A corrosion-resistant liquid chromatography column and its preparation method and application

Abstract

The present invention relates to the technical field of liquid chromatography columns, and in particular to a corrosion-resistant liquid chromatography column and a preparation method and application thereof. The inner hole of the corrosion-resistant liquid chromatography column has an inner hole roughness Ra controlled to be 0.01-0.1. Through a large number of experiments, the present invention creatively finds that by controlling the inner hole roughness Ra of the chromatographic column within the range of 0.01-0.1, it is beneficial to improve the smoothness of the inner hole of the chromatographic column tube, reduce the contact surface condition of the metal material, and thus improve the corrosion resistance of the liquid chromatography column.

Description

Technical Field

[0001] The invention relates to the technical field of liquid chromatography columns, and in particular to a corrosion-resistant liquid chromatography column and a preparation method and application thereof. Background Art

[0002] Liquid chromatography, as an extremely important separation and analysis technology, has unique technical characteristics. The medium of liquid chromatography includes stationary phase and mobile phase. Among them, the stationary phase presents various forms. For example, paper, thin plate, packed bed, etc. can be used as specific forms of stationary phase. Liquid acts as the mobile phase of liquid chromatography. The mobile phase of liquid chromatography has many characteristics:

[0003] (1) The purity requirement is extremely high to ensure that no impurities interfere with the subsequent analysis process. (2) The mobile phase has no dissolving effect on the stationary phase, otherwise it will destroy the structure of the stationary phase and affect the separation and analysis effect. (3) The mobile phase cannot cause any hindrance to the detection of sample components by the detector to ensure that the detector can accurately capture the signals of each component of the sample. (4) The mobile phase has sufficient dissolving capacity for the sample. Only in this way can the sample be fully dispersed in the mobile phase to achieve effective separation. (5) The mobile phase has a low viscosity, which can reduce resistance during the flow process and make the flow smoother. At the same time, the boiling point should be appropriately low, which is conducive to easier handling in some processes that require heating or evaporation. (6) The mobile phase should be as safe as possible and have low toxicity. This is not only related to the health of the operator, but also has important significance for the safety of the experimental environment. (7) Due to the wide variety of compounds that need to be analyzed and their properties are different, the mobile phase may have acidic, alkaline or buffer salt physicochemical properties. The presence of chemicals with these physicochemical properties will cause a certain degree of corrosion to the chromatographic filler and filler column. This corrosion may gradually damage the performance of the packing and the packed column, thus affecting the separation effect and service life of the liquid chromatography.

[0004] The HPLC column is mainly composed of six parts: filler, plug, column cap, filter (sieve) plate, and column tube. The filler mainly uses high-purity silica gel with a total metal impurity content of less than 20ppm. If the metal impurity content is too high, specific adsorption is likely to occur during the separation and analysis process, which will seriously interfere with the accuracy of the analysis results, so that some components in the sample cannot be separated in the chromatographic column as expected, thereby affecting the quality of liquid chromatography analysis. The plug is usually made of polyetheretherketone (PEEK), an engineering plastic that is resistant to acids, alkalis, salts, and solvents. PEEK material can ensure that the plug remains stable in a complex chemical environment, avoiding damage or deformation due to contact with various acids, alkalis, salts, and solvents, thereby ensuring the sealing and normal operation of the chromatographic column.

[0005] Based on the high requirements for pressure resistance, the column tubes, column caps and filter screens of current high-performance liquid chromatography columns are mostly made of 316L material. 316L stainless steel itself has excellent mechanical properties and certain corrosion resistance, can withstand high pressure, and meet the physical requirements of the chromatographic column during operation. Although 316L has the above advantages, it also has some problems. 316L has the phenomenon of metal ion dissolution, which is contrary to the corrosion resistance requirements of the chromatographic column. During the storage of the chromatographic column, as the mobile phase evaporates, the concentration of the acid, alkali or buffer salt originally remaining in the chromatographic column will gradually increase due to volatilization, and this concentration change will cause local corrosion. Chloride ions, in particular, have a serious impact on the corrosion resistance of 316L. Their presence will accelerate the corrosion process of 316L and reduce the service life and performance of the chromatographic column.

[0006] In order to improve the matching performance of chromatographic column tubes, plugs and fillers, the inert engineering plastic PEEK column tubes or corrosion-resistant bioactive coatings are currently mainly used on 316L column tubes. However, the chromatographic column needs to be filled under high pressure during the high-performance liquid phase filling process. Under the same inner diameter, in order to ensure the pressure resistance of the chromatographic column tube, the wall thickness of the PEEK column must be much higher than that of 316L, and the thermal conductivity drops sharply. Most liquid phase analysis is carried out in a constant temperature column oven through thermal radiation, which greatly limits the use of PEEK columns. For the deposition of metal coatings on 316L column tubes, the target material and operating conditions are relatively strict when using vapor phase chemical deposition, and the size of the deposition furnace limits the amount of deposition; and the purity of the target material will also affect the specific adsorption of the chromatographic column; the overall price of the deposited coating is expensive, and the scope of use has certain limitations. Summary of the invention

[0007] In view of the above problems, the present invention provides a corrosion-resistant liquid chromatography column and a preparation method and application thereof. Through a large number of experiments, the present invention creatively finds that by controlling the inner hole roughness Ra of the chromatography column within the range of 0.01-0.1, it is beneficial to improve the smoothness of the inner hole of the chromatography column tube, reduce the contact surface condition of the metal material, and thus improve the corrosion resistance of the liquid chromatography column.

[0008] In a first aspect, the present invention provides a corrosion-resistant liquid chromatography column, wherein the inner pore of the corrosion-resistant liquid chromatography column has an inner pore roughness Ra controlled at 0.01-0.1.

[0009] Preferably, the specification of the corrosion-resistant liquid chromatography column is inner diameter 1.0mm-4.6mm*length 50mm~250mm.

[0010] Preferably, the inner diameter of the corrosion-resistant liquid chromatography column is 1.0 mm, 2.1 mm, 3.0 mm, or 4.6 mm, and the length is 50 mm, 100 mm, 150 mm, or 250 mm.

[0011] In a second aspect, the present invention provides a method for preparing a corrosion-resistant liquid chromatography column. The preparation method comprises: Step A: cold drawing the steel pipe to obtain a tube blank with an inner hole having an inner hole roughness of Ra=0.4-0.6; Step B: mechanically polishing the steel pipe obtained in step A to an inner hole roughness Ra=0.2-0.4; Step C: electrochemically polishing the steel pipe obtained in step B until the inner hole roughness Ra=0.1-0.2; Step D: The steel pipe obtained in step C is polished by fluid until the inner hole roughness Ra=0.01-0.1.

[0012] Preferably, the cold drawing is performed by using tungsten steel as the core material and performing rotary cold drawing on the cold-rolled seamless steel pipe.

[0013] Preferably, the mechanical polishing is performed using grinding wheels or honing tools ranging from coarse to fine; preferably, mechanical polishing is performed using grinding wheels ranging from 400 mesh to 2000 mesh in sequence.

[0014] Preferably, the electrochemical polishing is performed by high pressure plasma or electroplating.

[0015] Preferably, the fluid polishing is extrusion fluid polishing.

[0016] Preferably, the fluid polishing is magnetic fluid polishing; preferably, the magnetic fluid polishing is designed to generate a rotational shear force perpendicular to the forward direction of the polishing fluid; more preferably, a magnetic substance with a particle size close to that of the abrasive is introduced into the polishing fluid, and in this case, the polishing fluid is a magnetic polishing fluid, and an annular magnetic field is arranged parallel to the circumferential direction of the chromatographic column to be processed, and the polishing fluid rotates rapidly along a circle perpendicular to the forward direction under the control of the magnetic field.

[0017] Preferably, the fluid polishing is rotary fluid polishing; preferably, a sealing structure and a rotating mechanism are designed in the advancing direction of the polishing fluid, and radial shearing is achieved through the relative rotation of the chromatographic column to be processed and the fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solution of the present invention, the following will be described in conjunction with the accompanying drawings. Obviously, the accompanying drawings are only for illustrating some embodiments of the present invention.

[0019] Figure 1 The results of 48h salt spray test on the chromatographic columns with different inner hole roughness (column tube 4.6*150mm) prepared in Example 1.

[0020] Figure 2 The results of 96 h salt spray test on the chromatographic columns with different inner hole roughness (column tube 4.6*150 mm) prepared in Example 1.

[0021] Figure 3 The results of 240h salt spraying of the chromatographic columns with different inner hole roughness (column tube 4.6*150mm) prepared in Example 1.

[0022] Figure 4 This is a comparison of different salt spray times of chromatographic columns with different inner hole roughness (column tube 4.6*150mm) prepared in Example 1.

[0023] Figure 5 The test results of the corrosion-resistant chromatographic column prepared in Example 1 and the commercially available chromatographic column are compared.

[0024] Figure 6 The test results of the corrosion-resistant chromatographic column prepared in Example 2 and the commercially available chromatographic column are compared. DETAILED DESCRIPTION

[0025] The present invention is further described by the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, but not to limit the present invention. Unless otherwise specified, the unit of roughness in the present invention is μm.

[0026] The present invention creatively finds through a large number of experiments that the inner hole roughness Ra of the chromatographic column is controlled within the range of 0.01-0.1, which is beneficial to improving the smoothness of the inner hole of the chromatographic column tube and reducing the contact surface condition of the metal material, thereby improving the corrosion resistance of the liquid chromatography column.

[0027] This is because: the smaller the roughness Ra of the inner hole of the chromatographic column, the higher the surface finish, the smaller the contact area between the sample or mobile phase and the inner wall of the chromatographic column, the easier it is to wash the sample, the easier it is to replace the mobile phase containing buffer salt, and the easier it is to remove the corrosive substances in the sample and mobile phase. At the same time, the higher the finish of the inner wall of the chromatographic column tube, the lower the surface activity, which can reduce the non-specific interaction between the sample molecules and the tube wall, reduce the risk of sample adsorption and degradation, and improve the separation efficiency and peak symmetry.

[0028] The inner diameter specifications of the commonly used analytical chromatographic columns in the prior art are usually 1.0mm, 2.1mm, 3.0mm, 4.6mm, etc., and the length specifications are usually 50mm, 100mm, 150mm, 250mm, etc. In other words, the aperture of the existing analytical chromatographic columns is small and the length is large. Different from the plane polishing, surface polishing, and large-diameter inner hole polishing of traditional mechanical processing, the inner hole polishing of the analytical chromatographic column is a high-precision polishing of the inner hole limited to a small space. When the inner hole of the liquid chromatography column is prepared by means of traditional mechanical processing, due to the large length and thin diameter of the grinding workpiece, as the length of the chromatographic column increases, the top vibration of the machining tool rod increases accordingly, resulting in the inability to achieve high-precision processing of slender and uniform channels, and the polishing equipment is also difficult to penetrate into the narrow inner hole for a long distance.

[0029] The present invention adopts the following technical scheme to prepare a corrosion-resistant liquid chromatography column with an inner hole roughness Ra controlled at 0.01-0.1. First, the seamless steel pipe is processed to a suitable pore size with an inner hole roughness Ra=0.4-0.6 by cold drawing, then the inner hole roughness Ra=0.2-0.4 is processed by mechanical polishing, then the inner hole roughness Ra=0.15-0.2 is processed by electrochemical polishing, and finally the inner hole roughness Ra=0.01-0.1 is processed by fluid polishing.

[0030] The present invention adopts a combination of mechanical polishing-electrochemical-fluid polishing to achieve the preparation of a chromatographic column with low roughness and a small diameter inner hole. During the fluid polishing process, the abrasive particles are not limited by the inner hole of the chromatographic column, and the peaks on the surface of the workpiece to be processed can be flattened to obtain an extremely smooth surface. In addition, the present invention arranges mechanical polishing at the beginning of the preparation method, which is convenient for efficiently and quickly obtaining a chromatographic column with a higher roughness; electrochemical polishing is arranged at the middle end of the preparation method, which can quickly achieve a further improvement in the finish; and fluid polishing is arranged at the end of the preparation method, so as to obtain the expected finish without pollution. The fluid polishing can be a flexible conformal polishing with a fluid polishing abrasive. As the morphology of the polished object changes, the polishing abrasive clings to the polished surface.

[0031] As an embodiment of the present invention, cold drawing refers to the production of cold-rolled seamless pipes using a three-roll mill, and the use of tungsten steel core material for rotary cold drawing to obtain a rough blank with an inner hole. This step can control the inner hole roughness Ra of the steel pipe to be 0.4-0.6. Through the cold drawing method, the obtained blank has high precision, relatively smooth inner and outer surfaces, good roundness and straightness, which can significantly shorten the machining time, improve material utilization, and at the same time help improve product quality.

[0032] As an embodiment of the present invention, mechanical polishing refers to further processing the inner hole surface using a grinding wheel or a honing tool from coarse to fine to ensure that the inner hole roughness Ra=0.2-0.4.

[0033] As an embodiment of the present invention, electrochemical polishing refers to using high-pressure plasma to make the roughness of the inner hole of the chromatographic column reach Ra=0.1-0.2. Due to the high current impact and fast removal, as the current flows, the level of the concave and convex surface of the workpiece changes continuously, and the rough surface is gradually leveled. Electrochemical polishing can also use an electroplating process to form an electroplating layer on the inner hole, so that the roughness of the inner hole of the chromatographic column reaches Ra=0.1-0.2.

[0034] As an embodiment of the present invention, fluid polishing refers to the use of magnetic fluid polishing to make the roughness of the inner hole of the chromatographic column reach Ra=0.01-0.1. Magnetorheological polishing technology uses magnetorheological polishing fluid to form a flexible "small grinding head" with viscoplastic behavior in a gradient magnetic field, which causes rapid relative movement between the workpiece and the surface of the workpiece, so that the workpiece surface is subjected to a large shear force, thereby removing the surface material of the workpiece. The composition of the magnetic polishing fluid may include magnetic tungsten balls, polycrystalline diamonds, and deionized water. Among them, the mass ratio of magnetic tungsten balls, polycrystalline diamonds, and deionized water can be 1:5~20:30~60.

[0035] Fluid polishing can be pure extrusion fluid polishing. Since there is only axial flushing, the polishing efficiency of extrusion fluid polishing needs to be further improved.

[0036] In order to further improve the fluid polishing efficiency, the present invention designs a rotational shear force perpendicular to the advancing direction of the polishing fluid (polishing liquid). Specifically, a magnetic material (such as a magnetic tungsten ball) with a particle size close to that of the abrasive is introduced into the polishing fluid containing abrasives (such as diamonds). In this case, the polishing fluid is a magnetic polishing fluid, and an annular magnetic field is arranged parallel to the circumferential direction of the chromatographic column to be processed. The polishing fluid rotates rapidly along the circumference perpendicular to the advancing direction under the control of the magnetic field, thereby improving the polishing efficiency. Alternatively, the present invention designs a sealing structure and a rotating mechanism in the advancing direction of the polishing fluid, and realizes radial shearing through the relative rotation of the chromatographic column to be processed and the fluid.

[0037] The prior art proposes a chromatographic column with an inner diameter of 30mm-200mm and a surface roughness of Ra 0.1-0.5 and its processing. However, the scenes of large-aperture polishing, plane polishing, and outer surface polishing are usually not limited by the construction space. However, the small-aperture chromatographic column described in the present invention is mainly for polishing the inner surface of the hole, which is largely limited by the construction scene of a small space. In view of this, the present invention creatively proposes a confined space processing method for an analytical chromatographic column with an aperture of 1mm-4.6mm.

[0038] In summary, the present invention proposes a universal preparation method for a corrosion-resistant and highly self-cleaning chromatographic column. When the aspect ratio of the relative diameter and length of the chromatographic column is relatively low, the inner hole rough blank is processed by rod machining, and the efficient and rapid production method of mechanical polishing-electrochemical polishing-fluid polishing is utilized to achieve the preparation of a corrosion-resistant liquid chromatography column with specific roughness requirements.

[0039] Chromatographic column cleaning. Chromatographic column cleaning is a conventional method in the art. As an embodiment of the present invention, the chromatographic column tube can be cleaned by deionized water / surfactant-passivation liquid-anhydrous ethanol.

[0040] Chromatographic column filling. Chromatographic column filling is a conventional method in this field. As an embodiment of the present invention, the chromatographic column is filled by high-pressure filling, and then the homogenate is immediately poured into the homogenate tank. After filling, the homogenate tank is covered and tightened; methanol is used as a displacement liquid to increase the pressure, maintain the pressure, and the filler in the homogenate is retained on the filter plate at the end of the column, while the homogenate is excluded from the column; after the pressure holding time is reached, the pressure is released and the pressure is gradually reduced to normal pressure; the filled column is disassembled and the column head with a sieve plate (filter) is assembled.

[0041] Chromatographic column detection. Chromatographic column detection is a conventional method in the art. The detection is performed according to the corresponding chromatographic column detection conditions.

[0042] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention. It should be noted that the description order of the following embodiments is not intended to limit the preferred order of the embodiments of the present invention.

[0043] Example 1

[0044] A three-roll mill is used to produce cold-rolled seamless pipes. The core material is made of 4.55mm outer diameter tungsten steel for rotary cold drawing to produce a tube blank with an outer diameter of 8mm, an inner diameter of 4.55mm, and an inner hole roughness of Ra = 0.5. The tube blank has good roundness and straightness, and is prepared into a tube blank with a length of 150mm after quantitative cutting.

[0045] The corresponding threads and wrench positions are processed at the pipe mouth, and the inner hole and surface are processed with grinding wheels ranging from 400 mesh to 2000 mesh. At the same time, soft wool felt is used to further polish the inner hole to ensure that the inner hole roughness Ra = 0.3.

[0046] The inner and outer surfaces are removed by high-pressure plasma impact. The current flows, the bumps and grooves change continuously, and the rough surface is gradually leveled to make the roughness of the chromatographic column inner hole Ra = 0.2. Continue to perform high-pressure plasma polishing, the rough surface is gradually leveled to make the roughness of the chromatographic column inner hole Ra = 0.1.

[0047] Magnetic fluid polishing is used. Magnetic tungsten balls, polycrystalline diamonds, and deionized water (the mass ratio of magnetic tungsten balls, polycrystalline diamonds, and deionized water is 1:10:40) are used to make a magnetic polishing liquid. An annular magnetic field is arranged parallel to the circumferential direction of the chromatographic column to be processed, and the magnetic polishing liquid rotates rapidly along the circumference perpendicular to the forward direction under the control of the magnetic field. The magnetic polishing liquid undergoes rheology in the gradient magnetic field, and the flexible "small grinding head" with viscoplastic behavior is formed, and the rapid relative movement between the inner hole of the chromatographic column causes a large shear force to be applied to the surface of the workpiece, so that the surface material of the workpiece is removed and the roughness of the inner hole of the chromatographic column reaches Ra=0.05. Continue to perform magnetic fluid polishing, and the rough surface is gradually leveled so that the roughness of the inner hole of the chromatographic column reaches Ra=0.01.

[0048] Chromatographic column cleaning: Use deionized water / surfactant-passivation solution-anhydrous ethanol to clean the column.

[0049] Chromatographic column filling. The chromatographic column is filled with high pressure, and the homogenate is immediately poured into the homogenate tank. After it is filled, the tank is covered and tightened; methanol is used as the displacement liquid to increase the pressure, maintain the pressure, and the filler in the homogenate is retained on the filter plate at the end of the column, while the homogenate is excluded from the column; after the pressure holding time is reached, the pressure is released and the pressure is gradually reduced to normal pressure; the filled column is removed and the column head with a sieve plate (filter) is assembled.

[0050] The chromatographic column prepared in Example 1 was used for detection and comparison with a commercially available chromatographic column. Figure 5 As shown in the figure, although the column efficiency of both columns can meet the inspection standards, the column efficiency of the corrosion-resistant chromatographic column with high finish is higher, and the tailing factor (characterizing the symmetry of the chromatographic peak) is closer to 1.

[0051] Example 2

[0052] The 316L bar was processed to a length of 50 mm. A three-roll mill was used to produce cold-rolled seamless pipes. The core material was made of 4.55 mm outer diameter tungsten steel for rotary cold drawing to produce a column blank with an outer diameter of 7 mm, an inner diameter of 3 mm, and an inner hole roughness of Ra = 0.4. The roundness and straightness of the column blank were good.

[0053] The corresponding threads and wrench positions are processed at the pipe mouth, and the inner hole and surface are processed with grinding wheels ranging from 400 mesh to 2000 mesh. At the same time, soft wool felt is used to further polish the inner hole to ensure that the inner hole roughness Ra = 0.2.

[0054] The inner and outer surfaces are removed by high-voltage plasma impact. The current flows, the concavity and convexity change continuously, and the rough surface is gradually leveled so that the roughness of the inner hole of the chromatographic column reaches Ra=0.1.

[0055] Magnetic fluid polishing is adopted. Magnetic tungsten balls, polycrystalline diamonds, and deionized water (the mass ratio of magnetic tungsten balls, polycrystalline diamonds, and deionized water is 1:10:40) are used to make a magnetic polishing liquid. An annular magnetic field is arranged parallel to the circumferential direction of the chromatographic column to be processed, and the magnetic polishing liquid rotates rapidly along the circumference perpendicular to the forward direction under the control of the magnetic field. The magnetic polishing liquid undergoes rheology in the gradient magnetic field, and the flexible "small grinding head" with viscoplastic behavior is formed, and the rapid relative movement between the inner hole of the chromatographic column causes a large shear force to be applied to the surface of the workpiece, so that the surface material of the workpiece is removed and the roughness of the inner hole of the chromatographic column reaches Ra=0.01.

[0056] Chromatographic column cleaning: Use deionized water / surfactant-passivation solution-anhydrous ethanol to clean the column.

[0057] Chromatographic column filling. The chromatographic column is filled with high pressure, and the homogenate is immediately poured into the homogenate tank. After it is filled, the tank is covered and tightened; methanol is used as the displacement liquid to increase the pressure, maintain the pressure, and the filler in the homogenate is retained on the filter plate at the end of the column, while the homogenate is excluded from the column; after the pressure holding time is reached, the pressure is released and the pressure is gradually reduced to normal pressure; the filled column is removed and the column head with a sieve plate (filter) is assembled.

[0058] The chromatographic column prepared in Example 2 was used for detection and comparison with a commercially available chromatographic column. Figure 6 As shown in the figure, although the column efficiency of both columns can meet the inspection standards, the high-finish corrosion-resistant chromatographic column has higher column efficiency, a tailing factor closer to 1, and better chromatographic peak symmetry.

[0059] Example 3

[0060] A three-roll mill is used to produce cold-rolled seamless pipes. The core material is made of 4.55mm outer diameter tungsten steel for rotary cold drawing to produce a tube blank with an outer diameter of 8mm, an inner diameter of 4.55mm, and an inner hole roughness of Ra=0.5. The tube blank has good roundness and straightness, and is prepared into a tube blank with a length of 250mm by quantitative cutting.

[0061] The corresponding threads and wrench positions are processed at the pipe mouth, and the inner hole and surface are processed with grinding wheels ranging from 400 mesh to 2000 mesh. At the same time, soft wool felt is used to further polish the inner hole to ensure that the inner hole roughness Ra = 0.3.

[0062] The inner and outer surfaces are removed by high-voltage plasma impact. The current flows, the concavity and convexity change continuously, and the rough surface is gradually leveled so that the roughness of the inner hole of the chromatographic column is Ra = 0.2.

[0063] The magnetic fluid polishing and magnetorheological polishing technology use magnetic tungsten balls, polycrystalline diamonds, and deionized water (the mass ratio of magnetic tungsten balls, polycrystalline diamonds, and deionized water is 1:10:40) to make a magnetic polishing liquid. An annular magnetic field is arranged parallel to the circumferential direction of the chromatographic column to be processed, and the magnetic polishing liquid rotates rapidly along the circumference perpendicular to the forward direction under the control of the magnetic field. The magnetic polishing liquid undergoes rheology in the gradient magnetic field, and the flexible "small grinding head" with viscoplastic behavior is formed, and the rapid relative movement between the inner hole of the chromatographic column causes a large shear force to be applied to the workpiece surface, so that the workpiece surface material is removed and the roughness of the inner hole of the chromatographic column is Ra = 0.01.

[0064] Chromatographic column cleaning: Use deionized water / surfactant-passivation solution-anhydrous ethanol to clean the column.

[0065] Chromatographic column filling. The chromatographic column is filled with high pressure, and the homogenate is immediately poured into the homogenate tank. After it is filled, the tank is covered and tightened; methanol is used as the displacement liquid to increase the pressure, maintain the pressure, and the filler in the homogenate is retained on the filter plate at the end of the column, while the homogenate is excluded from the column; after the pressure holding time is reached, the pressure is released and the pressure is gradually reduced to normal pressure; the filled column is removed and the column head with a sieve plate (filter) is assembled.

[0066] Example 4

[0067] The 316L rod is directly processed into a column blank with a length of 50mm. A three-roll rolling mill is used to produce cold-rolled seamless pipes. The core material is made of 2.1mm outer diameter tungsten steel for rotary cold drawing to produce a column blank with an outer diameter of 7mm, an inner diameter of 2.1mm, and an inner hole roughness of Ra=0.4. The roundness and straightness of the column blank are good.

[0068] The corresponding threads and wrench positions are processed at the pipe mouth, and the inner hole and surface are processed with grinding wheels ranging from 400 mesh to 2000 mesh. At the same time, soft wool felt is used to further polish the inner hole to ensure that the inner hole roughness Ra = 0.2.

[0069] The inner and outer surfaces are removed by high-voltage plasma impact. The current flows, the concavity and convexity change continuously, and the rough surface is gradually leveled so that the roughness of the inner hole of the chromatographic column is Ra = 0.1.

[0070] Magnetic fluid polishing is adopted. Magnetic tungsten balls, polycrystalline diamonds, and deionized water (the mass ratio of magnetic tungsten balls, polycrystalline diamonds, and deionized water is 1:10:40) are used to make a magnetic polishing liquid. An annular magnetic field is arranged parallel to the circumferential direction of the chromatographic column to be processed, and the magnetic polishing liquid rotates rapidly along the circumference perpendicular to the forward direction under the control of the magnetic field. The magnetic polishing liquid undergoes rheology in the gradient magnetic field, and the flexible "small grinding head" with viscoplastic behavior is formed, and the rapid relative movement between the inner hole of the chromatographic column causes a large shear force to be applied to the surface of the workpiece, so that the surface material of the workpiece is removed, and the roughness of the inner hole of the chromatographic column is Ra = 0.01.

[0071] Chromatographic column cleaning: Use deionized water / surfactant-passivation solution-anhydrous ethanol to clean the column.

[0072] Chromatographic column filling. The chromatographic column is filled with high pressure, and the homogenate is immediately poured into the homogenate tank. After it is filled, the tank is covered and tightened; methanol is used as the displacement liquid to increase the pressure, maintain the pressure, and the filler in the homogenate is retained on the filter plate at the end of the column, while the homogenate is excluded from the column; after the pressure holding time is reached, the pressure is released and the pressure is gradually reduced to normal pressure; the filled column is removed and the column head with a sieve plate (filter) is assembled.

[0073] The chromatographic column prepared in Example 4 was tested and compared with a commercially available chromatographic column. Although the column efficiencies of both columns met the inspection standard, the high-finish corrosion-resistant chromatographic column had a higher column efficiency, a tailing factor closer to 1, and good chromatographic peak symmetry.

[0074] Example 5

[0075] A three-roll mill is used to produce cold-rolled seamless pipes. The core material is made of 4.55mm outer diameter tungsten steel for rotary cold drawing to produce a tube embryo with an outer diameter of 8mm, an inner diameter of 4.55mm, and an inner hole roughness of Ra=0.5. The tube embryo has good roundness and straightness. Through quantitative cutting, a tube embryo with a length of 150mm is prepared.

[0076] The corresponding threads and wrench positions are processed at the pipe mouth, and the inner hole and surface are processed with grinding wheels ranging from 400 mesh to 2000 mesh. At the same time, soft wool felt is used to further polish the inner hole to ensure that the inner hole roughness Ra = 0.3.

[0077] The inner and outer surfaces are removed by high-voltage plasma impact. The current flows, the concavity and convexity change continuously, and the rough surface is gradually leveled so that the roughness of the inner hole of the chromatographic column is Ra = 0.2.

[0078] Rotary fluid polishing is adopted. The polishing liquid is made of polycrystalline diamond and deionized water (the mass ratio of polycrystalline diamond to deionized water is 10:40). A sealing structure and a rotating mechanism are designed in the forward direction of the polishing liquid to realize the relative rotation of the chromatographic column to be processed and the fluid, and to achieve radial shearing. The rapid relative movement between the polishing liquid and the inner hole of the chromatographic column causes a large shear force to be applied to the surface of the workpiece, so that the surface material of the workpiece is removed and the roughness of the inner hole of the chromatographic column is Ra = 0.01.

[0079] Chromatographic column cleaning: Use deionized water / surfactant-passivation solution-anhydrous ethanol to clean the column.

[0080] Chromatographic column filling. The chromatographic column is filled with high pressure, and the homogenate is immediately poured into the homogenate tank. After it is filled, the tank is covered and tightened; methanol is used as the displacement liquid to increase the pressure, maintain the pressure, and the filler in the homogenate is retained on the filter plate at the end of the column, while the homogenate is excluded from the column; after the pressure holding time is reached, the pressure is released and the pressure is gradually reduced to normal pressure; the filled column is removed and the column head with a sieve plate (filter) is assembled.

[0081] The chromatographic column prepared in Example 5 was tested and compared with a commercially available chromatographic column. Although the column efficiencies of both columns met the inspection standard, the high-finish corrosion-resistant chromatographic column had a higher column efficiency and a tailing factor closer to 1.

[0082] Example 6

[0083] A three-roll mill is used to produce cold-rolled seamless pipes. The core material is made of 4.55mm outer diameter tungsten steel for rotary cold drawing to produce a tube embryo with an outer diameter of 8mm, an inner diameter of 4.55mm, and an inner hole roughness of Ra=0.5. The tube embryo has good roundness and straightness. Through quantitative cutting, a tube embryo with a length of 150mm is prepared.

[0084] The corresponding threads and wrench positions are processed at the pipe mouth, and the inner hole and surface are processed with grinding wheels ranging from 400 mesh to 2000 mesh. At the same time, soft wool felt is used to further polish the inner hole to ensure that the inner hole roughness Ra = 0.3.

[0085] The inner and outer surfaces are electroplated, the electroplating layer is gradually deposited, the concavity and convexity are constantly changing, and the rough surface is gradually leveled so that the roughness of the inner hole of the chromatographic column Ra = 0.2.

[0086] Rotary fluid polishing is adopted. The polishing liquid is made of polycrystalline diamond and deionized water (the mass ratio of polycrystalline diamond to deionized water is 10:40). A sealing structure and a rotating mechanism are designed in the forward direction of the polishing liquid to realize the relative rotation of the chromatographic column to be processed and the fluid, and to achieve radial shearing. The rapid relative movement between the polishing liquid and the inner hole of the chromatographic column causes a large shear force to be applied to the surface of the workpiece, so that the surface material of the workpiece is removed and the roughness of the inner hole of the chromatographic column is Ra = 0.01.

[0087] Chromatographic column cleaning: Use deionized water / surfactant-passivation solution-anhydrous ethanol to clean the column.

[0088] Chromatographic column filling. The chromatographic column is filled with high pressure, and the homogenate is immediately poured into the homogenate tank. After it is filled, the tank is covered and tightened; methanol is used as the displacement liquid to increase the pressure, maintain the pressure, and the filler in the homogenate is retained on the filter plate at the end of the column, while the homogenate is excluded from the column; after the pressure holding time is reached, the pressure is released and the pressure is gradually reduced to normal pressure; the filled column is removed and the column head with a sieve plate (filter) is assembled.

[0089] The chromatographic column prepared in Example 6 was tested and compared with a commercially available chromatographic column. Although the column efficiencies of both columns met the inspection standard, the high-finish corrosion-resistant chromatographic column had a higher column efficiency, a tailing factor closer to 1, and good chromatographic peak symmetry.

[0090] The present invention processes chromatographic column tubes with Ra=0.3, 0.2, 0.1, 0.05, and 0.01. The surface roughness of Mitutoyo is measured and confirmed, and the overall value meets the requirements, and laser dot marking is performed.

[0091] Carry out salt spray test according to national standard GB / T 10125 and record the test results respectively.

[0092] Figure 1 This is the 48h salt spray result of the chromatographic column with different inner pore roughness (column tube 4.6*150mm) prepared in Example 1. Under the condition of salt spray for 48h, different corrosion conditions appeared on the surface of column tubes with different roughness. Continuous yellow rust with an area of ​​about 10% appeared on the surface of the column tube with inner pore roughness Ra0.3. Flake yellow rust with an area of ​​about 3% appeared on the surface of the column tube with inner pore roughness Ra0.2. Flake yellow rust with an area of ​​about 1% appeared on the surface of the column tube with inner pore roughness Ra0.1. Black rust spots appeared on the surface of the column tube with inner pore roughness Ra0.05. No obvious corrosion spots appeared on the surface of the column tube with inner pore roughness Ra0.01.

[0093] Figure 2This is the 96h salt spray result of the chromatographic column with different inner pore roughness (column tube 4.6*150mm) prepared in Example 1. Under the condition of salt spray for 96h, different corrosion conditions appeared on the surface of column tubes with different roughness. Continuous yellow rust with an area of ​​about 30% appeared on the surface of the column tube with inner pore roughness Ra0.3. Flake yellow rust with an area of ​​about 5% appeared on the surface of the column tube with inner pore roughness Ra0.2, and a large amount of mist corrosion layer appeared on the surface. Flake rust with an area of ​​about 3% appeared on the surface of the column tube with inner pore roughness Ra0.1. Yellow rust with an area of ​​about 1% appeared on the surface of the column tube with inner pore roughness Ra0.05, and a large number of brown spots were seen in the rough surface grooves. No obvious traces of rust appeared on the surface of the column tube with inner pore roughness Ra0.01, and brown spots were occasionally seen in the rough surface grooves.

[0094] Figure 3 This is the 240h salt spray result of the chromatographic column with different inner hole roughness (column tube 4.6*150mm) prepared in Example 1. Under the condition of salt spray for 480h, different corrosion conditions appeared on the surface of column tubes with different roughness. Continuous yellow rust with an area of ​​about 50% appeared on the surface of the column tube with inner hole roughness Ra0.3. Flaky yellow rust with an area of ​​about 10% appeared on the surface of the column tube with inner hole roughness Ra0.2, and black corrosion pits covered 70% of the surface area. Flaky rust with an area of ​​about 5% appeared on the surface of the column tube with inner hole roughness Ra0.1, and a large amount of white misty oxide layer appeared on the surface. Yellow rust with an area of ​​about 2% appeared on the surface of the column tube with inner hole roughness Ra0.05, and a large number of brown spots were seen in the rough surface grooves. No obvious traces of rust appeared on the inner hole roughness Ra0.01, and brown spots appeared in the rough surface grooves.

[0095] Figure 4 This is a comparison of different salt spray times of chromatographic columns with different inner hole roughness (column tube 4.6*150mm) prepared in Example 1. It can be seen that:

[0096] (1) As the roughness of the chromatographic column decreases and the smoothness improves, the corrosion degree of the chromatographic column decreases and the corrosion rate slows down.

[0097] (2) For column tubes with a roughness of Ra = 0.2-0.3, due to the uneven surface, it contains more corrosive substances and it is difficult to form a dense oxide layer. In addition, as the salt spray time increases, the corrosion intensifies. For example, for column tubes with a roughness of Ra = 0.3, as the salt spray time increases, the deterioration and rust area increases rapidly.

[0098] (3) For the column tube with roughness Ra = 0.1, after 240 hours of salt spray test, the rust area of ​​the chromatographic column is still about 5% of the whole column tube, and no obvious continuous flaky rust is formed, and a dense foggy transparent oxide layer is formed on the surface.

[0099] (4) For a column tube with a roughness of Ra = 0.01, after a 240-h salt spray test, no obvious rust spots appeared on the inner hole of the column.

[0100] Combined with the above results, the most preferred technical solution is that the inner hole roughness Ra of the corrosion-resistant self-cleaning chromatographic column is in the range of 0.1-0.01.

[0101] It should be understood that the above embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the above examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values ​​​​in the above examples.

Claims

1. A corrosion-resistant liquid chromatography column, characterized in that: The inner hole of the corrosion-resistant liquid chromatography column has an inner hole roughness Ra controlled at 0.01-0.

1.

2. The corrosion-resistant liquid chromatography column according to claim 1, characterized in that: The specifications of the corrosion-resistant liquid chromatography column are inner diameter 1.0mm-4.6mm*length 50mm-250mm.

3. The corrosion-resistant liquid chromatography column according to claim 1 or 2, characterized in that: The inner diameter specifications of the corrosion-resistant liquid chromatography column are 1.0mm, 2.1mm, 3.0mm, and 4.6mm, and the length specifications are 50mm, 100mm, 150mm, and 250mm.

4. The method for preparing a corrosion-resistant liquid chromatography column according to any one of claims 1 to 3, characterized in that: The preparation method comprises: Step A: cold drawing the steel pipe to obtain a tube blank with an inner hole having an inner hole roughness of Ra=0.4-0.6; Step B: mechanically polishing the steel pipe obtained in step A to an inner hole roughness Ra=0.2-0.4; Step C: electrochemically polishing the steel pipe obtained in step B until the inner hole roughness Ra=0.1-0.2; Step D: The steel pipe obtained in step C is polished by fluid until the inner hole roughness Ra=0.01-0.

1.

5. The preparation method according to claim 4, characterized in that: The cold drawing adopts tungsten steel as the core material and performs rotary cold drawing on the cold-rolled seamless steel pipe.

6. The preparation method according to claim 4 or 5, characterized in that: The mechanical polishing is performed using grinding wheels or honing tools with mesh sizes ranging from coarse to fine. Preferably, mechanical polishing is performed using grinding wheels with mesh sizes ranging from 400 to 2000 in sequence.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The electrochemical polishing is performed by high pressure plasma or electroplating.

8. The preparation method according to any one of claims 4 to 7, characterized in that: The fluid polishing is extrusion type fluid polishing.

9. The preparation method according to any one of claims 4 to 7, characterized in that: The fluid polishing is magnetic fluid polishing; preferably, the magnetic fluid polishing is designed to produce a rotational shear force perpendicular to the forward direction of the polishing fluid; more preferably, a magnetic substance with a particle size close to that of the abrasive is introduced into the polishing fluid, and in this case, the polishing fluid is a magnetic polishing fluid, and an annular magnetic field is arranged parallel to the circumferential direction of the chromatographic column to be processed, and the polishing fluid rotates rapidly along a circle perpendicular to the forward direction under the control of the magnetic field.

10. The preparation method according to any one of claims 4 to 7, characterized in that: The fluid polishing is a rotary fluid polishing; preferably, a sealing structure and a rotating mechanism are designed in the advancing direction of the polishing fluid, and radial shearing is achieved through the relative rotation of the chromatographic column to be processed and the fluid.

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