Patent Publication Number: US-2023132609-A1

Title: Flow-path member used in analysis device and liquid chromatograph

Description:
BACKGROUND 
     Technical Field 
     The present invention relates to a flow-path member used in an analysis device and a liquid chromatograph including the flow-path member. 
     Description of Related Art 
     In a liquid chromatograph, separation columns having small particle diameters have been available in recent years, a peak appearing in a chromatogram is sharper as compared with conventional separation columns and a high separation resolution of a sample can be achieved. With use of such a separation column, many results with excellent separation resolutions can be obtained in a short period of time. On the other hand, however, extra-column dispersion (system dispersion) more greatly influences a theoretical plate number and a peak separation resolution, and dispersion performance of a system has become important in regard to ultra-high performance liquid chromatographs. 
     It is important to suppress dispersion in a pipe and other components used in a device in order to suppress extra-column dispersion. In JP 2009-276355 A, an attempt is made to provide a liquid chromatograph excellent in separation performance by reducing the internal volume of a flow path around an injection port to suppress extra-column dispersion. In addition, there is a method of using a corrugated pipe as a method of suppressing extra-column dispersion. In the corrugated pipe, it is possible to suppress a difference in flow velocity between a pipe wall-surface portion and a center portion and suppress the extra-column dispersion. 
     SUMMARY 
     As described above, it is possible to improve analysis accuracy in an analysis device by using the corrugated pipe. However, when the corrugated pipe is arranged in a column oven, the temperature of a sample flowing through the corrugated column increases. There is a problem that retention property of a sample in the separation column is degraded when the temperature of the sample increases. In this manner, even in a case in which the corrugated pipe is used, there is a factor that interferes with improvement of analysis accuracy in the analysis device. 
     An object of the present invention is to provide a flow-path member with which high analysis accuracy in an analysis device can be maintained. 
     A flow-path member according to one aspect of the present invention which is used in an analysis device and through which a sample flows in the analysis device, includes a pipe, and a covering member that covers the pipe, wherein the pipe has a first portion including a first direction, which is orthogonal to a direction in which the flow-path member extends as a whole, as at least an element of a local extending direction, a second portion including a second direction, which is opposite to the first direction, as at least an element of a local extending direction, a first bent portion in which a local extending direction changes from the first portion to the second portion, and a second bent portion in which a local extending direction changes from the second portion to the first portion, and a space is formed between the covering member and the pipe at least in the first portion and the second portion. 
     The present invention is also directed to a liquid chromatograph including the flow-path member used in the above-mentioned analysis device. 
     Other features, elements, characteristics, and advantages of the present disclosure will become more apparent from the following description of preferred embodiments of the present disclosure with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG.  1    is an overview of a liquid chromatograph according to the present embodiment; 
         FIG.  2    is a side view showing a flow-path member according to a first embodiment; 
         FIG.  3    is a cross sectional side view of an end portion of the flow-path member according to the first embodiment; 
         FIG.  4    is a diagram for comparison between chromatograms of a corrugated pipe with a covering member and a corrugated pipe without a covering member; 
         FIG.  5    is a cross sectional side view of an end portion of a flow-path member according to a second embodiment; 
         FIG.  6    is a cross sectional view taken along the line VI-VI of the flow-path member shown in  FIG.  5   ; 
         FIG.  7    is a cross-sectional view of a flow-path member according to a modified example of the second embodiment; 
         FIG.  8    is a diagram for comparison between chromatograms of a corrugated pipe with a covering member and a filling member, and a corrugated pipe without a covering member; and 
         FIG.  9    is a diagram for explaining the effect of the corrugated pipe. 
     
    
    
     DETAILED DESCRIPTION 
     A flow-path member and a liquid chromatograph according to embodiments of the present invention will now be described with reference to the attached drawings. 
     [1] First Embodiment 
     (1) Configuration of Liquid Chromatograph 
       FIG.  1    is a diagram showing a liquid chromatograph  1  which is an analysis device of the present embodiment. The liquid chromatograph  1  includes a solution tank  2 , a liquid sending pump  3 , an autosampler  4 , a column unit  5  and a detector  6 . The column unit  5  includes a separation column  50  and a column oven  51 . The autosampler  4  and the separation column  50  are connected to each other by the flow-path member  10 . The flow-path member  10  extends into the column oven  51  and is connected to an end portion of the separation column  50 . 
     The solution tank  2  stores a solvent which is a mobile phase. The liquid sending pump  3  pumps the solvent stored in the solution tank  2  to an analysis flow path. The autosampler  4  injects a sample into the analysis flow path. The sample that has been injected by the autosampler  4  flows through the flow-path member  10  together with the solvent and is sent to the separation column  50 . In the separation column  50 , the sample is separated into components based on a difference in magnitude of interaction of a stationary phase. The components into which the sample has been separated in the separation column  50  are detected by the detector  6 . 
     (2) Configuration of Flow-Path Member  10   
       FIG.  2    is a side view of the flow-path member  10  according to a first embodiment. The flow-path member  10  includes a pipe  11 , sleeves  12  covering the both end portions of the pipe  11  and a covering member  13  covering the pipe  11  except for part of the both ends of the pipe  11 . The pipe  11  includes a straight pipe  111  and a corrugated pipe  112 . Straight pipes  111  are provided at both end portions of the pipe  11  and extend linearly in the longitudinal direction of the flow-path member  10 . The corrugated pipe  112  extends in a corrugated shape in the longitudinal direction of the flow-path member  10 . The straight pipes  111  are connected to the both ends in the longitudinal direction of the corrugated pipe  112 . 
       FIG.  3    is a cross sectional side view of an end portion of the flow-path member  10  according to the first embodiment. While  FIG.  3    shows one end portion of the flow-path member  10 , the both end portions of the flow-path member  10  have the same structure. The sleeve  12  is a cylindrical member. The straight pipe  111  is arranged in the sleeve  12 . The flow-path member  10  is connected to the autosampler  4  by the sleeve  12  at one end portion and connected to the separation column  50  by the sleeve  12  at the other end portion. The covering member  13  covers the entire corrugated pipe  112  and part of the sleeve  12 . A portion of the covering member  13  covering the sleeve  12  is formed with an enlarged diameter portion  131  having a large diameter. The covering member  13  is made of an elastic member such as a heat-shrinkable tube. For example, a polyolefin resin is used for the covering member  13 . 
     As shown in  FIG.  3   , the corrugated pipe  112  includes a first portion  112 A and a second portion  112 B. The first portion  112 A includes a first direction DA, which is orthogonal to a direction D 1  in which the flow-path member  10  extends as a whole, as at least an element of a local extending direction. The second portion  112 B includes a second direction DB, which is opposite to the first direction DA, as at least an element of the local extending direction. In a first bent portion  113 A, the extending direction of the corrugated pipe  112  changes from the first portion  112 A to the second portion  112 B. In a second bent portion  113 B, the extending direction of the corrugated pipe  112  changes from the second portion  112 B to the first portion  112 A. In the present embodiment, the corrugated pipe  112  extends in the direction D 1  as a whole while changing the local direction in a plane including the first direction DA and the second direction DB. Further, because many first bent portions  113 A and second bent portions  113 B are provided, the corrugated pipe  112  extends while changing its local extending direction multiple times. 
       FIG.  9    is a diagram showing the effect of the corrugated pipe  112 . In A 1 , A 2  and A 3  in the diagram, the flow velocities of a mobile phase flowing through the corrugated pipe  112  are indicated by the lengths of the arrows. As shown in A 1 , in a portion in which the pipe  11  extends linearly, the flow velocities in the portions close to the wall surface are lower than the flow velocity in the center portion. This difference in flow velocity causes extra-column dispersion. As indicated in A 2 , in the second bent portion  113 B, the flow velocity in a portion farther outward in the curve is higher than that in a portion farther inward in the curve due to an eddy of a mobile phase generated in the pipe. As indicated in A 3 , in the first bent portion  113 A, the flow velocity in a portion farther outward in the curve is higher than that in a portion farther inward in the curve due to an eddy of a mobile phase generated in the pipe. With such a configuration, the flow velocities in the wall-surface portion and the center portion of the corrugated pipe  112  are averaged, and the difference in flow velocity is reduced. Thus, extra-column dispersion can be suppressed. 
     As shown in  FIG.  2   , the entire corrugated pipe  112  is covered with the covering member  13 . Thus, as shown in  FIG.  3   , a space  15  is formed between the corrugated pipe  112  and the covering member  13 . As described above, part of the flow-path member  10  is arranged in the column oven  51 . The flow-path member  10  arranged in the column oven  51  receives heat from a heater of the column oven  51 . Generally, the temperature of the column oven  51  is adjusted to a high temperature such as 40 degrees. However, because being formed between the corrugated pipe  112  and the covering member  13 , the space  15  forms an air layer and functions as a heat insulating layer against the heat of the column oven  51 . Thus, it is possible to suppress an increase in temperature of a sample in the flow-path member  10  leading to the separation column  50  and maintain high separation performance in the separation column  50 . That is, it is possible to avoid a phenomenon in which the temperature of a sample increases and it is difficult for column particles to retain sample components. In this manner, the flow-path member  10  of the present embodiment can maintain high separation performance in the separation column  50  by forming an air layer using the covering member  13  while suppressing extra-column dispersion by having the corrugated pipe  112 . 
     Further, because the entire corrugated pipe  112  is covered with the covering member  13 , it is possible to protect the corrugated pipe  112 . Thus, durability of the flow-path member  10  can be enhanced. Further, the covering member  13  is provided across the sleeve  12  and the first portion  112 A or the sleeve  12  and the second portion  112 B. Thus, the sleeve  12  and the corrugated pipe  112  are prevented from being bent excessively, so that the flow-path member  10  is prevented from being damaged. 
     (3) Result of Measurement 
       FIG.  4    is a diagram comparing the results of measurement in regard to a same sample under same analysis conditions obtained by the liquid chromatograph  1  of the first embodiment and a liquid chromatograph having a corrugated pipe that is not covered with a covering member. A chromatogram C 1  in the lower field of  FIG.  4    shows a result of analysis measured in the liquid chromatograph having a corrugated pipe that is not covered with a covering member. A chromatogram C 2  in the upper field of  FIG.  4    shows a result of analysis measured in the liquid chromatograph  1  of the first embodiment, that is, with use of the corrugated pipe covered with a covering member. It is found that, a peak P 2  in the chromatogram C 2  has a longer retention time than a peak P 1  in the chromatogram C 1 , and a theoretical plate number and peak separation resolution are improved. Further, it is found that a peak height of each peak in the chromatogram C 2  is equal to or higher than that of each peak in the chromatogram C 1 . 
     [2] Second Embodiment 
     (1) Configuration of Flow-Path Member  10   
       FIG.  5    is a cross sectional side view of an end portion of a flow-path member  10 M according to a second embodiment. Differently from the flow-path member  10  of the first embodiment, the flow-path member  10 M of the second embodiment is provided with a filling member  14  in a covering member  13 . The configuration of the flow-path member  10 M is similar to that of the flow-path member  10  shown in  FIG.  2    except for provision of the filling member  14 . The configuration of the rest of the liquid chromatograph  1  is similar to that shown in  FIG.  1    except for provision of the filling member  14 . As shown in  FIG.  5   , the filling member  14  extends linearly substantially parallel to the direction D 1  in which the flow-path member  10 M extends. The filling member  14  is a metal member, for example. 
       FIG.  6    is a cross sectional view taken along the line VI-VI of the flow-path member  10 M shown in  FIG.  5   . As shown in the diagram, the filling member  14  is arranged next to the corrugated pipe  112 . Because the filling member  14  is arranged in the space  15 , the space volume of the space  15  is smaller than that of the first embodiment. Alternatively, as shown in  FIG.  7   , the two filling members  14  may be arranged with a corrugated pipe  112  interposed therebetween. Thus, the space volume of the space  15  is further reduced. 
     In this manner, with the flow-path member  10 M of the second embodiment, the volume of an air layer formed in the covering member  13  can be reduced. In the first embodiment, an air layer is ensured in the covering member  13 , and an increase in temperature of a sample caused by the heat of the column oven  51  is suppressed. However, a user who has replaced a conventional liquid chromatograph with the liquid chromatograph  1  of the first embodiment wishes to make a comparison in regard to a specific analysis process under the same conditions as those with which a result of conventional measurement is obtained. As such, in regard to such a wish of the user, comparison with a result of conventional measurement is enabled with use of the flow-path member  10 M. Further, it is possible to improve the strength of the flow-path member  10 M by inserting the filling member  14  into the covering member  13 . 
     (2) Result of Measurement 
       FIG.  8    is a diagram for comparison between the results of measurement obtained by the liquid chromatograph  1  of the second embodiment and a liquid chromatograph having a corrugated pipe that is not covered with a covering member in regard to the same sample under the same analysis conditions. A chromatogram C 1  in the lower field of  FIG.  8    shows a result of analysis measured in the liquid chromatograph having a corrugated pipe that is not covered with a covering member. A chromatogram C 3  in the upper field of  FIG.  8    shows a result of analysis measured in the liquid chromatograph  1  of the second embodiment, that is, with use of the corrugated pipe that is covered with the covering member and provided with the filling member. It is found that a peak P 3  in the chromatogram C 3  has almost equal retention time to that of a peak P 1  in the chromatogram C 1 . 
     [3] Modified Example 
     In the above-mentioned embodiment, the first portion  112 A and the second portion  112 B of the corrugated pipe  112  are arranged in the plane including the first direction DA and the second direction DB, by way of example. However, the first portion  112 A and the second portion  112 B do not have to be arranged in the same plane. The first portion  112 A may include the first direction DA as at least an element of the extending direction, and the second portion  112 B may include the second direction DB as at least an element of the extending direction. 
     In the present embodiment, the space  15  is formed not only on the outer peripheries of the first portion  112 A and the second portion  112 B but also on the outer peripheries of the first bent portion  113 A and the second bent portion  113 B. That is, in  FIG.  3   , the space  15  is also formed in a portion located farther forward in the first direction DA than the first bent portion  113 A and a portion located farther forward in the second direction DB than the second bent portion  113 B. However, this is merely one example, and the space  15  may be formed at least on the outer peripheries of the first portion  112 A and the second portion  112 B. 
     In the second embodiment, the filling member  14  is a bar member having a substantially circular cross section, by way of example. This is merely one example, and the cross sectional shape of the filling member  14  may be another shape. For example, it is possible to further reduce the volume of an air layer by making the cross sectional shape of the filling member  14  be close to that of the space  15 . 
     [4] Aspects 
     It will be appreciated by those skilled in the art that the exemplary embodiments described above are illustrative of the following aspects. 
     (Item 1) 
     A flow-path member according to one aspect which is used in an analysis device and through which a sample flows in the analysis device, includes a pipe, and a covering member that covers the pipe, wherein the pipe has a first portion including a first direction, which is orthogonal to a direction in which the flow-path member extends as a whole, as at least an element of a local extending direction, a second portion including a second direction, which is opposite to the first direction, as at least an element of a local extending direction, a first bent portion in which a local extending direction changes from the first portion to the second portion, and a second bent portion in which a local extending direction changes from the second portion to the first portion, and a space is formed between the covering member and the pipe at least in the first portion and the second portion. 
     It is possible to provide a flow-path member with which high analysis accuracy can be maintained in an analysis device. 
     (Item 2) 
     The flow-path member which is used in an analysis device according to item 1, wherein the analysis device may include an autosampler and a separation column, and the flow-path member may connect the autosampler and the separation column to each other. 
     Extra-column dispersion in the flow path between the autosampler and the separation column can be reduced. 
     (Item 3) 
     The flow-path member which is used in an analysis device according to item 2, wherein an end portion connected to the separation column of the flow-path member may be arranged in a column oven. 
     The space formed in the covering member functions as a heat insulating layer, and an increase in temperature of a sample due to the heat of the column oven can be reduced. 
     (Item 4) 
     The flow-path member which is used in an analysis device according to any one of items 1 to 3, wherein the covering member may be constituted by an elastic member. 
     The covering member can be attached to fit the shape of the flow-path member. 
     (Item 5) The flow-path member which is used in an analysis device according to item 4, wherein a sleeve having a diameter larger than diameters of the first portion and the second portion may be provided at an end portion of the pipe, and the covering member may be provided across the sleeve and the first portion, or the sleeve and the second portion. 
     It is possible to prevent the pipe from being excessively bent with respect to the sleeve and improve durability of the flow-path member. 
     (Item 6) 
     The flow-path member which is used in an analysis device according to any one of items 1 to 5, wherein a filling member for reducing a volume of the space may be arranged in the covering member. 
     It is easy to compare a result of analysis performed by the analysis device having this flow-path member with a result of analysis obtained by a conventional analysis device. 
     (Item 7) 
     The flow-path member which is used in an analysis device according to item 6, wherein the filling member may be a bar member extending substantially parallel to a direction in which the flow-path member extends as a whole. 
     The filling member can be inserted along the flow-path member. 
     (Item 8) 
     A liquid chromatograph according to another aspect of the present invention includes the flow-path member which is used in an analysis device according to any one of items 1 to 7. 
     While preferred embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.