System for measuring polyphosphate content in fertilizer

Abstract

The utility model relates to a system for measuring the content of polyphosphate in a fertilizer. Comprising an elution unit and a compressed gas driving unit for controlling the elution unit, the elution unit comprises a plurality of pre-elution pieces which are connected in parallel, the tail ends of the pre-elution pieces are respectively connected with inlets of the ion exchange columns, and the tail ends of the ion exchange columns are connected with the collection part; the collection part comprises collection bottles in one-to-one correspondence with the pre-elution pieces; the compressed gas driving unit comprises a compressed gas part; the compressed gas part is respectively connected with a pneumatic valve assembly in the pre-elution piece and a pneumatic valve at the front part of the collection bottle through a gas compression pipeline; the device has the characteristics of reducing the requirement on the experience of operators, reducing the labor intensity, avoiding misoperation to the greatest extent, improving the detection efficiency and improving the accuracy of a detection result.

Description

Technical Field

[0001] The utility model relates to the technical field of fertilizer phosphorus nutrient form detection, in particular to a system for measuring the polyphosphate content in fertilizer. Background Art

[0002] Phosphorus is one of the key elements necessary for plant growth, and is also one of the important elements that constitute fertilizers. Furthermore, polyphosphate has the characteristics of slow release and chelation compared to orthophosphate. Based on this, detecting the polyphosphate content in fertilizers can effectively evaluate the performance of fertilizers. There are currently three main technical means for detecting the polyphosphate content in fertilizers, namely nuclear magnetic resonance, ion chromatography, and ion exchange column method. The first two methods require special equipment and instruments, which are expensive. It is a waste of resources to only use them to measure polyphosphate indicators in fertilizers and are not suitable for promotion. The third method, the ion exchange column method, currently relies mainly on manual control of flow rate and switching of eluent. The above process has very high requirements for the experience of the operator, and the elution cycle is long and the detection efficiency is low. The operational differences between different operators will lead to large deviations in the test results. Utility Model Content

[0003] The purpose of the utility model is to provide a system for measuring the polyphosphate content in fertilizers, so as to overcome the defects in the prior art.

[0004] To achieve the above objectives, the present invention provides the following technical solutions:

[0005] A system for determining the polyphosphate content in fertilizers, comprising an elution unit and a compressed gas drive unit for controlling the elution unit; the elution unit comprises a plurality of parallel pre-elution components, the ends of the pre-elution components being respectively connected to the inlets of ion exchange columns, the ends of the ion exchange columns being respectively connected to a collection section; the collection section comprises collection bottles corresponding one to one with the pre-elution components; and the compressed gas drive unit comprises a compressed gas section, which is respectively connected to a pneumatic valve assembly in the pre-elution component and a pneumatic valve at the front of the collection bottle via a gas compression pipeline.

[0006] The beneficial effects of the present invention are as follows: the elution unit established by a plurality of parallel pre-elution parts can classify and recover residual liquid and effective components; further, the valve in the pre-elution part is controlled by a compressed gas drive unit to achieve the characteristics of no need for operator monitoring all the time, easy adjustment of flow rate, and reduced labor intensity of detection; at the same time, it can ensure the stability of elution speed, reduce system fluctuations, reduce detection errors and improve detection accuracy.

[0007] Preferably, the pre-elution component includes a pear-shaped measuring bottle, the top of which is connected to the gas compression pipeline, a first tee is provided between the pear-shaped measuring bottle and the gas compression pipeline, and the third end of the first tee is used for a syringe filled with liquid phase; the outlet of the pear-shaped measuring bottle is provided with a pneumatic valve assembly, the pneumatic valve assembly includes a first piston valve and a breathable valve arranged in sequence, and the liquid phase outlet of the breathable valve is connected to the inlet of the ion exchange column 1; the pneumatic valve at the front of the collecting bottle is a second piston valve.

[0008] Preferably, the breathable valve includes a first cavity and a second cavity, and a hydrophobic breathable membrane is provided between the first cavity and the second cavity; a gas-liquid inlet is provided at the top of the first cavity, a liquid phase outlet is provided at the bottom of the first cavity 9, and a gas phase outlet is provided on the second cavity.

[0009] Preferably, the first piston valve and the second piston valve are both piston valves, the piston valve includes a piston cavity, the upper part of the piston cavity is provided with a liquid inlet, the piston cavity corresponding to the lower part of the liquid inlet is provided with a liquid outlet, and the two sides of the piston cavity are provided with a connecting end and a closing end, and the inside of the connecting end and the closing end is provided with a control rod running through the inside of the piston cavity, and the control rod is equipped with a piston member adapted to the inside of the piston cavity.

[0010] Preferably, the piston member includes a first silicone plug and a second silicone plug. When the piston valve is in a closed state, the first silicone plug is located between the liquid inlet and the liquid outlet, and the second silicone plug is in contact with the inner wall of the piston cavity on the connecting end side; when the piston valve is in a connecting state, the first silicone plug and the second silicone plug are located on both sides of the liquid inlet and the liquid outlet, and a micro exhaust hole is provided on the piston cavity on the side of the second silicone plug close to the connecting end.

[0011] Preferably, the gas phase outlet of the breathable valve is respectively connected to the closed end of the first piston valve and the closed end of the corresponding second piston valve, a second tee is provided between the gas phase outlet of the breathable valve and the closed end of the first piston valve, and the third end of the second tee is connected to the communicating end of the first piston valve in the adjacent pre-elution component; a third tee is provided between the gas phase outlet of the breathable valve and the closed end of the second piston valve, and the third end of the third tee is connected to the communicating end of the adjacent second piston valve.

[0012] Preferably, the compressed gas part includes an air compressor, which is connected to the first section of the gas compression pipeline through a pressure buffer chamber and a pressure control valve. The middle part of the gas compression pipeline is connected to the inlet of several pear-shaped measuring bottles of parallel pre-elution parts, and a third piston valve is provided at the end of the gas compression pipeline.

[0013] Preferably, the gas phase outlet of the breathable valve in the terminal pre-elution component is respectively connected to the communicating end of the third piston valve and the closing end of the corresponding second piston valve.

[0014] Preferably, the pre-elution parts are four groups, namely, a sample pear-shaped measuring bottle, a first eluent pear-shaped measuring bottle, a second eluent pear-shaped measuring bottle and a resin regeneration liquid pear-shaped measuring bottle, the pear-shaped measuring bottle inlets are connected, the sample pear-shaped measuring bottle is connected to the ion exchange column 1 through the corresponding first piston valve and the air valve, and the ion exchange column is connected to the first waste liquid collection bottle through the corresponding second piston valve; the first eluent pear-shaped measuring bottle is connected to the ion exchange column through the corresponding first piston valve and the air valve, and the ion exchange column is connected to the first sample collection bottle through the corresponding second piston valve; the second eluent pear-shaped measuring bottle is connected to the ion exchange column through the corresponding first piston valve and the air valve, and the ion exchange column is connected to the second sample collection bottle through the corresponding second piston valve; the resin regeneration liquid pear-shaped measuring bottle is connected to the ion exchange column through the corresponding first piston valve and the air valve, and the ion exchange column is connected to the second waste liquid collection bottle through the corresponding second piston valve; the gas phase outlet of the corresponding air valve in the sample pear-shaped measuring bottle The closed end of the first piston valve and the closed end of the second piston valve corresponding to the sample pear-shaped measuring bottle, and the connecting end and the connecting end of the first piston valve and the second piston valve corresponding to the first eluent pear-shaped measuring bottle are respectively connected; the gas phase outlet of the corresponding breathable valve in the first eluent pear-shaped measuring bottle is respectively connected to the closed end of the first piston valve and the closed end of the second piston valve corresponding to the first eluent pear-shaped measuring bottle, and the connecting end and the connecting end of the first piston valve and the second piston valve corresponding to the second eluent pear-shaped measuring bottle; the gas phase outlet of the corresponding breathable valve in the second eluent pear-shaped measuring bottle is respectively connected to the closed end of the first piston valve and the closed end of the second piston valve corresponding to the second eluent pear-shaped measuring bottle, and the connecting end and the connecting end of the first piston valve and the second piston valve corresponding to the resin regeneration liquid pear-shaped measuring bottle; the gas phase outlet of the corresponding breathable valve in the resin regeneration liquid pear-shaped measuring bottle is respectively connected to the closed end of the second piston valve and the connecting end of the third piston valve corresponding to the resin regeneration liquid pear-shaped measuring bottle; a buffer bin is correspondingly provided at the front of the closed end of the first piston valve.

[0015] A system for determining the polyphosphate content in fertilizers made in accordance with the above scheme, through the rearrangement of the elution unit, makes several pre-elution parts correspond one to one with the collection bottle in the collection part through the ion exchange column, thereby realizing the classified recovery of waste liquid and effective components. Furthermore, the utility model can stably provide a constant driving pressure through the compressed gas drive unit, and stably control the elution flow rate within the required range without the need for constant adjustment by personnel, thereby achieving the purpose of reducing the requirements for the operator's operating experience and improving the accuracy of the test results, and at the same time being able to control the characteristics of the relevant pneumatic valves; further, the process of the compressed gas drive unit controlling the relevant pneumatic valves in the utility model is the relevant control performed after the liquid phase in the corresponding pear-shaped measuring bottle is completed, which has the characteristics of further reducing the operator's operating experience and avoiding misoperation, while improving the accuracy of the test results; the breathable valve described in the utility model The pneumatic valve is composed of a first cavity, a second cavity and a hydrophobic breathable membrane. When liquid passes through, it is blocked by the hydrophobic breathable membrane to prevent the liquid from entering the second cavity from the first cavity. When the liquid enters the gas phase after passing through, the gas phase enters the second cavity through the hydrophobic breathable membrane to achieve the control of the action of the relevant pneumatic valve; the first cavity and the second cavity can use the same components to achieve the characteristics of easy processing and maintenance at low cost; the utility model is also provided with a piston valve, which is used in conjunction with the aforementioned breathable valve to realize the connection and disconnection of the piston valve when the liquid passes through. The above process can effectively reduce human operation, thereby avoiding misoperation and affecting the detection results; it has the characteristics of improving detection efficiency, reducing the requirements for operator experience, reducing labor intensity, avoiding misoperation to the greatest extent and improving the accuracy of detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural diagram of the present utility model.

[0017] Figure 2 This is a schematic structural diagram of the pre-washing component of the present invention.

[0018] Figure 3 It is a structural diagram of the collecting part of the utility model.

[0019] Figure 4 This is a structural diagram of the ventilation valve of the utility model.

[0020] Figure 5 This is a structural diagram of the utility model when the piston valve is disconnected.

[0021] Figure 6 This is a structural diagram of the utility model when the piston valve is connected.

[0022] Figure: 1, ion exchange column; 2, collection bottle; 3, pear-shaped measuring bottle; 4, first three-way valve; 5, syringe; 6, first piston valve; 7, breathable valve; 8, second piston valve; 9, first cavity; 10, second cavity; 11, hydrophobic breathable membrane; 12, gas-liquid inlet; 13, liquid phase outlet; 14, gas phase outlet; 15, piston cavity; 16, liquid inlet; 17, liquid outlet; 18, connecting end; 19, closing end; 20, control rod; 21, first silicone plug; 22, second silicone plug Rubber stopper; 23. Micro vent hole; 24. Second three-way valve; 25. Third three-way valve; 26. Air compressor; 27. Pressure buffer chamber; 28. Pressure control valve; 29. Third piston valve; 30. Pear-shaped measuring bottle for sample; 31. Pear-shaped measuring bottle for first eluent; 32. Pear-shaped measuring bottle for second eluent; 33. Pear-shaped measuring bottle for resin regeneration liquid; 34. First waste liquid collection bottle; 35. First sample collection bottle; 36. Second sample collection bottle; 37. Second waste liquid collection bottle; 38. Buffer chamber. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0024] Reference Figure 1-6As shown, a system for determining the polyphosphate content in fertilizers includes an elution unit and a compressed gas drive unit for controlling the elution unit; the elution unit includes a plurality of parallel pre-elution components, the ends of the pre-elution components are respectively connected to the inlet of an ion exchange column 1, and the ends of the ion exchange column 1 are connected to a collecting part; the collecting part includes a collecting bottle 2 corresponding to each pre-elution component; the compressed gas drive unit includes a compressed gas part, which is respectively connected to the pneumatic valve assembly in the pre-elution component and the pneumatic valve in front of the collecting bottle 2 through a gas compression pipeline. The elution unit described in the present invention is composed of several pre-elution parts connected in parallel, and the several pre-elution parts are respectively matched one by one with the collecting bottles 2 in the collecting part through the ion exchange column 1. The above method can realize the separation of waste liquid and effective combination, and avoid the influence of misoperation on the detection results. The present invention is also provided with a compressed gas drive unit. The compressed gas in the compressed gas drive unit can stabilize the flow rate of the corresponding liquid phase by passing through the pre-elution parts, thereby achieving the characteristic of improving the detection efficiency. At the same time, it can realize the control of the pneumatic valve assembly and the pneumatic valve after the liquid phase flows out of the pre-elution parts, so as to achieve the characteristic of reducing the difficulty of operation for the operator; the pre-elution parts described in the present invention can be set according to actual conditions, that is, three groups of pre-elution parts in parallel, four groups of pre-elution parts in parallel, five groups of pre-elution parts in parallel, six groups of pre-elution parts in parallel or seven groups of pre-elution parts in parallel, wherein the collecting bottles in the collecting part 2 has a one-to-one correspondence with the aforementioned pre-elution parts. For example, when three groups of pre-elution parts are connected in parallel, there are three collecting bottles 2 in the collecting part. The first pre-elution part can correspond to the first collecting bottle 2, the second pre-elution part can correspond to the second collecting bottle 2, and the third pre-elution part can correspond to the third collecting bottle 2. The above-mentioned first collecting bottle 2 is used to collect the liquid phase of the first pre-elution part passing through the ion exchange column 1, the second collecting bottle 2 is used to collect the liquid phase of the second pre-elution part passing through the ion exchange column 1, and the third collecting bottle 2 is used to collect the liquid phase of the third pre-elution part passing through the ion exchange column 1. Further, as mentioned above, the compressed gas drive unit described in the present invention not only participates in the control of the pneumatic valve assembly or the pneumatic valve, but can also use this as power to stabilize the flow rate of the liquid phase. Therefore, the compressed gas drive unit in the present invention controls the corresponding pneumatic valve assembly and pneumatic valve, which is not a traditional control form.

[0025] Furthermore, the pre-elution unit includes a pear-shaped measuring bottle 3, the top of which is connected to a compressed gas pipeline. A first tee 4 is provided between the pear-shaped measuring bottle 3 and the compressed gas pipeline. The third end of the first tee 4 is used to accommodate a syringe 5 for the liquid phase. A pneumatic valve assembly is provided at the outlet of the pear-shaped measuring bottle 3. The pneumatic valve assembly includes a first piston valve 6 and a breather valve 7, which are arranged in sequence. The liquid phase outlet of the breather valve 7 is connected to the inlet of the ion exchange column 1. The pneumatic valve at the front of the collection bottle 2 is a second piston valve 8. The pear-shaped measuring bottle 3 described in the present invention is not only used to store the relevant eluent but also to pass compressed air. This compressed air propels the eluent in the pear-shaped measuring bottle 3 steadily through subsequent devices and controls the corresponding pneumatic valves after the eluent is pushed.

[0026] Furthermore, the breathable valve 7 includes a first cavity 9 and a second cavity 10, with a hydrophobic breathable membrane 11 disposed between the first cavity 9 and the second cavity 10. A gas-liquid inlet 12 is disposed at the top of the first cavity 9, a liquid outlet 13 is disposed at the bottom of the first cavity 9, and a gas outlet 14 is disposed on the second cavity 10. The breathable valve 7 of the present invention is composed of the first cavity 9, the second cavity 10, and the hydrophobic breathable membrane 11. The hydrophobic breathable membrane 11 is capable of preventing water from passing through while allowing air to pass through. Based on this principle, the present invention can prevent the liquid phase of the first cavity 9 from entering the second cavity 10 when the liquid phase passes through, and allow the gas phase to enter the second cavity 10 from the first cavity 9 when the gas phase passes through, thereby achieving control of the piston valve. The above process can control the corresponding piston valve based on whether the spray liquid has completely passed through, thereby avoiding the occurrence of human error.

[0027] Furthermore, the first piston valve 6 and the second piston valve 8 are both piston valves, which include a piston cavity 15, a liquid inlet 16 being provided at the top of the piston cavity 15, a liquid outlet 17 being provided at the bottom of the corresponding piston cavity 15, a connecting end 18 and a closing end 19 being provided on both sides of the piston cavity 15, a control rod 20 being provided inside the connecting end 18 and the closing end 19 and penetrating the interior of the piston cavity 15, and a piston member being mounted on the control rod 20 and adapted to the interior of the piston cavity 15. The above arrangement enables compressed air to control the connection and disconnection of the piston valves through the connecting end 18 and the closing end 19, that is, when compressed air enters the connecting end 18, the control rod 20 is pushed to move, thereby connecting the liquid phase in the corresponding elution part, and when compressed air enters the closing end 19, the control rod 20 is pushed to move, thereby disconnecting the liquid phase in the corresponding elution part; the piston valve cooperates with the aforementioned breathable valve 7 to control the pneumatic valve assembly in the pre-elution part and the pneumatic valve in the collection bottle 2.

[0028] Furthermore, the piston member includes a first silicone plug 21 and a second silicone plug 22. When the piston valve is in the closed state, the first silicone plug 21 is positioned between the liquid inlet 16 and the liquid outlet 17, while the second silicone plug 22 abuts against the inner wall of the piston cavity 15 on the side of the connecting end 18. When the piston valve is in the connected state, the first and second silicone plugs 21 and 22 are positioned on either side of the liquid inlet 16 and the liquid outlet 17. A micro-vent hole 23 is formed in the piston cavity 15 on the side of the second silicone plug 22 near the connecting end 18. Compressed air acts on the end surface of the second silicone plug 22 through the connecting end 18 to connect the liquid inlet 16 and the liquid outlet 17. Compressed air acts on the end surface of the first silicone plug 21 through the closed end 19 to disconnect the liquid inlet 16 and the liquid outlet 17. The provision of the micro-vent hole 23 allows the piston valve to slowly release internal pressure through the micro-vent hole after it is opened by pressure, allowing the piston valve to close smoothly when the pressure on the other side increases.

[0029] Furthermore, the gas phase outlet of the breathable valve 7 is connected to the closed end of the first piston valve 6 and the closed end of the corresponding second piston valve 8, respectively. A second three-way valve 24 is provided between the gas phase outlet of the breathable valve 7 and the closed end of the first piston valve 6, and the third end of the second three-way valve 24 is connected to the connecting end 18 of the first piston valve 6 in the adjacent pre-elution unit. A third three-way valve 25 is provided between the gas phase outlet of the breathable valve 7 and the closed end of the second piston valve 8, and the third end of the third three-way valve 25 is connected to the connecting end 18 of the adjacent second piston valve 8. This arrangement can achieve the purpose of controlling the corresponding and adjacent first piston valve 6 and second piston valve 8 after the liquid phase passes through the breathable valve 7. The above process can better grasp the timing of pipeline switching and avoid the occurrence of erroneous operation.

[0030] Furthermore, the compressed gas section includes an air compressor 26, which is connected to the first section of a compressed gas pipeline via a pressure buffer chamber 27 and a pressure control valve 28. The middle section of the compressed gas pipeline is connected to the inlet of the pear-shaped measuring bottles 3 of several parallel pre-elution units. A third piston valve 29 is provided at the end of the compressed gas pipeline. The compressed gas section described in the present invention overlaps with the pre-elution unit via the compressed gas pipeline, enabling control of the pneumatic valve assembly while maintaining a stable eluent flow rate.

[0031] Furthermore, the gas phase outlet of the breathable valve 7 in the terminal pre-elution component is connected to the communicating end 18 of the third piston valve 29 and the closed end of the corresponding second piston valve 8 respectively.

[0032] Furthermore, the pre-elution parts are divided into four groups, namely, a sample pear-shaped measuring bottle 30, a first eluent pear-shaped measuring bottle 31, a second eluent pear-shaped measuring bottle 32 and a resin regeneration liquid pear-shaped measuring bottle 33. The inlets of the pear-shaped measuring bottles 3 are connected, the sample pear-shaped measuring bottle 30 is connected to the ion exchange column 1 through the corresponding first piston valve 6 and the air valve 7, and the ion exchange column 1 is connected to the first waste liquid collection bottle 34 through the corresponding second piston valve 8; the first eluent pear-shaped measuring bottle 31 is connected to the ion exchange column 1 through the corresponding first piston valve 6 and the air valve 7, and the ion exchange column 1 is connected to the first waste liquid collection bottle 34. The first sample collection bottle 35 is connected to the second piston valve 8; the second eluent pear-shaped measuring bottle 32 is connected to the ion exchange column 1 through the corresponding first piston valve 6 and the breathable valve 7, and the ion exchange column 1 is connected to the second sample collection bottle 36 through the corresponding second piston valve 8; the resin regeneration liquid pear-shaped measuring bottle 33 is connected to the ion exchange column 1 through the corresponding first piston valve 6 and the breathable valve 7, and the ion exchange column 1 is connected to the second waste liquid collection bottle 37 through the corresponding second piston valve 8; the gas phase outlet of the corresponding breathable valve 7 in the sample pear-shaped measuring bottle 30 is respectively connected to the first piston valve 6 and the breathable valve 7. The closed end of the first piston valve 6 and the closed end of the second piston valve 8 corresponding to the sample pear-shaped measuring bottle 30, and the connecting end 18 of the first piston valve 6 and the connecting end 18 of the second piston valve 8 corresponding to the first eluent pear-shaped measuring bottle 31; the gas phase outlet of the corresponding breathable valve 7 in the first eluent pear-shaped measuring bottle 31 is respectively connected to the closed end of the first piston valve 6 and the closed end of the second piston valve 8 corresponding to the first eluent pear-shaped measuring bottle 31, and the connecting end 18 of the corresponding first piston valve 6 and the connecting end 18 of the second piston valve 8 in the second eluent pear-shaped measuring bottle 32; the second eluent pear-shaped The gas phase outlet corresponding to the breathable valve 7 in the measuring bottle 32 is respectively connected to the closed end of the first piston valve 6 and the closed end of the second piston valve 8 in the second eluent pear-shaped measuring bottle 32, as well as the connecting end 18 of the first piston valve 6 and the connecting end 18 of the second piston valve 8 in the resin regeneration liquid pear-shaped measuring bottle 33. The gas phase outlet corresponding to the breathable valve 7 in the resin regeneration liquid pear-shaped measuring bottle 33 is respectively connected to the closed end of the second piston valve 8 and the connecting end 18 of the third piston valve 29 in the resin regeneration liquid pear-shaped measuring bottle 33. A buffer chamber 38 is provided in front of the closed end of the first piston valve 6. It should be noted that the present invention, by providing the buffer chamber 38 in conjunction with the aforementioned gas circuit control system, can achieve the final closure of the first piston valve 6, thereby ensuring that the corresponding valve in front of it completes its corresponding action smoothly and ensures the smooth flow of the process.

[0033] A method for measuring the polyphosphate content in fertilizer using a system comprising the following steps:

[0034] Step 1: Pour deionized water into the sample pear-shaped measuring bottle 30, inject the first eluent into the first eluent pear-shaped measuring bottle 31, inject the second eluent into the second eluent pear-shaped measuring bottle 32, and inject the resin regeneration liquid into the resin regeneration liquid pear-shaped measuring bottle 33;

[0035] Step 2: Turn on the air compressor 26 to increase the pressure in the pressure buffer chamber 27, and adjust the flow rate of the pear-shaped measuring bottle 3 to the collection bottle 2 through the pressure control valve 28 to stabilize the flow rate at 3.4-4.5 mL / min;

[0036] Step 3: Open the first piston valve 6 corresponding to the sample pear-shaped measuring bottle 30, and deionized water passes through the corresponding first piston valve 6 and the air valve 7. When the deionized water level drops to the first piston valve 6, the fertilizer solution to be measured is injected through the first three-way valve 4. When the fertilizer solution level to be measured drops to the air valve 7, the compressed gas enters the second cavity 10 through the hydrophobic breathable membrane 11 and is discharged from the gas phase outlet 14 in the second cavity 10. During the discharge process, the first piston valve 6 and the second piston valve 8 corresponding to the sample pear-shaped measuring bottle 30 are closed. Step 3: Open the first piston valve 6 corresponding to the sample pear-shaped measuring bottle 30, and the deionized water passes through the first piston valve 6 and the air valve 7. When the deionized water level drops to the first piston valve 6, the fertilizer solution to be measured is injected through the first three-way valve 4. When the fertilizer solution level to be measured drops to the air valve 7, the compressed gas enters the second cavity 10 through the hydrophobic breathable membrane 11 and is discharged from the gas phase outlet 14 in the second cavity 10. During the discharge process, the first piston valve 6 and the second piston valve 8 corresponding to the sample pear-shaped measuring bottle 30 are closed. The first piston valve 6 and the second piston valve 8 corresponding to the first eluent pear-shaped measuring bottle 31 are opened; a buffer chamber 38 is provided to achieve a slow pressure increase; when the second piston valve 8 is closed and the first piston valve 6 and the second piston valve 8 corresponding to the first eluent pear-shaped measuring bottle 31 are opened, the first piston valve 6 corresponding to the sample pear-shaped measuring bottle 30 is closed; during the above process, the waste liquid of the deionized water and the fertilizer solution to be measured after passing through the ion exchange column 1 respectively enters the first waste liquid collection bottle 34, and the phosphate and polyphosphate in the sample are adsorbed by the ion exchange column 1;

[0037] Step 4: After the valve adjustment in step 3 is completed, the first eluent passes through the corresponding first piston valve 6 and breathable valve 7. When the liquid level of the first eluent drops to the breathable valve 7, the compressed gas enters the second chamber 10 through the hydrophobic breathable membrane 11 and is discharged from the gas phase outlet 14 in the second chamber 10. During the discharge process, the first piston valve 6 and the second piston valve 8 corresponding to the first eluent pear-shaped measuring bottle 31 are closed, and the first piston valve 6 and the second piston valve 8 corresponding to the second eluent pear-shaped measuring bottle 32 are opened. The buffer chamber 38 is provided to achieve a slow increase in pressure. When the second piston valve 8 is closed and the first piston valve 6 and the second piston valve 8 corresponding to the second eluent pear-shaped measuring bottle 32 are opened, the first piston valve 6 corresponding to the first eluent pear-shaped measuring bottle 31 is closed. In the above process, component A of the first eluent after passing through the ion exchange column 1 enters the first sample collection bottle 35.

[0038] Step 5: After the valve adjustment in step 4 is completed, the second eluent passes through the corresponding first piston valve 6 and breathable valve 7. When the liquid level of the second eluent drops to the breathable valve 7, the compressed gas enters the second chamber 10 through the hydrophobic breathable membrane 11 and is discharged from the gas phase outlet 14 in the second chamber 10. During the discharge process, the first piston valve 6 and the second piston valve 8 corresponding to the second eluent pear-shaped measuring bottle 32 are closed, and the first piston valve 6 and the second piston valve 8 corresponding to the resin regeneration liquid pear-shaped measuring bottle 33 are opened. The buffer chamber 38 is provided to achieve a slow increase in pressure. When the second piston valve 8 is closed and the first piston valve 6 and the second piston valve 8 corresponding to the resin regeneration liquid pear-shaped measuring bottle 33 are opened, the first piston valve 6 corresponding to the second eluent pear-shaped measuring bottle 32 is closed. In the above process, component B of the second eluent after passing through the ion exchange column 1 enters the second sample collection bottle 36.

[0039] Step 6: After the valve adjustment in step 5 is completed, the resin regeneration liquid passes through the corresponding first piston valve 6 and breathable valve 7. When the liquid level of the resin regeneration liquid drops to the breathable valve 7, the compressed gas enters the second cavity 10 through the hydrophobic breathable membrane 11 and is discharged from the gas phase outlet 14 in the second cavity 10. During the discharge process, the second piston valve 8 corresponding to the pear-shaped measuring bottle 33 of the resin regeneration liquid is closed, and the third piston valve 29 is opened, and the entire system is emptied. In the above process, the waste liquid after the resin regeneration liquid passes through the ion exchange column 1 enters the second waste liquid collection bottle 37;

[0040] Step 7: Turn off the air compressor 26 and the pressure control valve 28 to shut down the entire system; remove the phosphorus content of each component according to B.2.2 Available phosphorus content in "HG / T5939-2021 Fertilizer Grade Ammonium Polyphosphate" and determine the phosphorus content.

[0041] Compared to the traditional ion exchange column method, the present invention reconstructs a system capable of automatically eluting and separating polyphosphate components with different polymerization degrees. The system provides stable elution power through a pressure buffer chamber, ensuring a stable elution speed, reducing system fluctuations, and lowering detection errors. Compared to conventional ion exchange columns, the system eliminates the need for operators to constantly monitor and adjust the flow rate, significantly reducing detection labor intensity. The system pressure is adjusted by a pressure control valve to precisely control the elution speed and improve detection accuracy. Furthermore, the system's elution drive unit and control unit share a compressed gas system, enabling linkage between the drive unit and the control unit without the use of sensors, forming a linkage system that automatically switches between different eluents. Compared to conventional ion exchange columns, manual eluent replacement is no longer required, significantly reducing detection labor intensity. Furthermore, since manual opening of the system to replace the eluent is avoided, the system's drive pressure is stabilized and flow rate adjustment is reduced. Automatic eluent switching eliminates the need for operators to constantly monitor the eluent level, avoiding test failures caused by air entering the ion exchange column due to untimely eluent replacement. The key feature of this linkage system lies in the linkage between the steam trap and the piston valve. Leveraging the material properties of the hydrophobic, breathable membrane, it achieves integrated level monitoring and pipeline switching, replacing traditional automation solutions with monitoring and control components such as level gauges and solenoid valves, enabling automatic pipeline switching. The linkage system utilizes readily available materials and a simple structure. The steam trap utilizes two identical cavities to squeeze the hydrophobic, breathable membrane. This simplicity reduces the complexity of custom component manufacturing and ensures high component versatility and interchangeability, facilitating overall system fabrication and maintenance. Furthermore, the integrated detection system significantly reduces operator monitoring and operation frequency, reducing labor intensity. It also prevents test failures caused by misoperation, improving labor efficiency and enhancing system stability and accuracy. The detection system can separate multiple polyphosphate components by replicating the basic unit, including orthophosphate and pyrophosphate. By adding additional units, orthophosphate, pyrophosphate, and tripolyphosphate can also be measured. The system can be adjusted to meet specific testing needs.

[0042] In order to explain the present invention more clearly, the following is a further description of the present invention in conjunction with specific embodiments. The specific embodiments are as follows:

[0043] Example 1

[0044] The sample fertilizer to be tested is prepared by mixing 15g of industrial monoammonium phosphate (phosphorus pentoxide content 61%), 20g of industrial potassium pyrophosphate (phosphorus pentoxide content 43%), 30g of agricultural urea (nitrogen content 46.2%), 20g of agricultural potassium sulfate (potassium oxide content 52%), and 15g of agricultural potassium chloride (potassium oxide content 60%). The above raw materials are then crushed to 60 mesh to prepare the sample fertilizer to be tested. The theoretical total phosphorus pentoxide content of the sample fertilizer to be tested is 17.8%, of which the phosphorus pentoxide content in the form of orthophosphate is 9.2% and the phosphorus pentoxide content in the form of pyrophosphate is 8.6%. 3.0126g of the sample to be tested is weighed and dissolved in distilled water to a volume of 250mL. 10mL is drawn up using a syringe (5).

[0045] The first eluent used to elute orthophosphate was 110 mL of a 0.15 mol / L potassium chloride solution, and the second eluent used to elute pyrophosphate was 150 mL of a 0.25 mol / L potassium chloride solution. The resin regeneration solution was 200 mL of a 2 mol / L hydrochloric acid solution.

[0046] The ion exchange column 1 used for determining polyphosphate is filled with 717 type strong basic anion exchange resin, which is modified by soaking in hydrochloric acid and crushed to a suitable fineness so that the flow rate can be controlled within a suitable range.

[0047] A method for measuring the polyphosphate content in fertilizer using a system comprising the following steps:

[0048] Step 1: Pour 200 ml of deionized water into the sample pear-shaped measuring bottle 30, inject the first eluent into the first eluent pear-shaped measuring bottle 31, inject the second eluent into the second eluent pear-shaped measuring bottle 32, and inject the resin regeneration liquid into the resin regeneration liquid pear-shaped measuring bottle 33;

[0049] Step 2: Turn on the air compressor 26 to increase the pressure in the pressure buffer chamber 27, and adjust the flow rate of the pear-shaped measuring bottle 3 to the collection bottle 2 through the pressure control valve 28 to stabilize the flow rate at 3.4-4.5 mL / min;

[0050] Step 3: Open the first piston valve 6 corresponding to the sample pear-shaped measuring bottle 30, and deionized water passes through the corresponding first piston valve 6 and the air valve 7. When the deionized water level drops to the first piston valve 6, the fertilizer solution to be measured is injected through the first three-way valve 4. When the fertilizer solution level to be measured drops to the air valve 7, the compressed gas enters the second cavity 10 through the hydrophobic air-permeable membrane 11 and is discharged from the gas phase outlet 14 in the second cavity 10. During the discharge process, the first piston valve 6 and the second piston valve 8 corresponding to the sample pear-shaped measuring bottle 30 are closed, and the first eluent pear-shaped measuring bottle 30 is filled with water. The first piston valve 6 and the second piston valve 8 corresponding to the measuring bottle 31 are opened; a buffer chamber 38 is provided to achieve a slow increase in pressure. After the second piston valve 8 is closed and the first piston valve 6 and the second piston valve 8 corresponding to the first eluent pear-shaped measuring bottle 31 are opened, the first piston valve 6 corresponding to the sample pear-shaped measuring bottle 30 is closed. During the above process, the deionized water and the cations in the fertilizer solution to be measured pass through the ion exchange column 1 and enter the first waste liquid collection bottle 34. The anions in the fertilizer solution to be measured are adsorbed by the ion exchange column 1 and remain in the ion exchange column 1.

[0051] Step 4: After the valve adjustment in step 3 is completed, the first eluent passes through the corresponding first piston valve 6 and breathable valve 7. When the liquid level of the first eluent drops to the breathable valve 7, the compressed gas enters the second chamber 10 through the hydrophobic breathable membrane 11 and is discharged from the gas phase outlet 14 in the second chamber 10. During the discharge process, the first piston valve 6 and the second piston valve 8 corresponding to the first eluent pear-shaped measuring bottle 31 are closed, and the first piston valve 6 and the second piston valve 8 corresponding to the second eluent pear-shaped measuring bottle 32 are opened. The buffer chamber 38 is provided to achieve a slow increase in pressure. When the second piston valve 8 is closed and the first piston valve 6 and the second piston valve 8 corresponding to the second eluent pear-shaped measuring bottle 32 are opened, the first piston valve 6 corresponding to the first eluent pear-shaped measuring bottle 31 is closed. In the above process, after the first eluent passes through the ion exchange column 1, the orthophosphate adsorbed on the ion exchange column 1 is eluted into the first sample collection bottle 35, which is component A.

[0052] Step 5: After the valve adjustment in step 4 is completed, the second eluent passes through the corresponding first piston valve 6 and breathable valve 7. When the liquid level of the second eluent drops to the breathable valve 7, the compressed gas enters the second chamber 10 through the hydrophobic breathable membrane 11 and is discharged from the gas phase outlet 14 in the second chamber 10. During the discharge process, the first piston valve 6 and the second piston valve 8 corresponding to the second eluent pear-shaped measuring bottle 32 are closed, and the first piston valve 6 and the second piston valve 8 corresponding to the resin regeneration liquid pear-shaped measuring bottle 33 are opened. The buffer chamber 38 is provided to achieve a slow increase in pressure. When the second piston valve 8 is closed and the first piston valve 6 and the second piston valve 8 corresponding to the resin regeneration liquid pear-shaped measuring bottle 33 are opened, the first piston valve 6 corresponding to the second eluent pear-shaped measuring bottle 32 is closed. In the above process, after the second eluent passes through the ion exchange column 1, the pyrophosphate adsorbed on the ion exchange column 1 is eluted into the second sample collection bottle 36 as component B.

[0053] Step 6: After the valve adjustment in step 5 is completed, the resin regeneration liquid passes through the corresponding first piston valve 6 and breathable valve 7. When the liquid level of the resin regeneration liquid drops to the breathable valve 7, the compressed gas enters the second cavity 10 through the hydrophobic breathable membrane 11 and is discharged from the gas phase outlet 14 in the second cavity 10. During the discharge process, the second piston valve 8 corresponding to the pear-shaped measuring bottle 33 of the resin regeneration liquid is closed, and the third piston valve 29 is opened, and the entire system is emptied. During the above process, the waste liquid after the resin regeneration liquid passes through the ion exchange column 1 enters the second waste liquid collection bottle 37; the ion regeneration liquid regenerates the ion exchange column 1, washes off all the anions adsorbed thereon, and enters the second waste liquid collection bottle 37;

[0054] Step 7: Turn off the air compressor 26 and the pressure control valve 28 to shut down the entire system; transfer the phosphorus content of each component according to the 6.3 effective phosphorus content in "HG / T5939-2021 Fertilizer Grade Ammonium Polyphosphate". The specific measurement method is as follows: transfer the collected components A and B to a 250mL volumetric flask and adjust the volume. Transfer 5mL of the liquid after the components A and B are adjusted to the volume. According to "HG / T 5939-2021 Fertilizer Grade Ammonium Polyphosphate" B.2.2, the absorbance is 0.587 and 0.558 respectively. The measured calibration curve is y=0.007481x (x is the absorbance, y is the phosphorus pentoxide content in the measured solution, in mg / mL), R 2 =0.9999, and the content of phosphorus pentoxide in the form of orthophosphate of the sample to be tested is calculated to be 9.1%, and the content of phosphorus pentoxide in the form of pyrophosphate is 8.7%.

[0055] Example 2

[0056] The sample fertilizer to be tested is prepared by mixing 10g of industrial monoammonium phosphate (phosphorus pentoxide content 61%), 10g of industrial potassium pyrophosphate (phosphorus pentoxide content 43%), 15g of industrial sodium tripolyphosphate (phosphorus pentoxide content 54%), 30g of agricultural urea (nitrogen content 46.2%), 20g of agricultural potassium sulfate (potassium oxide content 52%), and 15g of agricultural potassium chloride (potassium oxide content 60%). The above raw materials are then crushed to 60 mesh to prepare the sample fertilizer to be tested. The theoretical total phosphorus pentoxide content of the sample fertilizer to be tested is 18.5%, of which the phosphorus pentoxide content in the form of orthophosphate is 6.1%, the phosphorus pentoxide content in the form of pyrophosphate is 4.3%, and the phosphorus pentoxide content in the form of tripolyphosphate is 8.1%. 3.0254g of the sample to be tested is weighed and dissolved in distilled water to a volume of 250mL. 10mL is drawn up using a syringe (5).

[0057] The first eluent used to elute orthophosphate was 150 mL of a 0.25 mol / L potassium chloride solution, and the second eluent used to elute pyrophosphate was 150 mL of a 0.40 mol / L potassium chloride solution. The resin regeneration solution was 200 mL of a 2 mol / L hydrochloric acid solution.

[0058] The ion exchange column 1 used for determining polyphosphate is filled with 717 type strong basic anion exchange resin, which is modified by soaking in hydrochloric acid and crushed to a suitable fineness so that the flow rate can be controlled within a suitable range.

[0059] A method for measuring the polyphosphate content in fertilizer using a system comprising the following steps:

[0060] Step 1: Pour 300 ml of deionized water into the sample pear-shaped measuring bottle 30, inject the first eluent into the first eluent pear-shaped measuring bottle 31, inject the second eluent into the second eluent pear-shaped measuring bottle 32, and inject the resin regeneration liquid into the resin regeneration liquid pear-shaped measuring bottle 33;

[0061] Step 2: Turn on the air compressor 26 to increase the pressure in the pressure buffer chamber 27, and adjust the flow rate of the pear-shaped measuring bottle 3 to the collection bottle 2 through the pressure control valve 28 to stabilize the flow rate at 3.4-4.5 mL / min;

[0062] Step 3: Open the first piston valve 6 corresponding to the sample pear-shaped measuring bottle 30, and deionized water passes through the corresponding first piston valve 6 and the air valve 7. When the deionized water level drops to the first piston valve 6, the fertilizer solution to be measured is injected through the first three-way valve 4. When the fertilizer solution level to be measured drops to the air valve 7, the compressed gas enters the second cavity 10 through the hydrophobic air-permeable membrane 11 and is discharged from the gas phase outlet 14 in the second cavity 10. During the discharge process, the first piston valve 6 and the second piston valve 8 corresponding to the sample pear-shaped measuring bottle 30 are closed, and the first eluent pear-shaped measuring bottle is filled with water. The first piston valve 6 and the second piston valve 8 corresponding to the pear-shaped measuring bottle 31 are opened; a buffer chamber 38 is provided to achieve a slow increase in pressure. When the second piston valve 8 is closed and the first piston valve 6 and the second piston valve 8 corresponding to the first eluent pear-shaped measuring bottle 31 are opened, the first piston valve 6 corresponding to the sample pear-shaped measuring bottle 30 is closed. During the above process, the deionized water and the cations in the fertilizer solution to be measured pass through the ion exchange column 1 and enter the first waste liquid collection bottle 34; the anions in the fertilizer solution to be measured are adsorbed by the ion exchange column 1 and remain in the ion exchange column 1.

[0063] Step 4: After the valve adjustment in step 3 is completed, the first eluent passes through the corresponding first piston valve 6 and breathable valve 7. When the liquid level of the first eluent drops to the breathable valve 7, the compressed gas enters the second chamber 10 through the hydrophobic breathable membrane 11 and is discharged from the gas phase outlet 14 in the second chamber 10. During the discharge process, the first piston valve 6 and the second piston valve 8 corresponding to the first eluent pear-shaped measuring bottle 31 are closed, and the first piston valve 6 and the second piston valve 8 corresponding to the second eluent pear-shaped measuring bottle 32 are opened. The buffer chamber 38 is provided to achieve a slow increase in pressure. When the second piston valve 8 is closed and the first piston valve 6 and the second piston valve 8 corresponding to the second eluent pear-shaped measuring bottle 32 are opened, the first piston valve 6 corresponding to the first eluent pear-shaped measuring bottle 31 is closed. In the above process, after the first eluent passes through the ion exchange column 1, the orthophosphate and pyrophosphate adsorbed in the ion exchange column 1 are eluted into the first sample collection bottle 35 as component A.

[0064] Step 5: After the valve adjustment in step 4 is completed, the second eluent passes through the corresponding first piston valve 6 and breathable valve 7. When the liquid level of the second eluent drops to the breathable valve 7, the compressed gas enters the second chamber 10 through the hydrophobic breathable membrane 11 and is discharged from the gas phase outlet 14 in the second chamber 10. During the discharge process, the first piston valve 6 and the second piston valve 8 corresponding to the second eluent pear-shaped measuring bottle 32 are closed, and the first piston valve 6 and the second piston valve 8 corresponding to the resin regeneration liquid pear-shaped measuring bottle 33 are opened. The buffer chamber 38 is provided to achieve a slow increase in pressure. When the second piston valve 8 is closed and the first piston valve 6 and the second piston valve 8 corresponding to the resin regeneration liquid pear-shaped measuring bottle 33 are opened, the first piston valve 6 corresponding to the second eluent pear-shaped measuring bottle 32 is closed. In the above process, after the second eluent passes through the ion exchange column 1, the tripolyphosphate adsorbed in the ion exchange column 1 is eluted into the second sample collection bottle 36 as component B.

[0065] Step 6: After the valve adjustment in step 5 is completed, the resin regeneration liquid passes through the corresponding first piston valve 6 and breathable valve 7. When the liquid level of the resin regeneration liquid drops to the breathable valve 7, the compressed gas enters the second cavity 10 through the hydrophobic breathable membrane 11 and is discharged from the gas phase outlet 14 in the second cavity 10. During the discharge process, the second piston valve 8 corresponding to the pear-shaped measuring bottle 33 of the resin regeneration liquid is closed, and the third piston valve 29 is opened, and the entire system is emptied. During the above process, the waste liquid after the resin regeneration liquid passes through the ion exchange column 1 enters the second waste liquid collection bottle 37; the ion regeneration liquid regenerates the ion exchange column 1, washes off all the anions adsorbed thereon, and enters the second waste liquid collection bottle 37;

[0066] Step 7: Turn off the air compressor 26 and the pressure control valve 28 to shut down the entire system; transfer the phosphorus content of each component according to the 6.3 effective phosphorus content in "HG / T5939-2021 Fertilizer Grade Ammonium Polyphosphate". The specific measurement method is as follows: transfer the collected components A and B to a 250mL volumetric flask and adjust the volume. Transfer 5mL of the liquid after the components A and B are adjusted to the volume. According to "HG / T 5939-2021 Fertilizer Grade Ammonium Polyphosphate" B.2.2, the absorbance is 0.719 and 0.568 respectively. The measured calibration curve is y=0.007481x (x is the absorbance, y is the phosphorus pentoxide content in the measured solution, in mg / mL), R 2 =0.9999, and the calculated phosphorus pentoxide content in the form of orthophosphate and pyrophosphate of the sample is 10.3%, and the phosphorus pentoxide content in the form of tripolyphosphate is 8.2%.

[0067] It can be seen from this embodiment that the utility model has the characteristics of reducing the requirement for operator experience, reducing labor intensity, avoiding misoperation to the greatest extent, and improving the accuracy of detection results.

[0068] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A system for determining the polyphosphate content in fertilizers, characterized in that: The system includes an elution unit and a compressed gas drive unit for controlling the elution unit; The elution unit comprises a plurality of pre-elution parts connected in parallel, the ends of the pre-elution parts are respectively connected to the inlet of the ion exchange column (1), and the end of the ion exchange column (1) is connected to the collection part; the collection part comprises collection bottles (2) corresponding to the pre-elution parts one by one; The compressed gas drive unit comprises a compressed gas part, which is respectively connected to the pneumatic valve assembly in the pre-elution part and the pneumatic valve in the front of the collecting bottle (2) through a gas compression pipeline.

2. A system for measuring the polyphosphate content in fertilizers according to claim 1, characterized in that: The pre-elution component includes a pear-shaped measuring bottle (3), the top of the pear-shaped measuring bottle (3) is connected to the gas compression pipeline, a first tee (4) is provided between the pear-shaped measuring bottle (3) and the gas compression pipeline, and the third end of the first tee (4) is used for a syringe (5) for filling the liquid phase; The outlet of the pear-shaped measuring bottle (3) is provided with a pneumatic valve assembly, which includes a first piston valve (6) and a breathable valve (7) arranged in sequence, and the liquid phase outlet of the breathable valve (7) is connected to the inlet of the ion exchange column (1); The pneumatic valve at the front of the collecting bottle (2) is a second piston valve (8).

3. A system for measuring the polyphosphate content in fertilizers according to claim 2, characterized in that: The breathable valve (7) comprises a first cavity (9) and a second cavity (10), wherein a hydrophobic breathable membrane (11) is provided between the first cavity (9) and the second cavity (10); A gas-liquid inlet (12) is provided at the top of the first cavity (9), a liquid phase outlet (13) is provided at the bottom of the first cavity (9), and a gas phase outlet (14) is provided on the second cavity (10).

4. A system for measuring the polyphosphate content in fertilizers according to claim 3, characterized in that: The first piston valve (6) and the second piston valve (8) are both piston valves, and the piston valves include a piston cavity (15). The upper part of the piston cavity (15) is provided with a liquid inlet (16), and the piston cavity (15) corresponding to the lower part of the liquid inlet (16) is provided with a liquid outlet (17). Both sides of the piston cavity (15) are provided with a connecting end (18) and a closing end (19). The connecting end (18) and the closing end (19) are provided with a control rod (20) that runs through the interior of the piston cavity (15), and the control rod (20) is provided with a piston member that is compatible with the interior of the piston cavity (15).

5. A system for measuring the polyphosphate content in fertilizers according to claim 4, characterized in that: The piston member comprises a first silicone plug (21) and a second silicone plug (22). When the piston valve is in a closed state, the first silicone plug (21) is located between the liquid inlet (16) and the liquid outlet (17), and the second silicone plug (22) is in contact with the inner wall of the piston cavity (15) on the side of the connecting end (18); when the piston valve is in a connected state, the first silicone plug (21) and the second silicone plug (22) are located on both sides of the liquid inlet (16) and the liquid outlet (17), and a micro vent hole (23) is provided on the piston cavity (15) on the side of the second silicone plug (22) close to the connecting end (18).

6. A system for measuring the polyphosphate content in fertilizers according to claim 5, characterized in that: The gas phase outlet of the breathable valve (7) is connected to the closed end of the first piston valve (6) and the closed end of the corresponding second piston valve (8), respectively. A second three-way connection (24) is provided between the gas phase outlet of the breathable valve (7) and the closed end of the first piston valve (6), and a third end of the second three-way connection (24) is connected to the communication end (18) of the first piston valve (6) in the adjacent pre-elution component; A third three-way connection (25) is provided between the gas phase outlet of the breathable valve (7) and the closed end of the second piston valve (8), and the third end of the third three-way connection (25) is connected to the communication end (18) of the adjacent second piston valve (8).

7. A system for measuring the polyphosphate content in fertilizers according to claim 6, characterized in that: The compressed gas unit includes an air compressor (26), which is connected to the first section of the gas compression pipeline through a pressure buffer chamber (27) and a pressure control valve (28). The middle of the gas compression pipeline is connected to the inlets of a plurality of pear-shaped measuring bottles (3) of parallel pre-elution components, and the end of the gas compression pipeline is provided with a third piston valve (29).

8. A system for measuring polyphosphate content in fertilizers according to claim 7, characterized in that: The gas phase outlet of the breathable valve (7) in the terminal pre-elution component is respectively connected to the communicating end (18) of the third piston valve (29) and the closed end of the corresponding second piston valve (8).

9. A system for measuring the polyphosphate content in fertilizers according to claim 8, characterized in that: The pre-elution parts are four groups, namely a sample pear-shaped measuring bottle (30), a first eluent pear-shaped measuring bottle (31), a second eluent pear-shaped measuring bottle (32) and a resin regeneration liquid pear-shaped measuring bottle (33), the inlets of the pear-shaped measuring bottles (3) are connected. The sample pear-shaped measuring bottle (30) is connected to the ion exchange column (1) through the corresponding first piston valve (6) and the air-permeable valve (7), and the ion exchange column (1) is connected to the first waste liquid collection bottle (34) through the corresponding second piston valve (8); The first eluent pear-shaped measuring bottle (31) is connected to the ion exchange column (1) via a corresponding first piston valve (6) and a breathable valve (7), and the ion exchange column (1) is connected to the first sample collection bottle (35) via a corresponding second piston valve (8); The second eluent pear-shaped measuring bottle (32) is connected to the ion exchange column (1) via a corresponding first piston valve (6) and a breathable valve (7), and the ion exchange column (1) is connected to the second sample collection bottle (36) via a corresponding second piston valve (8); The resin regeneration liquid pear-shaped measuring bottle (33) is connected to the ion exchange column (1) through the corresponding first piston valve (6) and the air-permeable valve (7), and the ion exchange column (1) is connected to the second waste liquid collection bottle (37) through the corresponding second piston valve (8); The gas phase outlet of the corresponding air permeable valve (7) in the sample pear-shaped measuring bottle (30) is respectively connected to the closed end of the first piston valve (6) and the closed end of the second piston valve (8) corresponding to the sample pear-shaped measuring bottle (30), and the communicating end (18) of the corresponding first piston valve (6) and the communicating end (18) of the second piston valve (8) in the first eluent pear-shaped measuring bottle (31); The gas phase outlet of the corresponding air permeable valve (7) in the first eluent pear-shaped measuring bottle (31) is respectively connected to the closed end of the first piston valve (6) and the closed end of the second piston valve (8) corresponding to the first eluent pear-shaped measuring bottle (31), and the communicating end (18) of the corresponding first piston valve (6) and the communicating end (18) of the second piston valve (8) in the second eluent pear-shaped measuring bottle (32); The gas phase outlet of the corresponding air permeable valve (7) in the pear-shaped measuring bottle (32) of the second eluent is respectively connected to the closed end of the first piston valve (6) and the closed end of the second piston valve (8) corresponding to the pear-shaped measuring bottle (32) of the second eluent, and the connecting end (18) of the corresponding first piston valve (6) and the connecting end (18) of the second piston valve (8) in the pear-shaped measuring bottle (33) of the resin regeneration liquid; The gas phase outlet of the corresponding breathable valve (7) in the resin regeneration liquid pear-shaped measuring bottle (33) is respectively connected to the closed end of the second piston valve (8) and the connecting end (18) of the third piston valve (29) corresponding to the resin regeneration liquid pear-shaped measuring bottle (33); A buffer chamber (38) is correspondingly provided in front of the closed end of the first piston valve (6).

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