A multi-link synchronous determination method for the determination of nitrogen tetroxide chloride content

Abstract

The invention discloses a multi-joint synchronous determination method for determining the chloride content of dinitrogen tetroxide, and relates to the technical field of determination of the chloride content of dinitrogen tetroxide. The multi-joint synchronous determination method comprises the steps of: preparing chlorine-free distilled water that meets the requirements of third-grade water → using the chlorine-free distilled water prepared in step S1 to prepare a standard working solution and other related pharmaceutical reagents, and making a standard working curve → preparing a sample gasification container, vacuumizing and sealing and cooling the screw-mouth gasification bottle → weighing the initial mass of the sample gasification container → injecting a quantitative sample into the sample gasification container → building a multi-joint determination group → connecting a nitrogen purge pipeline → performing synchronous nitrogen purge → merging and titrating the absorption liquid → determining the absorbance and chloride ion content. The multi-joint synchronous determination method of the present invention has the advantages of good data reproducibility, short time consumption for laboratory determination, and accurate chloride content determination data by carrying out multiple parallel determinations in the same time period.

Description

Technical Field

[0001] This invention relates to the field of chloride content determination technology for dinitrogen tetroxide, and specifically to a multi-stage simultaneous determination method for dinitrogen tetroxide chloride content determination. Background Technology

[0002] Nitrogen tetroxide, a conventional liquid propellant, is primarily used in space launches, such as missiles and launch vehicles. Excessive chloride content in liquid propellants can severely corrode propellant loading pipelines. Furthermore, the combustion product of chlorides, hydrogen chloride, releases free chlorine atoms upon contact with hydroxyl groups in nature. These chlorine atoms act as catalysts for ozone layer depletion; they are not consumed in the chemical reaction themselves, contributing to the cyclical destruction of the ozone layer. Therefore, in major space launch missions, determining the chloride content in nitrogen tetroxide is a crucial indicator of whether it meets the requirements for high-purity liquid propellants. Chloride content determination is a mandatory test item in nitrogen tetroxide testing, with a technical requirement that the chloride mass fraction not exceed 0.040%. GJB1964A-2015 specifies the working curve method for chloride content determination, and this method is also used in the determination of chloride content in high-purity nitrogen tetroxide for spacecraft. This method is based on the law of light absorption—Beer-Lambert law. That is, when a beam of monochromatic light passes through a homogeneous solution, the absorbance of the solution is directly proportional to the product of the concentration of the absorbing substance and the thickness of the liquid layer. The law of light absorption only applies within a certain concentration range, and only then is there a linear relationship between absorbance and concentration. In spectrophotometric analysis, this linear relationship is often used to determine the content of substances.

[0003] In the existing technique for determining chloride in dinitrogen tetroxide, approximately 10g of dinitrogen tetroxide sample, accurate to 0.10g, is taken. The sample is then injected into a vaporization flask, and nitrogen gas is immediately and slowly used to purge the sample through two water-filled absorption flasks until the sample is completely evaporated. Finally, the solutions from the two absorption flasks are collected in a beaker, and relevant indicators and auxiliary reagents are added. The beaker is then heated on a sealed electric furnace to evaporate to near dryness. Subsequently, the chloride content in dinitrogen tetroxide is determined by spectrophotometry and an established standard working curve.

[0004] In actual work of determining chloride content, it is often found that the standard curve is not linear. Even if a blank solution is used as a reference solution and the absorbance of the spectrophotometer is adjusted to zero, the standard curve will still shift upward.

[0005] In addition, obtaining the required 10g sample is also a challenge. Current practice involves measuring a certain volume of nitrogen tetroxide sample using a graduated cylinder based on experience, then pouring the sample into the vaporization flask all at once, and calculating the actual mass of the sample in the vaporization flask using a differential method. However, in actual weighing, the mass of the vaporization flask containing the sample is difficult to stabilize at room temperature, significantly interfering with the final reading and experimental results. Furthermore, during subsequent nitrogen purging, the continuous introduction of nitrogen and the vapor pressure of nitrogen tetroxide at room temperature increase the pressure inside the vaporization flask. This can cause the glass stopper to pop open under internal pressure, resulting in stopper damage and nitrogen tetroxide leakage, affecting the continuity and accuracy of subsequent chloride content determination. On the other hand, due to limitations in production technology, the stopper of the vaporization bottle and the glass stopper cannot be perfectly sealed, which can cause partial leakage during nitrogen purging. Although applying sealing grease to the bottle mouth can enhance the sealing effect, there is still a possibility that the glass stopper may loosen during nitrogen purging, making it impossible to guarantee that the nitrogen tetroxide sample will be completely vaporized under sealed conditions, resulting in a high failure rate in chloride content determination.

[0006] Furthermore, GJB1964A-2015 stipulates that at least three samples should be taken for each test when determining chloride content. Excluding the time required for reagent preparation, spectrophotometer setup, and standard curve preparation, each sample requires at least four hours to complete the test, and each sample requires at least twelve hours to determine chloride content. However, in actual testing, the results of chloride content determination are not ideal, mainly due to low parallelism and high randomness. This necessitates multiple repeated tests and careful screening and comparison of the data to obtain satisfactory results. This is clearly impractical for real-world testing tasks and cannot meet the demands of rapid testing capabilities for extremely high intensity, density, and difficulty. The reasons for this may be:

[0007] (1) Poor sealing of the vaporization bottle and absorption bottle leads to the escape of some sample gas, making it difficult to maintain uniformity in parallel determination of chloride content in samples and increasing randomness;

[0008] (2) Although the distilled water used has been filtered through ion exchange resin, there is still a possibility that the distilled water contains chloride ions, which will cause a certain degree of interference to the standard working curve and the actual determination of chloride content.

[0009] (3) The nitrogen gas flow rate was inconsistent in each parallel measurement, which led to inconsistent rates at which chloride entered the water in the absorption bottle. This resulted in differences in the absorption rate of water in different measurements, and thus poor parallelism of the actual chloride content measurement results.

[0010] If chloride content is measured on two or more samples at the same time, the measurement time will be much longer, and the test results cannot be obtained in a short period of time. This will put a lot of psychological pressure on the laboratory personnel and will not be conducive to obtaining accurate test results in a timely manner. Summary of the Invention

[0011] To address the shortcomings of the aforementioned technologies, this invention provides a multi-stage simultaneous determination method for the content determination of dinitrogen tetroxide chloride.

[0012] The technical solution adopted by the present invention to achieve the above-mentioned technical effects is as follows:

[0013] A multi-stage simultaneous determination method for the content of dinitrogen tetroxide chloride includes the following steps:

[0014] S1. Connect the distillation apparatus to redistill the purified water produced by the ultrapure water machine and collect the resulting chlorine-free distilled water.

[0015] S2. Use the chlorine-free distilled water obtained in step S1 to prepare a standard working solution and other relevant reagents to create a standard working curve.

[0016] S3. Take the screw-top vaporization bottle, evacuate it, and place it in a sealed environment at 0℃ for 3 hours to cool and store for later use.

[0017] S4. Take out the screw-top vaporization bottle and weigh it.

[0018] S5. Connect the sampling bottle containing dinitrogen tetroxide and the screw-top vaporization bottle through a polytetrafluoroethylene tube. First, open the valve of the sampling bottle, and then slowly open the air inlet of the screw-top vaporization bottle (1) so that the dinitrogen tetroxide sample slowly flows into the screw-top vaporization bottle until the specified volume scale line is reached. Then weigh the mass of the screw-top vaporization bottle containing the sample again.

[0019] S6. Connect the screw-top vaporization bottle from step S5 in series with two absorption bottles that have been pre-filled with 40mL of chlorine-free distilled water to form a set of measurements. The set of measurements shall be arranged in at least three units and placed on a refrigeration and heating instrument.

[0020] S7. Connect the outlet of the nitrogen cylinder to a multi-port pipe with at least three outlets. Connect each branch outlet of the multi-port pipe to a small flow meter. Connect the outlet of the small flow meter to a screw-type vaporization bottle in a set of measurement on the corresponding route.

[0021] S8. Adjust the temperature of the cooling and heating instrument (3) to 10℃, open the outlet control valve of the nitrogen cylinder, and then adjust the pressure to a suitable range through the pressure stabilizing device. Adjust the knob of the small flow meter so that the bubbles in each absorption bottle emerge evenly at a rate of 2 per second. The flow meter flow rate is controlled at the same value between parallel measurement samples.

[0022] S9. After the sample in the screw-top vaporization bottle has completely evaporated, immediately combine the absorbent liquids of the corresponding samples in each test group, place them in beakers, add 3 drops of 2,4-dinitrophenol indicator solution, and neutralize with ammonia water until yellow, which is the endpoint.

[0023] S10. Place the beaker from step S9 above in the heating zone of the refrigeration and heating apparatus and evaporate until 20 mL of solution remains. Then, measure the absorbance of the solution according to the standard working curve preparation process and find out the corresponding chloride ion content from the working curve.

[0024] Preferably, in the above-mentioned multi-stage simultaneous determination method for determining the chloride content of dinitrogen tetroxide, the ultrapure water machine in step S1 adopts reverse osmosis membrane technology, and the chlorine-free distilled water produced meets the requirements of grade III water.

[0025] Preferably, in the above-described multi-stage synchronous determination method for determining the content of dinitrogen tetroxide chloride, it is ensured that the nitrogen cylinder in step S7 is filled with sufficient nitrogen, so that its maximum pressure can reach 15 MPa for long-term use, and the nitrogen content by volume fraction is at least 99.99%.

[0026] Preferably, in the above-described multi-stage synchronous determination method for determining the chloride content of dinitrogen tetroxide, the nitrogen pressure stabilizing device is connected between the outlet of the nitrogen cylinder and the inlet of the multi-stage tube, and the outlet of the nitrogen cylinder is provided with a two-stage pressure reducer for coarsely controlling the flow rate of the nitrogen cylinder.

[0027] Preferably, in the above-described multi-stage synchronous determination method for determining the content of dinitrogen tetroxide chloride, the flow rate range of the small flow meter is controlled within 2.5–25 mL / min.

[0028] Preferably, in the above-described multi-stage simultaneous determination method for determining the chloride content of dinitrogen tetroxide, in step S5, when introducing the dinitrogen tetroxide sample from the sampling bottle into the screw-top vaporization bottle, the process should be completed as quickly as possible using standardized operating procedures to avoid changes in the quality of the screw-top vaporization bottle due to temperature rise.

[0029] Preferably, in the above-described multi-stage simultaneous determination method for determining the chloride content of dinitrogen tetroxide, the screw-top vaporization bottle includes a glass bottle body with a screw cap and a polytetrafluoroethylene (PTFE) cap threaded onto the screw cap of the glass bottle body. The glass bottle body is provided with graduation lines. A slow-flowing glass tube with its upper end closed is sealed through the middle of the cap. An inlet port is formed on one side of the slow-flowing glass tube, and an outlet port communicating with the slow-flowing glass tube is formed on the other side. A nitrogen purging pipe extending to the bottom of the bottle is integrally formed on the inlet port within the glass bottle body. Both the inlet port and the outlet port are provided with PTFE stopcock valves.

[0030] Preferably, in the above-described multi-stage simultaneous determination method for determining the chloride content of dinitrogen tetroxide, the refrigeration and heating instrument includes a sample cooler and an absorbent heater assembled separately. The sample cooler includes an assembled housing and a housing base. The upper surface of the housing is formed with an installation port, and a cold groove is fixed on the installation port. The cold groove contains, from top to bottom, a tightly fitted refrigeration tray, a cold plate, a semiconductor refrigeration chip, and heat dissipation fins. The cold end of the semiconductor refrigeration chip is tightly fitted with the lower surface of the cold plate, and the hot end of the semiconductor refrigeration chip is tightly fitted with the upper surface of the heat dissipation fins. The refrigeration tray is formed with a refrigeration groove for fixing the screw-top vaporization bottle. The housing contains a heat insulation plate that divides the internal space of the housing into an outer cavity and an inner cavity. The housing base is provided with a horizontal power supply cover and a vertical fixing frame. A circuit control board is fixed on the outer side of the vertical fixing frame. The horizontal power supply cover contains a refrigeration power supply that is electrically connected to the circuit control board and the semiconductor refrigeration chip.

[0031] Preferably, in the above-described multi-stage simultaneous determination method for determining the chloride content of dinitrogen tetroxide, the absorbent heater includes a housing with an open outer end, the outer end of which is connected to the inner end of the casing. The housing is provided with an electric heating plate and an array of fixed slots. The fixed slots are used to fix the absorption bottle. The electric heating plate is used to heat the beaker containing the sample absorbent liquid from the same determination group in step S10. The housing is equipped with a heating power supply at a position corresponding to the electric heating plate, and the heating power supply is connected to a heating control switch.

[0032] Preferably, in the above-described multi-stage simultaneous determination method for determining the content of dinitrogen tetroxide chloride, the cold end cooling temperature of the semiconductor refrigeration chip is 10°C.

[0033] The beneficial effects of this invention are as follows: The multi-parallel synchronous determination method of this invention has the advantages of good data reproducibility, short testing time, and accurate chloride content determination data by carrying out multiple parallel determinations in the same time period. By fixing the screw-top vaporization bottle and absorption bottle in each determination group through a cooling and heating device, the connection and arrangement of pipelines can be facilitated, and the bottles can be prevented from tipping over during pipeline connection operations. At the same time, the screw-top vaporization bottle can be kept at a constant temperature of 10°C, and the final sample absorption liquid can be heated and evaporated. All testing operations do not need to be transferred between multiple platforms, further improving the parallelism of determinations between different samples of the same sample. Attached Figure Description

[0034] Figure 1 This is a flowchart of the present invention;

[0035] Figure 2 This is a structural diagram of the screw-top vaporization bottle described in this invention;

[0036] Figure 3 This is a pipeline layout diagram of the triple measurement group in one embodiment of the present invention;

[0037] Figure 4 This is a structural diagram of the absorption bottle described in this invention;

[0038] Figure 5 This is a perspective view of the refrigeration and heating device described in this invention;

[0039] Figure 6 This is a diagram showing the internal structure of the refrigeration and heating device described in this invention.

[0040] Figure 7 This is a perspective view of the housing base described in this invention;

[0041] Figure 8 This is a pipeline layout diagram of the six-unit measurement group in one embodiment of the present invention. Detailed Implementation

[0042] To provide a further understanding of the present invention, the invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0043] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0044] Please see Figure 1 , Figure 2 and Figure 3 As shown in the figure, an embodiment of the present invention proposes a multi-stage simultaneous determination method for the content of dinitrogen tetroxide chloride, the method comprising the following steps:

[0045] Step S1: Prepare chlorine-free distilled water. Connect a distillation device to redistill the purified water produced by the ultrapure water machine and collect the obtained chlorine-free distilled water. The ultrapure water machine adopts reverse osmosis membrane technology, and the chlorine-free distilled water produced meets the requirements of grade III water.

[0046] Step S2: Using the chlorine-free distilled water obtained in Step S1, prepare the standard working solution and other relevant reagents to create a standard working curve. Specifically, the preparation of the standard working solution and the creation of the standard working curve are carried out using the prior art disclosed in GJB1964A-2015, and the specific process will not be described in detail here. The relevant reagents include 2,4-dinitrophenol indicator solution and ammonia water, as well as ferric ammonium sulfate solution, saturated mercuric thiocyanate ethanol solution, and chloride ion standard solution used to create the standard working curve. Specifically, the 2,4-dinitrophenol indicator solution is prepared according to HG / T4015, the ammonia water used meets the relevant requirements in GB / T631, and the ferric ammonium sulfate solution is prepared according to GB / T1279. The saturated mercuric thiocyanate ethanol solution is prepared by dissolving 100 mg of mercuric thiocyanate in 100 mL of 95% ethanol, filtering, and storing in the dark for later use. The chloride ion standard solution was prepared by dissolving 1.649 g of dried sodium chloride (meeting the requirements of GB1253) in the chlorine-free distilled water obtained in step S1, and diluting it to the mark in a 500 mL volumetric flask, resulting in a chloride ion concentration of 2.0 mg / mL. Then, 1.00 mL of the above chloride ion solution was transferred to a 200 mL volumetric flask and diluted to the mark with the chlorine-free distilled water obtained in step S1. The solution was then shaken well, resulting in a chloride ion concentration of 0.01 mg / mL.

[0047] Step S3: Prepare the sample vaporization container. Take the screw-top vaporization bottle 1, evacuate it, and place it in a 0℃ environment for sealed cooling for 3 hours, and keep it for later use. By pre-sealing and cooling the screw-top vaporization bottle 1 in a 0℃ environment, the bottle temperature of the screw-top vaporization bottle 1 can be maintained at a temperature significantly lower than the boiling point of dinitrogen tetroxide, preventing the volatilization of dinitrogen tetroxide during the subsequent sample injection process.

[0048] Step S4: Weigh the initial mass of the sample vaporization container, take out the screw-top vaporization bottle 1, and weigh its mass.

[0049] Step S5: Inject a quantitative amount of sample into the sample vaporization container. Connect the sampling bottle containing dinitrogen tetroxide and the screw-top vaporization bottle 1 using a PTFE tube. First, open the valve of the sampling bottle, then slowly open the inlet of the screw-top vaporization bottle 1, allowing the dinitrogen tetroxide sample to slowly flow into the screw-top vaporization bottle 1 until the specified volume mark is reached. Then, weigh the screw-top vaporization bottle 1 containing the sample again. For easy observation, the volume mark on the screw-top vaporization bottle 1 is marked with a raised graduation line at the 7 mL position, allowing the experimenter to better observe the injection endpoint when injecting a quantitative amount of sample into the screw-top vaporization bottle 1. Weigh 10g of sample. Traditional sampling methods use the mass difference method to control the sampling value. However, using mass weighing is not easy to control precisely, not only due to the problem of display fluctuations on the electronic scale, but also due to sample vaporization leakage, which affects the continuity and accuracy of subsequent chloride content determination. Specifically, at 20°C, the density of dinitrogen tetroxide is 1.446 g / mL. Assuming a mass of 10 g for the oxidized dinitrogen tetroxide sample, the sample volume of dinitrogen tetroxide can be calculated to be approximately 7 mL according to the density calculation formula.

[0050] Step S6: Construct a multi-unit measurement group. Connect the screw-top vaporization bottle 1 from step S5 in series with two absorption bottles 2, each containing 40 mL of chlorine-free distilled water prepared in step S1, to form a multi-unit measurement group 10. This multi-unit measurement group 10 is used to measure one sample. Specifically, as shown... Figure 3 As shown, the measurement group 10 is arranged in at least three units, such as... Figure 3 As shown in "A, B, C", each measurement group 10 is placed on the cooling and heating apparatus 3. This apparatus 3 serves two purposes: firstly, it provides fixation for the screw-cap vaporization bottle 1 and the absorption bottle 2, ensuring that the screw-cap vaporization bottle-absorption bottle-absorption bottle sequence of each measurement group 10 is on a straight path, facilitating subsequent pipeline connections. Secondly, the apparatus 3 provides a constant temperature of 10°C for the screw-cap vaporization bottle 1, preventing excessively high sample temperatures that could affect the evaporation rate and maintaining a stable evaporation state. Simultaneously, the apparatus 3 also heats the subsequent sample absorption liquid, allowing all analytical operations to be completed on the same platform.

[0051] Step S7: Connect the nitrogen purging line, such as... Figure 3 As shown, the outlet of the nitrogen cylinder 5 is connected to a multi-pipe 4 with at least three outlets. Each branch outlet of the multi-pipe 4 is connected to a small flow meter 6. The outlet of the small flow meter 6 is connected to a screw-top vaporization bottle 1 in a measurement group 10 on the corresponding route.

[0052] Step S8: Perform synchronous nitrogen purging. Adjust the temperature of the cooling and heating instrument 3 to 10℃, open the outlet control valve of the nitrogen cylinder 5, and then adjust the pressure to a suitable range using the nitrogen pressure stabilizing device 7. Adjust the knob of the small flow meter 6 to ensure that bubbles in each absorption bottle 2 emerge uniformly at a rate of 2 per second, purging the sample in the screw-top vaporization bottle 1 of each test group 10 with nitrogen. For the three sets of samples being measured in parallel, the flow rate of the small flow meter 6 on each test group 10 is controlled at the same value. By controlling the nitrogen purging speed using the small flow meter 6, the smooth purging of the sample in the screw-top vaporization bottle 1 with nitrogen can be better controlled.

[0053] Step S9: Combining and titrating the absorption solutions. After the sample in the screw-top vaporization bottle 1 has completely evaporated, immediately combine the absorption solutions of the corresponding samples in each set of determinations 10, place them in beakers, add 3 drops of 2,4-dinitrophenol indicator solution, and neutralize with ammonia water until the solution turns yellow, which is the endpoint.

[0054] Step S10: Measure absorbance and chloride ion content. Place the beaker from step S9 above in the heating zone of the refrigeration and heating instrument 3 to evaporate until 20 mL of solution remains. Then, measure the absorbance of the solution according to the standard working curve preparation process, and find the corresponding chloride ion content from the working curve.

[0055] Furthermore, in a preferred embodiment of the present invention, it is necessary to ensure that the nitrogen cylinder 5 in step S7 has sufficient nitrogen so that its maximum pressure can reach 15 MPa, which is convenient for long-term use, so as to complete the gas consumption time required for at least the parallel determination of three sets of samples of one sample, and the nitrogen content by volume fraction is at least 99.99%.

[0056] Furthermore, in a preferred embodiment of the present invention, such as Figure 3 As shown, to ensure a stable gas supply to the pipeline, the nitrogen pressure stabilizing device 7 is connected between the outlet of the nitrogen cylinder 5 and the inlet of the multi-connector 4. The appropriate gas supply pressure can be adjusted according to the pipeline composition and the number of test samples. To further increase the gas supply flow rate, a two-stage pressure reducer (not shown in the figure) is also connected to the outlet of the nitrogen cylinder 5. The two-stage pressure reducer can roughly control the gas flow rate of the nitrogen cylinder 5.

[0057] Furthermore, in a preferred embodiment of the present invention, the flow rate range of the small flow meter 6 is controlled within 2.5–25 mL / min. In step S5, when introducing the nitrogen tetroxide sample from the sampling bottle into the screw-top vaporization bottle 1, the process should be completed as quickly as possible using standardized operating procedures to avoid gas leakage and quality changes caused by temperature rise in the screw-top vaporization bottle 1.

[0058] Furthermore, in a preferred embodiment of the present invention, such as Figure 2As shown, the screw-top vaporization bottle 1 includes a glass bottle body 11 with a screw cap and a polytetrafluoroethylene (PTFE) cap 12 threaded onto the screw cap of the glass bottle body 11. Specifically, the glass bottle body 11 has graduation lines, with raised graduation lines at the 7mL graduation positions for easy observation by the experimenter. A slow-flow glass tube 13, sealed at the top, is passed through the center of the cap 12. One side of the slow-flow glass tube 13 has an inlet port 131, and the other side has an outlet port 132 communicating with the slow-flow glass tube 13. Specifically, the inlet port 131 has a nitrogen purge tube 1311 integrally formed inside the glass bottle body 11, extending to the bottom of the bottle. To control the opening and closing of the inlet and outlet, both the inlet port 131 and the outlet port 132 are equipped with PTFE stopcock valves 14. The stopcock valve 14 on the screw-top vaporization bottle 1 uses a stopcock valve body with a through hole as the opening and closing element. When the through hole is facing the direction of the air inlet pipe, fluid can pass through the stopcock valve body. As a preferred embodiment, the air inlet pipe 131, the air outlet pipe 132, and the slow-flow glass tube 13 are integrally formed. The bottom of the glass bottle 11 is a round-mouth bottom, and the volume of the glass bottle 11 is 20-30 mL. Specifically, in step S5, the sampling bottle containing dinitrogen tetroxide and the screw-top vaporization bottle 1 are connected through a polytetrafluoroethylene tube. First, the stopcock valve 14 on the air outlet pipe 132 of the screw-top vaporization bottle 1 is closed, the sampling bottle valve is opened, and then the stopcock valve 14 on the air inlet pipe 131 of the screw-top vaporization bottle 1 is slowly opened, that is, the air inlet of the screw-top vaporization bottle 1 is opened, so that the dinitrogen tetroxide sample slowly flows into the screw-top vaporization bottle 1. Once the specified volume mark is reached, close the stopcock valve 14 on the intake port pipe 131.

[0059] Furthermore, in a preferred embodiment of the present invention, such as Figure 4 As shown, the structure of absorption bottle 2 is similar to that of screw-top vaporization bottle 1, including a glass absorption bottle body 21, a polytetrafluoroethylene (PTFE) absorption cap 22 connected to the glass absorption bottle body 21, and an inlet pipe 23 and an outlet pipe 24 connecting the glass absorption bottle body 21 via the PTFE absorption cap 22. The lower end of the inlet pipe 23 is close to the bottom of the bottle, and the lower end of the outlet pipe 24 is close to the bottle opening. To maintain a high absorption rate, the solution level should not be too low, and the volume of the glass absorption bottle body 21 is 50–60 mL.

[0060] Furthermore, in a preferred embodiment of the present invention, such as Figure 5 As shown, the refrigeration and heating apparatus 3 includes a sample cooler 31 and an absorbent heater 32, which are assembled separately. The sample cooler 31 is used to fix the screw-top vaporization bottle 1 and provide constant temperature cooling at 10°C. The absorbent heater 32 is used to fix the absorption bottle 2 and heat the absorbent after the sample in the screw-top vaporization bottle 1 has been vaporized. Specifically, as shown... Figure 5As shown, the sample cooler 31 includes an assembled housing 311 and a housing base 312. Specifically, the upper surface of the housing 311 has a mounting opening 3111, and a cold groove 313 is fixed on the mounting opening 3111. The cold groove 313 contains, from top to bottom, a tightly fitted cooling tray 314, a cold plate 315, a thermoelectric cooler 316, and heat dissipation fins 317. The cold end of the thermoelectric cooler 316 is in close contact with the lower surface of the cold plate 315, and the hot end of the thermoelectric cooler 316 is in close contact with the upper surface of the heat dissipation fins 317. In a preferred embodiment of the invention, the cooling temperature of the cold end of the thermoelectric cooler 316 is 10°C. The refrigeration tray 314 has a refrigeration groove 3131 formed on it for fixing the screw-top vaporization bottle 1. The groove edge of the refrigeration groove 3131 is provided with three elastically deformable clamping springs 33, evenly spaced in a ring along the groove edge. The clamping springs 33 not only fix the bottom of the screw-top vaporization bottle 1 in the refrigeration groove 3131, but also, through contact with the glass bottle body 11, better cool the screw-top vaporization bottle 1. Figure 6 As shown, the housing 311 has a heat insulation plate 3114 formed inside, dividing the internal space of the housing into an outer cavity 3112 and an inner cavity 3113. The housing base 312 is equipped with a horizontal power supply cover 318 and a vertical mounting bracket 3121. A circuit control board 319 is fixed to the outer side of the vertical mounting bracket 3121. The horizontal power supply cover 318 contains a cooling power supply electrically connected to the circuit control board 319 and the semiconductor cooling chip 316. After the housing 311 and housing base 312 are assembled and fixed, the heat insulation plate 3114 separates the horizontal power supply cover 318 and the vertical mounting bracket 3121 into two different spaces, so that the circuit control board 319 corresponds to the outer cavity 3112, and the cooling power supply corresponds to the inner cavity 3113, thus preventing the heat emitted by the heat dissipation fins 317 from adversely affecting the circuit control board 319. The horizontal power supply cover 318 is made of heat-insulating material and is horizontally positioned at the bottom of the inner cavity 3113. This prevents the heat dissipation fins 317 from concentrating on the cooling power supply. The housing 311 also has a heat dissipation vent (not shown in the figure) on the left side wall corresponding to the inner cavity 3113, which connects to the outside. An exhaust fan is installed inside the heat dissipation vent to dissipate the heat from the inner cavity 3113. To further prevent heat from entering the outer cavity 3112 from the inner cavity 3113, the housing base 312 has a sealing slot 3122 located between the horizontal power supply cover 318 and the vertical mounting bracket 3121. The lower edge of the heat insulation plate 3114 is adapted to the sealing slot 3122. When the housing 311 and the housing base 312 are assembled and connected, the lower edge of the heat insulation plate 3114 is inserted into the sealing slot 3122 to isolate the inner cavity 3113 from the outer cavity 3112.

[0061] Furthermore, in a preferred embodiment of the present invention, such as Figure 7As shown, the absorbent heater 32 includes a housing with an open outer end, the outer end of which is fitted to the inner end of the housing 311. Specifically, the housing is provided with an electric heating plate 322 and an array of fixing grooves 321. The fixing grooves 321 are used to fix the absorbent bottle 2. To better fix the absorbent bottle 2, the groove edge of the fixing groove 321 is provided with elastically deformable clamping springs 34. Three clamping springs 34 are evenly spaced and arranged in a ring along the groove edge of the fixing groove 321. The structure of the clamping springs 34 is the same as that of the clamping springs 33. The electric heating plate 322 is used to heat the beaker containing the sample absorbent liquid from the same determination group 10 in step S10, i.e. Figure 2 In the "A" combination assay, the absorbent solutions from both absorption bottles 2 are combined into one beaker A; in the "B" combination assay, the absorbent solutions from both absorption bottles 2 are combined into one beaker B; and in the "C" combination assay, the absorbent solutions from both absorption bottles 2 are combined into one beaker C. Then, beakers A, B, and C are heated separately until the remaining absorbent solution is 20 mL. The absorbance of the solution is then measured according to the standard working curve preparation process, and the corresponding chloride ion content is determined from the working curve. Specifically, as follows... Figure 5 As shown, a heating power supply 324 is provided inside the housing at the position corresponding to the electric heating plate 322, and the heating power supply 324 is connected to a heating control switch 325.

[0062] As some other embodiments of the present invention, such as Figure 8 As shown, a six-unit measurement group can also be set up, including two multi-unit pipes 4 with three air outlets each and one two-part pipe 41 with two air outlets. The multi-unit pipe 4 has one air inlet pipe and three air outlet branches, and the two-part pipe 41 has one air inlet pipe and two air outlet branches. Specifically, the air inlet pipes of the two multi-unit pipes 4 are respectively connected to the two air outlet branches of the two-part pipe 41, the three air outlet branches of one multi-unit pipe 4 are respectively connected to one measurement group 10, and one multi-unit pipe 4 corresponds to three measurement groups 10. Through this six-unit measurement group, the measurement of six groups of samples of two samples can be completed simultaneously and in parallel.

[0063] Specifically, in a preferred embodiment of the present invention, the linear correlation of the standard working curve prepared with the relevant solution made with chlorine-free distilled water can reach up to 0.9994, and the standard working curve passes through the origin, which is much better than the standard working curve obtained with undistilled ultrapure water, avoiding the situation where the standard working curve shifts upward as a whole and does not pass through the origin.

[0064] Furthermore, in a preferred embodiment of the present invention, in order to shorten the experimental cycle and conduct multiple parallel determinations within the same time period, while preventing the sample temperature from being too high and affecting the evaporation rate, the screw-top vaporization bottle 1 is placed in the cooling bath 3131 to provide it with constant temperature cooling at 10°C, which can keep the sample in a stable volatilization state. The gas flow rate at the inlet of the screw-top vaporization bottle 1 is further adjusted by a small flow meter 6 to ensure that the inlet pressure is consistent between parallel determinations. With the above improvements, the results of the 6 repeated tests before the improvement and the data of the 6 parallel experiments conducted at the same time after the improvement are compared, as shown in Tables 1 and 2.

[0065] Table 1

[0066]

[0067] Table 2

[0068]

[0069]

[0070] As can be seen from Tables 1 and 2, although the maximum range before the improvement met the requirement of not exceeding 0.004%, the results of the parallel determination experiment were not ideal. This can be seen from the relative standard deviation results, which reached 10.29%. This indicates that the reproducibility of the experimental data of the original method is poor, and only data that meets the requirements can be selected from multiple experimental data. This method is not feasible and greatly reduces the efficiency of the test.

[0071] The improved method has significantly smaller maximum range and relative standard deviation, and the experimental data meets the testing requirements. Even with such low chloride content, it still satisfactorily meets the requirements for parallel determination results. While the original method appears fine in terms of data range alone, it would struggle to meet the requirements under conditions of high chloride content.

[0072] Furthermore, analysis of the testing time before and after the improvement shows that the total time for 6 repeatable experiments was 24 hours, while the time for the improved test was reduced to 4 hours, significantly shortening the testing cycle. In cases with a large number of samples, simply increasing the number of branches in the tubing, i.e., the number of test groups 10, can simultaneously meet the testing requirements, enabling rapid determination of various hypochlorite contents.

[0073] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A multi-link synchronous determination method for determining the content of nitrogen tetroxide chloride, characterized in that: Includes steps: S1. Connect a distillation device to redistill the pure water produced by the ultrapure water machine, and collect the obtained chlorine-free distilled water; S2. Prepare a standard working solution and other relevant pharmaceutical reagents using the chlorine-free distilled water prepared in step S1 to prepare a standard working curve; S3, take the screw-cap gasification bottle (1), evacuate it, seal it and cool it at 0°C for 3 hours, and set it aside for later use; S4, taking out the screw-cap gasification bottle (1) and weighing its mass; S5. Connect the sampling bottle containing dinitrogen tetroxide and the screw-capped gasification bottle (1) through a polytetrafluoroethylene tube, first open the valve of the sampling bottle, then slowly open the air inlet of the screw-capped gasification bottle (1), so that the dinitrogen tetroxide sample slowly flows into the screw-capped gasification bottle (1) until it reaches the specified volume scale line, and then weigh the mass of the screw-capped gasification bottle (1) containing the sample again; S6, connecting the screw-capped gasification bottle (1) in step S5 in series with two absorption bottles (2) pre-filled with 40 mL of chlorine-free distilled water to form a measurement group (10), wherein the measurement group (10) is arranged in at least three groups and is placed on a cooling and heating device (3); S7, connecting the gas outlet of the nitrogen bottle (5) to a multi-joint pipe (4) having at least three gas outlets, each branch gas outlet of the multi-joint pipe (4) is connected to a small flow meter (6), and the outlet end of the small flow meter (6) is connected to a screw-mouth gasification bottle (1) in a measurement group (10) on a corresponding route; S8, adjust the temperature of the refrigeration and heating device (3) to 10°C, open the outlet control valve of the nitrogen bottle (5), and then adjust the pressure to a suitable range through the nitrogen pressure stabilizing device (7), and adjust the knob of the small flow meter (6) so that the bubbles in each absorption bottle (2) emerge evenly at a rate of 2 bubbles per second, and control the flow rate of the flow meter between parallel measurement samples to the same value; S9. After the sample in the screw-capped vaporizing bottle (1) is completely volatilized, immediately combine the absorption liquid of the corresponding sample in each joint determination group (10), place them in a beaker, add 3 drops of 2,4-dinitrophenol indicator solution, and neutralize with ammonia water until the solution turns yellow, which is the end point; S10, placing the beaker in the above step S9 in the heating zone of the refrigeration and heating device (3) to evaporate until the solution remains 20 mL, then measuring the absorbance of the solution according to the standard working curve preparation process, and finding the corresponding chloride ion content from the working curve.

2. The multi-link synchronous determination method for determining the content of nitrogen tetroxide chloride according to claim 1, characterized in that: The ultrapure water machine in step S1 adopts reverse osmosis membrane technology, and the chlorine-free distilled water produced meets the requirements of grade tertiary water.

3. The multi-link synchronous determination method for determining the content of nitrogen tetroxide chloride according to claim 1, characterized in that: Ensure that the nitrogen in the nitrogen bottle (5) in step S7 is sufficient so that its maximum pressure can reach 15 MPa, which is convenient for long-term use, and the nitrogen content is at least 99.99% by volume.

4. The multi-link synchronous determination method for determining the content of nitrogen tetroxide chloride according to claim 1, characterized in that: The nitrogen pressure stabilizing device (7) is connected between the gas outlet of the nitrogen bottle (5) and the gas inlet of the multi-connected pipe (4), and the gas outlet end of the nitrogen bottle (5) is provided with a two-stage pressure reducer for roughly controlling the gas outlet flow rate of the nitrogen bottle (5).

5. The multi-link synchronous determination method for determining the content of nitrogen tetroxide chloride according to claim 1, characterized in that: The flow rate range of the small flow meter (6) is controlled within the range of 2.5 to 25 mL / min.

6. The multi-link synchronous determination method for determining the content of nitrogen tetroxide chloride according to claim 1, characterized in that: In step S5, when introducing the nitrogen tetroxide sample in the sampling bottle into the screw-capped gasification bottle (1), the process is completed as quickly as possible using standardized operating techniques to avoid changes in the quality of the screw-capped gasification bottle (1) due to temperature rise.

7. The multi-link synchronous determination method for determining the content of nitrogen tetroxide chloride according to claim 1, characterized in that: The screw-mouth gasification bottle (1) comprises a glass bottle body (11) with a screw mouth, and a polytetrafluoroethylene bottle cap (12) threadedly connected to the screw mouth of the glass bottle body (11); the glass bottle body (11) is provided with scale lines; a slow-flow glass tube (13) with a closed upper end is sealed and penetrated through the middle of the bottle cap (12); an air inlet interface pipe (131) is formed on one side of the slow-flow glass tube (13); and an air outlet pipe interface (132) connected to the slow-flow glass tube (13) is formed on the other side; the air inlet interface pipe (131) is integrally formed with a nitrogen purge pipe (1311) whose lower end extends to the bottom of the bottle in the glass bottle body (11); and polytetrafluoroethylene stopcocks (14) are provided on both the air inlet interface pipe (131) and the air outlet pipe interface (132).

8. The multi-link synchronous determination method for determining the content of nitrogen tetroxide chloride according to claim 1, characterized in that: The refrigeration and heating device (3) comprises a sample refrigerator (31) and an absorption liquid heater (32) which are assembled separately. The sample refrigerator (31) comprises an assembled casing (311) and a casing base (312). The upper surface of the casing (311) is formed with a mounting opening (3111). A cold groove (313) is fixed on the mounting opening (3111). The cold groove (313) is provided with a tightly fitting refrigeration tray (314), a cold plate (315), a semiconductor refrigeration sheet (316) and a heat dissipation fin (317) from top to bottom. The cold end of the semiconductor refrigeration sheet (316) is tightly fitted with the lower surface of the cold plate (315). The hot end is tightly fitted with the upper surface of the heat dissipation fin (317), the refrigeration tray (314) is formed with a refrigeration groove (3131) for fixing the screw-capped gasification bottle (1), the casing (311) is formed with a heat insulation plate (3114) for dividing the internal space of the casing into an outer cavity (3112) and an inner cavity (3113), the casing base (312) is provided with a horizontal power supply cover (318) and a vertical fixing frame (3121), the outer side surface of the vertical fixing frame (3121) is fixed with a circuit control board (319), and the horizontal power supply cover (318) is provided with a refrigeration power supply electrically connected to the circuit control board (319) and the semiconductor refrigeration plate (316).

9. The multi-connected synchronous determination method for determining the content of nitrogen tetroxide chloride according to claim 8, characterized in that: The absorption liquid heater (32) comprises a shell with an open outer end, the outer end of the shell is butt-jointed with the inner end of the casing (311), the shell is provided with an electric heating plate (322) and array-distributed fixing grooves (321), the fixing grooves (321) are used to fix the absorption bottle (2), the electric heating plate (322) is used to heat the beaker of the sample absorption liquid in the same joint determination group (10) in step S10, and a heating power supply (324) is provided inside the shell at a position corresponding to the electric heating plate (322), and the heating power supply (324) is connected to a heating control switch (325).

10. The multi-connected synchronous determination method for determining the content of nitrogen tetroxide chloride according to claim 8, characterized in that: The cold end refrigeration temperature of the semiconductor refrigeration sheet (316) is 10°C.

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