Tubular body for use in column for liquid chromatograph

Abstract

A tubular body according to the present disclosure comprises: a first tube including a ceramic; and a second tube positioned on the outer circumferential side of the first tube and including a metal or a resin. The inner circumferential surface of the second pipe is abutted, joined, or fastened to the outer circumferential surface of the first pipe. The tubular body according to the present disclosure may be used in an analysis component such as a column for a liquid chromatograph.

Description

Tubular body for use in liquid chromatographic columns

[0001] The present disclosure relates to tubular bodies for use in liquid chromatography columns, such as columns used in high performance liquid chromatography (HPLC), ultra high performance liquid chromatography (UHPLC), and the like.

[0002] In liquid chromatography, a column is used to separate the components of a sample (hereinafter sometimes referred to as a sample liquid) that is supplied to the column together with a mobile phase. Columns are typically made of a metal tube such as stainless steel packed with a packing material (stationary phase) such as silica gel.

[0003] Patent Document 1 describes a column in which a metal tube made of stainless steel or the like is filled with a packing material, and both end openings of the column tube are closed with porous frits. The inner wall of the metal tube is coated with a ceramic layer made of a metal oxide film such as a zirconium oxide film. By coating the inner wall of the metal tube with a ceramic layer, the sample band does not come into contact with the metal surface of the inner wall of the column tube as the sample band moves along the column tube, and disturbance of the sample band is suppressed, thereby improving separation efficiency.

[0004] Japanese Patent Application Laid-Open No. 2004-37266

[0005] The tubular body of the present disclosure includes a first tube containing ceramic and a second tube containing metal or resin, the second tube being positioned on the outer periphery of the first tube. The tubular body of the present disclosure may be used in analytical components such as liquid chromatography columns.

[0006] 1A ; FIG. 1B is a perspective view of a tubular body according to an embodiment of the present disclosure; FIG. 1C is a schematic cross-sectional view of the tubular body shown in FIG. 1A ; FIG. 1D is a schematic partial cross-sectional view of a tubular body showing an example in which the length of the second tube is greater than the length of the first tube; FIG. 1E is a schematic partial cross-sectional view of a tubular body showing an example in which the length of the first tube is greater than the length of the second tube; FIG. 1F is a schematic partial cross-sectional view of a tubular body showing an example in which the thickness of the first tube is greater than the thickness of the second tube; FIG. 1G is a schematic partial cross-sectional view of a tubular body showing an example in which the thickness of the second tube is greater than the thickness of the first tube; FIG. 1H is a schematic partial cross-sectional view of a tubular body having different thicknesses at both ends of the first and second tubes; FIG. 1I is a schematic partial cross-sectional view of a tubular body having a step at the joining surface between the first and second tubes; FIG. 1J is a schematic partial cross-sectional view of a tubular body having a step with an inclined surface at the joining surface between the first and second tubes; FIG. 1J is a schematic partial cross-sectional view of a tubular body in which a filler is filled between the first and second tubes; FIG. 1I is a schematic partial cross-sectional view of a tubular body having a concave end portion at one end of the first tube; FIG. 1J is a schematic partial cross-sectional view of a tubular body having concave end portions at both ends of the first tube; FIG. 1J is a schematic partial cross-sectional view of a tubular body having convex end portions at both ends of the first tube. 9B is a schematic partial cross-sectional view of a tubular body in which a concave end is provided at one end of a first tube and a convex end is provided at the other end. FIG. 9C is a schematic partial cross-sectional view of a tubular body in which a first tube and a second tube are joined via a bonding material. FIG. 9D is a schematic partial cross-sectional view of a tubular body in which a first tube and a second tube are joined at a center portion via a bonding material. FIG. 9E is a schematic partial cross-sectional view of the tubular body in FIG. 9A having a recessed groove provided at an end. FIG. 9F is a schematic partial cross-sectional view of a tubular body in which a first tube and a second tube are fastened together. FIG. 9G is a schematic partial cross-sectional view of a tubular body in which a first tube and a second tube are fastened together with a gap therebetween. FIG. 9H is a schematic partial cross-sectional view of a tubular body in which a first tube and a second tube are fastened together with a gap therebetween. FIG. 9I is a schematic partial cross-sectional view of a tubular body in which a first tube and a second tube are fastened together with a gap therebetween. 1A and 1B are cross-sectional views showing still another example of a tubular body in which a first pipe and a second pipe are fastened together using a screw; FIG. 1C are schematic cross-sectional views showing another example of a fastening structure between a first pipe and a second pipe; and FIG. 1D are schematic cross-sectional views showing still another example of a fastening structure between a first pipe and a second pipe.

[0007] Hereinafter, a tubular body according to an embodiment of the present disclosure will be described with reference to the drawings. However, for the sake of convenience, the drawings referred to below show simplified embodiments of the present disclosure. Therefore, the tubular body disclosed below may include any components not shown in the drawings referred to. Furthermore, the dimensions of the components in the drawings do not faithfully represent the actual dimensions of the components, the dimensional ratios of the components, etc.

[0008] The column described in Patent Document 1 has a high bonding stress between the metal tube and the ceramic membrane, resulting in weak bonding strength, which can lead to peeling of the ceramic membrane and displacement of the ceramic membrane from the metal tube. Furthermore, when pressure from the sample liquid and mobile phase (hereinafter sometimes referred to as the analyte liquid) is repeatedly applied to the column, friction repeatedly occurs between the packing material packed in the column tube and the inner wall of the column tube. The ceramic membrane formed on the inner wall of the column tube described in Patent Document 1 has low strength, so this friction easily wears the ceramic membrane. When the ceramic membrane is formed thinly, pinholes penetrating from the surface to the metal tube are likely to occur in the ceramic membrane. When the ceramic membrane is formed thickly, the bonding stress between the metal tube and the ceramic membrane is particularly high, and the residual stress within the membrane is also large, making the ceramic membrane prone to cracking.

[0009] When a ceramic membrane develops wear, pinholes, and cracks, the liquid sample flowing through the column tube comes into contact with the surface of the metal tube, making metal tubes with low corrosion resistance susceptible to corrosion. Furthermore, there is a risk of metal components leaking into the sample liquid. As a result, component analysis of the sample liquid may become impossible or analytical accuracy may deteriorate. Abrasion and cracks in the ceramic membrane may also cause components to leak into the sample liquid as particles. Because pinholes affect analytical accuracy as described above, it is necessary to use columns without pinholes. However, because the ceramic membrane is coated on the inner wall of the column tube, it is difficult to perform pinhole inspections, such as visual inspections, to check for pinholes.

[0010] Furthermore, in Patent Document 1, the ceramic membrane, which has a lower thermal conductivity than metal, is thin, resulting in poor column insulation. Therefore, in HPLC, a sample liquid is passed through the column under high temperature and pressure, which can easily cause temperature changes within the column.

[0011] An embodiment of the present disclosure provides a tubular body (hereinafter sometimes simply referred to as a tubular body) for use in analytical components such as liquid chromatography columns, which reduces misalignment of ceramics located on the inner periphery of a metal tube, reduces the outflow of metal or ceramic components or particles into a sample liquid, has high thermal insulation properties, and facilitates pinhole inspection of the ceramics.

[0012] FIG. 1A is a perspective view showing a tubular body 100 according to one embodiment of the present disclosure, and FIG. 1B is a schematic cross-sectional view thereof. The tubular body 100 is used in a liquid chromatography column. As shown in FIG. 1B, the tubular body 100 includes a first tube 1 containing ceramics and a second tube 2 positioned on the outer circumferential side of the first tube 1. The second tube 2 contains a metal or a resin. Specifically, as described below, the inner circumferential surface 2b of the second tube 2 is abutted, joined, or fastened to the outer circumferential surface 1a of the first tube 1. Furthermore, there may be a gap between the first tube 1 and the second tube 2.

[0013] The first tube 1 has through-holes 3, which are filled with a packing material (stationary phase). Any substance conventionally used as a stationary phase, such as silica gel, can be used as the packing material. In this embodiment, the packing material and the frits fixed to the openings at both ends of the column tube are not shown.

[0014] The tubular body 100 has a first tube 1 containing ceramic on the inner periphery, so when used as a column, it has high corrosion resistance against the liquid to be analyzed, high abrasion resistance against the filler, and is less likely to crack. Furthermore, since the second tube 2 containing metal or resin is located on the outer periphery of the first tube 1, the first tube 1 is less likely to crack even if the internal pressure of the tubular body 100 increases.

[0015] The first tube 1 containing ceramics is preferably a ceramic tube whose main component is, for example, zirconia, alumina, silicon nitride, forsterite, steatite, mullite, cordierite, etc. In the case of zirconia, a stabilizer may be contained. The stabilizer is, for example, Y ２ O ３ At least one selected from CaO and MgO can be used. Zirconia is highly tough and break-resistant, so it is unlikely to break even under high pressure as the first tube 1, and can maintain high bonding strength with the second tube 2. The term "major component" in ceramics refers to a component that accounts for 85% by mass or more of the total 100% by mass of the components that make up the ceramic. The major component of ceramics can be determined by identifying the crystalline phase of the major component using an X-ray diffraction device (XRD), then determining the content of the metal elements that make up the major component using an X-ray fluorescence analyzer (XRF) or an inductively coupled plasma (ICP) emission spectrometer (ICP), and converting this to the content of the major component.

[0016] The second tube 2 includes a metal or a resin. The metal or resin is used in the form of a tube. Examples of materials for metal tubes include stainless steel, titanium, titanium alloys, copper, copper alloys, cemented carbide, aluminum, and aluminum alloys. Examples of materials for resin tubes include epoxy resin, polystyrene resin, polyacetal resin, polycarbonate resin, polyphenylene sulfide (PPS) resin, and aromatic polyether ketone (PEEK) resin. When the second tube 2 is primarily composed of metal, the mechanical impact resistance of the second tube 2 is particularly high. Furthermore, when the tubular body 100 is used as a column for analytical work or when replacing the column, the second tube 2 is less likely to break if it is made of metal.

[0017] The thickness Tc of the first tube 1 is preferably 0.5 mm or more and 4 mm or less. When the thickness Tc of the first tube 1 is 0.5 mm or more, pinholes, cracks, etc. are less likely to occur in the first tube 1. When the thickness Tc of the first tube 1 is 4 mm or less, workability is improved, and increases in manufacturing costs can be reduced. Furthermore, the ratio Tc / Tm of the thickness Tc of the first tube 1, which is a ceramic tube, to the thickness Tm of the second tube 2, which is a metal or resin tube, is preferably Tc / Tm = 0.2 to 3. Therefore, when Tc = 0.5 mm, Tm = 0.166 to 1 mm, and when Tc = 4 mm, Tm = 1.33 to 20 mm. When Tc / Tm = 0.2 to 3, even if the internal pressure of the tubular body 100 increases, the amount of deformation of the first tube 1 and the second tube 2 is reduced, thereby reducing the amount of misalignment between the first tube 1 and the second tube 2 and making the first tube 1 less likely to crack.

[0018] The tubular body 100 formed by abutting or joining a first tube 1 (ceramic tube) and a second tube 2 (metal tube or resin tube) has the following dimensions, for example: inner diameter: 0.1 mm to 100 mm, outer diameter: 1 mm to 200 mm, length: 50 mm to 150 mm.

[0019] It is preferable that the arithmetic mean roughness Ra1 of the outer peripheral surface 1a of the first tube 1 is different from the arithmetic mean roughness Ra2 of the inner peripheral surface 2b of the second tube 2. In other words, when the first tube 1 and the second tube 2 are joined by abutment or with an adhesive, it is preferable that the frictional resistance between the first tube 1 and the second tube 2 is large, making it difficult for the relative positions of the first tube 1 and the second tube 2 to change (i.e., reducing misalignment). If the difference between the arithmetic mean roughness Ra1 of the outer peripheral surface 1a of the first tube 1 and the arithmetic mean roughness Ra2 of the inner peripheral surface 2b of the second tube 2 is 0.2 μm or more, misalignment is further reduced.

[0020] Specifically, when the flow of the mobile phase begins and the pressure inside the tubular body 100 increases, the pressure increases from the outer peripheral surface 1a of the first tube 1 to the inner peripheral surface 2b of the second tube 2. At this time, if the average roughness Ra1 of the outer peripheral surface 1a of the first tube 1 is greater than the average roughness Ra2 of the inner peripheral surface 2b of the second tube 2, the increase in pressure is dispersed from the outer peripheral surface 1a of the first tube 1 to the inner peripheral surface 2b of the second tube 2. This makes it possible to reduce the occurrence of cracks originating from the outer peripheral surface 1a of the first tube 1.

[0021] If the average roughness Ra2 of the inner circumferential surface 2b of the second pipe 2 is greater than the average roughness Ra1 of the outer circumferential surface 1a of the first pipe 1, the pressure increase from the outer circumferential surface 1a of the first pipe 1 is dispersed on the inner circumferential surface 2b of the second pipe 2. This reduces the occurrence of cracks originating from the outer circumferential surface 1a of the first pipe 1.

[0022] The arithmetic mean roughness Ra of at least one of the outer circumferential surface 1a of the first tube 1 and the inner circumferential surface 2b of the second tube 2 is preferably 0.2 μm or more. When Ra is 0.2 μm or more, the increase in pressure from the outer circumferential surface 1a of the first tube 1 to the inner circumferential surface 2b of the second tube 2 is further reduced, or the increase in pressure from the outer circumferential surface 1a of the first tube 1 is further dispersed to the inner circumferential surface 2b of the second tube 2. This ensures high strength when the first tube 1 and the second tube 2 are abutted or joined, reducing the occurrence of misalignment between them and the occurrence of cracks in the first tube 1.

[0023] The inner surface 1b of the first tube 1, which is a ceramic tube, preferably has a sintered surface. A sintered surface refers to a fired surface that has not been polished or ground. Because the sintered surface is a fired surface that has not been subjected to processing such as polishing or grinding, it reduces the occurrence of ceramic crystal detachment caused by processing and the occurrence of microcracks that can cause ceramic crystal detachment. A filler material is sealed within the through-hole 3 formed by the inner surface 1b of the first tube 1. A liquid for analysis (liquid to be analyzed) flows through the gaps in this filler material. If the inner surface of the first tube 1 is a sintered surface, it reduces the detachment of ceramic crystals from inside the first tube 1 due to friction between the inner surface and the filler material and contact between the inner surface and the liquid to be analyzed.

[0024] Next, various embodiments of the tubular body 100 will be shown. Figures 2A and 2B each show an example in which the first tube 1 and the second tube 2 have different lengths. For convenience, Figures 2A, 2B and subsequent figures only show a cross section of the tubular body 100 above the axis (shown by the dashed line).

[0025] 2A shows an example in which the end faces 2c, 2d of the second tube 2 are located axially outward of the end faces 1c, 1d of the first tube 1. In FIG. 2A, both end faces 2c, 2d of the second tube 2 are located outward of both end faces 1c, 1d of the first tube 1, but it is sufficient that at least one of the end faces 2c, 2d of the second tube 2 is located outward of the end faces 1c, 1d of the first tube 1. Because at least one end face 1c, 1d of the first tube 1 is located inward of the end faces 2c, 2d of the second tube 2, stress is less likely to concentrate on the end faces 1c, 1d of the first tube 1, which reduces the occurrence of cracks on the end faces 1c, 1d of the first tube 1 that are located inward of the end faces 2c, 2d of the second tube 2.

[0026] 2B shows an example in which the end faces 1c, 1d of the first tube 1 are located axially outward of the end faces 2c, 2d of the second tube 2. In FIG. 2B, both end faces 1c, 1d of the first tube 1 are located outward of both end faces 2c, 2d of the second tube 2. However, it is sufficient that at least one of the end faces 1c, 1d of the first tube 1 is located outward of the end faces 2c, 2d of the second tube 2. Because at least one end face 2c, 2d of the second tube 2 is located inward of the end faces 1c, 1d of the first tube 1, stress is less likely to concentrate on the end faces 1c, 1d of the first tube 1, reducing the likelihood of cracks occurring in the end faces 1c, 1d of the first tube 1 located outward of the end faces 2c, 2d of the second tube 2. Because at least one end face 2c, 2d of the second tube 2 is located inward of the end faces 1c, 1d of the first tube 1, contact between the liquid to be analyzed and the second tube 2 can be reduced. This can particularly contribute to making the tubular body 100 bio-inert when the second tube 2 is a metal tube and the liquid to be analyzed is prone to be adsorbed by metal.

[0027] 3A and 3B show examples in which the first tube 1 and the second tube 2 have different thicknesses. This allows the thickness to be changed as needed, which has the advantage of increasing the design freedom of the tubular body 100. FIG. 3A shows an example in which the first tube 1 is thicker than the second tube 2. The first tube 1 and the second tube 2 may have the same thickness, but if the first tube 1 is thicker than the second tube 2, deformation of the first tube 1 can be made relatively smaller than deformation of the second tube 2 when pressure is applied to the inner circumferential surface of the tubular body 100 during pressure increase or decrease. Therefore, even when pressure is applied to the inner circumferential surface of the tubular body 100, cracking of the first tube 1 is reduced, and when the first tube 1 and the second tube 2 are joined, high joint strength can be maintained.

[0028] 3B shows an example in which the second tube 2 is thicker than the first tube 1. Even in such a configuration, for example, if the second tube 2 is made of metal, even if the first tube 1 tries to deform due to the internal pressure of the tubular body 100, the second tube 2 is less likely to deform because the amount of deformation is small, thereby reducing cracks in the first tube 1 and, when the first tube 1 and the second tube 2 are joined, maintaining high joint strength.

[0029] At least one of the first tube 1 and the second tube 2 may have different thicknesses at both ends. That is, as shown in FIG. 4 , the joining surface 5 of the first tube 1 and the second tube 2 is formed in an inclined shape. This makes it difficult for the first tube 1 to shift to the right of the page and the second tube 2 to shift to the left of the page after joining the first tube 1 and the second tube 2. As a result, misalignment between the first tube 1 and the second tube 2 is reduced. If the joining surface 5 is inclined so as to approach the inner circumferential surface 1b of the first tube 1 along the flow direction of the liquid to be analyzed, the outer circumferential surface 1a of the first tube 1 is pressed against the inner circumferential surface 2b of the second tube 2 even when the liquid to be analyzed flows through the first tube 1 at high speed, further reducing misalignment.

[0030] In addition to the inclined surface shown in Fig. 4, the joining surface 5 may have at least one step 6 as shown in Fig. 5A. Furthermore, the joining surface 5 may have a step 61 having an inclined surface as shown in Fig. 5B. When the step 6 and the step 61 are located on the inflow side of the liquid to be analyzed, even if the liquid to be analyzed flows through the first tube 1 at high speed, the step 6 and the step 61 located on the outer circumferential surface 1a of the first tube 1 are pressed against the opposing surfaces of the step 6 and the step 61 located on the inner circumferential surface 2b of the second tube 2, thereby further reducing misalignment.

[0031] FIG. 6 shows an example in which a filler 4 having a lower thermal conductivity than the first and second tubes 1 and 2 is interposed between the first and second tubes 1 and 2. This facilitates thermal insulation between the first and second tubes 1 and 2, thereby reducing temperature changes in the liquid to be analyzed flowing through the through-hole 3. As a result, when the tubular body 100 is used as a column for a liquid chromatograph, temperature changes in the liquid to be analyzed flowing through the through-hole 3 are reduced regardless of the temperature environment around the column, improving analytical accuracy. The filler 4 is filled in a recess 7 formed in the center of at least one of the first and second tubes 1 and 2. The "center" refers to the region excluding both ends of the first and second tubes 1 and 2. This does not necessarily mean the entire region, but may be only a portion of the region (the same applies below). The filler 4 may be a material with a lower thermal conductivity than the first and second tubes 1 and 2 (e.g., a resin foam), or simply air. The air filled in the recess 7 is sealed in an enclosed space, providing its own insulating effect. Furthermore, the heat insulating effect can be enhanced by creating a vacuum state inside the sealed space of the recess 7. Note that "the recess 7 is filled with the filler 4" does not necessarily mean that the filler 4 completely fills the space of the recess 7, and gaps, voids, etc. may exist inside the recess 7.

[0032] 7A to 7D illustrate another embodiment of the present disclosure. As shown in FIGS. 7A and 7B, the first tube 1 has a concave end 10 at one or both ends on the inner circumferential surface 1b side. Examples of the concave end 10 include a curved or rounded surface. Providing such a concave end 10 facilitates filling the through-hole 3 with filler material and reduces chipping of the end of the first tube 1. As shown in FIG. 7C, the first tube 1 may have convex end 11 at both ends on the inner circumferential side. The convex end 11 may be formed only at one end on the inner circumferential surface 1b side. Examples of the convex end 11 include a protrusion, a convex curved surface, and the like. Providing such a convex end 11 reduces leakage of the filler material filled in the through-hole 3. FIG. 7D illustrates an example in which the concave end 10 and the convex end 11 are used in combination. For example, if the structure has a concave end 10 on the inlet side of the liquid to be analyzed and a convex end 11 on the outlet side, it becomes easier to fill the filler into the through hole 3 and the possibility of the filler leaking out of the through hole 3 can be reduced even if the liquid to be analyzed flows at high speed.

[0033] Next, a method for manufacturing the tubular body 100 of the present disclosure will be described. As described above, the tubular body 100 is manufactured by abutting, joining, or fastening the outer peripheral surface 1 a of the first tube 1 and the inner peripheral surface 2 b of the second tube 2. The manufacturing method will be described below in order.

[0034] <Manufacturing method by abutment> Abutting the outer peripheral surface 1a of the first pipe 1 with the inner peripheral surface 2b of the second pipe 2 means joining at least a part of the first pipe 1 with at least a part of the second pipe 2 without using an adhesive. Therefore, even if internal pressure (positive pressure) is applied to the through hole 3 of the tubular body 100, the expansion of the diameter of the through hole 3 is reduced. As a result, fluidization and leakage of the filler material in the through hole 3 can be reduced. The following two methods can be used for the abutment structure.

[0035] (Press-Fit Method) The first tube 1 (ceramic tube) is press-fitted into the inside of the second tube 2 (metal tube or resin tube). Therefore, the inner diameter DM of the second tube 2 before press-fitting and the outer diameter DC of the first tube 1 before press-fitting at the abutting portion have the following relationship: DM≦DC. (Shrink-Fit Method) The first tube 1 (ceramic tube) is joined to the inside of the second tube 2 (metal tube) by shrink-fitting. In the shrink-fit method, a metal tube is used as the second tube 2. That is, the metal tube is maintained at a high temperature of several hundred degrees Celsius (e.g., 150 degrees Celsius or higher) to expand its inner diameter, and then a ceramic tube (e.g., room temperature) is inserted into the metal tube. The temperature is then lowered to room temperature. When cooled, the metal tube contracts, reducing its inner diameter, and the outer periphery of the metal tube and the outer periphery of the ceramic tube are pressed against each other to be joined.

[0036] <Manufacturing method using bonding material> In this manufacturing method, as shown in Fig. 8, the outer peripheral surface 1a of the first tube 1 and the inner peripheral surface 2b of the second tube 2 are bonded together via a bonding material 8. In the tubular body 100 manufactured in this manner, even when a positive pressure is repeatedly applied to the through hole 3, causing the first tube 1 to elastically deform in the thickness direction and repeatedly undergo slight diameter expansion, the bonding material 8 elastically deforms, making it difficult for the pressure of the diameter expansion of the first tube 1 to be transmitted to the second tube 2. Therefore, the bonding strength between the first tube 1 and the second tube 2 can be maintained high for a long period of time, and misalignment can also be reduced.

[0037] As the bonding material 8, for example, an epoxy resin adhesive (e.g., "Araldite" (registered trademark)) can be used. Different resins may be used to maintain the temperature of the tubular body 100 constant. For example, if a resin with high thermal conductivity is used, when used as a column, the temperatures of the first tube 1 and the second tube 2 can be quickly maintained constant. Therefore, the temperature of the liquid to be analyzed can also be quickly maintained constant, thereby shortening the analysis time. Conversely, if a resin with low thermal conductivity is used as a column, temperature changes in the liquid to be analyzed can be reduced regardless of the temperature environment around the column, improving analysis accuracy.

[0038] 9A , the bonding material 8 may be configured to bond the first pipe 1 and the second pipe 2 near the center of the outer circumferential surface 1a of the first pipe 1 and the inner circumferential surface 2b of the second pipe 2. This reduces leakage of the bonding material 8 from the end of the tubular body 100 to the outside. The bonding material 8 may be filled into a recess 7 formed around the entire circumference near the center of the outer circumferential surface 1a of the first pipe 1. The recess 7 may be a long groove formed along the axial direction near the center of the tubular body 100. It is preferable to arrange a plurality of long grooves in the circumferential direction of the outer circumferential surface 1a of the first pipe 1.

[0039] FIG. 9B shows a further development of the embodiment shown in FIG. 9A , which includes a groove 9 formed circumferentially toward the end of the recess 7 filled with the bonding material 8. While two grooves 9 are shown side by side in FIG. 9B , at least one groove is sufficient. The reason for providing such a groove 9 is as follows. When manufacturing the tubular body 100, the recess 7 is filled with the bonding material 8 before the first tube 1 is inserted into the second tube 2. If the first tube 1 is inserted into the second tube 2 with the bonding material 8 filled in the recess 7, the bonding material 8 will overflow from the recess 7 and leak out from the end. Therefore, by providing the groove 9, the overflowing bonding material 8 is contained within the groove 9, thereby reducing leakage to the outside. For this reason, the groove 9 may be formed at only one of the end portions, but it may also be formed at both end portions. When the groove 9 is provided at only one end, the groove 9 is positioned at the end opposite to the direction in which the first pipe 1 is inserted into the second pipe 2, thereby making it possible to accommodate the bonding material 8 that protrudes from the recess 7.

[0040] <Manufacturing Method by Fastening> This is a method of fastening the first tube 1 and the second tube 2 by screwing or the like. FIG. 10A shows the first tube 1 and the second tube 2 fastened together by threading a screw 12 from the outer periphery of the second tube 2 through a screw insertion hole 13 into a threaded hole 14 in the first tube 1. FIG. 10B shows the first tube 1 and the second tube 2 fastened together with a gap 15 between them. Screwing is preferably performed at multiple locations along the circumferential direction of the tubular body 100. Pinning may also be used instead of screwing. Pinning is a method of fastening the first tube 1 and the second tube 2 by inserting a pin, such as a parallel pin, tapered pin, dowel pin, or spring pin made of metal or resin, into holes formed in the first tube 1 and the second tube 2 that are slightly smaller in diameter than the pin by press-fitting or the like, and utilizing the plastic deformation, elastic force, or the like of the pin. 11A and 11B show a first pipe 1 and a second pipe 2 fastened together at their ends, and other features are the same as those in Figures 10A and 10B, so the same reference numerals are used and detailed descriptions are omitted. Note that, as shown in Figure 11B, in order to fasten together at their ends, a spacer 16 made of metal, ceramic, plastic, or the like may be interposed between the first pipe 1 and the second pipe 2 at least in the screw-fastened portion.

[0041] 12A to 12C show other fastening structures according to the present disclosure. FIG. 12A shows an example using a screw 17 with a concave cross section. This screw 17 has a thread groove 17a formed on the inner circumferential surface of the recess and a through hole 17b in the center that communicates with the through hole 3 of the tubular body 100. The second tube 2, located on the outer periphery of the first tube 1, has thread grooves formed at both ends on the outer periphery that engage with the thread groove 17a. The concave cross-sectional screws 17 are disposed at both ends of the tubular body 100, respectively. The ends of the first tube 1 and the second tube 2 are accommodated within the recesses, and the thread groove 17a threadably engages with the thread groove formed on the outer periphery of the second tube 2, thereby fastening the first tube 1 and the second tube 2 together at both ends. The first tube 1 is fixed by being sandwiched between the bottom surfaces of the recesses of the screws 17 located at both ends of the first tube 1.

[0042] FIG. 12B shows an example in which a convex-section thread 18 is used instead of the concave-section thread 17 shown in FIG. 12A . This thread 18 has a thread groove 18a formed on the outer peripheral surface of the small-diameter portion of the convex portion, and a through-hole 18b in the center that communicates with the through-hole 3 of the tubular body 100. The end of the second tube 2, located on the outer periphery of the first tube 1, protrudes beyond the end of the first tube 1, and a thread groove that threads into the thread groove 18a of the thread 18 is formed on the inner peripheral surface of the protruding portion. The convex-section thread 18 fastens the first tube 1 and the second tube 2 at both ends by threading the thread groove 18a into a thread groove formed on the inner periphery of the second tube 2. The first tube 1 is fixed by being sandwiched between the convex portions of the threads 18 located at both ends of the first tube 1. In FIGS. 12A and 12B , a gap 15 is formed between the first tube 1 and the second tube 2. The voids 15 improve the heat insulating properties of the tubular body 100. The voids 15 may be formed around the entire circumference of the tubular body 100, or may be in the form of a plurality of narrow grooves extending in the axial direction, or the voids 15 may not even be present.

[0043] 12C shows an example in which both fastening and joining are used. Specifically, a convex-section screw 19 has a thread groove 19a formed on the outer peripheral surface of the small-diameter portion of the convex portion. The central portion has a through hole 19b that communicates with the through hole 3 of the tubular body 100, and a recessed groove 19c that communicates with the through hole 19b and accommodates the end of the first pipe 1. The inner peripheral surface 2b of each end of the second pipe 2 has thread grooves that mesh with the thread groove 19a of the screw 19. A gap 20 is provided between the first pipe 1 and the second pipe 2, and the center of the gap 20 is filled with the joining material 8. In this state, the screw 19 is placed at the ends of the first pipe 1 and the second pipe 2, and the thread groove 19a of the screw 19 is threadedly engaged with the thread groove of the second pipe 2, while simultaneously accommodating the end of the first pipe 1 in the recessed groove 19c. In this example, at least the central portion in the longitudinal direction is bonded with the bonding material 8, and therefore the gap 20 without the bonding material 8 can reduce the outflow of the bonding material 8. Furthermore, the gap 20 is an air layer filled with air, and therefore the insulating effect can reduce the temperature change of the column.

[0044] 13A and 13B illustrate yet another fastening structure according to the present disclosure. In the embodiment shown in FIG. 13A , male threads 21a and 21b are located at both ends of the outer circumferential surface 1a of a first pipe 1, and female threads 22a and 22b are located at both ends of the inner circumferential surface 2b of a second pipe 2. The male threads 21a and 21b are threadedly engaged with the female threads 22a and 22b, respectively. During manufacturing, the male threads 21a and 21b of the first pipe 1 are first threadedly engaged with the female threads 22b of the second pipe 2. While rotating the first pipe 1, the male threads 21a and 21b are simultaneously threadedly engaged with the female threads 22a and 22b, respectively, to fasten the first pipe 1 to the second pipe 2. The first pipe 1 may be inserted into either of the openings at both ends of the second pipe 2.

[0045] 13B , the second pipe 2 has a female thread 22c located over the entire inner circumferential surface 2b. The first pipe 1 has male threads 21a, 21b located at both ends of its outer circumferential surface 1a. In this case, the first pipe 1 can be fastened to the second pipe 2 using the same method as described above. That is, the male thread 21a of the first pipe 1 is threadedly engaged with the female thread 22c at one end of the second pipe 2, and the first pipe 1 is then rotated to the other end of the second pipe 2, thereby fastening the first pipe 1 to the second pipe 2.

[0046] As described above, the tubular body 100 of this embodiment uses the first tube 1 containing ceramics, rather than a ceramic membrane. Therefore, by abutting, joining, or fastening the first tube 1 and the second tube 2 containing metal or resin, it is possible to reduce misalignment between the first tube 1 and the second tube 2. Furthermore, because the first tube 1 is a relatively thick tube, it is less likely to develop wear, pinholes, or cracks, unlike ceramic membranes. This reduces the leakage of components from the metal tube or ceramic membrane and the leakage of particles into the sample liquid, and also provides excellent thermal insulation and ease of testing for pinholes in ceramics.

[0047] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various modifications and improvements are possible within the scope of the present disclosure. For example, each of the embodiments shown in Figures 1 to 13 may be used alone or in combination with at least two or more of the embodiments. Specific examples include a combination of the embodiment shown in Figure 2A or 2B regarding the length of the first tube 1 and the second tube 2 with the embodiment shown in Figure 3A or 3B regarding the thickness of the first tube 1 and the second tube 2, or a combination with any of the embodiments shown in Figures 7A to 7D in which the first tube 1 has a concave end 10 and / or a convex end 11. The embodiments to be combined may be selected as needed and are not particularly limited.

[0048] REFERENCE SIGNS LIST 1 First pipe 1a Outer peripheral surface 1b Inner peripheral surface 1c, 1d End surface of first pipe 2 Second pipe 2b Inner peripheral surface 2c, 2d End surface of second pipe 3 Through hole 4 Filler 5 Joining surface 6, 61 Step portion 7 Recessed portion 8 Joining material 9 Groove 10 Concave end portion 11 Convex end portion 12 Screw 13 Screw insertion hole 14 Screw hole 15 Gap portion 16 Spacer 17, 18, 19 Screw 17a, 18a, 19a Thread groove 17b, 18b, 19b Through hole 19c Groove 20 Gap portion 21a, 21b Male thread portion 22a, 22b, 22c Female thread portion 100 Tubular body

Claims

1. A tubular body for use in a liquid chromatography column, comprising a first tube containing ceramic and a second tube containing metal or resin, the second tube being positioned on the outer periphery of the first tube.

2. A tubular body as described in claim 1, wherein the inner peripheral surface of said second pipe is abutted, joined or fastened to the outer peripheral surface of said first pipe.

3. A tubular body according to claim 1 or 2, wherein the average roughness Ra1 of the outer peripheral surface of the first tube is different from the average roughness Ra2 of the inner peripheral surface of the second tube.

4. A tubular body according to any one of claims 1 to 3, wherein at least one end face of the first tube is located at a different position from the end face of the second tube.

5. A tubular body according to any one of claims 1 to 4, wherein the thickness Tc of the first tube is greater than the thickness Tm of the second tube.

6. A tubular body according to any one of claims 1 to 4, wherein the thickness Tm of the second tube is greater than the thickness Tc of the first tube.

7. A tubular body according to any one of claims 1 to 6, wherein the inner peripheral surface of the first tube has a hardened surface.

8. A tubular body according to any one of claims 1 to 7, wherein the average roughness Ra of at least one of the outer circumferential surface of the first tube and the inner circumferential surface of the second tube is 0.2 μm or more.

9. A tubular body according to any one of claims 1 to 8, wherein a filler having a lower thermal conductivity than the first and second tubes is interposed between the first and second tubes.

10. A tubular body according to any one of claims 1 to 9, wherein the outer peripheral surface of the first tube and the inner peripheral surface of the second tube are joined to each other in the axial direction at their central portions, excluding their ends, via a joining material.

11. The tubular body according to claim 10, wherein a recessed groove is located along the circumferential direction at the end of at least one of the outer circumferential surface of the first tube and the inner circumferential surface of the second tube.

12. A tubular body according to any one of claims 1 to 11, wherein the ceramic contained in the first tube is mainly composed of zirconia.

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