The auto-sampler for chromatographs includes a needle for sampling configured to move while a tip end thereof faces vertically downward; a switching valve having a plurality of ports to which channels constituting a chromatograph are connected, the switching valve switching between port connecting conditions to switch between channel configurations; and an injection port including an opening at an upper surface thereof through which a tip end of the needle is inserted to make the needle fluidically communicate with a pipe connected to one port of the switching valve, and a needle seal configured to get into contact with an outer circumferential surface of the tip end portion to make the needle fluidically communicate with the pipe in a liquid-tight manner when the tip end of the needle is inserted through the opening.

TECHNICAL FIELD

The present invention is related to an auto-sampler used for chromatographs such as a liquid chromatograph and a supercritical fluid chromatograph.

BACKGROUND

According to the liquid chromatograph or the supercritical fluid chromatograph, auto-samplers are often used that automatically inject sample into an analysis channel in which mobile phase flows. The auto-sampler includes a switching vale for switching between the channel configurations, a needle for sampling, and a syringe pump for sucking liquid through the needle (Refer to Patent Citation 1).

SUMMARY

The injecting port of the auto-sampler includes an opening on an upper surface thereof, and the needle is inserted through the opening to fluidically communicate the needle with a different channel. The injecting port includes a needle seal that keeps the fluid-tightness at a connection portion with the needle inserted through the opening of the upper surface. If this type of the injection port is directly provided at the switching valve, the structure of switching valve would become complicated, and it would become necessary to perform a difficult process on the housing of the switching valve, thereby increasing cost. Therefore, in some cases, the injecting port is provided separately from the switching valve, and the port of the switching valve and the injecting port are fluidically connected with each other through a pipe.

In a case where the port of the switching valve and the injecting port are fluidically connected with each other, a connecting method of using a male nut and a ferrule for connecting the pipe and the needle seal is generally employed. However, according to this method, it is necessary for a worker to fasten the nut while pressing the end surface of pipe against the needle seal, so that depending skill levels of the workers, a gap, which will become dead volume, may generate between the end surface of the pipe and the needle seal.

Since the connecting portion between the end surface of the pipe and the needle seal exist at a flow passage of analysis subject, the dead volume at this portion might cause diffusion of sample or carry-over, thereby adversely affecting result of the analysis. Therefore, structure of the injecting port is needed that can surely adhere the end surface of the pipe to the needle seal.

In addition, since the pipe that connects the injecting port and the port of the switching valve needs to be replaced with one having different inner diameter depending on the sample or the analyzing condition, the pipe is needed to be easily attached to or detached from the injecting port.

Accordingly, it is an object of the present invention to surely adhere the surface of the pipe to the needle seal of the injecting port and to make it easy for the pipe to be attached to or detached from the injecting port

The present invention is related to an auto-sampler for chromatographs that injects sample into an analysis channel for chromatography. The auto-sampler for chromatographs according to the present invention includes a needle for sampling configured to move while a tip end thereof faces vertically downward; a switching valve having a plurality of ports to which channels constituting a chromatograph are connected, the switching valve switching between port connecting conditions to switch between channel configurations; and an injection port including an opening at an upper surface thereof through which a tip end of the needle is inserted to make the needle fluidically communicate with a pipe connected to one port of the switching valve, and a needle seal configured to get into contact with an outer circumferential surface of the tip end portion to make the needle fluidically communicate with the pipe in a liquid-tight manner when the tip end of the needle is inserted through the opening. The pipe has an end surface close to the injecting port facing vertically upward, and a broad member is fixed to an end portion of the pipe close to the injecting port, and the end surface of the pipe appears on an upper surface of the broad member. The injecting port includes a housing having a recess that accommodates the broad member, fixed to the end portion of the pipe, with the broad member being fitted in the recess from above, and a cap attached to the housing and having a through hole defining the opening. The needle seal is disposed on the upper surface of the broad member that is fitted in the recess of the housing, and is pressed against the end surface of the pipe by the cap that is attached to the housing.

The meaning of the end surface of the pipe “appears” on the upper surface of the broad member is that either the end surface of the pipe is disposed within the same plane of the upper surface of the broad member or the end surface of the pipe protrude from the upper surface of the broad member.

In the auto-sampler for chromatographs according to the present invention, the injection-port-side end surface of the pipe for fluidically communication the port of switching valve and the injecting port faces vertically upward, the broad member is fixed to the injection-port-side end portion of the pipe, the end surface of the pipe appears on the upper surface of the broad member, the housing of the injecting port is provided with a recess into which the broad member is fitted from above and is accommodated, the needle seal is disposed on the upper surface of the broad member that is fitted in the recess of the housing, and the needle seal is pressed against the end surface of the pipe by the cap attached to the housing. According to this structure, the end surface of the pipe is surely adhered to the needle seal of the injecting port, and the pipe can be easily attached to or detached from the injecting port easily.

DETAILED DESCRIPTION

Below, referring to the figures, one embodiment of an auto-sampler for chromatographs will be explained. An auto-sampler for a liquid chromatograph will be explained as an example, but the present invention can be applied to an auto-sampler used for a supercritical fluid chromatograph as well.

An auto-sampler2mainly includes a needle4for sampling, a sample loop6, a switching valve8, a syringe pump10(pump portion), and an injecting port12.

The needle4has a tip end and a base end, and the tip end faces vertically downward to suck sample. To the base end of the needle4, one end of the sample loop6is fluidically connected. The sample loop6is a channel for keeping the sample sucked through the tip end of the needle4, and has another end on the opposite side of the needle4, which is in fluid connection to one port (1) of the switching valve8. The needle4is moved in the vertical direction and directions within a horizontal plane by a motion mechanism (not shown).

The switching valve8switches between channel configurations, and is a six port valve in this embodiment. To each port of the switching valve8, the syringe pump10, a pipe14communicated with the injecting port12, a drain passage16, a mobile phase supply passage18, and an analysis channel22are connected, other than the sample loop6. The mobile phase supply passage18is a channel for supplying mobile phase through a liquid delivery pump20. The analysis channel22is a channel in which a separation column24and a detector26are provided. The switching valve8switches between a condition in which the mobile phase supply passage18and the analysis channel22are directly connected (the port (5) and the port (6) are communicated) and a condition in which the sample loop6and the needle (4) are intervened between the mobile phase supply passage18and the analysis channel22(the port (1) and the port (6) are communicated, and the port (2) and the port (3) are communicated, and the port (4) and the port (5) are communicated, as shown inFIG.1).

The syringe pump10is provided to be in fluid communication with the needle4by the switching valve8through the sample loop6, and sucks the sample through the needle4.

The injecting port12is in fluid communication with one port of the switching valve8through the pipe14, and leads the sample that has been sucked through the tip end of the needle4and retained in the sample loop6, to the analysis channel22.

Referring toFIG.2, the structure of the injecting port12will be explained.

The injecting port12includes an opening32through which the needle4is inserted from above, and the needle4inserted through the opening32is in fluid communication with a pipe14that is connected on one port (4) of the switching valve8. The injecting port12includes a housing34, a needle seal38, a spacer40, and a cap42.

An end portion of the pipe14close to the injecting port12is held in the housing34of the injecting port12while an end surface15faces vertically upward. To the outer surface of the end portion of the pipe14close to the injecting port12, a broad member28is fixed that is cylindrical and is made of metal. The method of securing the broad member28to the pipe14is not especially limited, and includes a securing method such as welding for tightly fixing the metals. The end surface15of the pipe14appears on an upper surface30of the broad member28. “Appear” means that either the end surface15of the pipe14is positioned within the same plane of the upper surface30of the broad member28or the end surface15of the pipe14projects from the upper surface30of the broad member28. InFIG.2, the end surface15of the pipe14projects upward from the upper surface30of the broad member28.

The housing34includes a recess36opening upward for receiving the broad member28from above. The broad member28is fitted in the recess36. The broad member28is fitted in the recess36of the housing34, and the lower surface of the broad member28is in contact with the bottom surface of the recess36, so that position of the end surface15of the pipe14in the housing34is fixed.

The needle seal38and the spacer40are disposed on the upper surface30of the broad member28, which is fitted in the recess36of the housing34. The needle seal38is in directly contact with the tip end portion of needle4inserted through the opening32to fluidically communicate the needle4with the pipe14in a liquid tight manner. The spacer40is an annular member located between the outer circumferential surface of needle seal38and the inner circumferential surface of the recess36to fix position of needle seal38. Since the end surface15of the pipe14appears on the upper surface30of the broad member28, simply disposing the needle seal38on the broad member28allows the end surface15of the pipe14and the lower surface of needle seal38to be into contact with each other. The needle seal38is press-fitted in the spacer40to be one integral component. The spacer40is fitted in the recess36of the housing34.

The cap42is attached to the housing34so as to cover an upper portion35of the housing34. The inner circumferential surface of the cap42is formed with a screw to be screwed with a screw formed on the outer circumferential surface of the upper portion35of the housing34. By rotating the cap42relative to the housing34within a horizontal plane, the cap42is attached to or detached from the housing34. The cap42is provided with a through hole defining an opening32thorough which the needle4is inserted from above. The lower surface of cap42is formed with a pressing portion44extending downward from a periphery of the through hole defining the opening32. When the cap42is attached to the housing34, the pressing portion44gets into contact with the upper surface of needle seal38and presses the needle seal38against the end surface15of the pipe14according to the tightening of the cap42.

The mechanism of attaching the cap42to the housing34is not limited to one using screwing by screws. Any mechanisms can be employed so long as it is possible to attach the cap42to the housing34while generating a pressing force on the needle seal40.

The housing34is formed with a slit46extending in the vertical direction. The slit46has a width larger than the outer diameter of the pipe14. As shown in inFIG.3, when the broad member28fixed to the end portion of the pipe14is fitted into the recess36or the broad member28is taken out of the recess36, the pipe14passes though the slit46. The slit46allows the pipe14to be easily attached to or be detached from injecting port12.

According to the above-described structure, by simply fitting the broad member28fixed to the end portion of the pipe14into the recess36of the housing34, disposing the needle seal38and the spacer40on the broad member28, attaching the cap42to the upper portion35of the housing34and fastening the cap42, the lower surface of needle seal38are pressed against the end surface15of the pipe14to surely keep fluid-tight between the pipe14and the needle seal38. Especially, as shown inFIG.2, since the end surface15of the pipe14projects from the upper surface of the broad member28, stress generated in the needle seal38due to the fastening of the cap42concentrates on small contact surfaces between the end surface15and the needle seal38, thereby ensuring high sealing property and improving pressure resistance.

The auto-sampler2described above employs “total-volume injection manner”, wherein after the sample is sucked through the tip end of needle4, and the total amount of the sucked sample is injected into the analysis channel22. However, the present invention is not limited to the previously described manner. The auto-sampler including the structure of “loop injecting method” (for example, refer to FIG. 7 of Patent Citation 1), wherein a certain amount of the sample sucked by the needle is injected into a different sample loop and is introduced into the analysis channel.

One embodiment an auto-sampler for chromatographs according to the present invention includes a needle (4) for sampling configured to move while a tip end thereof faces vertically downward; a switching valve (8) having a plurality of ports to which channels constituting a chromatograph are connected, the switching valve (8) switching between port connecting conditions to switch between channel configurations; and an injection port including an opening (32) at an upper surface thereof through which a tip end of the needle (4) is inserted to make the needle (4) fluidically communicate with a pipe (14) connected to one port of the switching valve (8), and a needle seal (38) configured to get into contact with an outer circumferential surface of the tip end portion to make the needle fluidically communicate with the pipe in a liquid-tight manner when the tip end of the needle (4) is inserted through the opening (32). The pipe (14) has an end surface (15) close to the injecting port (12) facing vertically upward, and a broad member (28) is fixed to an end portion of the pipe (14) close to the injecting port (12), and the end surface of the pipe (14) appears on an upper surface (30) of the broad member (28). The injecting port (12) includes a housing (34) having a recess (36) that accommodates the broad member (28), fixed to the end portion of the pipe (14), with the broad member (28) being fitted in the recess (36) from above, and a cap (42) attached to the housing (34) and having a through hole defining the opening (32). The needle seal (38) is disposed on the upper surface (30) of the broad member (28) that is fitted in the recess (36) of the housing (34), and is pressed against the end surface (15) of the pipe (14) by the cap (42) that is attached to the housing (34).

According to an aspect [1] of the previously described embodiment, the end surface (15) of the pipe (14) close to the injecting port (12) projects from the upper surface (30) of the broad member (28). Accordingly, since the stress in the needle seal (38) caused by the cap (42) concentrates on small contact surfaces between the end surface (15) of the pipe (14) and the needle seal (38), high sealing property is ensured and pressure resistance is improved.

According to an aspect [2] of the previously described embodiment, the pipe (14) and the broad member (28) are made of metal, and the broad member (28) is welded to the pipe (14). Accordingly, the broad member (28) is tightly fixed to the pipe (14). Accordingly, even if the cap (42) is attached to the housing (34) with a strong force, and the needle seal (38) is strongly pressed against the end surface (15) of the pipe14, the broad member (28) does not deviate from the pipe (14), thereby obtaining high pressure resistance.

According to an aspect [3] of the previously described embodiment, a side surface of the housing (34) of the injecting port (12) is formed wish the slit (46) that allows the pipe (14) to pass through when the broad member (28) is fitted into or is taken out of the recess (36). Accordingly, the pipe (14) can be easily attached to or be detached from the injecting port (12).

According to an aspect [4] of the previously described embodiment, the cap (842) of the injecting port (12) is attached to the housing (34) by screwing of screws. Accordingly, it is possible to adjust pressing force of the needle seal (38) to the end surface (15) of the pipe (14) the housing (34) by degree of fastening of the cap (42).

According to an aspect [5] of the previously described embodiment, the cap (42) of the injecting port (12) includes a pressing portion (44) that extends downward from a periphery of the through hole to press the upper surface of the needle seal (38) from above. Accordingly, when the cap (42) is attached to the housing (34), the needle seal (38) can be efficiently pressed against the end surface (15) of the pipe (14).

According to an aspect [6] of the previously described embodiment, the injecting port (12) includes the spacer (40). The spacer (40) is interposed between the inner circumferential surface of the recess (36) and the outer circumferential surface of the needle seal (38) to fix position of the needle seal (38). Accordingly, it is possible to prevent positional shift of the needle seal (38).

The aspects [1]-[6] can be freely combined with each other.

REFERENCE SIGNS LIST