A cobalt wire phosphate selective electrode and its preparation method and application

Abstract

The application discloses a cobalt wire phosphate selective electrode and a preparation method and application thereof. The cobalt wire phosphate selective electrode is prepared by treating the simple cobalt wire electrode by high-voltage constant potential. The cobalt wire phosphate selective electrode has a response sensitivity and anti-interference ability improved by treating the electrode by high-voltage constant potential, and the detection range of the cobalt wire phosphate selective electrode for phosphate is 10 ‑5 ~ 10 ‑1 M, the response time is between 4s and 40s (≤40s), the highest response sensitivity is 67.22mV / dec R 2 Value is 0.9939. And the service life is not less than 7 weeks. The cobalt wire phosphate selective electrode is suitable for on-line detection and long-time remote monitoring of the phosphate ion content in domestic water, aquaculture water and industrial water.

Description

TECHNICAL FIELD

[0001] The present application relates to a cobalt wire phosphate selective electrode and its preparation method and application, belonging to the field of ion selective electrode. BACKGROUND

[0002] Phosphate is considered to be one of the main components of groundwater and surface water, and is also an essential nutrient for all plants. With the development of economy and the growth of population, the discharge of a large amount of phosphorus-containing wastewater causes excessive proliferation of algae, leading to water eutrophication, which has a destructive impact on ecological balance and human life. In order to protect the ecological environment, it is crucial to control the concentration of phosphate in real time according to monitoring data. At present, the most effective method for detecting phosphate is the phosphomolybdenum blue spectrophotometric method, which has the advantages of wide linear range, simple operation, etc., but has the disadvantages of complicated steps, large workload, many interference factors and inconvenience for on-site rapid detection and real-time monitoring.

[0003] At present, there are three main detection methods for phosphate in water, which are optical detection method, ion chromatography method and ion selective electrode method. Optical method is a common method for analyzing ion content. For most inorganic ions, their content can be detected by their own optical properties. However, because of the particularity of phosphate ions, i.e. they cannot absorb ultraviolet and visible light, certain chemical auxiliary means is needed to convert phosphate into a form that is easier to detect. In contrast, ion chromatography does not require complex pre-conversion and post-treatment. Although the conversion of phosphorus element is not required, manual sampling and pre-treatment are required for each measurement, and the cost is also high. Ion selective electrode, also known as ion electrode, is a kind of electrochemical sensor that measures the activity or concentration of ions in solution by membrane potential. The sensor can convert the chemical content of the measured ions into an electrical physical quantity through a series of electrochemical techniques and signal detection techniques, so as to achieve the purpose of detection.

[0004] At present, according to the structure of the selective membrane and whether the ion selective electrode has internal liquid, the ion selective electrode can be divided into two types: liquid electrode and all-solid-state electrode. Single cobalt-based phosphate ion selective electrode, no matter whether it is a liquid or a solid phosphate ion selective electrode, the slope of most research results is between-21mV / dec and-39mV / dec, and it is very easy to be disturbed by the content of dissolved oxygen in water. The service life, stability and detection results of the electrode are difficult to meet the requirements of practical application. SUMMARY

[0005] Invention purposes: The first purpose of the present application is to provide a cobalt wire phosphate selective electrode with high sensitivity and capable of real-time determination of phosphate potential on site, so as to solve the problems of poor stability, easy interference of dissolved oxygen and short service life in the existing cobalt-based phosphate selective electrode. The second purpose of the present application is to provide a preparation method of the cobalt wire phosphate selective electrode. The third purpose of the present application is to provide the application of the cobalt wire phosphate selective electrode in detecting phosphate in water.

[0006] Technical scheme: The preparation method of the cobalt wire phosphate selective electrode comprises the following steps:

[0007] (1) grinding the cobalt wire to obtain a pretreated cobalt wire;

[0008] (2) connecting the cobalt wire with a metal wire, winding a sealing film at the connection part to fix, sleeving a polyvinyl chloride sleeve to completely cover the sealing film, and sealing and fixing the two ends of the polyvinyl chloride sleeve with epoxy resin;

[0009] (3) polishing the exposed part of the cobalt wire with alumina powder, and sequentially cleaning in ethanol and acetone solution by ultrasonic cleaning to obtain a common polished cobalt wire electrode;

[0010] (4) taking the common polished cobalt wire electrode as a working electrode, a platinum wire electrode as a counter electrode, and performing high-voltage constant potential pretreatment in a sodium hydroxide solution, cleaning and drying to obtain the cobalt wire phosphate selective electrode.

[0011] Further, in step (1), the grinding is polishing with sandpaper to remove the oxide film possibly formed on the surface.

[0012] Further, in step (1), the purity of the cobalt wire is 99-99.99%, and the diameter is 0.3-0.8mm.

[0013] Further, in step (2), the cobalt wire is connected with the metal wire by welding.

[0014] Further, in step (2), the length of the polyvinyl chloride sleeve is 5-10cm, and the diameter of the polyvinyl chloride sleeve is 0.3-0.5mm.

[0015] Further, in step (2), when the polyvinyl chloride sleeve is sleeved, the exposed length of the cobalt wire needs to be at least 1cm.

[0016] Further, in step (2), the metal wire is a copper wire or a tinned copper wire.

[0017] Further, in step (3), the particle size of the alumina powder is 0.5-1.5um.

[0018] Further, in step (3), the ultrasonic cleaning time is 10-15 min.

[0019] Further, in step (4), the molar concentration of the sodium hydroxide solution is 0.1-0.5 M.

[0020] Further, in step (4), the high-voltage constant potential pretreatment potential is 10-60 V, and the high-voltage constant potential pretreatment time is 300-1200 s.

[0021] Further, preferably, the high-voltage constant potential pretreatment potential is 20-50 V, and the high-voltage constant potential pretreatment time is 600-750 s. Most preferably, the high-voltage constant potential pretreatment potential is 30 V, and the high-voltage constant potential pretreatment time is 600 s.

[0022] The cobalt filament phosphate selective electrode prepared by the preparation method.

[0023] The application of the cobalt filament phosphate selective electrode in detecting phosphate in water.

[0024] Further, in application, the cobalt filament phosphate selective electrode is soaked in a water solution to be detected containing 10 -5 M of phosphate for 30-60 min of activation, and the pH of the water is 4-8.

[0025] Further, the cobalt filament phosphate selective electrode has a detection range of 10 -5 -10 -1 M of phosphate, and a response time of 4-40 s.

[0026] The reasons for the high sensitivity response of the present application may be three: on the one hand, the change in the oxidation state of the film after the electrode contacts the solution may cause a certain non-Nernst response of the mixed oxide layer on the electrode surface; secondly, the existence of multiple oxidation states of cobalt (Co 3+ / Co 2+ ) and non-oxidation-reduction reactions in the oxide film may produce a mixed potential response that helps to improve the sensitivity of the sensor; thirdly, after the activation treatment of the cobalt oxide film, a part of the cobalt oxide is converted into the form of cobalt phosphate, and the generation of cobalt phosphate can effectively improve the reaction speed with the ions to be detected in the solution, thereby achieving the effect of improving the sensitivity.

[0027] Advantages: Compared with the prior art, the present application has the following obvious advantages:

[0028] (1) The application selects a self-made cobalt wire electrode as the basis, and a cobalt wire phosphate selective electrode with high sensitivity and capable of real-time determination on site is obtained by high-voltage constant potential treatment on the cobalt wire electrode. The cobalt wire phosphate selective electrode has high response sensitivity and anti-interference ability.

[0029] (2) The cobalt wire phosphate selective electrode has a detection range of 10 -5 ~ 10 -1 M for phosphate, a response time of 4-40 s (≤40 s), a response sensitivity of 67.22 mV / dec, and an R 2 value of 0.9939, which is much higher than that of the cobalt wire electrode without pretreatment.

[0030] (3) The cobalt wire phosphate selective electrode is less affected by interference factors such as dissolved oxygen, and has a service life of not less than 7 weeks. It is suitable for online detection and long-term remote monitoring of phosphate ion content in domestic water, aquaculture water and industrial water. It has far-reaching significance for preventing and controlling water pollution and protecting the environment. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a preparation and structural schematic diagram of the cobalt wire phosphate selective electrode of the application;

[0032] Figure 2 It is a physical diagram of the cobalt wire phosphate selective electrode of the application;

[0033] Figure 3 It is a response performance curve diagram of the cobalt wire phosphate selective electrode prepared in Example 1 and a common polished cobalt wire electrode in a sodium dihydrogen phosphate standard solution;

[0034] Figure 4 It is a response performance curve and sensitivity change comparison diagram of the cobalt wire phosphate selective electrodes prepared in Examples 1-5 in a sodium dihydrogen phosphate standard solution;

[0035] Figure 5 It is a response performance curve of the cobalt wire phosphate selective electrodes prepared in Examples 6-10 in a sodium dihydrogen phosphate standard solution

[0036] Figure 6 It is a short-term repeated use potential change trend diagram of the cobalt wire phosphate selective electrode prepared in Example 10 in a sodium dihydrogen phosphate standard solution;

[0037] Figure 7 It is a long-term use potential change trend diagram of the cobalt wire phosphate selective electrode prepared in Example 11 in a sodium dihydrogen phosphate standard solution;

[0038] Figure 8The comparison chart of the use of the cobalt wire phosphate selective electrode prepared in Example 12 under different pH environments;

[0039] Figure 9 The response time chart of the cobalt wire phosphate selective electrode prepared in Example 13 in sodium dihydrogen phosphate standard solution with different concentrations;

[0040] Figure 10 The chart of the interference of common anions (chloride, nitrate and sulfate) and dissolved oxygen in water to the cobalt wire phosphate selective electrode prepared in Example 14;

[0041] Figure 11 The response sensitivity change trend chart of the cobalt wire phosphate selective electrode prepared in Example 15 in long-term use of sodium dihydrogen phosphate standard solution. DETAILED DESCRIPTION

[0042] The technical solutions of the present application are further described below with reference to the accompanying drawings.

[0043] Example 1

[0044] (1) The cobalt wire with a purity of 99.9% and a diameter of 0.3 mm is cut to a length of about 5 cm and polished on sandpaper to remove the possible oxide film formed on the surface;

[0045] (2) The cobalt wire is connected to the tinned copper wire by welding, and the welding part is fixed by wrapping the sealing film; the polyvinyl chloride sleeve with a length of 5 cm and a diameter of 0.5 mm is sleeved, and the two ends of the polyvinyl chloride sleeve are sealed and fixed with epoxy resin, and the exposed length of the cobalt wire is about 1 cm;

[0046] (3) After the epoxy resin is completely cured, the exposed part of the cobalt wire is polished on the polishing cloth with alumina powder with a particle size of 0.5 um, and then sequentially cleaned in ethanol and acetone solutions for 10 min each by ultrasonic cleaning to remove other possible organic impurities on the surface, thereby obtaining a common polished cobalt wire electrode.

[0047] (4) The common polished cobalt wire electrode prepared above is used as a working electrode, and a platinum wire (1 cm x 0.5 mm) electrode is used as a counter electrode. The pretreated cobalt wire electrode, i.e. the cobalt wire phosphate selective electrode, is prepared by constant potential pretreatment in 0.5 M sodium hydroxide solution at a voltage of 30 V for 600 s. The results are shown in Figures 1-2 . Figure 1 The cobalt wire phosphate selective electrode prepared by the present application and the structure schematic diagram thereof; wherein, 101 is a cobalt wire metal layer, and 102 is a passivation film layer after pretreatment. Figure 2 The cobalt wire phosphate selective electrode prepared by the present application and the structure schematic diagram thereof; wherein, 101 is a cobalt wire metal layer, and 102 is a passivation film layer after pretreatment.

[0048] The ordinary polished cobalt wire electrode prepared in this example and the cobalt wire phosphate selective electrode were placed in 10 -5 M sodium dihydrogen phosphate standard solution for 30 min, and after the electrode potential was stable, 10 -5 M sodium dihydrogen phosphate standard solution was prepared in 0.025 mM potassium hydrogen phthalate buffer solution, and the dynamic response of the cobalt wire phosphate selective electrode and the ordinary polished cobalt wire electrode was tested. -1 M sodium dihydrogen phosphate standard solution was prepared in 0.025 mM potassium hydrogen phthalate buffer solution, and the dynamic response of the cobalt wire phosphate selective electrode and the ordinary polished cobalt wire electrode was tested. Figure 3 M sodium dihydrogen phosphate standard solution was prepared in 0.025 mM potassium hydrogen phthalate buffer solution, and the dynamic response of the cobalt wire phosphate selective electrode and the ordinary polished cobalt wire electrode was tested. Figure 3 M sodium dihydrogen phosphate standard solution was prepared in 0.025 mM potassium hydrogen phthalate buffer solution, and the dynamic response of the cobalt wire phosphate selective electrode and the ordinary polished cobalt wire electrode was tested. -5 M sodium dihydrogen phosphate standard solution was prepared in 0.025 mM potassium hydrogen phthalate buffer solution, and the dynamic response of the cobalt wire phosphate selective electrode and the ordinary polished cobalt wire electrode was tested. -1 M sodium dihydrogen phosphate standard solution was prepared in 0.025 mM potassium hydrogen phthalate buffer solution, and the dynamic response of the cobalt wire phosphate selective electrode and the ordinary polished cobalt wire electrode was tested. 2 M sodium dihydrogen phosphate standard solution was prepared in 0.025 mM potassium hydrogen phthalate buffer solution, and the dynamic response of the cobalt wire phosphate selective electrode and the ordinary polished cobalt wire electrode was tested. -5 M sodium dihydrogen phosphate standard solution was prepared in 0.025 mM potassium hydrogen phthalate buffer solution, and the dynamic response of the cobalt wire phosphate selective electrode and the ordinary polished cobalt wire electrode was tested. -1 M sodium dihydrogen phosphate standard solution was prepared in 0.025 mM potassium hydrogen phthalate buffer solution, and the dynamic response of the cobalt wire phosphate selective electrode and the ordinary polished cobalt wire electrode was tested. 2 M sodium dihydrogen phosphate standard solution was prepared in 0.025 mM potassium hydrogen phthalate buffer solution, and the dynamic response of the cobalt wire phosphate selective electrode and the ordinary polished cobalt wire electrode was tested.

[0049] Example 2

[0050] (1) A cobalt wire with a purity of 99.9% and a diameter of 0.3 mm was cut to a length of about 5 cm and polished on sandpaper to remove the oxide film that may form on the surface;

[0051] (2) The cobalt wire was connected to a tinned copper wire by welding, and the welded part was wrapped with a sealing film for fixation; the cobalt wire was sleeved into a polyvinyl chloride sleeve with a length of 5 cm and a diameter of 0.5 mm, and the two ends of the polyvinyl chloride sleeve were sealed and fixed with epoxy resin, leaving a bare length of the cobalt wire of 1 cm;

[0052] (3) After the epoxy resin was completely cured, the bare part of the cobalt wire was polished with aluminum oxide powder with a particle size of 0.5 um on a polishing cloth; after polishing, it was sequentially cleaned in ethanol and acetone solutions for 10 min each to remove other organic impurities that may exist on the surface, and an ordinary polished cobalt wire electrode was prepared.

[0053] (4) The ordinary polished cobalt wire electrode prepared above was used as the working electrode, and a platinum wire (1 cm x 0.5 mm) electrode was used as the counter electrode. In 0.5 M sodium hydroxide solution, constant potential pretreatment was carried out at a voltage of 30 V, and the pretreatment time was 300 s, to prepare a pretreated cobalt wire electrode, i.e. a cobalt wire phosphate selective electrode.

[0054] The cobalt wire phosphate selective electrode prepared in this example was placed in 10 -5Activate the solution of sodium dihydrogen phosphate (M) for 30 min until the electrode potential stabilizes. Then, prepare 10 solutions of sodium dihydrogen phosphate buffer solution with 0.025 mM potassium hydrogen phthalate buffer. -5 ~10 -1 The dynamic response of the cobalt wire phosphate selective electrode was tested in a standard phosphate solution of M. The results are as follows: Figure 4 As shown in (a), by Figure 4 (a) As can be seen, the cobalt wire phosphate selective electrode prepared in this embodiment exhibits good performance at a phosphate concentration of 10... -5 M to 10 -1 The response sensitivity between M and R is -44.24 mV / dec. 2 =0.9383.

[0055] Example 3

[0056] (1) Cut a cobalt wire with a purity of 99.9% and a diameter of 0.3 mm into a length of about 5 cm and polish it on sandpaper to remove any oxide film that may form on the surface;

[0057] (2) The cobalt wire and the tin-plated copper wire are connected by welding, and the weld is fixed by wrapping the sealing film; a polyvinyl chloride sleeve is inserted, the sleeve is 5cm long and 0.5mm in diameter, and the connection of the two ends of the polyvinyl chloride sleeve is sealed with epoxy resin, leaving 1cm of the cobalt wire exposed.

[0058] (3) After the epoxy resin is completely cured, the exposed part of the cobalt wire is polished on the polishing cloth with alumina powder with a particle size of 0.5 μm; after polishing, it is placed in ethanol and acetone solutions for ultrasonic cleaning for 10 min each to remove other organic impurities that may exist on the surface, and a common polished cobalt wire electrode is obtained.

[0059] (4) Using the ordinary polished cobalt wire electrode prepared above as the working electrode, a platinum wire (1cm×0.5mm) electrode is used as the counter electrode. In a 0.5M sodium hydroxide solution, a constant potential pretreatment is performed at a voltage of 30V for 750s to obtain a pretreated cobalt wire electrode, namely a cobalt wire phosphate selective electrode.

[0060] The cobalt wire phosphate selective electrode prepared in this embodiment was placed at 10 -5 Activate the solution of sodium dihydrogen phosphate (M) for 30 min until the electrode potential stabilizes. Then, prepare 10 solutions of sodium dihydrogen phosphate buffer solution with 0.025 mM potassium hydrogen phthalate buffer. -5 ~10 -1 The dynamic response of the cobalt wire phosphate selective electrode was tested in a standard phosphate solution of M. The results are as follows: Figure 4 As shown in (c), by Figure 4 (c) As can be seen, the cobalt wire phosphate selective electrode prepared in this embodiment exhibits good performance at a phosphate concentration of 10...-5 M to 10 -1 The response sensitivity between M and R is -65.61 mV / dec. 2 =0.9676.

[0061] Example 4

[0062] (1) Cut a cobalt wire with a purity of 99.9% and a diameter of 0.3 mm into a length of about 5 cm and polish it on sandpaper to remove any oxide film that may form on the surface;

[0063] (2) The cobalt wire and the tin-plated copper wire are connected by welding, and the weld is fixed by wrapping the sealing film; a polyvinyl chloride sleeve is inserted, the sleeve is 5cm long and 0.5mm in diameter, and the connection of the two ends of the polyvinyl chloride sleeve is sealed with epoxy resin, leaving 1cm of the cobalt wire exposed.

[0064] (3) After the epoxy resin is completely cured, the exposed part of the cobalt wire is polished on the polishing cloth with alumina powder with a particle size of 0.5 μm; after polishing, it is placed in ethanol and acetone solutions for ultrasonic cleaning for 10 min each to remove other organic impurities that may exist on the surface, and a common polished cobalt wire electrode is obtained.

[0065] (4) Using the ordinary polished cobalt wire electrode prepared above as the working electrode, a platinum wire (1cm×0.5mm) electrode is used as the counter electrode. In a 0.5M sodium hydroxide solution, a constant potential pretreatment is performed at a voltage of 30V for 900s to obtain a pretreated cobalt wire electrode, namely a cobalt wire phosphate selective electrode.

[0066] The cobalt wire phosphate selective electrode prepared in this embodiment was placed at 10 -5 Activate the solution of sodium dihydrogen phosphate (M) for 30 min until the electrode potential stabilizes. Then, prepare 10 solutions of sodium dihydrogen phosphate buffer solution with 0.025 mM potassium hydrogen phthalate buffer. -5 ~10 -1 The dynamic response of the cobalt wire phosphate selective electrode was tested in a standard phosphate solution of M. The results are as follows: Figure 4 As shown in (d), by Figure 4 (d) As can be seen, the cobalt wire phosphate selective electrode prepared in this embodiment exhibits good performance at a phosphate concentration of 10... -5 M to 10 -1 The response sensitivity between M and R is -57.58 mV / dec. 2 =0.9479.

[0067] Example 5

[0068] (1) Cut a cobalt wire with a purity of 99.9% and a diameter of 0.3 mm into a length of about 5 cm and polish it on sandpaper to remove any oxide film that may form on the surface;

[0069] (2) The cobalt wire and the tinned copper wire are connected by welding, and the welding part is fixed by wrapping the sealing film. The polyvinyl chloride sleeve with a length of 5 cm and a diameter of 0.5 mm is sleeved, and the two ends of the polyvinyl chloride sleeve are sealed and fixed by epoxy resin;

[0070] (3) After the epoxy resin is completely cured, the exposed part of the cobalt wire is polished on the polishing cloth with aluminum oxide powder with a particle size of 0.5 um. After polishing, the cobalt wire is sequentially cleaned in ethanol and acetone solutions for 10 min each to remove other possible organic impurities on the surface, thereby obtaining a common polished cobalt wire electrode.

[0071] (4) The common polished cobalt wire electrode prepared above is used as a working electrode, and a platinum wire electrode (1 cm x 0.5 mm) is used as a counter electrode. The pretreated cobalt wire electrode, i.e., a cobalt wire phosphate selective electrode, is prepared by constant potential pretreatment in a 0.5 M sodium hydroxide solution at a voltage of 30 V for 1200 s.

[0072] The cobalt wire phosphate selective electrode prepared in this example is activated in a 10 -5 M sodium dihydrogen phosphate standard solution for 30 min, and after the electrode potential is stable, the dynamic response of the cobalt wire phosphate selective electrode is tested in 10 -5 ~ 10 -1 M standard phosphate solutions prepared by using 0.025 mM potassium hydrogen phthalate buffer solution. The results are shown in FIG. Figure 4 (e), and Figure 4 (e) shows that the response sensitivity of the cobalt wire phosphate selective electrode prepared in this example is -54.40 mV / dec between the concentrations of 10 -5 M and 10 -1 M, and R 2 = 0.9394.

[0073] Figure 4 The response performance curves and sensitivity changes of the cobalt wire electrodes prepared in Examples 1-5 with different pretreatment times in a sodium dihydrogen phosphate standard solution are compared, wherein a-e are the response performance curves of the electrodes with pretreatment times of 300 s, 600 s, 750 s, 900 s, and 1200 s, respectively, and f is the sensitivity change comparison chart of the electrodes with different pretreatment times. As can be seen from the entire Figure 5 , the pretreatment operation can effectively improve the sensitivity of the electrode, and the electrode with a pretreatment time of 600 s has the highest response sensitivity.

[0074] Example 6

[0075] (1) The cobalt wire with a purity of 99.9% and a diameter of 0.3 mm was cut to a length of about 5 cm and polished on sandpaper to remove the possible oxide film formed on the surface;

[0076] (2) The cobalt wire was connected to the tin-plated copper wire by welding, and the welded part was wrapped with sealing film for fixation; the polyvinyl chloride sleeve with a length of 5 cm and a diameter of 0.5 mm was sleeved, and the two connecting parts of the polyvinyl chloride sleeve were sealed and fixed with epoxy resin;

[0077] (3) After the epoxy resin was completely cured, the exposed part of the cobalt wire was polished on a polishing cloth with aluminum oxide powder with a particle size of 0.5 um; after polishing, it was sequentially ultrasonically cleaned in ethanol and acetone solutions for 10 min each to remove other possible organic impurities on the surface, thereby obtaining a general polished cobalt wire electrode.

[0078] (4) The general polished cobalt wire electrode prepared above was used as a working electrode, and a platinum wire (1 cm x 0.5 mm) electrode was used as a counter electrode. In a 0.5 M sodium hydroxide solution, a constant potential pretreatment was performed at a voltage of 10 V, and the pretreatment time was 600 s, thereby obtaining a pretreated cobalt wire electrode, i.e., a cobalt wire phosphate selective electrode.

[0079] The cobalt wire phosphate selective electrode prepared in this example was activated in a 10 -5 M sodium dihydrogen phosphate standard solution for 30 min, and after the electrode potential was stable, the dynamic response of the cobalt wire phosphate selective electrode was tested in 10 -5 ~ 10 -1 M standard phosphate solutions prepared in 0.025 mM potassium hydrogen phthalate buffer solution, respectively. The results are shown in Figure 5 (a). Figure 5 (a) shows that the cobalt wire phosphate selective electrode prepared in this example has a response sensitivity of -33.20 mV / dec between the concentrations of 10 -4 M to 10 -1 M, and R 2 = 0.8645.

[0080] Example 7

[0081] (1) The cobalt wire with a purity of 99.9% and a diameter of 0.3 mm was cut to a length of about 5 cm and polished on sandpaper to remove the possible oxide film formed on the surface;

[0082] (2) The cobalt wire was connected to the tin-plated copper wire by welding, and the welded part was wrapped with sealing film for fixation; the polyvinyl chloride sleeve with a length of 5 cm and a diameter of 0.5 mm was sleeved, and the two connecting parts of the polyvinyl chloride sleeve were sealed and fixed with epoxy resin;

[0083] (3) After the epoxy resin is completely cured, the exposed part of the cobalt wire is polished with 0.5-μm alumina powder on a polishing cloth; after polishing, the cobalt wire is sequentially cleaned in ethanol and acetone solutions for 10 min each to remove other possible organic impurities on the surface, thereby obtaining a common polished cobalt wire electrode.

[0084] (4) The common polished cobalt wire electrode prepared above is used as a working electrode, and a platinum wire electrode (1 cm x 0.5 mm) is used as a counter electrode. The cobalt wire electrode is pretreated at a voltage of 20 V in a 0.5-M sodium hydroxide solution for 600 s, thereby obtaining a pretreated cobalt wire electrode, i.e., a cobalt wire phosphate-selective electrode.

[0085] The cobalt wire phosphate-selective electrode prepared in this example is activated in a 10 -5 -M sodium dihydrogen phosphate standard solution for 30 min, and after the electrode potential is stabilized, the dynamic response of the cobalt wire phosphate-selective electrode is tested in 10 -5 -10 -1 -M standard phosphate solutions prepared by sequentially diluting a 0.025-mM potassium hydrogen phthalate buffer solution. The results are shown in Figure 5 (b). Figure 5 (b) shows that the cobalt wire phosphate-selective electrode prepared in this example has a response sensitivity of 46.95 mV / dec for the concentration of phosphate from 10 -5 M to 10 -1 M, and R 2 = 0.9885.

[0086] Example 8

[0087] (1) A cobalt wire with a purity of 99.9% and a diameter of 0.3 mm is cut to a length of about 5 cm and polished on sandpaper to remove possible oxide films on the surface.

[0088] (2) The cobalt wire is connected to a tinned copper wire by welding, and the welded part is fixed by wrapping a sealing film; the cobalt wire is sleeved into a polyvinyl chloride sleeve with a length of 5 cm and a diameter of 0.5 mm, and the two ends of the polyvinyl chloride sleeve are sealed and fixed with epoxy resin.

[0089] (3) After the epoxy resin is completely cured, the exposed part of the cobalt wire is polished with 0.5-μm alumina powder on a polishing cloth; after polishing, the cobalt wire is sequentially cleaned in ethanol and acetone solutions for 10 min each to remove other possible organic impurities on the surface, thereby obtaining a common polished cobalt wire electrode.

[0090] (4) The above-prepared ordinary polished cobalt wire electrode was used as the working electrode, and a platinum wire (1 cm x 0.5 mm) electrode was used as the counter electrode. The pretreated cobalt wire electrode, i.e., the cobalt wire phosphate selective electrode, was prepared by constant potential pretreatment in 0.5 M sodium hydroxide solution at a voltage of 40 V for 600 s.

[0091] The cobalt wire phosphate selective electrode prepared in this example was placed in 10 -5 M sodium dihydrogen phosphate standard solution for 30 min. After the electrode potential was stable, the cobalt wire phosphate selective electrode was tested in 10 -5 ~ 10 -1 M standard phosphate solution, and the dynamic response of the cobalt wire phosphate selective electrode was tested. The results are shown in Figure 5 (c), and the response sensitivity of the cobalt wire phosphate selective electrode prepared in this example was 51.14 mV / dec in the concentration range of 10 Figure 5 (c) shows that the cobalt wire phosphate selective electrode prepared in this example has a response sensitivity of 51.14 mV / dec in the concentration range of 10 -5 M to 10 -1 M, and R 2 = 0.9394.

[0092] Example 9

[0093] (1) A cobalt wire with a purity of 99.9% and a diameter of 0.3 mm was cut to a length of about 5 cm and polished on sandpaper to remove the oxide film that may be formed on the surface;

[0094] (2) The cobalt wire was connected to a tinned copper wire by welding, and the welded part was fixed by wrapping a sealing film. The cobalt wire was sleeved into a polyvinyl chloride sleeve with a length of 5 cm and a diameter of 0.5 mm, and the two ends of the polyvinyl chloride sleeve were sealed and fixed with epoxy resin;

[0095] (3) After the epoxy resin was completely cured, the exposed part of the cobalt wire was polished with aluminum oxide powder with a particle size of 0.5 um on a polishing cloth. After polishing, the cobalt wire was sequentially ultrasonically cleaned in ethanol and acetone solutions for 10 min each to remove other organic impurities that may exist on the surface, and an ordinary polished cobalt wire electrode was prepared.

[0096] (4) The above-prepared ordinary polished cobalt wire electrode was used as the working electrode, and a platinum wire (1 cm x 0.5 mm) electrode was used as the counter electrode. The pretreated cobalt wire electrode, i.e., the cobalt wire phosphate selective electrode, was prepared by constant potential pretreatment in 0.5 M sodium hydroxide solution at a voltage of 40 V for 600 s.

[0097] The cobalt wire phosphate selective electrode prepared in this example was placed in 10 -5The cobalt wire phosphate selective electrode was activated in a 10 mM sodium dihydrogen phosphate standard solution for 30 min, and then the electrode potential was stabilized. The dynamic response of the cobalt wire phosphate selective electrode was tested in 10 mM standard phosphate solutions prepared using 0.025 mM potassium hydrogen phthalate buffer solution, and the results are shown in Fig. 4. -5 ~10 -1 The dynamic response of the cobalt wire phosphate selective electrode was tested in 10 mM standard phosphate solutions prepared using 0.025 mM potassium hydrogen phthalate buffer solution, and the results are shown in Fig. 4. Figure 5 (d) The cobalt wire phosphate selective electrode prepared in this example had a response sensitivity of 31.80 mV / dec in the concentration range of 10 Figure 5 (d) The cobalt wire phosphate selective electrode prepared in this example had a response sensitivity of 31.80 mV / dec in the concentration range of 10 -4 M to 10 -1 M, and the R 2 = 0.9899.

[0098] Example 10

[0099] (1) A cobalt wire with a purity of 99.9% and a diameter of 0.3 mm was cut to a length of about 5 cm and polished on sandpaper to remove the oxide film that may have formed on the surface;

[0100] (2) The cobalt wire was connected to a tinned copper wire by welding, and the welded part was fixed by wrapping a sealing film. The cobalt wire was then sleeved into a polyvinyl chloride sleeve with a length of 5 cm and a diameter of 0.5 mm, and the two ends of the sleeve were sealed and fixed with epoxy resin.

[0101] (3) After the epoxy resin was completely cured, the exposed part of the cobalt wire was polished with aluminum oxide powder with a particle size of 0.5 um on a polishing cloth. After polishing, the cobalt wire was placed in ethanol and acetone solutions for ultrasonic cleaning for 10 min each to remove other organic impurities that may exist on the surface, and a common polished cobalt wire electrode was prepared.

[0102] (4) The common polished cobalt wire electrode prepared above was used as the working electrode, and a platinum wire (1 cm x 0.5 mm) electrode was used as the counter electrode. A pretreated cobalt wire electrode, i.e., a cobalt wire phosphate selective electrode, was prepared by constant potential pretreatment in a 0.5 M sodium hydroxide solution at a voltage of 60 V for a pretreatment time of 600 s.

[0103] The cobalt wire phosphate selective electrode prepared in this example was activated in a 10 mM sodium dihydrogen phosphate standard solution for 30 min, and then the electrode potential was stabilized. The dynamic response of the cobalt wire phosphate selective electrode was tested in 10 mM standard phosphate solutions prepared using 0.025 mM potassium hydrogen phthalate buffer solution, and the results are shown in Fig. 4. -5 M to 10 -5 ~10 -1 M, and the R Figure 5 (e) The cobalt wire phosphate selective electrode prepared in this example had a response sensitivity of 31.80 mV / dec in the concentration range of 10 Figure 5 (e) The cobalt wire phosphate selective electrode prepared in this example had a response sensitivity of 31.80 mV / dec in the concentration range of 10 -3 M to 10-1 The response sensitivity between M and M is 61.21 mV / dec, R 2 = 0.9926.

[0104] Figure 6 The response performance curves and sensitivity changes of the cobalt wire electrodes prepared in Examples 6-10 with different pretreatment times in the sodium dihydrogen phosphate standard solution are compared, wherein a-e are the response performance curves of the pretreatment voltages of 10 V, 20 V, 40 V, 50 V, and 60 V, respectively, and the entire Figure 6 It can be seen that when the pretreatment time is 600 s, the voltage size of the pretreatment affects the sensitivity of the electrode to a certain extent. A lower potential may require a longer time to form a relatively complete composite passivation film layer on the surface. For a higher potential, a pretreatment time of 600 s is easy to produce a passivation layer with a large degree of surface cracking. During the detection process, there may be a situation of film layer peeling off, thereby affecting the stability and detection interval of the electrode.

[0105] Example 11

[0106] (1) A cobalt wire with a purity of 99.9% and a diameter of 0.3 mm was cut to a length of about 5 cm and polished on sandpaper to remove the oxidation film that may form on the surface;

[0107] (2) The cobalt wire was connected to the tinned copper wire by welding, and the welding site was fixed by wrapping the sealing film. The cobalt wire was sleeved into a polyvinyl chloride sleeve with a length of 5 cm and a diameter of 0.5 mm, and the two ends of the polyvinyl chloride sleeve were sealed and fixed with epoxy resin.

[0108] (3) After the epoxy resin was completely cured, the exposed part of the cobalt wire was polished on a polishing cloth with an aluminum oxide powder of 0.5 um in particle size. After polishing, it was sequentially cleaned in ethanol and acetone solutions for 10 min each to remove other organic impurities that may exist on the surface, thereby preparing a general polished cobalt wire electrode.

[0109] (4) The above-prepared general polished cobalt wire electrode was used as the working electrode, and a platinum wire (1 cm x 0.5 mm) electrode was used as the counter electrode. In a 0.5 M sodium hydroxide solution, a constant potential pretreatment was performed at a voltage of 30 V, and the pretreatment time was 600 s, thereby preparing a pretreated cobalt wire electrode, i.e., a cobalt phosphate selective electrode.

[0110] The cobalt phosphate selective electrode prepared in this example was activated in a 10 -5 M sodium dihydrogen phosphate standard solution for 30 min, and after the electrode potential was stable, 10 repeated measurements were performed at room temperature, and the surface was cleaned with deionized water after each measurement to study the stability of the cobalt phosphate selective electrode prepared in this example. As shown in Figure 6 Figure 7 ​The potential change trend chart of the cobalt wire phosphate selective electrode prepared in Example 11 in the short-term repeated use of sodium dihydrogen phosphate standard solution is shown in FIG. 2, and the potential change trend chart of the cobalt wire phosphate selective electrode prepared in Example 11 in the long-term use of sodium dihydrogen phosphate standard solution is shown in FIG. 3. Figure 7 It can be seen that the cobalt wire phosphate selective electrode prepared in this embodiment has a potential change range of-0.005 V in the short-term use of 10 M sodium dihydrogen phosphate solution. -5 The average response potential is-337.53 mV, and the RSD is 1.07%. It shows that the electrode has good short-term stability.

[0111] Further, the actual scene not only needs good short-term use but also needs long-term stability of online detection. In order to approach the actual environment and verify the possibility of long-term online detection (without stirring and constant temperature), the cobalt wire phosphate selective electrode prepared in this embodiment is placed in 10 M sodium dihydrogen phosphate solution for continuous detection for 24 hours. -5 The detection potential drift is shown in FIG. 4. Figure 7 Figure 8 The potential change trend chart of the cobalt wire phosphate selective electrode prepared in Example 11 in the long-term use of sodium dihydrogen phosphate standard solution is shown in FIG. 3. Figure 8 It can be seen that the potential signal is stable within the initial 15 hours, and the floating range is ±0.005 V. After 15 h of continuous monitoring, the potential signal rises to a certain extent. This may be the result of the continuous reaction of the oxidation layer on the electrode surface with the phosphate in the to-be-detected solution. The final signal is stable near 322.8 mV, the average value of the signal within 24 hours is-331.4 mV, the maximum drift value is 17 mV, the average potential drift value per hour is 0.71 mV / h, and the overall trend is relatively stable.

[0112] Example 12

[0113] (1) The cobalt wire with a purity of 99.9% and a diameter of 0.3 mm is cut to a length of about 5 cm and polished on sandpaper to remove the oxidation film that may be formed on the surface;

[0114] (2) The cobalt wire is connected to the tinned copper wire by welding, and the welding part is fixed by wrapping the sealing film. The cobalt wire is sleeved into a polyvinyl chloride sleeve with a length of 5 cm and a diameter of 0.5 mm, and the two ends of the polyvinyl chloride sleeve are sealed and fixed with epoxy resin.

[0115] (3) After the epoxy resin is completely cured, the exposed part of the cobalt wire is polished on a polishing cloth with an aluminum oxide powder with a particle size of 0.5 um. After polishing, it is sequentially ultrasonically cleaned in ethanol and acetone solutions for 10 min each to remove other organic impurities that may exist on the surface, thereby preparing a general polished cobalt wire electrode.

[0116] ​(4) The above-prepared common polished cobalt wire electrode was used as the working electrode, and a platinum wire (1 cm x 0.5 mm) electrode was used as the counter electrode. The pretreated cobalt wire electrode, i.e., the cobalt wire phosphate selective electrode, was prepared by constant potential pretreatment in a 0.5 M sodium hydroxide solution at a voltage of 30 V for 600 s.

[0117] The cobalt wire phosphate selective electrode prepared in this example was activated in a 10 -5 M sodium dihydrogen phosphate standard solution for 30 min, and after the electrode potential was stable, the adaptability of the electrode to the pH of the use environment was further investigated. The performance of the electrode was evaluated under the conditions of pH values of 2, 4, 6, 8, and 10 using 10 -6 M to 10 -1 M sodium dihydrogen phosphate as the standard solution. The results are shown in FIG. 2. Figure 8 Figure 9 FIG. 1 is a comparison chart of the use of the cobalt wire phosphate selective electrode prepared in Example 12 under different pH environments, in which (a) the pH value is 2, (b) the pH value is 4, (c) the pH value is 6, (d) the pH value is 8, and (e) the pH value is 10. Figure 9 As can be seen from FIG. 1, under the conditions of pH values of 2 and 10, the cobalt wire phosphate selective electrode does not exhibit linearity in the concentration range of 10 -6 M to 10 -1 M, and has a good response change trend in neutral, weakly acidic, and weakly alkaline environments, so the working range is determined to be between pH 4.0 and 8.0.

[0118] Example 13

[0119] (1) A cobalt wire with a purity of 99.9% and a diameter of 0.3 mm was cut to a length of about 5 cm and polished on sandpaper to remove the oxide film that may be formed on the surface.

[0120] (2) The cobalt wire was connected to a tinned copper wire by welding, and the welded part was fixed by wrapping a sealing film. The cobalt wire was sleeved into a polyvinyl chloride sleeve with a length of 5 cm and a diameter of 0.5 mm, and the two ends of the polyvinyl chloride sleeve were sealed and fixed with epoxy resin.

[0121] (3) After the epoxy resin was completely cured, the exposed part of the cobalt wire was polished on a polishing cloth with an aluminum oxide powder with a particle size of 0.5 um, and then was sequentially cleaned in ethanol and acetone solutions for 10 min each by ultrasonic cleaning to remove other organic impurities that may exist on the surface, thereby preparing a common polished cobalt wire electrode.

[0122] ​(4) The above prepared common polished cobalt wire electrode was used as a working electrode, and a platinum wire (1 cm x 0.5 mm) electrode was used as a counter electrode. The cobalt wire electrode was prepared by constant potential pretreatment in 0.5 M sodium hydroxide solution at a voltage of 30 V for 600 s, to obtain a pretreated cobalt wire electrode, i.e., a cobalt wire phosphate selective electrode.

[0123] The cobalt wire phosphate selective electrode prepared in this example was activated in 10 -5 M sodium dihydrogen phosphate standard solution for 30 min, and then was placed in 10 -5 M to 10 -1 M sodium dihydrogen phosphate standard solution for testing. The response time of the electrode in the standard solution was as shown in Figure 9 , Figure 10 Figures showing the response time of the cobalt wire phosphate selective electrode prepared in Example 13 in different concentrations of sodium dihydrogen phosphate standard solution, wherein (a) is a figure showing the response time of the electrode in different concentrations of standard solution, (b) is a figure showing the response time of the electrode in 10 -5 M to 10 -4 M standard solution, (c) is a figure showing the response time of the electrode in 10 -4 M to 10 -3 M standard solution, and (d) is a figure showing the response time of the electrode in 10 -2 M to 10 -1 M standard solution, and it can be seen that the cobalt wire phosphate selective electrode generates a stable signal in about 4-40 s after being placed in the test solution. Figure 10

[0124] Example 14

[0125] (1) A cobalt wire with a purity of 99.9% and a diameter of 0.3 mm was cut to a length of about 5 cm and polished on sandpaper to remove the oxide film that may be formed on the surface;

[0126] (2) The cobalt wire was connected to a tinned copper wire by welding, and the welded part was fixed by wrapping a sealing film; the cobalt wire was sleeved into a polyvinyl chloride sleeve with a length of 5 cm and a diameter of 0.5 mm, and the two ends of the polyvinyl chloride sleeve were sealed and fixed with epoxy resin;

[0127] (3) After the epoxy resin was completely cured, the exposed part of the cobalt wire was polished with aluminum oxide powder with a particle size of 0.5 um on a polishing cloth; after polishing, the cobalt wire was sequentially ultrasonically cleaned in ethanol and acetone solutions for 10 min each to remove other organic impurities that may exist on the surface, to obtain a common polished cobalt wire electrode.

[0128] ​(4) The above-mentioned general polishing cobalt wire electrode was used as the working electrode, and a platinum wire (1 cm x 0.5 mm) electrode was used as the counter electrode. The pretreated cobalt wire electrode, i.e., the cobalt wire phosphate selective electrode, was prepared by constant potential pretreatment in a 0.5 M sodium hydroxide solution at a voltage of 30 V for 600 s.

[0129] The cobalt wire phosphate selective electrode prepared in this example was placed in a 10 -5 M sodium dihydrogen phosphate standard solution for activation for 30 min. After the electrode potential was stable, 10 -5 M to 10 -1 M NaNO3, Na2CO3, NaCl, Na2SO4, and NaH2PO4 solutions were used to evaluate the interference of nitrate ions, carbonate ions, chloride ions, and sulfate ions in common anions in water on the cobalt wire phosphate selective electrode. The cobalt wire phosphate selective electrode was first detected in the phosphate standard solution, and then different concentrations of anions were measured. The results are shown in Figure 10 Figure 10 Figure showing the interference of common anions (chloride, carbonate, nitrate, and sulfate) and dissolved oxygen in water on the cobalt wire phosphate selective electrode prepared in Example 14; (a) is a graph showing the interference of common anions (chloride, carbonate, nitrate, sulfate, and dihydrogen phosphate) on the cobalt wire phosphate selective electrode, and (b) is a graph showing the interference of dissolved oxygen in water on the cobalt wire phosphate selective electrode. As shown in Figure 11 (a), the cobalt wire phosphate selective electrode has a significant difference in sensitivity to phosphate and other interfering ions. The response sensitivity of the electrode to phosphate is 65.08 mV / dec, and the sensitivities to nitrate ions, carbonate ions, chloride ions, and sulfate ions are 10.02, 14.14, 8.57, and 17.70 mV / dec, respectively. Other anions hardly cause changes in the potential signal of the cobalt wire phosphate selective electrode with increasing concentration, and the change in sensitivity is almost negligible.

[0130] Further, the effect of dissolved oxygen content in water on the pretreated cobalt wire electrode was investigated. The cobalt wire phosphate selective electrode was sequentially placed in 10 -5 M sodium dihydrogen phosphate standard solution at room temperature and room pressure under three different dissolved oxygen concentrations of 21%, 0%, and 100%. As shown in Figure 11 (b), when the dissolved oxygen concentration increased from 21% to 100%, the potential signal value of the cobalt wire phosphate selective electrode increased by 53 mV in the positive direction, and the average signal value change was 8.7 mV per 10% increase in dissolved oxygen. This indicates that the electrode is less affected by dissolved oxygen in water.

[0131] Example 15​

[0132] (1) The cobalt wire with a purity of 99.9% and a diameter of 0.3 mm was cut to a length of about 5 cm and polished on sandpaper to remove the oxide film that may be formed on the surface;

[0133] (2) The cobalt wire was connected to the tinned copper wire by welding, and the welding site was fixed by wrapping the sealing film. The cobalt wire was sleeved into a polyvinyl chloride sleeve with a length of 5 cm and a diameter of 0.5 mm, and the two ends of the polyvinyl chloride sleeve were sealed and fixed with epoxy resin;

[0134] (3) After the epoxy resin was completely cured, the exposed part of the cobalt wire was polished on a polishing cloth with aluminum oxide powder with a particle size of 0.5 um; after polishing, it was sequentially ultrasonically cleaned in ethanol and acetone solutions for 10 min each to remove other organic impurities that may exist on the surface, thereby obtaining a general polished cobalt wire electrode.

[0135] (3) The above general polished cobalt wire electrode was used as the working electrode, and a platinum wire (1 cm x 0.5 mm) electrode was used as the counter electrode. In a 0.5 M sodium hydroxide solution, a constant potential pretreatment was performed at a voltage of 30 V, and the pretreatment time was 600 s, thereby obtaining a pretreated cobalt wire electrode, i.e., a cobalt wire phosphate selective electrode. The cobalt wire phosphate selective electrode prepared in this example was activated in a 10 -5 M sodium dihydrogen phosphate standard solution for 30 min, and after the electrode potential was stable. The service life of the cobalt wire phosphate selective electrode was tested, and the detection range was 10 -5 M to 10 -1 M, each concentration was measured in triplicate, the test period was 7 days / time, and after each test, the electrode was rinsed with deionized water and naturally air-dried. The results are shown in Figure 11 ​ Figure 1 shows the response sensitivity change trend of the cobalt wire phosphate selective electrode prepared in Example 15 during long-term use in a sodium dihydrogen phosphate standard solution. As can be seen from ​ , the sensitivity changed little in the first 5 weeks. After the 5th week, the response slope decreased slightly, but the overall sensitivity response trend was stable, with a maximum fluctuation of 1.3 mV / dec. The slope change between the 7th week measurements was less than 1.76 mV / dec·week -1 (RSD = 2.75%). After the 8th week, the sensitivity began to decrease significantly, the black oxide layer on the electrode surface began to gradually fall off, a silver-gray metal surface appeared, and the test error increased. Therefore, it can be considered that the sensor can be continuously used for more than 7 weeks, and it needs to be polished and re-constant voltage pretreated after 8 weeks.​

Claims

1. A method for preparing a cobalt wire phosphate selective electrode, characterized in that, Includes the following steps: (1) Polish the cobalt wire to obtain a pretreated cobalt wire; (2) Connect the cobalt wire to the metal wire, wrap the connection with sealing film to fix it, put the polyvinyl chloride sleeve in to completely cover the sealing film, and seal the connection of the two ends of the polyvinyl chloride sleeve with epoxy resin. (3) The exposed part of the cobalt wire is polished with alumina powder and then ultrasonically cleaned in ethanol and acetone solutions in turn to obtain a conventional polished cobalt wire electrode. (4) Using a common polished cobalt wire electrode as the working electrode and a platinum wire electrode as the counter electrode, the high voltage constant potential pretreatment was carried out in a 0.5 M sodium hydroxide solution, followed by cleaning and drying to obtain a cobalt wire phosphate selective electrode. The high voltage constant potential pretreatment potential was 30 V and the high voltage constant potential pretreatment time was 600 s.

2. The method for preparing the cobalt wire phosphate selective electrode according to claim 1, characterized in that, In step (1), the polishing is done by polishing with sandpaper to remove the oxide film that may form on the surface. The cobalt wire has a purity of 99~99.99% and a diameter of 0.3~0.8mm.

3. The method for preparing the cobalt wire phosphate selective electrode according to claim 1, characterized in that, In step (2), the cobalt wire is connected to the metal wire by welding. The length of the polyvinyl chloride sleeve is 5~10 cm and the diameter of the polyvinyl chloride sleeve is 0.3~0.5 mm.

4. The method for preparing the cobalt wire phosphate selective electrode according to claim 1, characterized in that, In step (2), when inserting the polyvinyl chloride sleeve, the exposed length of the cobalt wire needs to be at least 1 cm. The metal wire is copper wire or tin-plated copper wire.

5. The method for preparing the cobalt wire phosphate selective electrode according to claim 1, characterized in that, In step (3), the particle size of the alumina powder is 0.5~1.5um.

6. The method for preparing the cobalt wire phosphate selective electrode according to claim 1, characterized in that, In step (3), the ultrasonic cleaning time is 10~15 min.

7. The application of the cobalt wire phosphate selective electrode obtained by the preparation method according to any one of claims 1 to 6 in the detection of phosphate in water.

8. The application according to claim 7, characterized in that, The cobalt wire phosphate selective electrode is placed in a solution containing 10 -5 The phosphate of M is activated by soaking in the test aqueous solution for 30-60 min, and the pH of the water is 4-8.

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