Karl Fischer coulometry water electrolysis electrode

Abstract

The invention discloses a Karl Fischer coulometry water electrolysis electrode which comprises an electrolysis anode and an electrolysis cathode, a diaphragm tube is arranged between the electrolysis anode and the electrolysis cathode, and the diaphragm tube is detachable and can be timely and conveniently detached for cleaning or replacement, so that the electrolysis efficiency is continuously close to 100%, and the Karl Fischer coulometry water electrolysis electrode has extremely high practical value.

Description

Technical Field

[0001] The invention relates to a Karl Fischer coulometric water electrolysis electrode, which can be used for electrolysis and titration of elemental iodine in the Karl Fischer coulometric method. Background Art

[0002] The Karl Fischer coulometric method does not require calibration of the Karl Fischer solution. It directly uses the amount of electricity used for electrolysis to quickly determine the amount of water. It has the advantages of fast speed, accurate measurement, sensitivity, and low detection limit. It is widely used in the fields of medicine, food, petrochemicals, new energy, and materials. The electrolytic electrode is divided into an electrolytic electrode with a diaphragm and an electrolytic electrode without a diaphragm according to whether it has a diaphragm or not. The key material relationships are as follows:

[0003] H2O~I2~2e~H2~SO2

[0004] At present, both diaphragm electrolysis electrodes and non-diaphragm electrolysis electrodes are made of glass, and the electrodes are made of high-purity platinum. Among them, the diaphragm electrolysis electrode uses a glass sand core as a diaphragm, which can effectively separate the cathode and the anode, achieving an electrolysis efficiency close to 100% theoretical value. However, there is no diaphragm in the non-diaphragm electrode. At this time, the elemental iodine produced by anode electrolysis will partially contact the cathode, and the cathode will produce a side reaction that consumes elemental iodine, causing the electrolysis efficiency to be far less than 100%. Moreover, the electrolysis efficiency is unstable, and the electrolysis efficiency is related to factors such as the amount of solution in the titration cup, the stirring speed, and the specific structure of the electrode itself. Therefore, under the requirements of high sensitivity, high precision and high accuracy, non-diaphragm electrodes cannot be used, and diaphragm electrodes must be used. However, due to the small pore size of the glass sand core of the diaphragm electrode, it is very easy to have blockage, gas gap blocking and other faults, and the cleaning is cumbersome and the effect is not good.

[0005] Therefore, a new Karl Fischer coulometric water electrolysis electrode with a detachable diaphragm is needed, which can achieve high sensitivity, high precision and high accuracy and is easy to replace and maintain. Summary of the invention

[0006] In order to overcome the above problems, the inventors have conducted intensive research and designed a Karl Fischer coulometric water electrolysis electrode, which includes an electrolysis anode and an electrolysis cathode, and a diaphragm tube is arranged between the two. The diaphragm tube is detachable and can be disassembled, cleaned or replaced in a timely and convenient manner, thereby ensuring that the electrolysis efficiency continues to be close to 100%, which has extremely high practical value, thereby completing the present invention.

[0007] Specifically, the object of the present invention is to provide a Karl Fischer coulometric water electrolysis electrode, the electrode comprising an electrolysis anode 1 and an electrolysis cathode 2 mounted on an electrode rod 3,

[0008] The electrolytic anode 1 comprises an anode ring-shaped platinum mesh 11,

[0009] The electrolytic cathode 2 comprises a cathode annular platinum mesh 21,

[0010] The anode annular platinum mesh 11 is sleeved on the outside of the cathode annular platinum mesh 21.

[0011] A detachable diaphragm tube 9 is arranged between the anode annular platinum mesh 11 and the cathode annular platinum mesh 21 .

[0012] The electrolytic anode 1 further comprises an anode platinum wire 12, and the anode platinum wire 12 is welded and fixed to the anode annular platinum mesh 11.

[0013] The electrolytic cathode 2 further includes a cathode platinum wire 22 , and the cathode platinum wire 22 is welded and fixed to the cathode annular platinum mesh 21 .

[0014] The diameter of the anode platinum wire 12 and the cathode platinum wire 22 is 0.2 mm to 1 mm;

[0015] The mesh number of the anode annular platinum mesh 11 and the cathode annular platinum mesh 21 is 20-100 meshes; they are woven from platinum wires with a diameter of 0.02 mm-0.05 mm.

[0016] A detachable diaphragm cap 4 is also provided between the anode annular platinum mesh 11 and the cathode annular platinum mesh 21;

[0017] The detachable diaphragm cap 4 is screwed and fixed to the electrode rod 3 by means of threads;

[0018] The diaphragm tube 9 is restricted and fixed between the anode annular platinum mesh 11 and the cathode annular platinum mesh 21 by the detachable diaphragm cap 4 .

[0019] Wherein, two diaphragm windows 7 are symmetrically opened on the side wall of the removable diaphragm cap 4. When the removable diaphragm cap 4 is screwed onto the electrode rod 3, the anode annular platinum mesh 11 is located on the outside of the diaphragm window 7, and the cathode annular platinum mesh 21 is located on the inside of the diaphragm window 7;

[0020] Preferably, the removable diaphragm cap 4 is made of polytetrafluoroethylene.

[0021] The diaphragm window 7 includes circular holes arranged in a honeycomb pattern, the diameter of the circular holes is 2 mm, the spacing between the circular holes is 4 mm, and a perfluorosulfonic acid resin film is thermoplastically sealed on the circular holes.

[0022] A cathode liquid adding pipe 6 is also provided on the electrode rod 3.

[0023] Preferably, the cathode liquid adding pipe 6 is a polyfluoroethylene pipe.

[0024] More preferably, the polyperfluoroethylene tube has a length of 50 mm, an inner diameter of 1 mm, and an outer diameter of 2 mm.

[0025] Wherein, when the removable diaphragm cap 4 is an integrated removable diaphragm cap 8, the bottom of the integrated removable diaphragm cap 8 is a sealed cylindrical structure;

[0026] The diameter of the anode platinum wire 12 is 0.25 mm;

[0027] The mesh number of the anode ring-shaped platinum mesh 11 is 40 meshes, and it is woven from platinum wires with a diameter of 0.02 mm. The anode ring-shaped platinum mesh 11 is in the shape of a ring with a height of 10 mm and a diameter of 15 mm;

[0028] The diameter of the cathode platinum wire 22 is 0.25 mm;

[0029] The cathode annular platinum mesh 21 has a mesh number of 40 and is woven from platinum wires with a diameter of 0.02 mm. The cathode annular platinum mesh 21 is in the shape of an annulus with a height of 10 mm and a diameter of 7 mm.

[0030] Wherein, when the removable diaphragm cap 4 is a split-type removable diaphragm cap 10, the diameter of the anode platinum wire 12 is 0.30 mm;

[0031] The mesh number of the anode ring-shaped platinum mesh 11 is 50 meshes, and it is woven from platinum wire with a diameter of 0.015 mm. The anode ring-shaped platinum mesh 11 is in the shape of a ring with a height of 12 mm and a diameter of 15 mm;

[0032] The diameter of the cathode platinum wire 22 is 0.30 mm;

[0033] The cathode annular platinum mesh 21 has a mesh number of 20 to 100 and is woven from platinum wires with a diameter of 0.015 mm. The cathode annular platinum mesh 21 is in the shape of an annulus with a height of 12 mm and a diameter of 5 mm.

[0034] Among them, the inner diameter of the split detachable diaphragm cap 10 is 6mm, and the total length is 25mm, wherein the upper step length is 20mm, and the lower step length is 5mm; the outer diameter of the upper step is 10mm, and the outer diameter of the lower step is 12mm.

[0035] The diaphragm tube 9 is detachably mounted on the upper step.

[0036] The diaphragm tube 9 is a microporous polytetrafluoroethylene tube with an inner diameter of 10 mm, an outer diameter of 12 mm, a length of 15 mm, and a pore diameter of 5 μm.

[0037] The beneficial effects of the present invention include:

[0038] (1) According to the Karl Fischer coulometric water electrolysis electrode provided by the present invention, the diaphragm tube thereon can freely enter and exit between the two electrodes as needed, thereby ensuring that the cathode and the anode are separated by the diaphragm tube during the electrolysis process, and the diaphragm tube can be easily replaced or cleaned;

[0039] (2) According to the Karl Fischer coulometric water electrolysis electrode provided by the present invention, a diaphragm cap is provided at the diaphragm tube, and the diaphragm cap is used to fix the diaphragm tube. This can ensure that the diaphragm tube is located at a predetermined position during electrolysis and provide protection for the diaphragm tube. The diaphragm tube can also be disassembled and moved through the diaphragm cap. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The overall structure schematic diagram of the Karl Fischer coulometric water electrolysis electrode of the present application is shown;

[0041] Figure 2 A schematic diagram of the structure of the integrated detachable diaphragm cap of the present application is shown;

[0042] Figure 3 A schematic diagram of the split-type detachable diaphragm cap structure of the present application is shown.

[0043] Description of Reference Numerals

[0044] 1- Electrolysis anode

[0045] 11-Anode ring platinum mesh

[0046] 12-Anode platinum wire

[0047] 2-Electrolysis cathode

[0048] 21-Cathode ring platinum mesh

[0049] 22-Cathode platinum wire

[0050] 3-Upper electrode rod

[0051] 4-Removable diaphragm cap

[0052] 5-Upper electrode rod through hole

[0053] 6-Cathode liquid filling tube

[0054] 7-Diaphragm window

[0055] 8-One-piece removable diaphragm cap

[0056] 9-Diaphragm tube

[0057] 10-Split removable diaphragm cap DETAILED DESCRIPTION

[0058] The present invention will be further described in detail below through the accompanying drawings and embodiments. Through these descriptions, the characteristics and advantages of the present invention will become more clear and distinct.

[0059] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0060] The present invention provides a Karl Fischer coulometric water electrolysis electrode, such as Figure 1 As shown in FIG. , the electrode comprises an electrolytic anode 1 and an electrolytic cathode 2 mounted on an electrode rod 3.

[0061] The electrolytic anode 1 comprises an anode ring-shaped platinum mesh 11,

[0062] The electrolytic cathode 2 comprises a cathode annular platinum mesh 21,

[0063] The anode annular platinum mesh 11 is sleeved on the outside of the cathode annular platinum mesh 21, and the two are at the same level;

[0064] A detachable diaphragm tube 9 is provided between the anode annular platinum mesh 11 and the cathode annular platinum mesh 21. The diaphragm tube 9 can effectively separate the cathode from the anode, achieving an electrolysis efficiency close to a theoretical value of 100%.

[0065] In a preferred embodiment, the electrolytic anode 1 further comprises an anode platinum wire 12, and the anode platinum wire 12 is welded and fixed to the anode annular platinum mesh 11.

[0066] The electrolytic cathode 2 further includes a cathode platinum wire 22 , and the cathode platinum wire 22 is welded and fixed to the cathode annular platinum mesh 21 .

[0067] The diameter of the anode platinum wire 12 and the cathode platinum wire 22 is 0.2 mm to 1 mm;

[0068] The mesh number of the anode annular platinum mesh 11 and the cathode annular platinum mesh 21 is 20-100 meshes, and they are woven from platinum wires with a diameter of 0.02mm-0.05mm. The platinum in the present application is preferably high-purity metal platinum, and the higher its purity, the better the electrolysis effect.

[0069] In a preferred embodiment, a detachable diaphragm cap 4 is further provided between the anode annular platinum mesh 11 and the cathode annular platinum mesh 21;

[0070] The detachable diaphragm cap 4 is screwed and fixed to the electrode rod 3 by means of threads;

[0071] The diaphragm tube 9 is restricted and fixed between the anode annular platinum mesh 11 and the cathode annular platinum mesh 21 by the detachable diaphragm cap 4 .

[0072] Preferably, two diaphragm windows 7 are symmetrically opened on the side wall of the removable diaphragm cap 4, and when the removable diaphragm cap 4 is screwed onto the electrode rod 3, the anode annular platinum mesh 11 is located on the outside of the diaphragm window 7, and the cathode annular platinum mesh 21 is located on the inside of the diaphragm window 7;

[0073] Preferably, the removable diaphragm cap 4 is made of polytetrafluoroethylene; the size of the diaphragm window 7 is 15 mm×8 mm.

[0074] The total area of ​​the circular holes is proportional to the size of the internal and external anode and cathode resistances. The larger the resistance, the greater the voltage required for the same current, and the heat generation is proportional to the square of the resistance. The heating of the electrode will cause the solvent and water vapor to volatilize, affecting the accuracy of the moisture measurement, and even evaporate the cathode liquid. Therefore, the total area of ​​the circular holes should be appropriately increased. However, due to other releases produced by electrolysis, the local pressure of the cathode will be greater than that of the anode, which will force the membrane to undergo stress deformation or even rupture. The stress deformation will increase with the increase of the diameter of a single circular hole, so the diameter of the circular hole should be appropriately reduced. Based on this, the diaphragm window 7 described in the present application includes circular holes arranged in a honeycomb manner, the diameter of the circular holes is 2 mm, and the spacing between the circular holes is 4 mm. The measurement accuracy and service life are taken into account by the appropriate circular hole diameter.

[0075] A perfluorosulfonic acid resin membrane is thermoplastically sealed on the circular hole. The perfluorosulfonic acid resin membrane has strong chemical reaction inertness, high temperature tolerance, can fully tolerate Karl Fischer reagent and common moisture determination samples, and has good proton transfer performance, that is, extremely low resistivity. Therefore, the perfluorosulfonic acid resin membrane is the best ion conductive membrane. Other polystyrene anion and cation conductive membranes do not have the above properties.

[0076] In a preferred embodiment, a cathode liquid adding pipe 6 is also provided on the electrode rod 3.

[0077] Preferably, the cathode liquid adding pipe 6 is a polyfluoroethylene pipe.

[0078] More preferably, the polyperfluoroethylene tube has a length of 50 mm, an inner diameter of 1 mm, and an outer diameter of 2 mm.

[0079] The cathode liquid adding tube 6 needs to be installed in the cathode electrolysis chamber, so its size cannot be larger than the cathode electrolysis chamber. If the tube diameter is too small, the liquid adding speed will be affected. Based on this, a perfluoroethylene tube with a tube diameter of 2mm*1mm is selected in this application. Its length can be set more arbitrarily. In this application, it is selected to be set to 50mm to facilitate external connection with other quick connectors, such as Luer lock syringes.

[0080] In a preferred embodiment, Figure 2 As described in, when the removable diaphragm cap 4 is an integrated removable diaphragm cap 8,

[0081] The bottom of the integrated detachable diaphragm cap 8 is a sealed cylindrical structure;

[0082] In the present application, the one-piece structure does not have more contact surfaces, and its sealing performance is better than that of the split type.

[0083] The diameter of the anode platinum wire 12 is 0.25 mm;

[0084] The mesh number of the anode ring-shaped platinum mesh 11 is 40 meshes, and it is woven from platinum wires with a diameter of 0.02 mm. The anode ring-shaped platinum mesh 11 is in the shape of a ring with a height of 10 mm and a diameter of 15 mm;

[0085] The diameter of the cathode platinum wire 22 is 0.25 mm;

[0086] The cathode annular platinum mesh 21 has a mesh number of 40 and is woven from platinum wires with a diameter of 0.02 mm. The cathode annular platinum mesh 21 is in the shape of an annulus with a height of 10 mm and a diameter of 7 mm.

[0087] The finer the mesh, the more platinum wire is used, and the higher the cost. If the mesh is not enough, the surface area is too small, the resistance is too large, the electrolytic current is limited, and the heat generation is obvious. Based on this, the inventors found that the overall effect of selecting a 40-mesh platinum mesh is the best.

[0088] The wire diameter and wire diameter are mainly considered based on production cost and maximum current. Generally, the minimum wire diameter and wire diameter corresponding to the maximum current are selected to reduce the amount of platinum wire and reduce manufacturing cost. The mesh number, wire diameter and wire diameter of the platinum wire used in the integrated and split types are basically the same.

[0089] The internal thread of the integrated detachable diaphragm cap is screwed together with the external thread of the electrode rod.

[0090] The upper electrode rod 3 is made of polytetrafluoroethylene and has an outer diameter of 12 mm. Two upper electrode rod through holes 5 with a diameter of 3 mm are symmetrically drilled at a distance of 30 mm from the bottom of the upper electrode rod 3, and an M10 upper electrode rod external thread with a length of 5 mm is processed at the bottom.

[0091] In the present application, the electrode rod through hole 5 is for the hydrogen generated by the cathode to pass through, and then discharged through the drying tube of the anode titration cup to eliminate the pressure difference between the cathode and the cathode. Since a large amount of hydrogen is generated by cathode electrolysis, a phenomenon similar to "boiling" occurs in the cathode electrolytic cell. Therefore, in order to prevent the cathode and anode liquids from overflowing and mixing, it is necessary to be higher than the commonly used liquid level and lower than the sealing ground mouth. It is preferably selected to be located 10 mm below the sealing ground mouth.

[0092] The ion exchange membrane on the integrated detachable diaphragm cap 8 is on the outside of the diaphragm cap. Although being located inside or outside does not affect electrolysis, the inventors have found that being located outside is more conducive to the diffusion and mass transfer of iodine produced by anode electrolysis.

[0093] In a preferred embodiment, Figure 3 As described in, when the removable diaphragm cap 4 is a split-type removable diaphragm cap 10, the diameter of the anode platinum wire 12 is 0.30 mm;

[0094] The mesh number of the anode ring-shaped platinum mesh 11 is 50 meshes, and it is woven from platinum wire with a diameter of 0.015 mm. The anode ring-shaped platinum mesh 11 is in the shape of a ring with a height of 12 mm and a diameter of 15 mm;

[0095] The diameter of the cathode platinum wire 22 is 0.30 mm;

[0096] The mesh number of the cathode annular platinum 21 is 20-100 meshes, preferably 50 meshes, and is woven from platinum wires with a diameter of 0.015 mm. The cathode annular platinum mesh 21 is in the shape of a ring with a height of 12 mm and a diameter of 5 mm.

[0097] The external thread of the split-type detachable diaphragm cap is screwed together with the internal thread of the electrode rod.

[0098] The upper electrode rod 3 is made of polytetrafluoroethylene and has an outer diameter of 12 mm. Two upper electrode rod through holes 5 with a diameter of 3 mm are symmetrically drilled at a distance of 30 mm from the bottom of the upper electrode rod 3, and an M10 upper electrode rod internal thread with a length of 5 mm is processed at the bottom.

[0099] Preferably, the split-type detachable diaphragm cap 10 has an inner diameter of 6 mm and a total length of 25 mm, wherein the upper step is 20 mm long and the lower step is 5 mm long; the outer diameter of the upper step is 10 mm and the outer diameter of the lower step is 12 mm.

[0100] Preferably, the diaphragm tube 9 is detachably mounted on the upper step.

[0101] The diaphragm tube 9 is a microporous polytetrafluoroethylene tube with an inner diameter of 10 mm, an outer diameter of 12 mm, a length of 15 mm, and a pore diameter of 5 μm.

[0102] The size of the microporous polytetrafluoroethylene tube needs to be matched with the electrolytic cell, and the size of the cell body is related to the generally required electrolyte volume. Therefore, the inner and outer diameters and length are basically determined. The size of the pore size and wall thickness mainly affects the resistance to mass transfer and the conductivity coefficient. The wall thickness is also related to the mechanical strength. Based on this, the above-mentioned size is selected in this application to take into account both mass transfer and strength.

[0103] The electrolytic cell does not need to be cleaned or replaced during general use, but it is easy to get clogged when used with samples such as petroleum, lubricating oil, butter, and asphalt. Once a traditional electrolytic electrode is clogged, it can only be cleaned or replaced. In many cases, it cannot be cleaned completely and can only be replaced. Mettler and Wantong's electrolytic electrodes are basically priced at more than 10,000 yuan, and domestic ones also cost about 2,000 yuan. The electrode clogging situation depends on the sample, and there are cases where it cannot be cleaned and used in half a month.

[0104] The perfluorosulfonic acid membrane and other fluoroplastics used in the Karl Fischer coulometric water electrolysis electrode provided in the present application have good chemical resistance and good non-adhesion properties, and combined with the structural dimensions of the electrode and other related devices, the overall use effect is greatly improved. Among the first batch of samples in normal use, they have been in normal use for more than half a year, and there has been no clogging or difficulty in cleaning, and no membrane damage.

[0105] Example

[0106] Aviation lubricating oil with a water content of about 800 μg / g was selected as the sample to be electrolyzed, and electrolysis was performed using a Karl Fischer coulometric water electrolysis electrode. The parameters are as follows:

[0107] Stirring speed: 700 rpm;

[0108] Maximum electrolysis current: 200mA;

[0109] Minimum electrolysis current: 2mA;

[0110] Polarization current: 5μA;

[0111] Starting voltage: 500mV;

[0112] End point voltage: 150mV;

[0113] End point delay: 8s.

[0114] The Karl Fischer coulometric water electrolysis electrode comprises an electrolytic anode 1 and an electrolytic cathode 2 mounted on an electrode rod 3, wherein the electrolytic anode comprises an anode annular platinum mesh 11 woven from platinum wires with a diameter of 0.02 mm and a mesh number of 40, on which an anode platinum wire 12 with a diameter of 0.25 mm is welded; the electrolytic cathode comprises a cathode annular platinum mesh 21 woven from platinum wires with a diameter of 0.02 mm and a mesh number of 40, on which a cathode platinum wire 22 with a diameter of 0.25 mm is welded, and the anode annular platinum mesh is sleeved on the outside of the cathode annular platinum mesh.

[0115] A detachable diaphragm tube 9 and a detachable diaphragm cap 4 are arranged between the anode annular platinum mesh 11 and the cathode annular platinum mesh 21; two diaphragm windows 7 are symmetrically opened on the side wall of the detachable diaphragm cap, and the diaphragm window 7 includes circular holes arranged in a honeycomb manner, the diameter of the circular holes is 2 mm, the spacing between the circular holes is 4 mm, and a perfluorosulfonic acid resin film is thermoplastically sealed on the circular holes.

[0116] The electrode rod 3 is also provided with a cathode liquid adding tube 6 made of a polyperfluoroethylene tube, which has a tube length of 50 mm, an inner diameter of 1 mm and an outer diameter of 2 mm.

[0117] The average value of the first 4 samples was 809.7, with a relative standard deviation of 1.9%. The results of the subsequent 16 samples are as follows:

[0118]

[0119] The data in the above table show that after 20 consecutive injections, the precision and accuracy of the Karl Fischer coulometric water electrolysis electrode remained basically unchanged, meeting the test requirements.

[0120] Before and after the experiment, 10.0 μL of distilled water was injected using a 10 μL injection needle, and the measurement results were 9851 μg and 9930 μg, respectively, with recovery rates of 98.51% and 99.30%, which met the accuracy requirements of the experiment.

[0121] Comparative Example 1

[0122] The parameters are as follows: aviation lubricating oil with a water content of about 800 μg / g is selected as the sample to be electrolyzed, and the electrolysis operation is performed using an EMW-1 diaphragm electrode. The parameters are as follows:

[0123] Stirring speed: 700 rpm;

[0124] Maximum electrolysis current: 200mA;

[0125] Minimum electrolysis current: 2mA;

[0126] Polarization current: 5μA;

[0127] Starting voltage: 500mV;

[0128] End point voltage: 150mV;

[0129] End point delay: 8s.

[0130] The EMW-1 diaphragm electrode was used to repeat the experiment on 20 samples to be electrolyzed. The results are as follows:

[0131]

[0132]

[0133] The data in the table above show that in the 20 consecutive injections, the precision and accuracy remained basically unchanged in the first 8 injections, meeting the test requirements. However, with the subsequent injections, the results of the subsequent 12 experiments fluctuated greatly, and the values ​​also deviated from the initial measurement results;

[0134] Before and after 20 consecutive samples, 10.0 μL of distilled water was injected using a 10 μL injection needle, and the measurement results were 9972 μg and 12643 μg, respectively, with recoveries of 99.72% and 126.43%. It can be seen that the first 8 experiments of continuous injection met the accuracy requirements, but the subsequent 12 experiments did not.

[0135] Comparative Example 2

[0136] Aviation lubricating oil with a water content of about 800 μg / g was selected as the sample to be electrolyzed, and the EMW-2 type diaphragmless electrode was used for electrolysis. The parameters are as follows:

[0137] Stirring speed: 700 rpm;

[0138] Maximum electrolysis current: 200mA;

[0139] Minimum electrolysis current: 2mA;

[0140] Polarization current: 5μA;

[0141] Starting voltage: 500mV;

[0142] End point voltage: 150mV;

[0143] End point delay: 8s.

[0144] The EMW-2 type diaphragmless electrode was used to continuously repeat the experiment on 20 identical samples to be electrolyzed. The results are as follows:

[0145]

[0146] The data in the above table show that after 20 consecutive injections, there are errors in precision and accuracy, which deviate from the results of Example and Comparative Example 1.

[0147] Before and after 20 consecutive samples, 10.0 μL of distilled water was injected using a 10 μL injection needle. The measurement results were 10804 μg and 11122 μg, respectively, with recoveries of 108.04% and 111.22%. It can be seen that the accuracy before and after continuous sampling deviated from the requirement of 95% to 105%.

[0148] It can be seen from the above embodiments and comparative examples that the Karl Fischer coulometric water electrolysis electrode provided in the present application has a long service life and a high electrolysis rate.

[0149] The present invention has been described above in conjunction with preferred embodiments, but these embodiments are only exemplary and serve only as an illustration. On this basis, the present invention may be subjected to a variety of substitutions and improvements, all of which fall within the scope of protection of the present invention.

Claims

1. A Karl Fischer coulometric water electrolysis electrode, characterized in that: The electrode comprises an electrolytic anode (1) and an electrolytic cathode (2) mounted on an electrode rod (3). The electrolytic anode (1) comprises an anode ring-shaped platinum mesh (11), The electrolytic cathode (2) comprises a cathode annular platinum mesh (21), The anode annular platinum mesh (11) is sleeved on the outside of the cathode annular platinum mesh (21). A detachable diaphragm tube (9) is arranged between the anode annular platinum mesh (11) and the cathode annular platinum mesh (21).

2. The Karl Fischer coulometric water electrolysis electrode according to claim 1, characterized in that: The electrolytic anode (1) further comprises an anode platinum wire (12), wherein the anode platinum wire (12) is welded and fixed to the anode annular platinum mesh (11). The electrolytic cathode (2) further comprises a cathode platinum wire (22), wherein the cathode platinum wire (22) is welded and fixed to the cathode annular platinum mesh (21); The diameter of the anode platinum wire (12) and the cathode platinum wire (22) is 0.2 mm to 1 mm; The mesh numbers of the anode annular platinum mesh (11) and the cathode annular platinum mesh (21) are 20 to 100 meshes, and they are woven from platinum wires with a diameter of 0.02 mm to 0.05 mm.

3. The Karl Fischer coulometric water electrolysis electrode according to claim 1, characterized in that: A detachable diaphragm cap (4) is also provided between the anode annular platinum mesh (11) and the cathode annular platinum mesh (21); The detachable diaphragm cap (4) is screwed and fixed to the electrode rod (3) via a thread; The diaphragm tube (9) is restricted and fixed between the anode annular platinum mesh (11) and the cathode annular platinum mesh (21) by the detachable diaphragm cap (4).

4. The Karl Fischer coulometric water electrolysis electrode according to claim 3, characterized in that: Two diaphragm windows (7) are symmetrically provided on the side wall of the detachable diaphragm cap (4); when the detachable diaphragm cap (4) is screwed onto the electrode rod (3), the anode annular platinum mesh (11) is located on the outside of the diaphragm window (7), and the cathode annular platinum mesh (21) is located on the inside of the diaphragm window (7); Preferably, the removable diaphragm cap (4) is made of polytetrafluoroethylene.

5. The Karl Fischer coulometric water electrolysis electrode according to claim 4, characterized in that: The diaphragm window (7) comprises circular holes arranged in a honeycomb pattern, the diameter of the circular holes is 2 mm, the spacing between the circular holes is 4 mm, and a perfluorosulfonic acid resin film is thermoplastically sealed on the circular holes.

6. The Karl Fischer coulometric water electrolysis electrode according to claim 1, characterized in that: A cathode liquid adding pipe (6) is also provided on the electrode rod (3). Preferably, the cathode liquid adding pipe (6) is a polyfluoroethylene pipe. More preferably, the polyperfluoroethylene tube has a length of 50 mm, an inner diameter of 1 mm, and an outer diameter of 2 mm.

7. The Karl Fischer coulometric water electrolysis electrode according to claim 3, characterized in that: When the removable diaphragm cap (4) is an integrated removable diaphragm cap (8), the bottom of the integrated removable diaphragm cap (8) is a sealed cylindrical structure; The diameter of the anode platinum wire (12) is 0.25 mm; The mesh number of the anode ring-shaped platinum mesh (11) is 40 meshes, and it is woven from platinum wires with a diameter of 0.02 mm. The anode ring-shaped platinum mesh (11) is in the shape of a ring with a height of 10 mm and a diameter of 15 mm; The diameter of the cathode platinum wire (22) is 0.25 mm; The cathode annular platinum mesh (21) has a mesh number of 40 and is woven from platinum wires with a diameter of 0.02 mm. The cathode annular platinum mesh (21) is in the shape of an annulus with a height of 10 mm and a diameter of 7 mm.

8. The Karl Fischer coulometric water electrolysis electrode according to claim 3, characterized in that: When the removable diaphragm cap (4) is a split-type removable diaphragm cap (10), the diameter of the anode platinum wire (12) is 0.30 mm; The mesh number of the anode ring-shaped platinum mesh (11) is 50 meshes, and it is woven from platinum wires with a diameter of 0.015 mm. The anode ring-shaped platinum mesh (11) is in the shape of a ring with a height of 12 mm and a diameter of 15 mm; The diameter of the cathode platinum wire (22) is 0.30 mm; The cathode annular platinum mesh (21) has a mesh number of 20 to 100 and is woven from platinum wires with a diameter of 0.015 mm. The cathode annular platinum mesh (21) is in the shape of an annulus with a height of 12 mm and a diameter of 5 mm.

9. The Karl Fischer coulometric water electrolysis electrode according to claim 8, characterized in that: The split-type detachable diaphragm cap (10) has an inner diameter of 6 mm and a total length of 25 mm, wherein the length of the upper step is 20 mm and the length of the lower step is 5 mm; the outer diameter of the upper step is 10 mm and the outer diameter of the lower step is 12 mm.

10. The Karl Fischer coulometric water electrolysis electrode according to claim 9, characterized in that: The diaphragm tube (9) is detachably sleeved on the upper step. The diaphragm tube (9) is a microporous polytetrafluoroethylene tube with an inner diameter of 10 mm, an outer diameter of 12 mm, a length of 15 mm, and a pore diameter of 5 μm.

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