min, it is fixed in volume with ultra-high purity water with a total organic carbon content not exceeding 1 ppb;

[0040] S3. Dilution: The fixed-volume sucrose solution is gradually diluted to 200 μg / L, and the dilution water used is ultra-high purity water with a total organic carbon content not exceeding 1 ppb;

[0041] S4. Sub-packaging: In an operating box under a nitrogen atmosphere, first fill the packaging bottle with nitrogen for 70 s. Then sub-package the diluted sucrose solution into the packaging bottle. Finally, fill nitrogen above the packaging bottle containing the solution for 35 s, tighten the bottle cap, and store it refrigerated at 2 - 10 °C under vacuum.

[0042] Among them, the ultrapure water with a total organic carbon content not exceeding 5 ppb is prepared by the following method: The ultrapure water is successively irradiated by ultraviolet lamps with wavelengths of 10 nm, 185 nm, and 254 nm for 7 min, 5 min, and 6 min respectively; The ultrapure water with a total organic carbon content not exceeding 1 ppb is prepared by the following method: After the ultrapure water is successively irradiated by ultraviolet lamps with wavelengths of 10 nm, 185 nm, and 254 nm for 7 min, 5 min, and 6 min, it is then filtered using a Merck LC-Pak trace total organic carbon terminal filter. The total carbon content of the effluent from this terminal filter is less than 1 ppb, and the light absorptions at 200 nm, 205 nm, 210 nm, and 254 nm are <0.05 AU, <0.01 AU, <0.01 AU, and <0.005 AU respectively, and the evaporation residue is <0.0001% (ω / ω);

[0043] The vessels in contact with the sucrose solution and ultrapure water during the above operation process are pretreated by the following method: After being washed 6 times with tap water, they are first washed 6 times with pure water, then ultrasonically washed 5 times with ultrapure water with a total organic carbon content not exceeding 5 ppb for 7 min each time. Finally, they are soaked in ultrapure water with a total organic carbon content not exceeding 1 ppb for 52 h, and after soaking, they are washed 6 times with ultrapure water with a total organic carbon content not exceeding 1 ppb, and then immediately used after being dried with nitrogen.

[0044] The beneficial effects of the present invention are illustrated by the following experiments:

[0045] The process of the following experiment is as Figure 1 shown:

[0046] Experimental Example 1: Preparation of a standard substance for trace total organic carbon solution:

[0047] S1. Dissolution: Weigh an appropriate amount of GBW10067 sucrose purity standard substance in a drying dish. After placing the drying dish in an oven at 110 °C and drying it to a constant weight, store it in a desiccator for standby; Use a clean and dry 50 mL glass beaker to tare on the balance, accurately weigh 50 mg of sucrose in the drying dish, record the actual weighing data, slowly move the beaker containing sucrose into the glove operation box with a nitrogen atmosphere, slowly pour ultrapure water with a total organic carbon content not exceeding 1 ppb above the beaker wall, so that the ultrapure water covers the sucrose solid, continue to add ultrapure water until the total volume is about 50 mL, and stir the raw materials with a glass rod until completely dissolved;

[0048] S2. Constant volume: Transfer all the sucrose solution in the beaker to a 5-L volumetric flask. Rinse the beaker and glass rod at least 7 times repeatedly and transfer all the rinsing solutions to the volumetric flask. Before and after adding the solution, nitrogen gas needs to be filled into the volumetric flask, and the nitrogen filling time is 60 s. After the volumetric flask is kept at a constant temperature of 20.0 °C ± 0.5 °C in a thermostatic bath for 20 min, it is made up to the calibration line with primary water, shaken well, then nitrogen gas is supplemented into the volumetric flask, and the gas filling time after adding the liquid is 30 s. Seal the mouth of the volumetric flask with a sealing film;

[0049] S3. Dilution: Gradually dilute the prepared high-concentration solution to 200 μg / L. The dilution and volume fixation use ultra-high pure water with a total organic carbon content not exceeding 1 ppb;

[0050] S4. Sub-packaging: Open a clean and dry glove operation box, and place the solution to be sub-packaged, screw-cap bottles, plastic inner pads, plastic bottle caps, Brand continuous pipettor, 50-mL ground-glass bottles, and a clean beaker as a waste liquid cup in the glove operation box. Turn on the vacuum pump to pump out the air in the glove operation box, and then turn on the nitrogen generator to replace the air in the glove operation box with nitrogen. Pour 50 mL of total organic carbon solution reference material into the ground-glass bottle and suck it all into the pipettor for later use (try to reduce the contact of the solution with ambient gas and avoid strong light irradiation); in addition, hold the screw-cap bottle with the left hand and fill nitrogen into the screw-cap bottle, and use the pipettor with the right hand to inject 40 mL of total organic carbon solution reference material into the screw-cap bottle at a uniform speed. Fill nitrogen above the screw-cap bottle already filled with total organic carbon solution reference material. Add a plastic inner pad and a plastic lid to the screw-cap bottle already filled with the solution reference material and nitrogen, and tighten the lid. Before and after adding the solution, nitrogen gas needs to be filled into the volumetric flask. The nitrogen filling time before adding the liquid is 60 s, and the gas filling time after adding the liquid is 30 s. After supplementing nitrogen into the volumetric flask, seal the mouth of the volumetric flask with a sealing film and store it under refrigeration (2 °C - 10 °C) in the dark.

[0051] Among them, the ultra-high pure water with a total organic carbon content not exceeding 5 ppb is prepared by the following method: The ultra-pure water is irradiated by ultraviolet lamps with wavelengths of 10 nm, 185 nm, and 254 nm in sequence, and the irradiation time is 5 min for each; the ultra-high pure water with a total organic carbon content not exceeding 1 ppb is prepared by the following method: After the ultra-pure water is irradiated by ultraviolet lamps with wavelengths of 10 nm, 185 nm, and 254 nm for 5 min each, it is then filtered through a Merck LC-Pak trace total organic carbon terminal filter. The total carbon content of the effluent of this terminal filter is less than 1 ppb, and the light absorptions at 200 nm, 205 nm, 210 nm, and 254 nm are <0.05 AU, <0.01 AU, <0.01 AU, and <0.005 AU respectively, and the evaporation residue is <0.0001% (ω / ω);

[0052] During the above operation process, the vessels and sealing films for packaging that come into contact with the sucrose solution and ultrapure water are pretreated by the following method: After being washed 6 times with tap water, they are first washed 6 times with pure water, then ultrasonically washed 5 times with ultrapure water with an organic carbon content not exceeding 5 ppb for 7 minutes each time. Finally, they are soaked in ultrapure water with an organic carbon content not exceeding 1 ppb for 52 hours. After soaking, they are washed 6 times with ultrapure water with a total organic carbon content not exceeding 1 ppb, and then immediately used after being dried with nitrogen.

[0053] Experimental Example 2: Content of Organic Carbon in Ultrapure Water

[0054] The ultrapure water used in Experimental Example 1 was irradiated with ultraviolet lamps with wavelengths of 10 nm, 185 nm, and 254 nm to reduce the total organic carbon content in ordinary ultrapure water to less than 5 ppb. A micro total organic carbon terminal filter was added at the water intake. Under the condition that the influent total organic carbon content was less than 5 ppb, the total organic carbon content of the effluent water quality was not more than 1 ppb. Table 1 shows the comparison results of the total organic carbon content of three types of water quality.

[0055] Table 1 Total Organic Carbon Test Results in Three Types of Ultrapure Water

[0056]

[0057] Experimental Example 3: Detection and Repeatability Test of Total Organic Carbon Solution Standard Substance

[0058] Taking the national certified standard substance GBW(E)082053 total organic carbon solution standard substance in water as the reference standard, the reference standard was diluted to 200 μg / L, and all the solutions used in the test process were prepared and used immediately. All sample bottles were washed with ultrapure water with a total organic carbon content not exceeding 1 ppb, and the background signal was deducted from the blank total organic carbon solution standard substance. The samples and reference standards were tested using a HACH TOC analyzer. The instrument analysis conditions were: reactor temperature: 48 °C; carrier gas: high-purity nitrogen; oxidant solution: 2.5 g / L ammonium persulfate (containing 0.05% phosphoric acid matrix); injection volume: 6 mL - 8 mL; backwashing; sample measurement time: 30 minutes, and the results are shown in Table 2:

[0059] Table 2 Repeatability Investigation Data of Total Organic Carbon Test Method

[0060]

[0061] Experimental Example 4: Investigation of the Pretreatment Method of Encapsulation Bottles

[0062] The bottle body, bottle cap and inner gasket of the encapsulation bottle for the dispensed solution reference material have all been treated to reduce the impact of the total organic carbon dissolved from the encapsulation bottle on the stored solution reference material. Different treatment methods were investigated in the experiment for the test results of the total organic carbon content of the encapsulation bottle filled with ultrapure water. Three pretreatment methods for the encapsulation bottle were investigated in the experiment. For the 1# encapsulation bottle, it was used directly without cleaning. For the 2# encapsulation bottle, it was washed 5 times with tap water, 5 times with pure water, ultrasonically cleaned 5 times with ultrapure water with an organic carbon content not greater than 5 ppb, ultrasonically for 5 minutes each time. Finally, it was washed 5 times with ultrapure water with an organic carbon content not greater than 1 ppb and immediately used after nitrogen drying. For the 3# encapsulation bottle, it was washed 5 times with tap water, 5 times with pure water, ultrasonically cleaned 5 times with ultrapure water with an organic carbon content not greater than 5 ppb, ultrasonically for 5 minutes each time, then soaked in ultrapure water with an organic carbon content not greater than 1 ppb for 48 hours, and finally washed 5 times with ultrapure water with an organic carbon content not greater than 1 ppb and immediately used after nitrogen drying. The difference between 2# and 3# is that 3# adds the treatment procedure of soaking in ultrapure water with an organic carbon content not greater than 1 ppb for 48 hours.

[0063] For the encapsulation bottles with the pretreatment methods of 1#, 2#, and 3#, 24 treated encapsulation bottles were randomly selected and filled with about 40 mL of ultrapure water, sealed and stored for 6 months. At the 1st, 2nd, 3rd, and 6th months, 6 bottles were taken out of the packaging container blanks, and the total organic carbon content of the taken-out empty bottles was measured using a total organic carbon analyzer. The measured average value was taken as the final result, and the detection method was the same as that in Experimental Example 3. The experimental results are shown in Tables 3, 4, and 5. The investigation results in Tables 3 - 5 show that the pretreatment method of the 3# encapsulation bottle is the best, and the dissolution of total organic carbon in the stored ultrapure water for 6 months is less than 20 ppb.

[0064] Table 3 Investigation Results of the Pretreatment Method of the 1# Encapsulation Bottle

[0065]

[0066] Table 4 Investigation Results of the Pretreatment Method of the 2# Encapsulation Bottle

[0067]

[0068] Table 5 Investigation Results of the Pretreatment Method of the 3# Encapsulation Bottle

[0069]

[0070] Experimental Example 5: Investigation of the Water Loss Rate of the Encapsulation Bottle

[0071] The solution reference material is packaged by filling nitrogen inside the sealed bottle and adding a vacuum bag outside the sealed bottle and then evacuating the air. Seven bottles of 200 μg / L trace total organic carbon solution reference material were randomly selected, and the water loss rate was investigated by weighing at the 1st, 2nd, 3rd, and 6th months respectively. Each bottle was measured 3 times, and the average value of the test results of the 7 bottles was taken as the final measured value. The average water loss rate of the packaging container was calculated, and the analysis results are shown in Figure 2 .

[0072] From Figure 2 the water loss rate results, it can be seen that the overall water loss rate of the sealed bottle containing 40 mL of trace total organic carbon solution reference material is 0% after being stored for 6 months, and the influence of the water loss rate on the quantity value of the solution reference material can be ignored.

[0073] Experimental Example 6: Homogeneity Test of Total Organic Carbon Solution Reference Material

[0074] According to the specification JJF1343-2012 "General Principles and Statistical Principles for the Certification of Reference Materials", the homogeneity test of the reference material was carried out. If the total number of preparation units is denoted as N, when N ≤ 200, the number of sampled units is not less than 11. The specific method is as follows: The above-mentioned total organic carbon solution reference material with a concentration of 200 μg / L was randomly sampled in the early, middle, and late stages of sub-packaging, and a total of 11 bottles were sampled for homogeneity test. The content of total organic carbon was measured with a total organic carbon analyzer. To prevent the stability of the instrument and other factors during the measurement process from affecting the homogeneity test results, the measurements were carried out in a random order, and each bottle was measured 3 times. The average value of the 3 measurement values was taken as the measurement result of one bottle. According to JJF1343-2012 "General Principles and Statistical Principles for the Certification of Reference Materials", the one-way analysis of variance method was used for testing.

[0075] The homogeneity test results are shown in Tables 6 and 7. The results show that: F < F 0.05(10,22) , the reference material has good homogeneity and meets the requirements for the homogeneity of the reference material.

[0076] Table 6 One-way Analysis of Variance Test Results

[0077]

[0078] Table 7 One-way Analysis of Variance Results

[0079]

[0080] Experimental Example 7: Investigation on the Stability of the Transportation Conditions of Total Organic Carbon Solution Reference Material

[0081] Investigation on the stability of reference materials during simulated transportation. The specific method for short-term stability test is as follows: within 15 days, following the principle of initially dense and then sparse time intervals, test the samples stored under the conditions of 2°C - 10°C and 20°C - 30°C. Use a total organic carbon analyzer for testing. During each test process, strictly control the working conditions of the instrument to minimize the impact of instrument reproducibility. Randomly select 3 bottles each time, measure each bottle 3 times, and take the average of the 3 measurement results as the analysis result of 1 bottle, and take the average of the measurement results of 3 bottles as the test result of this time. According to the specification JJF1343-2012 "General Principles and Statistical Principles for the Certification of Reference Materials", perform a linear fitting of the molar concentration c against time T with the stability investigation results. If β 1 <t 0.95,n-2 ×s(β 1 ), it indicates that the slope of the straight line of the solution stability test result is not significant, and the stability of the reference material is good. If β 1 >t 0.95,n-2 ×s(β 1 ), it indicates that the slope of the straight line of the solution stability test result is significant, and the stability of the reference material is not good.

[0082] The test results are shown in Tables 8 and 9 as follows:

[0083] Table 8 Investigation Results of the Stability of 200 μg / L Total Organic Carbon Solution Reference Material under Simulated Transportation Conditions (2°C - 10°C)

[0084]

[0085] Table 9 Investigation Results of the Stability of 200 μg / L Total Organic Carbon Solution Reference Material under Simulated Transportation Conditions (20°C - 30°C)

[0086]

[0087] Therefore, during winter transportation, use multi-layer insulation bags and an insulation box for packaging to ensure that the temperature during transportation is not lower than 0°C; during summer transportation, use an insulation box with ice packs for packaging to ensure that the temperature during transportation is not higher than 10°C.

[0088] Experimental Example 8: Long-term Stability Investigation of Total Organic Carbon Solution Reference Material:

[0089] Within a 6-month period, following the principle of initially frequent and then sparse time intervals, the total organic carbon solution reference material stored under refrigerated conditions was subjected to long-term stability investigation using a total organic carbon analyzer. Each test strictly controlled the instrument operating conditions to minimize the impact of instrument reproducibility. Each time, 3 bottles were randomly selected, and each bottle was measured 3 times. The average of the 3 measurement results was taken as the measurement result of 1 bottle, and the average of the measurement results of 3 bottles was taken as the measurement result for that time. According to the specification JJF1343-2012 "General Principles and Statistical Principles for the Certification of Reference Materials", a linear fit of the molar concentration c against time T was made using the stability investigation results. If β 1 <t 0.95,n-2 ×s(β 1 ), it indicates that the slope of the straight line of the solution stability test result is not significant, and the reference material has good stability. If β 1 >t 0.95,n-2 ×s(β 1 ), it indicates that the slope of the straight line of the solution stability test result is significant, and the reference material has poor stability. The test results are shown in Table 10:

[0090] Table 10 Long-term Stability Investigation Results of the Total Organic Carbon Solution Reference Material at 200 μg / L

[0091]

[0092] The experimental results prove that the method for preparing the trace total organic carbon solution reference material is stable, reliable, and highly reproducible. Under the conditions of refrigerated transportation and 6-month long-term storage, the quantity value of this solution reference material is accurately determined and stable, and it can be used for the measurement calibration, quality control, proficiency testing, and method validation of total organic carbon in solutions. To ensure the comparability of trace total organic carbon in solutions in different regions and at different times, and to ensure the traceability of measurement results, a solution reference material with accurate quantity value, good homogeneity, and stability is provided for the field of trace total organic carbon detection.

[0093] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all are covered by the protection scope of the present invention.

Claims

1. A preparation method of a trace total organic carbon solution reference material, characterized in that, it includes the following steps: S1. Dissolution: Accurately weigh the GBW10067 sucrose purity reference material and dissolve it in an ultra-high purity water with a total organic carbon content not exceeding 1 ppb in an operating box under a nitrogen atmosphere; S2. Volume fixing: Fill the volumetric flask with nitrogen, then pour the dissolved sucrose into the volumetric flask. After maintaining a constant temperature of 20.0 °C ± 0.5 °C in a thermostatic bath for 20 min, fix the volume with ultra-high purity water with a total organic carbon content not exceeding 1 ppb; S3. Dilution: Gradually dilute the volume-fixed sucrose solution to 200 μg / L, and the dilution water is ultra-high purity water with a total organic carbon content not exceeding 1 ppb; S4. Sub-packaging: First fill the packaging bottle with nitrogen in an operating box under a nitrogen atmosphere, then sub-package the diluted sucrose solution into the packaging bottle. Finally, fill the packaging bottle containing the solution with nitrogen, tightly cap the bottle and store it refrigerated at 2 - 10 °C under a vacuum state; Among them, the utensils in contact with the sucrose solution and ultra-high purity water are pretreated by the following method: Wash with tap water at least 5 times, then wash with pure water at least 5 times, and then ultrasonically wash with ultra-high purity water with an organic carbon content not exceeding 5 ppb for at least 5 times, with each ultrasonic washing time being 5 - 7 min. Finally, soak in ultra-high purity water with an organic carbon content not exceeding 1 ppb for 45 - 52 h. After soaking, wash with ultra-high purity water with a total organic carbon content not exceeding 1 ppb at least 5 times, and immediately use after drying with nitrogen; The ultra-high purity water with a total organic carbon content not exceeding 1 ppb is prepared by the following method: The ultra-high purity water is irradiated by ultraviolet lamps with wavelengths of 10 nm, 185 nm, and 254 nm for 4 - 7 min in sequence, and then filtered through a trace total organic carbon filter.

2. The preparation method of a trace total organic carbon solution reference material according to claim 1, characterized in that, in step S1, the GBW10067 sucrose purity reference material is 50 mg, and the ultra-high purity water with a total organic carbon content not exceeding 1 ppb is 50 ml; in step S2, the volumetric flask is 5 L.

3. The preparation method of a trace total organic carbon solution reference material according to claim 1, characterized in that, the ultra-high purity water with a total organic carbon content not exceeding 5 ppb is prepared by the following method: The ultra-high purity water is irradiated by ultraviolet lamps with wavelengths of 10 nm, 185 nm, and 254 nm, and the irradiation time for each is 4 - 7 min.

4. The preparation method of a trace total organic carbon solution reference material according to claim 1, characterized in that, in step S2, the time for filling nitrogen into the volumetric flask is 50 - 70 s.

5. The preparation method of a trace total organic carbon solution reference material according to claim 1, characterized in that, in step S4, the time for filling nitrogen into the sub-packaging bottle before sub-packaging is 50 - 70 s, and the time for filling nitrogen after sub-packaging the solution is 25 - 35 s.

6. The preparation method of a trace total organic carbon solution reference material according to claim 1, It is characterized in that In step S4, the encapsulation bottle is a screw-thread bottle, and the dissolution of total organic carbon after dispensing the solution is less than 20 ppb.

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