Simultaneous automatic analysis system and device for total phosphorus and phosphate

Abstract

The application discloses a kind of total phosphorus and phosphate simultaneous automatic analysis system and device, belong to chemical analysis and quantitative technical field, for the simultaneous automatic determination of total phosphorus and phosphate content in water quality monitoring field and carry out relevant research.This application uses plunger pump to provide power for fluid, through the suction effect of plunger pump and three-way electromagnetic valve combination on-off electricity to realize the accurate quantification of reagent and sample volume;The pushing action of plunger pump sequentially injects different reagents and samples into the system flow path to produce color reaction and obtain response signal;During the heating digestion process of total phosphorus sample, the phosphate content in the sample can be determined simultaneously, which greatly reduces the overall analysis program time length;In addition, by changing the pushing speed of plunger pump, the retention time of reagent plug and sample plug in the system, i.e. reaction time, is adjusted, so that the effective detection range of total phosphorus and phosphate can be automatically switched.

Description

Technical Field

[0001] This invention relates to an automated system and apparatus for the simultaneous analysis of total phosphorus and phosphate, belonging to the technical field of chemical analysis and quantification. It is suitable for the rapid and accurate determination of total phosphorus and phosphate in various water samples. Technical Background

[0002] Phosphorus is widely found in natural water, domestic sewage, and industrial wastewater, typically in the form of orthophosphate, pyrophosphate, metaphosphate, polyphosphate, and organically bound phosphorus. Excessive phosphorus levels lead to eutrophication, causing excessive proliferation of algae and other aquatic organisms, resulting in reduced water transparency and deterioration of water quality. Therefore, accurate determination of phosphorus content has always been a crucial indicator in water quality monitoring.

[0003] Currently, the determination of total phosphorus and phosphate content in water samples often follows the detection principle outlined in GB / T 11893-1989, "Determination of Total Phosphorus in Water - Ammonium Molybdate Spectrophotometric Method." This method states that when a sample is digested with potassium persulfate at 120°C for 30 minutes under neutral conditions, all forms of phosphorus contained within it are oxidized to orthophosphate. In an acidic medium, orthophosphate reacts with ammonium molybdate, and in the presence of potassium antimony tartrate, phosphomolybdic acid is formed. This phosphomolybdic acid is then immediately reduced by ascorbic acid to form a blue complex. The absorbance is measured at 700 nm 15 minutes after this reaction. Under conditions of excess reagent, a good linear correlation is maintained between the total phosphorus concentration or phosphate concentration and the absorbance of the resulting complex. Based on the above reaction principle, manual methods for detecting total phosphorus and phosphate typically suffer from drawbacks such as cumbersome operation, slow analysis speed, and poor reproducibility. Flow injection analysis (FIA) and sequential injection analysis (SIA) are methods for achieving automated analysis. Introducing the phosphomolybdic blue reaction system into these methods can effectively solve the above problems.

[0004] The People's Republic of China Environmental Protection Standard HJ 671-2013, "Determination of Total Phosphorus in Water - Flow Injection - Ammonium Molybdate Spectrophotometric Method," has proposed a flow injection analysis system for determining total phosphorus. However, the peristaltic pump used in this system, which provides the fluid power, frequently experiences flow instability due to pump tubing deformation, necessitating frequent replacement of the peristaltic pump tubing. Furthermore, the multi-hole two-position switching metering valve used in traditional flow injection analysis systems is expensive due to its demanding manufacturing process, often relying on imported brands. These factors limit the healthy development of automated analysis methods. Additionally, this system fails to achieve simultaneous determination of total phosphorus and phosphate. Summary of the Invention

[0005] The purpose of this invention is to address the problems of cumbersome procedures, large operational errors, and high sample consumption in the current field of water quality analysis for the determination of total phosphorus and phosphate. It innovatively develops a new flow analysis scheme by combining the advantages of flow injection analysis (FIA) and sequential injection analysis (SIA) techniques. In this scheme, a miniature plunger pump replaces the peristaltic pump in the traditional FIA system to provide fluid power, and multiple miniature three-way solenoid valves replace the multi-port two-position switching quantitative valves in the traditional FIA system or the combination of a syringe pump and a multi-position selective switching valve in SIA to achieve accurate quantification of reagent and sample volumes. Based on this, the phosphomolybdic blue reaction system is introduced into this flow system, developing a novel fully automated system for the simultaneous determination of total phosphorus and phosphate. A portable analytical device built based on this system can be efficiently used for the accurate quantification of total phosphorus and phosphate in various water samples.

[0006] The technical solution of the present invention consists of an analytical flow path system and a measuring device.

[0007] The analytical system of the present invention includes a miniature plunger pump, eight three-way solenoid valves, four reagent or sample quantitative loops, a storage coil, a reaction coil, a spectrophotometer equipped with a flow cuvette, an online digestion module equipped with two high-temperature and high-pressure normally closed solenoid valves, a computer, and developed operating software to control the above components.

[0008] The measurement process of the present invention: the three-way solenoid valve for switching the current flow path is energized (2-2b connected), and the suction action of the plunger pump (1) draws the current liquid (20) into the pump cavity. Then the three-way solenoid valve for switching the waste flow path for the sample is energized (3-3b connected), and the plunger pump (1) smoothly pushes the current in the cavity through the detector (12). At this time, the computer (13) records a smooth blank baseline.

[0009] The sample waste discharge flow path switching three-way solenoid valve (3-3b connected), the detection flow path switching three-way solenoid valve (8-8b connected), and the digestion flow path switching three-way solenoid valve are energized (9-9b connected). The plunger pump (1) draws the digestion solution (25) to fill the fourth quantitative ring (18). Then the sample waste discharge flow path switching three-way solenoid valve (3-3b connected) and the sample flow path switching three-way solenoid valve (6-6b connected) are energized. The plunger pump (1) draws the actual sample solution (23) to fill the third (17), second (16), and first quantitative ring (15). Then all solenoid valves are de-energized. The plunger pump (1) pushes out the excess digestion solution and sample in the storage coil (14) to discharge waste (26).

[0010] When the three-way solenoid valve for switching the flow path is energized (2-2b connected), the suction action of the plunger pump (1) draws the flow liquid (20) into the pump chamber. Then, the three-way solenoid valve for switching the sample discharge flow path (3-3b connected), the three-way solenoid valve for switching the detection flow path (8-8b connected), the three-way solenoid valve for switching the digestion flow path (9-9b connected), and the normally closed high-temperature and high-pressure solenoid valve (10) are energized. Under the driving action of the plunger pump (1), the flow path injects the sample and digestion liquid in the quantitative loop into the digestion module (11). When all solenoid valves are de-energized, the digestion module is heated to 120°C. This process is maintained for 30 minutes to complete the digestion.

[0011] At the same time, the three-way solenoid valves for switching the waste flow path of the sample (3-3b connected), the three-way solenoid valves for switching the sample flow path (6-6b connected), the three-way solenoid valves for switching the waste flow path of the sample (3-3b connected), the three-way solenoid valves for switching the two flow paths of the mixed reagent (5-5b connected), the three-way solenoid valves for switching the waste flow path of the sample (3-3b connected), and the three-way solenoid valves for switching the one flow path of the mixed reagent (4-4b connected) are energized in sequence. Under the suction action of the plunger pump (1), the actual sample (23), the two mixed reagents (22), and the one mixed reagent (21) are filled with the third (17), the second (16), and the first quantitative ring (15) in sequence, respectively. Then, all the solenoid valves are de-energized, and the plunger pump (1) pushes the excess sample and reagent in the storage coil (14) to be discharged (26).

[0012] When the three-way solenoid valve for switching the flow path is energized (2-2b connected), the suction action of the plunger pump (1) draws the flow (20) into the pump chamber to full scale. Then, the three-way solenoid valve for switching the waste flow path is energized (3-3b connected). Under the driving action of the plunger pump (1), the flow path sequentially injects the mixed reagent 1, mixed reagent 2, and sample from the quantitative loop into the reaction coil (19). During the flow process, the reagents and samples permeate each other due to the dispersion effect and undergo a color reaction. When it flows through the detector (12), the computer (13) records the response signal of phosphate in the sample.

[0013] After digestion is completed, the three-way solenoid valve (3-3b connected), the three-way solenoid valve (8-8b connected), the three-way solenoid valve (9-9b connected), and the high-temperature and high-pressure normally closed solenoid valve (10) are energized. The plunger pump (1) draws the sample solution from the digestion module (11) to fill the fourth (18) and third quantitative loop (17). The three-way solenoid valve (3-3b connected) for the sample waste flow path and the three-way solenoid valve for the mixed reagent flow path are energized. The solenoid valve (5-5b connected), the sample waste discharge flow path switching three-way solenoid valve (3-3b connected), and the mixed reagent one flow path switching three-way solenoid valve (4-4b connected) are energized in sequence. Under the suction action of the plunger pump (1), mixed reagent two (22) and mixed reagent one (21) are filled with the second (16) and the first quantitative ring (15) in sequence, respectively. Then all solenoid valves are de-energized, and the plunger pump (1) pushes the excess sample and reagent in the storage coil (14) to discharge waste (26).

[0014] Finally, the three-way solenoid valve for switching the flow path is energized (2-2b connected), and the suction action of the plunger pump (1) draws the flow liquid (20) into the pump chamber to full scale. Then, the three-way solenoid valve for switching the waste flow path for the sample is energized (3-3b connected). Under the driving action of the plunger pump (1), the flow liquid sequentially injects the mixed reagent one, mixed reagent two, and sample from the quantitative loop into the reaction coil (19) to produce a color reaction. When it flows through the detector (12), the computer (13) records the response signal of total phosphorus in the sample.

[0015] After the above process is completed, the digestion module is cleaned with a carrier fluid; in addition, after a period of measurement, the standard sample solution (24) is introduced into the system and the above operation is repeated to complete the periodic calibration of the phosphate and total phosphorus standard curves.

[0016] The advantages and positive effects of this invention are: it realizes a sequential injection flow analysis system with a low-cost approach, and combines the advantages of flow injection analysis systems to achieve simultaneous determination of total phosphorus and phosphate. This method effectively saves reagents and samples, achieving accurate, rapid, and environmentally friendly detection. Attached Figure Description

[0017] Figure 1 Schematic diagram of a simultaneous automated analysis system for total phosphorus and phosphate.

[0018] In the figure, (1) is a miniature plunger pump, (2) is the common terminal of the three-way solenoid valve for switching the current flow path, (2a) is the de-energized connection terminal of the three-way solenoid valve for switching the current flow path, (2b) is the energized connection terminal of the three-way solenoid valve for switching the current flow path, (3) is the common terminal of the three-way solenoid valve for switching the sample waste flow path, (3a) is the de-energized connection terminal of the three-way solenoid valve for switching the sample waste flow path, (3b) is the energized connection terminal of the three-way solenoid valve for switching the sample waste flow path, (4) is the common terminal of the three-way solenoid valve for switching the mixed reagent flow path, and (4a) is the three-way solenoid valve for switching the mixed reagent flow path. (4b) Power-off connection terminal of the three-way solenoid valve for switching the first flow path of the mixed reagent; (5) Common terminal of the three-way solenoid valve for switching the second flow path of the mixed reagent; (5a) Power-off connection terminal of the three-way solenoid valve for switching the second flow path of the mixed reagent; (5b) Power-on connection terminal of the three-way solenoid valve for switching the second flow path of the mixed reagent; (6) Common terminal of the three-way solenoid valve for switching the sample flow path; (6a) Power-off connection terminal of the three-way solenoid valve for switching the sample flow path; (6b) Power-on connection terminal of the three-way solenoid valve for switching the sample flow path; (7) Common terminal of the three-way solenoid valve for switching the sample selection. (7a) Sample selection switching three-way solenoid valve de-energized connection terminal, (7b) Sample selection switching three-way solenoid valve energized connection terminal, (8) Detection flow path switching three-way solenoid valve common terminal, (8a) Detection flow path switching three-way solenoid valve de-energized connection terminal, (8b) Detection flow path switching three-way solenoid valve energized connection terminal, (9) Digestion flow path switching three-way solenoid valve common terminal, (9a) Digestion flow path switching three-way solenoid valve de-energized connection terminal, (9b) Digestion flow path switching three-way solenoid valve energized connection terminal, (10) Online digestion module Two high-temperature and high-pressure normally closed solenoid valves, (11) online digestion module, (12) visible spectrophotometer equipped with flow cuvette, (13) computer, (14) storage coil, (15) first quantitative loop, (16) second quantitative loop, (17) third quantitative loop, (18) fourth quantitative loop, (19) reaction coil, (20) carrier liquid, (21) mixed reagent one solution, (22) mixed reagent two solution, (23) actual water sample, (24) standard solution, (25) digestion solution, (26) waste liquid one, (27) waste liquid two.

[0019] Figure 2 Example 1: Response curve recording of phosphate standard sample solution

[0020] Figure 3 Example 2: Recording of response curves from multiple parallel determinations of phosphate standard sample solution

[0021] Figure 4 Example 3: Standard curve of total phosphorus and phosphate

[0022] Figure 5 Example 4: Phosphate standard curves obtained by varying the injection rate within different measurement ranges. Detailed Implementation

[0023] The embodiments of the present invention will be further described with reference to the accompanying drawings:

[0024] Example 1

[0025] The analysis system of the present invention (see) Figure 1 Following optimized system parameters (including optimal quantitative loop volume, storage coil length, reaction coil length, reagent and sample loading speed and duration, and reagent and sample injection speed), reaction reagent conditions (including optimal concentrations of ammonium molybdate, ascorbic acid, sulfuric acid, and potassium antimony tartrate), and measurement procedures, phosphate standard sample solutions ranging from 0 to 5 mg / L were measured. The resulting phosphate response curves are shown below. Figure 2 As shown.

[0026] Example 2

[0027] The 1 mg / L phosphate standard sample solution was measured 11 times repeatedly, and its response curve was obtained as follows: Figure 3 As shown, the results indicate that the system has good precision (the relative standard deviation of absorbance detection is 1.66%).

[0028] Example 3

[0029] The analysis system of the present invention (see) Figure 1 The standard curve of total phosphorus and phosphate obtained is as follows: Figure 4 As shown.

[0030] Example 4

[0031] By varying the injection rates of reagents and samples, phosphate standard curves for different detection ranges were obtained, as shown in the following figures. Figure 5 As shown.

Claims

1. A method for determining the content of total phosphorus and phosphate simultaneously using an automated analytical device, characterized in that: The automated analysis device consists of a plunger pump (1), a three-way solenoid valve for switching the flow path, a storage coil (14), a three-way solenoid valve for switching the sample waste flow path, a sample waste outlet (26), a first quantitative loop (15), a three-way solenoid valve for switching the first flow path of the mixed reagent, a second quantitative loop (16), a three-way solenoid valve for switching the second flow path of the mixed reagent, a third quantitative loop (17), a three-way solenoid valve for switching the sample flow path, a three-way solenoid valve for switching the sample selection, a fourth quantitative loop (18), a three-way solenoid valve for switching the detection flow path, a three-way solenoid valve for switching the digestion flow path, a digestion module (11) containing two high-temperature and high-pressure normally closed solenoid valves (10), a reaction coil (19), a flow-through spectrophotometer (12), a computer (13) containing operating software, and a reaction liquid outlet. The sample consists of waste outlet (27), corresponding carrier liquid (20), mixed reagent solution 1 (21), mixed reagent solution 2 (22), actual water sample (23), standard solution (24), and digestion solution (25); wherein, the plunger pump (1) is connected to the common end (2) of the three-way solenoid valve for switching the flow path; the guide tube of the carrier liquid (20) is connected to the de-energized connection end (2a) of the three-way solenoid valve for switching the flow path; one end of the storage coil (14) is connected to the energized connection end (2b) of the three-way solenoid valve for switching the flow path, and the other end is connected to the common end (3) of the three-way solenoid valve for switching the waste flow path of the sample; the guide tube of the waste outlet (26) is connected to the de-energized connection end (3a) of the three-way solenoid valve for switching the waste flow path of the sample; the first quantitative ring ( 15) One end is connected to the energized connection end (3b) of the sample waste discharge flow path switching three-way solenoid valve, and the other end is connected to the common end (4) of the mixed reagent flow path switching three-way solenoid valve; the liquid guide tube of mixed reagent solution 1 (21) is connected to the energized connection end (4b) of the mixed reagent flow path switching three-way solenoid valve; one end of the second quantitative ring (16) is connected to the de-energized connection end (4a) of the mixed reagent flow path switching three-way solenoid valve, and the other end is connected to the common end (5) of the mixed reagent flow path switching three-way solenoid valve; the liquid guide tube of mixed reagent solution 2 (22) is connected to the energized connection end (5b) of the mixed reagent flow path switching three-way solenoid valve; one end of the third quantitative ring (17) is connected to the de-energized connection end (5a) of the mixed reagent flow path switching three-way solenoid valve. a) Connect the other end to the common end (6) of the sample flow path switching three-way solenoid valve; connect the energized end (6b) of the sample flow path switching three-way solenoid valve to the common end (7) of the sample selection switching three-way solenoid valve; connect the liquid guide tube of the actual water sample (23) to the de-energized end (7a) of the sample selection switching three-way solenoid valve; connect the standard solution (24) to the energized end (7b) of the sample selection switching three-way solenoid valve; connect one end of the fourth quantitative loop (18) to the de-energized end (6a) of the sample flow path switching three-way solenoid valve, and connect the other end to the common end (8) of the detection flow path switching three-way solenoid valve; connect the energized end (8b) of the detection flow path switching three-way solenoid valve to the common end (9) of the digestion flow path switching three-way solenoid valve;The liquid guide tube of the digestion module (11) is connected to the de-energized connection end (9a) of the three-way solenoid valve for switching the digestion flow path; the liquid guide tube of the digestion liquid (25) is connected to the energized connection end (9b) of the three-way solenoid valve for switching the digestion flow path; one end of the reaction coil (19) is connected to the de-energized connection end (8a) of the three-way solenoid valve for switching the detection flow path, and the other end is connected to the inlet of the flow-through spectrophotometer (12); the outlet of the flow-through spectrophotometer (12) is connected to the waste outlet (27) of the reaction liquid; the operating software on the computer (13) controls the action and speed of the plunger pump, the combination of energized and de-energized solenoid valves, and the digestion... The module's heating temperature and duration, detector, and recording response signal; the measurement method includes: by controlling the appropriate on / off combination of the above three-way solenoid valves, using the suction action of the plunger pump (1), the digestion solution (25) and the actual water sample (23) are sequentially filled into their respective quantitative loops, and then the piston of the plunger pump (1) is pushed out to push out the excess digestion solution and sample for waste discharge; after the plunger pump (1) draws in the carrier liquid (20), it pushes the carrier liquid to inject the sample and digestion solution in the quantitative loop into the digestion module (11); while digestion is being carried out, the plunger pump (1) sequentially draws in the actual water sample (23), mixed Mixed reagent solution 2 (22) and mixed reagent solution 1 (21) are filled with their respective quantitative loops. Then, the plunger pump (1) pushes out the excess sample and reagents to discharge waste. After the plunger pump (1) draws the carrier liquid (20) to full scale, it pushes the carrier liquid to inject mixed reagent 1, mixed reagent 2 and sample in the quantitative loop into the reaction coil (19) in sequence. The reagents and samples merge through dispersion during the flow process, thereby causing a color reaction. When it passes through the flow-through spectrophotometer (12), the phosphate response signal is obtained and recorded by the software on the computer (13). After digestion is completed, The plunger pump (1) sequentially aspirates the digested sample, mixed reagent solution 2 (22), and mixed reagent solution 1 (21) to fill their respective quantitative loops, and then pushes out the excess sample and reagents for waste disposal; the plunger pump (1) aspirates the carrier liquid (20) to full scale, and then pushes the carrier liquid to sequentially inject mixed reagent 1, mixed reagent 2, and digested sample from the quantitative loop into the reaction coil (19) to produce a colorimetric reaction. When it passes through the flow-through spectrophotometer, the response signal of total phosphorus is recorded; in addition, the above process is repeated by introducing the standard solution (24) into the system to achieve periodic calibration of the standard curve.

2. The determination method of the automatic analytical device for simultaneously determining total phosphorus and phosphate content as described in claim 1, characterized in that: The determination of phosphate in the sample is completed simultaneously with the digestion of total phosphorus sample; these two procedures do not interfere with each other.

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