A preparation method of rubidium metasilicate and application of rubidium metasilicate

Abstract

The invention discloses a preparation method of rubidium metasilicate and an application of rubidium metasilicate, comprising the following steps: S1: weighing rubidium hydroxide and putting it into a beaker, adding a certain amount of pure water, stirring with a magnetic stirrer, adding a certain amount of metasilicic acid after it is completely dissolved, and continuing to stir until it is completely dissolved; S2: taking out the solution and putting it into a freeze dryer, after freeze drying, a white powder is obtained; S3: putting the white powder into a crucible, and then into a tubular furnace, passing nitrogen, setting a certain temperature and continuously annealing, and then cooling naturally to obtain an off-white powder. The invention has the beneficial effects of improving the preparation accuracy and yield of rubidium metasilicate, and greatly improving the detection accuracy and the service life of the detector through the application of rubidium metasilicate.

Description

Technical Field

[0001] The invention relates to the technical field of analytical chemical instruments, in particular to a preparation method of rubidium metasilicate and application of rubidium metasilicate. Background Art

[0002] Environmental and food safety issues are issues of great concern in today's society. In the two fields of environment and food, there is a very important and widely used device, namely the gas chromatograph. Among them, the gas chromatography nitrogen phosphorus detector (NPD) is often used in the analysis of nitrogen- and phosphorus-containing compounds. It has excellent performance such as ultra-high sensitivity, high selectivity and wide linear range. Therefore, NPD has become a gas chromatography-specific detector for detecting trace nitrogen- and phosphorus-containing compounds. It is one of the most commonly equipped selective detectors in gas chromatographs and is widely used in environmental monitoring, pharmaceutical analysis, clinical drug metabolism research, food analysis and other fields.

[0003] Rubidium metasilicate, as the core sensitive material of the NPD detector, its performance and life greatly determine the overall performance of the NPD detector. Since the synthesis and preparation process of materials such as rubidium metasilicate is quite complicated, it mainly includes high-temperature melting reaction, treatment under alkaline conditions, low-temperature crystallization, washing and purification processes. Therefore, there are several challenges in this series of preparation processes: First, in the high-temperature melting reaction, the strong volatility of rubidium salt leads to the easy loss of rubidium element, which affects the yield and quality of the final product; secondly, under alkaline conditions, the solubility of rubidium metasilicate is large, resulting in a low recovery rate of the product; thirdly, in the low-temperature crystallization process, due to the rapid precipitation rate, the formed grains are uneven, affecting the purity and performance of the product; in addition, when adjusting the pH value, due to the instability of silicate ions, silicate precipitation is easily produced, affecting the reaction process; finally, in the washing and purification step, the residual impurities are difficult to completely remove, making the purity of the final product unable to reach the ideal state. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing rubidium metasilicate to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing rubidium metasilicate, comprising the following steps:

[0006] S1: Weigh rubidium hydroxide and put it into a beaker, add a certain amount of pure water, stir it with a magnetic stirrer, add a certain amount of metasilicic acid after it is completely dissolved, and continue stirring until it is completely dissolved;

[0007] S2: taking out the solution and putting it into a freeze dryer to obtain a white powder after freeze drying;

[0008] S3: putting the white powder into a crucible, and then putting it into a tubular furnace, introducing nitrogen, setting a certain temperature and continuously annealing, and then cooling naturally to obtain an off-white powder.

[0009] Preferably, the step S1 specifically includes:

[0010] S1.1: Take a certain amount of rubidium hydroxide and put it into a beaker;

[0011] S1.2: Add a predetermined amount of pure water and start a magnetic stirrer, stirring until the rubidium hydroxide is completely dissolved;

[0012] S1.3: Slowly add a certain amount of metasilicic acid and continue stirring until the metasilicic acid is completely dissolved;

[0013] S1.4: Obtain a transparent solution without particles by observing the transparency of the solution and the number of particles in the solution.

[0014] Preferably, the step of completely dissolving rubidium hydroxide in step S1.2 comprises:

[0015] S1.2.1: Select an appropriate beaker size to ensure that the volume is at least 10% larger than the final solution volume;

[0016] S1.2.2: The stirring speed is set to 300 r / min and the stirring time is 10 minutes;

[0017] S1.2.3: Check the dissolution degree of rubidium hydroxide. When rubidium hydroxide is completely dissolved, the pH value of the solution should be no less than 13. If the pH value is lower than 13, stirring should be continued;

[0018] S1.2.4: Record the stirring time at this point and stop stirring to ensure that the solution is static.

[0019] Preferably, the metasilicic acid dissolving step in step S1.3 comprises:

[0020] S1.3.1: Slowly add metasilicic acid to the completely dissolved rubidium hydroxide solution;

[0021] S1.3.2: The stirring speed is set to 500 r / min and the stirring time is 15 minutes;

[0022] S1.3.3: Check the light transmittance of the solution. The light transmittance must be no less than 80%. When the light transmittance is lower than 80%, the stirring time needs to be extended.

[0023] S1.3.4: Ensure that the final solution is transparent and has no visible precipitation. Continue stirring for 3 minutes to consolidate the reaction effect.

[0024] Preferably, the freeze-drying step in step S2 comprises:

[0025] S2.1: Pour the stirred solution into a freeze-drying tray of appropriate size;

[0026] S2.2: Place the freeze drying tray into the freeze dryer, set the freezing temperature to -50°C, and the freezing time to 24 hours;

[0027] S2.3: Turn on the vacuum pump, set the vacuum degree to below 10 Pa, and the drying time to 72 hours;

[0028] S2.4: Check the moisture content of the white powder to ensure that it is not greater than 5%. If the moisture content is greater than 5%, the drying time needs to be extended.

[0029] Preferably, in step S3, the white powder obtained by freeze drying is placed in a ceramic crucible, and then placed in a tube furnace, nitrogen is introduced, a certain temperature is set and annealing is continued, and then naturally cooled to obtain an off-white powder, comprising:

[0030] S3.1: Place the crucible in a tube furnace heated to 800°C, turn on nitrogen protection, and set the flow rate to 5 mL / min;

[0031] S3.2: Raise the temperature to 1000°C and keep at this temperature for 4 hours;

[0032] S3.3: Cool to room temperature, ensuring that the cooling rate does not exceed 10 ℃ / min. When the cooling rate exceeds 10 ℃ / min, the cooling should be suspended and continued after the temperature stabilizes.

[0033] Preferably, the molar ratio of rubidium hydroxide to metasilicic acid is 2:1.

[0034] A method for using a nitrogen-phosphorus detector of a gas chromatograph, using the rubidium metasilicate obtained by the above-mentioned preparation method to detect the content of nitrogen in azobenzene and phosphorus in malathion, comprising the following steps:

[0035] Take a certain amount of rubidium metasilicate, dissolve it in pure water, add silicate cement powder, stir and mix evenly to obtain a viscous liquid;

[0036] The viscous liquid is coated on the coil of the nitrogen-phosphorus detector and placed in an oven for drying;

[0037] The dried detector was installed on a gas chromatograph for detection.

[0038] Preferably, the mass ratio of the rubidium metasilicate, water and silicate cement is 1:2:15.

[0039] Preferably, the parameters of the gas chromatograph nitrogen phosphorus detector are set as: injector temperature 220°C, split ratio 1:20, constant flow mode, column box temperature 150°C, detector temperature 300°C, hydrogen flow rate 3.8 mL / min, air flow rate 100 mL / min, nitrogen flow rate 20 mL / min, current 2.9 A, standard sample azobenzene 2 ng / uL and malathion 4 ng / uL mixed sample, injection volume 1 uL.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The method for preparing rubidium metasilicate provided in the embodiments of the present invention can reduce the rubidium loss problem caused by the strong volatility of rubidium salts in high-temperature melting reactions; the low product recovery problem caused by the high solubility of rubidium metasilicate under alkaline conditions; the problem of uneven grains caused by too fast precipitation speed during low-temperature crystallization; and the problem of silicic acid precipitation caused by the instability of silicate ions during pH adjustment.

[0042] 2. The method for using the nitrogen-phosphorus detector of a gas chromatograph provided in an embodiment of the present invention uses the rubidium metasilicate provided by the preparation method of rubidium metasilicate provided in an embodiment of the present invention as a material, combines water and silicate cement, and coats it on the coil of the nitrogen-phosphorus detector of a gas chromatograph. The minimum limits of N- and P-containing substances that can be detected are 120 fg / s and 80 fg / s respectively, and the actual service life exceeds 600 h, which greatly improves the detection accuracy and the service life of the detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a flow chart of a method for preparing rubidium metasilicate according to the present invention;

[0044] Figure 2 This is a flow chart of the dissolution of pure water and metasilicic acid in step S1;

[0045] Figure 3 This is a schematic diagram of the flow chart structure of the step of completely dissolving rubidium hydroxide in step S1.2;

[0046] Figure 4 This is a flow chart of complete dissolution of metasilicic acid in step S1.3;

[0047] Figure 5 is a process flow chart of freeze drying in step S2;

[0048] Figure 6 is a diagram of annealing steps in step S3;

[0049] Figure 7 A flow chart of a method for using a nitrogen-phosphorus detector of a gas chromatograph according to the present invention;

[0050] Figure 8 A life test curve of a nitrogen-phosphorus detector in a method for using a nitrogen-phosphorus detector of a gas chromatograph according to the present invention;

[0051] Fig. 9 The present invention provides a detection curve of N and P in a nitrogen-phosphorus detector standard sample in a method for using a nitrogen-phosphorus detector of a gas chromatograph. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] See also Figure 1 The present invention provides a technical solution: a method for preparing rubidium metasilicate, comprising the following steps:

[0054] S1: Weigh rubidium hydroxide and put it into a beaker, add a certain amount of pure water, stir it with a magnetic stirrer, add a certain amount of metasilicic acid after it is completely dissolved, and continue stirring until it is completely dissolved;

[0055] S2: The solution was taken out and placed in a freeze dryer, and after freeze drying, a white powder was obtained;

[0056] S3: putting the white powder into a crucible, and then putting it into a tube furnace, introducing nitrogen, setting a certain temperature and continuously annealing, and then cooling naturally to obtain an off-white powder.

[0057] See also Figure 2 In one embodiment of the present invention, step S1 specifically includes:

[0058] S1.1: Take a certain amount of rubidium hydroxide and put it into a beaker.

[0059] S1.2: Add a predetermined amount of pure water and start a magnetic stirrer, stirring until the rubidium hydroxide is completely dissolved. Specifically, in one embodiment, 10 g of rubidium hydroxide powder can be weighed and placed in a 250 mL beaker. Add a predetermined amount of pure water and start a magnetic stirrer, stirring until the rubidium hydroxide is completely dissolved. This step is to fully disperse the rubidium hydroxide, making it easier to contact with other reactants and promote subsequent reactions. For example, in the above embodiment, 100 mL of deionized water can be added and stirred at medium speed using a magnetic stirrer for about 10 minutes until the solution is clear and transparent, and no rubidium hydroxide powder is suspended.

[0060] S1.3: Slowly add a certain amount of metasilicic acid, and continue to stir until the metasilicic acid is completely dissolved. Slowly add a certain amount of metasilicic acid, and continue to stir until the metasilicic acid is completely dissolved. The key to this process is to control the speed of feeding to prevent the local excessive heat of reaction from causing the volatility of rubidium to increase, thereby reducing the loss of rubidium. For example, in one embodiment, 20g of metasilicic acid powder can be gradually added, and stirring is continued for 5 minutes after each small amount is added, until all the metasilicic acid is fully added and completely dissolved, and the solution is in a uniform state.

[0061] S1.4: Obtain a transparent solution without particles by observing the transparency of the solution and the number of particles in the solution. Ensure that the solution is transparent and without particles to prove that rubidium hydroxide and metasilicic acid are completely reacted. This inspection step is to judge whether the reaction is fully completed by observing the transparency of the solution. For example, in the above embodiment, the solution is visually confirmed to be free of turbidity and undissolved particles, and the reaction is further verified to be complete. In view of the problem of rubidium loss in high-temperature melting reactions, a closed system under inert gas protection is used for reaction. Inert gases such as nitrogen or argon can prevent the rapid volatilization of rubidium salts at high temperatures, thereby improving the yield and purity of the product. For example, before reacting, an inert gas can be introduced into a closed reaction vessel, and pressure balance can be maintained to effectively avoid the volatilization of rubidium salts.

[0062] In view of the low product recovery rate caused by the high solubility of rubidium metasilicate under alkaline conditions, the crystallization process of the product can be controlled by adjusting the reaction temperature and pH value. For example, in the later stage of the reaction, the temperature of the solution can be gradually lowered to room temperature, and the pH can be adjusted to a weakly alkaline range (such as pH 7-9) to promote the gradual precipitation of rubidium metasilicate and improve the product recovery rate. Specifically, in the above embodiment, after the reaction is completed, the solution is cooled to 25°C, and the pH is adjusted to 7.5 with a pH regulator (such as dilute sulfuric acid), and the product is filtered after stirring for 1 hour.

[0063] For the problem of uneven grains caused by too fast precipitation during low-temperature crystallization, a gradual cooling method is adopted to slow down the crystal growth rate and ensure the quality of the crystals. For example, during the cooling process after the reaction, the solution is placed in a 10°C constant temperature water bath, and the water bath temperature is lowered by 1°C every 10 minutes, and the temperature is continuously lowered to 0°C. After maintaining the constant temperature for 2 hours, the precipitated rubidium metasilicate crystals are more uniform.

[0064] Regarding the problem of silicic acid precipitation caused by the instability of silicate ions during pH adjustment, by selecting a suitable pH adjuster and adjusting gradually, the instantaneous pH fluctuation can be avoided. For example, in the above embodiment, dilute sulfuric acid with a concentration of 0.1 M can be selected as the pH adjuster, and a few drops can be added each time to gradually adjust the pH to 7.5. During the process, stirring is continued to avoid the local pH being too low to cause a large amount of silicate ion precipitation.

[0065] In the washing and purification step, in order to avoid the problem of insufficient purity caused by the difficulty in completely removing residual impurities, organic solvents can be used for recrystallization and purification multiple times. For example, after obtaining the preliminary rubidium metasilicate product, the rubidium metasilicate product can be washed with ethanol multiple times and dried in a vacuum drying oven. Specifically, the rubidium metasilicate product can be dispersed in an appropriate amount of ethanol, stirred and allowed to stand for 30 minutes, then filtered and the above process repeated 2-3 times, and finally the final product is placed in a 60°C vacuum drying oven and dried for 12 hours to ensure that the product purity reaches a high level. Through the above detailed process improvements and optimizations, a series of technical problems in the preparation process of rubidium metasilicate are effectively solved.

[0066] See also Figure 3 In one embodiment of the present invention, the step of completely dissolving rubidium hydroxide in step S1.2 comprises:

[0067] S1.2.1: Select a beaker of appropriate size to ensure that the volume is at least 10% larger than the final solution volume.

[0068] This step is to ensure that there is enough space to avoid overflow during the dissolution process, and it is also conducive to stirring operation. Generally, the volume of the beaker should be more than 10% larger than the final solution volume. This is because the appropriate additional space can reduce the risk of overflow caused by liquid gravity and facilitate the work of the stirrer, thereby improving the dissolution efficiency.

[0069] In the specific operation, select a suitable beaker according to the amount of rubidium metasilicate solution to be prepared. If it is expected that 500 ml of solution will be prepared in the end, the beaker capacity should not be less than 550 ml, that is, 10% more space should be added on the basis of 500 ml. In this example, if the actual solution capacity is 600 ml, it is necessary to select a 720 ml or larger beaker.

[0070] S1.2.2: Set the stirring speed to 300 r / min and the stirring time to 10 minutes. Next, set the stirring speed and time. Set the stirring speed to 300 r / min and the stirring time to 10 minutes. The speed and time are selected based on the dissolution rate of rubidium hydroxide and the uniformity requirements of the solution. Too low a stirring speed will result in incomplete dissolution, while too high a stirring speed may produce a large number of bubbles, affecting the transparency and uniformity of the solution.

[0071] In a laboratory setting, this can be achieved with an electric stirrer.

[0072] In one embodiment, a 600 W electric stirrer is used, set to 300 r / min, and a timer is started to check the dissolution after stirring for 10 minutes. This step ensures that the solution achieves sufficient mixing effect in a short time and promotes the full dissolution of rubidium hydroxide.

[0073] S1.2.3: Check the dissolution degree of rubidium hydroxide. When rubidium hydroxide is completely dissolved, the pH value of the solution should be no less than 13. If the pH value is lower than 13, continue stirring.

[0074] When testing the dissolution degree of rubidium hydroxide, the pH value of the solution should be ensured to be not less than 13. The pH value is an indicator of the acidity and alkalinity of the solution. pH ≥ 13 indicates that the solution is strongly alkaline, which indicates that the rubidium hydroxide has been completely dissolved. Test with pH test paper or electronic pH meter to ensure that the pH value meets the requirements. Specifically, in one embodiment, the experimenter uses an accurate pH meter to measure the pH value of the solution. The initial reading is 11.5. After stirring again for 5 minutes and re-measuring, it is found that the pH value has risen to 13.2, proving that the rubidium hydroxide has been completely dissolved.

[0075] If the pH value of the solution still does not meet the condition of pH ≥ 13, continue stirring until the pH value reaches the required range. Continue stirring to further disperse the undissolved rubidium hydroxide particles until they are completely dissolved. Record the stirring time at this time and stop stirring. This is to accurately record the time point when the solution reaches the predetermined state to ensure the consistency and reliability of subsequent experimental data.

[0076] S1.2.4: Record the stirring time at this point and stop stirring to ensure that the solution is static.

[0077] When the rubidium hydroxide is completely dissolved, ensure that the solution is in a static state to prevent bubbles generated during the stirring process from interfering with subsequent operations. For example, in a specific embodiment, after the rubidium hydroxide is completely dissolved and the pH reaches 13, the total stirring time is recorded as 15 minutes, and the agitator is turned off, and the beaker is left to stand for 10 minutes to allow the bubbles in the solution to completely escape and ensure that the solution is clear and transparent. This operation helps to maintain the stability of the experimental process and the accuracy of the results.

[0078] See also Figure 4 In one embodiment of the present invention, the metasilicic acid dissolution step in step S1.3 includes:

[0079] S1.3.1: Slowly add metasilicic acid to the completely dissolved rubidium hydroxide solution.

[0080] The purpose of this step is to allow metasilicic acid and rubidium hydroxide to fully react and promote the subsequent reaction. In order to prevent local overconcentration and uneven reaction, the addition rate of metasilicic acid should be controlled.

[0081] S1.3.2: The stirring speed is set to 500 r / min and the stirring time is 15 minutes.

[0082] The purpose of stirring is to fully mix the metasilicic acid and rubidium hydroxide solution to form a uniform solution. The stirring speed is set to 500 r / min to provide sufficient mechanical energy to ensure the mixing uniformity of the solution without wasting energy or causing uneven mixing at a low speed. For example, in one embodiment, the stirrer is set to 500 r / min for continuous stirring for 15 minutes to ensure uniform dispersion of metasilicic acid and rubidium hydroxide throughout the process.

[0083] S1.3.3: Check the light transmittance of the solution. The light transmittance must be no less than 80%. When the light transmittance is lower than 80%, the stirring time needs to be extended.

[0084] Detecting the transmittance can determine whether the metasilicic acid has been fully dissolved without precipitation or turbidity. The setting of the transmittance of not less than 80% is based on the requirement of clear and transparent solution so that the subsequent steps can proceed smoothly. When the transmittance is less than 80%, the stirring time needs to be extended until the target transmittance is reached. For example, in one embodiment, the transmittance of the solution is detected by a spectrophotometer, and it is found that the initial measurement is 75%, so the stirring time is extended by 10 minutes, and the transmittance reaches 83% when the test is repeated.

[0085] S1.3.4: Ensure that the final solution is transparent and has no visible precipitation. Continue stirring for 3 minutes to consolidate the reaction effect.

[0086] This step is to further confirm that the metasilicic acid has been completely dissolved without any tiny particles or undissolved matter. The stirring time is extended by 3 minutes to enhance the mixing effect and ensure the stability of the solution. For example, in one embodiment, after preliminary stirring and transmittance testing, stirring is continued for 3 minutes, and visual inspection is performed to confirm that the solution is completely transparent without any visible precipitation.

[0087] See also Figure 5 In one embodiment of the present invention, the freeze-drying step in step S2 comprises:

[0088] S2.1: pour the stirred solution into a freeze drying tray of suitable size. The purpose of this step is to ensure that the solution is evenly distributed on the freeze drying tray so that the subsequent freezing process can be carried out more efficiently. Specifically, in one embodiment, the stirred rubidium metasilicate solution is slowly poured into the freeze drying tray to avoid bubbles or stratification of the solution during the pouring process.

[0089] S2.2: Place the freeze drying tray into a freeze dryer, with the preset freezing temperature of -50°C and the freezing time of 24 hours. The purpose of this step is to quickly freeze the solution into a solid state to prevent the solvent from volatilizing unevenly during the drying process, thereby affecting the quality of the final product. In one embodiment, the preset temperature of the freeze dryer is set to -50°C and the freezing time is 24 hours. Such low temperatures and longer time settings can ensure that the solution is fully frozen and reaches an ideal state. In this process, the temperature range is generally between -30°C and -60°C, preferably -50°C, because this temperature can effectively freeze the water in the solution quickly without damaging the active ingredients in the solution.

[0090] S2.3: Turn on the vacuum pump, set the vacuum degree to less than 10 Pa, and the drying time to 72 hours. This step is to evaporate the frozen water under vacuum conditions, that is, the sublimation process. By maintaining a low vacuum degree and a long drying time, it can be ensured that the solvent gradually sublimates at low temperatures without boiling or volatilization of the solvent. Specifically, in one embodiment, the vacuum degree is set to 8 Pa and the drying time is set to 72 hours. The range of vacuum degree is generally between 1 Pa and 10 Pa, and 10 Pa is a commonly used upper limit value because a lower vacuum degree can better promote the sublimation of water. However, too low a vacuum degree will lead to increased equipment costs and complicated operations, so 10 Pa is considered to be a balance point. 72 hours is a relatively sufficient drying time, which can ensure that the water is fully removed and avoid the risk of water re-condensation during subsequent processing.

[0091] S2.4: Check the moisture content of the white powder to ensure that the moisture content is not greater than 5%. If the moisture content is greater than 5%, the drying time needs to be extended. The purpose of this step is to confirm whether the drying is complete to ensure the purity and stability of the final product. If the test results do not meet the requirement that the moisture content is less than or equal to 5%, the drying time needs to be extended. For example, specifically, the moisture content can be tested by an infrared moisture analyzer or the Karl Fischer method. If the initial test results show that the moisture content is 6%, the product needs to be put back into the freeze dryer and continue drying until the moisture content reaches or falls below the 5% standard.

[0092] See also Figure 6In one embodiment of the present invention, the annealing step of step S3 includes: first, placing the white powder obtained by freeze drying into a ceramic crucible. The key to this step is to ensure that the powder is evenly distributed in the crucible for subsequent processing. Freeze drying can effectively remove moisture from the powder and ensure the purity and stability of the powder. For example, in one embodiment, after the white powder is weighed, it is poured into a ceramic crucible that has been cleaned and preheated in advance to ensure that no impurities are mixed in. The specific operation steps include:

[0093] S3.1: Place the crucible in a tubular furnace that has been heated to 800°C, turn on nitrogen protection, and set the flow rate to 5 mL / min. In this step, pre-heating and nitrogen protection are to prevent oxidation reactions of the powder during high temperature processes. At the same time, a stable nitrogen flow rate ensures the consistency and purity of the gas filling. Specifically, the heating process of the tubular furnace can be completed within 1 hour, and the nitrogen flow rate of 5 mL / min is an optimized choice based on experimental results, which can effectively avoid oxidation without affecting other physical and chemical properties.

[0094] S3.2: Raise the temperature to 1000℃ and keep it at this temperature for 4 hours. This step is the core step of the annealing process. High temperature treatment can promote the growth of rubidium metasilicate grains and optimize the structure. The temperature and time are set to the best conditions obtained through multiple tests. For example, experiments show that keeping the temperature at 1000℃ for 4 hours can obtain a rubidium metasilicate product with high crystallinity and stable structure. If the temperature is too low or the holding time is insufficient, the product may not be fully crystallized; otherwise, it may cause sintering and other problems.

[0095] S3.3: Cool to room temperature, ensuring that the cooling rate does not exceed 10 ℃ / min. When the cooling rate exceeds 10 ℃ / min, the cooling must be suspended and continued after the temperature stabilizes. The cooling rate is controlled within 10 ℃ / min to prevent internal stress of the material caused by rapid temperature changes, thereby affecting the performance of the product. For example, in a specific embodiment, the cooling process is to naturally cool to 800 ℃ after turning off the heating power, and then gradually adjust the vents of the furnace to control the cooling rate to no more than 10 ℃ / min until it drops to room temperature. This ensures that the product will not crack or have other defects due to sudden cooling.

[0096] After cooling, an off-white powder is obtained, which is rubidium metasilicate.

[0097] In one embodiment of the present invention, in step S1, the molar ratio of rubidium hydroxide to metasilicic acid is 2:1.

[0098] See also Figure 7The embodiment of the present invention also provides a method for using a gas chromatograph nitrogen-phosphorus detector, which uses the rubidium metasilicate obtained by the preparation method of the above embodiment to detect the content of nitrogen in azobenzene and phosphorus in malathion, comprising the following steps:

[0099] S100: Take a certain amount of rubidium metasilicate, dissolve it in pure water, add silicate cement powder, stir and mix evenly to obtain a viscous liquid;

[0100] S200: coating the viscous liquid on the nitrogen-phosphorus detector coil and placing it in an oven for drying;

[0101] S300: Install the dried detector on a gas chromatograph for detection.

[0102] In one embodiment of the present invention, the mass ratio of rubidium metasilicate, water and silicate cement in step S100 is 1:2:15.

[0103] In one embodiment of the present invention, the parameters of the gas chromatograph nitrogen phosphorus detector are set as follows: injector temperature 220°C, split ratio 1:20, constant current mode, column box temperature 150°C, detector temperature 300°C, hydrogen flow rate 3.8 mL / min, air flow rate 100 mL / min, nitrogen flow rate 20 mL / min, current 2.9 A, standard sample azobenzene 2 ng / uL and malathion 4 ng / uL mixed sample, injection volume 1 uL.

[0104] See also Figure 8 and Fig. 9 In one embodiment, a method for using a gas chromatograph nitrogen-phosphorus detector is used to perform minimum limit detection of N-containing and P-containing substances using an NPD detector. Table 1 shows the data comparison of standard substances. The detection results show that the method can detect the minimum limits of N-containing and P-containing substances of 120 fg / s and 80 fg / s, respectively.

[0105] Standards Retention time (min) Peak area (μV / min) RSD repeatability (%) 1 Azobenzene 4.56 2070.8 0.62 2 Malathion 6.32 10009.2 1.19 The actual service life is more than 600 hours. Its performance is close to that of NPD detectors from imported manufacturers.

[0106] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing rubidium metasilicate, characterized in that: The steps include: S1: Weigh rubidium hydroxide and put it into a beaker, add a certain amount of pure water, stir it with a magnetic stirrer, add a certain amount of metasilicic acid after it is completely dissolved, and continue stirring until it is completely dissolved to obtain a uniformly stirred solution; S2: taking out the stirred solution and putting it into a freeze dryer to obtain a white powder after freeze drying; S3: putting the white powder into a crucible, placing the crucible in a tube furnace, introducing nitrogen, setting a certain temperature and continuously annealing, and then cooling naturally to obtain an off-white powder.

2. The method for preparing rubidium metasilicate according to claim 1, wherein: The step S1 specifically includes: S1.1: Take a certain amount of rubidium hydroxide and put it into a beaker; S1.2: Add a predetermined amount of pure water and start a magnetic stirrer, stirring until the rubidium hydroxide is completely dissolved; S1.3: Slowly add a certain amount of metasilicic acid and continue stirring until the metasilicic acid is completely dissolved; S1.4: Obtain a transparent solution without particles by observing the transparency of the solution and the number of particles in the solution.

3. A method for preparing rubidium metasilicate according to claim 2, characterized in that: The step of completely dissolving rubidium hydroxide in step S1.2 comprises: S1.2.1: Select a suitable beaker size to ensure that the volume is at least 10% larger than the final solution volume; S1.2.2: The stirring speed is set to 300r / min and the stirring time is 10 minutes; S1.2.3: Check the dissolution degree of rubidium hydroxide. When rubidium hydroxide is completely dissolved, the pH value of the solution should be no less than 13. If the pH value is lower than 13, stirring should be continued; S1.2.4: Record the stirring time at this point and stop stirring to ensure that the solution is static.

4. The method for preparing rubidium metasilicate according to claim 3, characterized in that: The metasilicic acid dissolution step in step S1.3 includes: S1.3.1: Slowly add metasilicic acid to the completely dissolved rubidium hydroxide solution; S1.3.2: The stirring speed is set to 500r / min and the stirring time is 15 minutes; S1.3.3: Check the light transmittance of the solution. The light transmittance must be no less than 80%. When the light transmittance is lower than 80%, the stirring time needs to be extended. S1.3.4: Ensure that the final solution is transparent and has no visible precipitation. Continue stirring for 3 minutes to consolidate the reaction effect.

5. The method for preparing rubidium metasilicate according to claim 4, characterized in that: The freeze-drying step in step S2 comprises: S2.1: Pour the stirred solution into a freeze-drying tray of appropriate size; S2.2: Place the freeze drying tray into the freeze dryer, set the freezing temperature to -50°C, and the freezing time to 24 hours; S2.3: Turn on the vacuum pump, set the vacuum degree to below 10Pa, and the drying time to 72 hours; S2.4: Check the moisture content of the white powder to ensure that it is not greater than 5%. If the moisture content is greater than 5%, the drying time needs to be extended.

6. The method for preparing rubidium metasilicate according to claim 5, characterized in that: In step S3, the white powder obtained by freeze drying is placed in a ceramic crucible, and then placed in a tube furnace, nitrogen is introduced, a certain temperature is set and annealing is continued, and then naturally cooled to obtain an off-white powder, including: S3.1: Place the crucible in a tubular furnace heated to 800°C, turn on nitrogen protection, and set the flow rate to 5 mL / min; S3.2: Raise the temperature to 1000°C and keep at this temperature for 4 hours; S3.3: Cool to room temperature, ensuring that the cooling rate does not exceed 10℃ / min. When the cooling rate exceeds 10℃ / min, the cooling should be suspended and continued after the temperature stabilizes.

7. The method for preparing rubidium metasilicate according to claim 1, characterized in that: The molar ratio of the rubidium hydroxide to the metasilicic acid is 2:

1.

8. A method for using a nitrogen-phosphorus detector of a gas chromatograph, using the rubidium metasilicate obtained by the preparation method according to any one of claims 1 to 7 to detect the content of nitrogen in azobenzene and phosphorus in malathion, characterized in that: The steps include: Take a certain amount of rubidium metasilicate, dissolve it in pure water, add silicate cement powder, stir and mix evenly to obtain a viscous liquid; The viscous liquid is coated on the coil of the nitrogen-phosphorus detector and placed in an oven for drying; The dried detector was installed on a gas chromatograph for detection.

9. The method for using a gas chromatograph nitrogen-phosphorus detector according to claim 8, characterized in that: The mass ratio of the rubidium metasilicate, water and silicate cement is 1:2:

15.

10. The method for using a gas chromatograph nitrogen-phosphorus detector according to claim 9, characterized in that: The parameters of the gas chromatograph nitrogen phosphorus detector were set as follows: injector temperature 220°C, split ratio 1:20, constant current mode, column box temperature 150°C, detector temperature 300°C, hydrogen flow rate 3.8mL / min, air flow rate 100mL / min, nitrogen flow rate 20mL / min, current 2.9A, standard sample azobenzene 2ng / uL and malathion 4ng / uL mixed sample, injection volume 1uL.

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