Flow path switching valve and liquid chromatograph

Abstract

A flow path switching valve comprising a stator having a first passage (131) through a sixth passage (136) that open along the circumference of a single circle and having a seventh passage (137) that opens at a distance from the circumference, and a rotor that assumes a first rotation position, a second rotation position, and a third rotation position, wherein the rotor has: a first flow path groove (151) that connects the first passage and the second passage in the first rotation position and connects the second passage and the third passage in the second rotation position; a second flow path groove (152) that connects the fifth passage and the sixth passage in the first rotation position and connects the first passage and the sixth passage in the second rotation position; and a third flow path groove (153) that connects the third passage and the fourth passage in the first rotation position, connects the fourth passage and the fifth passage in the second rotation position, and connects the first passage and the seventh passage in the third rotation position.

Description

Flow path switching valve and liquid chromatograph

[0001] The present invention relates to a flow path switching valve and a liquid chromatograph equipped with the same.

[0002] In a liquid chromatograph, when a pump that delivers a mobile phase (a mobile phase pump) generates bubbles or the like and causes a liquid delivery failure, a pump flow path purge is performed in which the mobile phase is delivered at a high flow rate in order to discharge the bubbles or the like from the mobile phase pump (see, for example, Patent Document 1).When performing the pump flow path purging, it is necessary to change the destination of the mobile phase pump's delivery from the column to the drain in advance to prevent bubbles discharged from the mobile phase pump from flowing into the column and damaging the column.

[0003] In analyses using liquid chromatography, automatic sample injection devices (autosamplers) are sometimes used to automatically introduce multiple liquid samples into a column in sequence. Such autosamplers are broadly classified into two types of injection methods. One is the total injection method, in which the entire amount of sample liquid collected from a sample container is injected into the mobile phase flow path. The other is the loop injection method (also called the partial injection method), in which a portion of the sample liquid collected from a sample container is injected into the mobile phase flow path. Both of these autosamplers are equipped with a flow path switching valve, which is typically a six-port, two-position valve.

[0004] In a total injection autosampler, a sample loop for holding a sample is directly connected to the base end of a sampling needle, and sample injection is performed as follows: First, a predetermined amount of sample is aspirated from a sample container using the sampling needle, thereby filling the sample loop. Next, the tip of the sampling needle is inserted into the injection port (sample injection port), and the flow path is switched using the flow path selector valve, thereby inserting the sample loop, sampling needle, and injection port into the mobile phase flow path leading from the mobile phase pump to the column. As a result, the predetermined amount of sample held in the sample loop and sampling needle is swept away by the mobile phase and introduced into the column.

[0005] On the other hand, in a loop injection autosampler, a sample collection flow path including a sampling needle is provided independently of the sample loop, and sample injection is performed as follows: First, a predetermined amount of sample is aspirated from a sample container using the sampling needle. Then, the tip of the sampling needle is inserted into the injection port to inject the sample into the injection port. At this time, the injection port is connected to the sample loop via the flow path switching valve, and the sample injected into the injection port fills the sample loop. Then, the flow path is switched using the flow path switching valve, inserting the sample loop into the mobile phase flow path leading from the mobile phase pump to the column. As a result, of the predetermined amount of sample collected from the sample container, only the sample held in the sample loop is swept by the mobile phase and introduced into the mobile phase flow path.

[0006] Patent No. 7120435

[0007] In a liquid chromatograph equipped with a total injection autosampler, when a liquid delivery failure occurs during analysis and pump flow path purging is performed, the sample loop (as well as the sampling needle and injection port) is disconnected from the mobile phase flow path by switching the flow path with the flow path selector valve, the sampling needle is moved from the injection port to a drain (e.g., a drain container), and then the sample loop is connected to the mobile phase pump by switching the flow path with the flow path selector valve. This changes the destination of the mobile phase delivered by the mobile phase pump from the column to the drain, and the pump flow path can then be purged by increasing the flow rate of the mobile phase pump. However, when purging the pump flow path in a conventional total injection autosampler, as described above, the sampling needle must be moved from the injection port to a drain container, etc., which poses a problem of time required after a liquid delivery failure occurs and before pump flow path purging can be initiated.

[0008] On the other hand, in a loop injection autosampler, the mobile phase pump is always connected to the column via a flow path switching valve, and the destination of the mobile phase pump cannot be changed from the column to the drain by switching the flow path using the flow path switching valve or by moving the sampling needle. Therefore, in order to purge the pump flow path in a liquid chromatograph equipped with such a loop injection autosampler, a valve (hereinafter referred to as a purge valve) must be installed between the mobile phase pump and the flow path switching valve to switch the mobile phase from being introduced into the column (strictly speaking, introduced into the column via the flow path switching valve) to being introduced into the drain. However, if the purge valve is configured to be switched manually, there is a problem of reduced operational efficiency, and if it is configured to be switched automatically, there is a problem of increased manufacturing costs.

[0009] The present invention has been made in view of the above points, and an object of the present invention is to enable automatic purging of the pump flow path in a liquid chromatograph equipped with a loop injection type autosampler without incurring a significant increase in manufacturing costs, or to enable purging of the pump flow path to be started quickly after a liquid delivery failure occurs in a liquid chromatograph equipped with a total injection type autosampler.

[0010] The flow path switching valve according to the present invention, which has been made to solve the above problems, is a flow path switching valve comprising: a rotor; and a stator disposed opposite to the rotor in the axial direction of a rotation axis of the rotor, wherein the rotor rotates in a sliding manner relative to the stator; wherein the stator has, on a sliding surface that faces the rotor, a first passage, a second passage, a third passage, a fourth passage, a fifth passage, and a sixth passage that open in this order at a distance from one another on the circumference of a single circle centered on the rotation axis of the rotor; and a seventh passage that opens on the sliding surface at a position spaced from the circumference of the circle; wherein the rotor takes a first rotation position, a second rotation position, and a third rotation position; and wherein the flow path switching valve has: a first flow path groove that connects the first passage and the second passage at the first rotation position, and that connects the second passage and the third passage at the second rotation position; a third flow channel that connects the third passage and the fourth passage at the first rotation position, connects the fourth passage and the fifth passage at the second rotation position, and connects the first passage and the seventh passage at the third rotation position.

[0011] When the flow path switching valve according to the present invention having the above configuration is applied to a liquid chromatograph equipped with a loop injection autosampler, a mobile phase pump is connected to the first passage, a column is connected to the second passage, and one end of a sample loop is connected to the third passage. Furthermore, an injection port is connected to the fourth passage, the other end of the sample loop is connected to the sixth passage, and the fifth and seventh passages are connected to a drain. This allows the mobile phase pump and the column to be connected without a sample loop by setting the rotor to the first rotational position, the mobile phase pump and the column to be connected via the sample loop by setting the rotor to the second rotational position, and the mobile phase pump to be connected to a drain by setting the rotor to the third rotational position. In other words, the destination of the mobile phase delivered by the mobile phase pump can be easily changed from the column to the drain by switching the flow path using the flow path switching valve, without providing a new valve (the above-mentioned purge valve) between the mobile phase pump and the flow path switching valve. Therefore, the flow path switching valve according to the present invention makes it possible to automatically purge the pump flow path in a liquid chromatograph equipped with a loop injection type autosampler without incurring a significant increase in manufacturing costs.

[0012] Furthermore, when the flow path switching valve according to the present invention having the above configuration is applied to a liquid chromatograph equipped with a total injection autosampler, a mobile phase pump is connected to the first passage and a column is connected to the second passage. An injection port is connected to the third passage and a metering pump is connected to the fifth passage. One end of a sample loop having a sampling needle connected to the other end is connected to the sixth passage, and the fourth and seventh passages are connected to a drain. In this way, by setting the rotor to the first rotational position, the mobile phase pump can be connected to the column without via the sample loop. By setting the rotor to the second rotational position with the tip of the sampling needle inserted into the injection port, the mobile phase pump can be connected to the column via the sample loop, the sampling needle, and the injection port. Furthermore, by setting the rotor to the third rotational position, the mobile phase pump can be connected to the drain. That is, unlike conventional liquid chromatographs equipped with a total volume injection autosampler, it is possible to easily change the destination of the mobile phase delivered by the mobile phase pump from the column to the drain by switching the flow path with the flow path switching valve, without having to move the sampling needle from the injection port to a drain container, etc. Therefore, the flow path switching valve according to the present invention makes it possible to quickly start purging the pump flow path after a liquid delivery failure occurs in a liquid chromatograph equipped with a total volume injection autosampler.

[0013] FIG. 1 is a schematic configuration diagram of a liquid chromatograph according to a first embodiment of the present invention, showing the flow of liquid when the flow path switching valve is in the loading position; FIG. 2 is a cross-sectional view showing the configuration of the flow path switching valve in the same embodiment; FIG. 3 is a block diagram showing the configuration of a main part of a control unit in the same embodiment; FIG. 4 is a flowchart showing the operation of the liquid chromatograph; FIG. 5 is a diagram showing the flow of liquid when the flow path switching valve in the liquid chromatograph is in the injecting position; FIG. 6 is a diagram showing the flow of liquid when the flow path switching valve in the liquid chromatograph is in the purging position; FIG. 7 is a schematic configuration diagram of a liquid chromatograph according to a second embodiment of the present invention, showing the flow of liquid when the flow path switching valve is in the loading position; FIG. 8 is a diagram showing the flow of liquid when the flow path switching valve in the liquid chromatograph is in the injecting position; FIG. 9 is a diagram showing the flow of liquid when the flow path switching valve in the liquid chromatograph is in the purging position; FIG. 10 is a schematic diagram showing a state where a flow path switching valve according to another configuration example of the present invention is in the loading position; FIG. 11 is a schematic diagram showing a state where the flow path switching valve is in the injecting position; and FIG. 12 is a schematic diagram showing a state where the flow path switching valve is in the purging position.

[0014] [Embodiment 1] A first embodiment of the present invention will be described with reference to Figures 1 to 6. Figure 1 is a schematic diagram of a liquid chromatograph according to this embodiment. This liquid chromatograph includes a mobile phase pump 102 that draws a mobile phase from a mobile phase container 101, a column 103, an autosampler 110 that injects a sample into a mobile phase flow path 104 that extends from the mobile phase pump 102 to the column 103, a pressure sensor 105 that is provided in the mobile phase flow path 104 and detects the pressure within the mobile phase flow path 104, i.e., the liquid delivery pressure of the mobile phase pump 102, a detector 106 that is provided downstream of the column 103, and a control unit 180 that controls the mobile phase pump 102 and the autosampler 110 and performs predetermined processing based on the output signal of the pressure sensor 105.

[0015] The autosampler 110 in this embodiment injects a sample by a loop injection method, and includes a sample collection section 170 , a flow path switching valve 120 , a sample loop 161 , and an injection port 162 .

[0016] The sampling unit 170 includes a sample rack 172 for arranging sample containers 171 containing samples, sampling needles 173 for aspirating samples from the sample containers 171, a needle drive mechanism (not shown) for moving the sampling needles 173 up and down, back and forth, and left and right, and a metering pump 175 connected to the base end of the sampling needles 173 via a sample collection loop 174. In addition to the above, the sampling unit 170 also includes a cleaning mechanism for cleaning the sampling needles 173 and the like, but this is not directly related to the present invention and will not be shown or described here.

[0017] FIG. 2 is a longitudinal cross-sectional view of the flow path switching valve 120. As shown in the figure, the flow path switching valve 120 includes a cylindrical housing 121, a stator 122 fixed to cover an opening at one end of the housing 121, and a disk-shaped rotor 123 housed within the housing 121. Seven passages connectable to external flow paths are formed in the stator 122. Hereinafter, the seven passages will be referred to as a first passage 131, a second passage 132, a third passage 133, a fourth passage 134, a fifth passage 135, a sixth passage 136, and a seventh passage 137. Furthermore, when it is not necessary to distinguish between the passages 131 to 137, they will be collectively referred to simply as a passage 130. One end of each passage 130 opens to the surface of the stator 122 facing the rotor 123 (the lower surface in FIG. 2 , hereinafter referred to as the stator-side facing surface 124). The stator-side opposing surface 124 corresponds to the sliding surface in the present invention. For convenience, in FIG. 1 and FIGS. 5 and 6 described below, the stator 122 is omitted from the illustration, and only the contact surface of the rotor 123 with the stator 122 (hereinafter referred to as the rotor-side opposing surface 125) is illustrated. The opening positions of the seven passages 130 on the stator-side opposing surface 124 are illustrated, with reference numerals 131 to 137 indicating the corresponding passages 130 (the same applies to FIG. 7 and subsequent figures). The other end of each passage 130 opens on the surface of the stator 122 that does not face the rotor 123 (the upper surface in FIG. 2). The mobile phase pump 102 is connected to the other end of the first passage 131, and the column 103 is connected to the other end of the second passage 132. One end (hereinafter referred to as the first end) of a sample loop 161 is connected to the other end of the third passage 133, and an injection port 162 is connected to the other end of the fourth passage 134. One end of a first drain flow path 163 is connected to the other end of the fifth passage 135, and the other end (hereinafter referred to as the second end) of the sample loop 161 is connected to the other end of the sixth passage 136. One end of a second drain flow path 164 is connected to the other end of the seventh passage 137. The other ends of the first drain flow path 163 and the second drain flow path 164 are inserted into drain containers (not shown) or the like.

[0018] On the other hand, three flow passage grooves are provided in the rotor-side opposing surface 125 to connect two of the openings of the seven passages 130 in the stator-side opposing surface 124 (i.e., to connect two of the seven passages 130). Hereinafter, these three flow passage grooves will be referred to as a first flow passage groove 151, a second flow passage groove 152, and a third flow passage groove 153, respectively. Furthermore, when it is not necessary to distinguish between the flow passage grooves 151 to 153, they will be collectively referred to simply as flow passage groove 150.

[0019] The rotor 123 is pressed against the stator 122 by a spring 126, and this pressure maintains liquid-tightness between the rotor-side opposing surface 125 and the stator-side opposing surface 124. A shaft 127 is fixed to the center of the surface of the rotor 123 opposite the rotor-side opposing surface 125, and by rotating the shaft 127 with a drive source such as a stepping motor (not shown), the rotor 123 can be rotated about its central axis 128.

[0020] As shown in FIG. 1 , the first passage 131, the second passage 132, the third passage 133, the fourth passage 134, the fifth passage 135, and the sixth passage 136 open at equal intervals on the circumference of a single imaginary circle centered on the central axis 128 (not shown in FIG. 1 ) of the rotor 123 on the stator-side opposing surface 124 (not shown in FIG. 1 ), and the seventh passage 137 opens at a position spaced away from the opening position of the first passage 131 toward the center of the circle.

[0021] The first flow channel 151 is an arc-shaped groove that is approximately 60° of the circumference of the circle, and the second flow channel 152 is an arc-shaped groove that is approximately 60° of the circumference and is provided at an interval corresponding to the arc of approximately 60° of the circumference in a counterclockwise direction from one end of the first flow channel 151. The third flow channel 153 is a groove that is provided at an interval corresponding to the arc of approximately 60° of the circumference in a clockwise direction from the other end of the first flow channel 151 (the end farther from the second flow channel 152), and both ends of the third flow channel are located at both ends of the arc of approximately 60° of the circumference. The region between the two end portions of the third flow channel 153 (corresponding to the first and second portions in this invention) has a portion (hereinafter referred to as an inward extending portion 154) that extends from the center portion of the arc (corresponding to the third portion in this invention) into the inside of the circle, and the tip of the inward extending portion 154 (the end portion closer to the center of the circle) is connected to one of the two end portions, and the base end of the inward extending portion 154 is connected to the other of the two end portions. The tip of the inward extending portion 154 corresponds to the fourth portion in this invention.

[0022] These flow path grooves 151 to 153 connect two adjacent passages among the first passage 131, the second passage 132, the third passage 133, the fourth passage 134, the fifth passage 135, and the sixth passage 136, or connect the first passage 131 and the seventh passage 137, thereby forming an internal flow path in the flow path switching valve 120, and further, the flow path is switched by rotating the rotor 123 around the central axis 128 to change the communication state of the seven passages 130.

[0023] Specifically, the flow path switching valve 120 can be positioned at a loading position (corresponding to a first rotational position in the present invention) shown in FIG. 1, an injecting position (corresponding to a second rotational position in the present invention) shown in FIG. 5, and a purging position (corresponding to a third rotational position in the present invention) shown in FIG. 6, by rotation of the rotor 123.

[0024] In the loading position (FIG. 1), the first flow groove 151 connects the first passage 131 and the second passage 132, the second flow groove 152 connects the fifth passage 135 and the sixth passage 136, and the third flow groove 153 connects the third passage 133 and the fourth passage 134.

[0025] The injecting position (FIG. 5) is a state in which the rotor 123 is rotated 60° clockwise from the loading position. In this position, the first flow groove 151 connects the second passage 132 and the third passage 133, the second flow groove 152 connects the first passage 131 and the sixth passage 136, and the third flow groove 153 connects the fourth passage 134 and the fifth passage 135.

[0026] The purging position (FIG. 6) is a state in which the rotor 123 is rotated 150° clockwise from the injecting position. In this position, the first passage 131 and the seventh passage 137 are connected by the inward extension 154 of the third flow channel 153.

[0027] As shown in FIG. 3 , the control unit 180 includes an analysis schedule storage unit 181 and functional blocks including a flow path switching valve control unit 182, a mobile phase pump control unit 183, a needle drive control unit 184, a metering pump control unit 185, and a liquid transfer failure determination unit 186. Of these functional blocks, the liquid transfer failure determination unit 186 corresponds to the determination unit in the present invention, and the flow path switching valve control unit 182 and the mobile phase pump control unit 183 correspond to the control unit in the present invention. The functions of the control unit 180 are realized by a computer including a CPU, memory, a large-capacity storage medium (e.g., a hard disk), and the like. While the computer may be a dedicated computer built into the liquid chromatograph, it is typically a general-purpose computer such as a personal computer. A predetermined program is pre-installed on the computer, and the functions of the functional blocks are realized in software by the CPU executing the program. The functions of the analysis schedule storage unit 181 are realized by a large-capacity storage medium provided in the computer. The computer is connected to an input unit 187 for the user to input various instructions and a display unit 188 for displaying various information. The display unit 188 is configured, for example, by a liquid crystal display, and the input unit 187 is configured, for example, by a keyboard, a pointing device such as a mouse, or a touch panel attached to the display unit 188.

[0028] The operation of the liquid chromatograph according to this embodiment when performing scheduled analysis will be described with reference to the flowchart in Figure 4. Here, scheduled analysis refers to a series of analyses performed according to a preset analysis schedule. The analysis schedule defines at least the order in which analyses are performed on samples stored in one or more sample containers 171 on the sample rack 172, and is created in advance by the user and stored in the analysis schedule storage unit 181.

[0029] First, the flow path switching valve control unit 182 controls the drive source to set the flow path switching valve 120 to the loading position ( FIG. 1 ) (step 1). This connects the mobile phase pump 102 and the column 103 without the sample loop 161. Furthermore, the injection port 162 is connected to the first end of the sample loop 161, and the first drain flow path 163 is connected to the second end. Under the control of the mobile phase pump control unit 183, the mobile phase pump 102 delivers the mobile phase at a flow rate (hereinafter referred to as the analysis flow rate) predetermined as the flow rate of the mobile phase during analysis. Next, the needle drive control unit 184 controls the needle drive mechanism to insert the tip of the sampling needle 173 into the sample container 171 specified in the analysis schedule. The metering pump control unit 185 then controls the metering pump 175 to aspirate a predetermined amount of sample into the sampling needle 173 and retain it in the sample collection loop 174 (step 2). Thereafter, the needle drive control unit 184 controls the needle drive mechanism to insert the tip of the sampling needle 173 into the injection port 162, and the metering pump control unit 185 causes the metering pump 175 to perform a discharge operation, thereby injecting the sample in the sample collection loop 174 into the injection port 162 via the sampling needle 173 (step 3). The sample injected into the injection port 162 passes through the fourth passage 134, the third flow channel 153, and the third passage 133 of the flow path switching valve 120 and is held in the sample loop 161.

[0030] Next, under the control of the flow path switching valve control unit 182, the flow path switching valve 120 is switched to the above-mentioned injecting position ( FIG. 5 ) (step 4). As a result, the sample loop 161 is inserted into the mobile phase flow path 104 extending from the mobile phase pump 102 to the column 103, and the mobile phase drawn from the mobile phase container 101 is sent to the column 103 via the first passage 131, the second flow path groove 152, the sixth passage 136, the sample loop 161, the third passage 133, the first flow path groove 151, and the second passage 132. As a result, the sample held in the sample loop 161 is introduced into the column 103 along with the flow of the mobile phase. The various components (compounds) contained in the sample are separated from one another as they pass through the column 103, sequentially eluted from the column 103, and detected by the detector 106.

[0031] While such sample analysis is being performed, the pressure in the mobile phase flow path 104 is measured by the pressure sensor 105. The output signal of the pressure sensor 105 is converted into digital data by an A / D converter (not shown) and input to the control unit 180. In the control unit 180, the liquid delivery failure determination unit 186 monitors the fluctuation range of the liquid delivery pressure by the mobile phase pump 102 based on the digital data, and determines whether a liquid delivery failure has occurred in the mobile phase pump 102 based on the fluctuation range (step 5). Specifically, the fluctuation range is compared with a predetermined threshold, and if the fluctuation range exceeds the threshold, it is determined that a liquid delivery failure has occurred in the mobile phase pump 102.

[0032] This determination is repeatedly made at predetermined time intervals while the flow path switching valve 120 is in the injecting position (i.e., while the sample is being analyzed), and if no liquid transfer failure is detected by the time the sample analysis is completed (Yes in step 6 of FIG. 4), the control unit 180 then refers to the analysis schedule stored in the analysis schedule storage unit 181 to determine whether or not there is a sample to be analyzed next (step 7). If there is a sample to be analyzed, the process returns to step 1 and the next sample is analyzed; if there is no sample to be analyzed next (i.e., the analysis of all samples specified in the analysis schedule has been completed), the series of scheduled analyses ends.

[0033] On the other hand, if a liquid delivery failure is detected during the sample analysis (Yes in step 5), the scheduled analysis is interrupted, and under the control of the flow path switching valve controller 182, the flow path switching valve 120 is switched to the purging position ( FIG. 6 ) described above (step 8). This connects the first passage 131 and the seventh passage 137 of the flow path switching valve 120 via the third flow path groove 153, and the mobile phase delivered by the mobile phase pump 102 is discharged from the second drain passage 164 without flowing into the column 103. Thereafter, under the control of the mobile phase pump controller 183, the liquid delivery flow rate of the mobile phase pump 102 is changed to a predetermined flow rate (hereinafter referred to as the "purge flow rate") that is greater than the analysis flow rate (step 9). After the delivery of the mobile phase at the purge flow rate has been performed for a predetermined period of time, the liquid delivery failure determination unit 186 determines whether the liquid delivery failure has been resolved (step 10). Specifically, the flow rate of the mobile phase pump 102 is returned to the analysis flow rate, and the mobile phase is pumped for a predetermined time. If the fluctuation range of the pressure measured by the pressure sensor 105 during that time becomes equal to or less than the threshold value (or a second threshold value smaller than the threshold value), it is determined that the pumping problem has been resolved. If it is determined in step 10 that the pumping problem has not been resolved, it is then determined whether the number of pump flow rate purges performed during the schedule analysis has reached a predetermined upper limit (step 11). If the upper limit has been reached, it is determined that there is an abnormality in the mobile phase pump 102, and this fact is displayed on the display unit 188, and the series of processes is terminated. On the other hand, if the number of purges has not reached the upper limit, the process returns to step 9, and the mobile phase is pumped again at the purge flow rate.

[0034] Furthermore, if it is determined in step 10 that the liquid transfer problem has been resolved, the process returns to step 7 to determine whether there is a sample to be analyzed next, and if there is a sample to be analyzed, the process returns to step 1; if there is no sample to be analyzed, the series of scheduled analyses ends.

[0035] Here, after the liquid transfer failure is resolved, the analysis of the sample that was interrupted due to the liquid transfer failure is skipped and the analysis of the next sample is carried out (if there is no next sample, the series of scheduled analyses is terminated), but this is not limited to this, and the analysis of the interrupted sample may be restarted from the beginning.

[0036] In addition, in the above, it is described that a determination is made as to whether or not a liquid transfer failure has occurred while the flow path switching valve 120 is in the injecting position, but this is not limited to this, and it is also possible to determine whether or not a liquid transfer failure has occurred while the flow path switching valve 120 is in the loading position.

[0037] In the above description, when the liquid delivery failure determination unit 186 determines that a liquid delivery failure has occurred, pump flow path purging is automatically performed. However, in addition to or instead of this, when a user instructs the execution of pump flow path purging via the input unit 187, pump flow path purging (i.e., switching the flow path switching valve 120 to the purging position and delivering the mobile phase at the purge flow rate) may be performed in accordance with the instruction.

[0038] As described above, in the liquid chromatograph according to this embodiment, the destination of the mobile phase sent by the mobile phase pump 102 can be easily changed from the column 103 to the drain (specifically, the second drain flow path 164) by switching the flow path switching valve 120. Therefore, in a liquid chromatograph equipped with a loop injection autosampler 110, it is possible to automatically purge the pump flow path without providing a new valve (the above-mentioned purge valve) between the mobile phase pump 102 and the flow path switching valve 120.

[0039] [Embodiment 2] Next, a liquid chromatograph according to a second embodiment of the present invention will be described with reference to Figures 7 to 9. Note that in Figures 7 to 9, components that are the same as or correspond to those shown in Figure 1 are denoted by reference numerals with the same last two digits, and descriptions thereof will be omitted where appropriate.

[0040] The autosampler 210 in this embodiment injects a sample by a total injection method. In this autosampler 210, the sampling needle 273 is directly connected to one end (first end) of the sample loop 261.

[0041] In the autosampler 210 according to this embodiment, a mobile phase pump 202 is connected to a first passage 231 of the passage switching valve 220, and a column 203 is connected to a second passage 232. An injection port 262 is connected to a third passage 233, and one end of a first drain passage 263 is connected to a fourth passage 234. A metering pump 275 is connected to a fifth passage 235, and the other end (second end) of a sample loop 261 is connected to a sixth passage 236. Furthermore, one end of a second drain passage 264 is connected to a seventh passage 237. The other ends of the first drain passage 263 and the second drain passage 264 are inserted into drain containers or the like (not shown).

[0042] In addition to the above, the autosampler 210 is provided with a cleaning mechanism for cleaning the sampling needle 273 and the like, but as this is not directly related to the present invention, it will not be shown or described here.

[0043] In this embodiment as well, the flow path switching valve 220 can take three positions by rotating the rotor 223: a loading position (FIG. 7), an injecting position (FIG. 8), and a purging position (FIG. 9).

[0044] The operation of the liquid chromatograph apparatus according to this embodiment when performing a schedule analysis is substantially the same as that described in the flowchart of FIG. 4 . However, in this embodiment, when the flow path selector valve 220 is set to the loading position in step 1 of the flowchart, the mobile phase pump 202 and the column 203 are connected without the sample loop 261, and the second end of the sample loop 261 is connected to the metering pump 275 ( FIG. 7 ). Then, in the subsequent step 2, the sampling needle 273 is inserted into the sample container 271, and the metering pump 275 performs a suction operation, thereby aspirating a predetermined amount of sample from the sample container 271 and retaining it in the sample loop 261. Furthermore, in this embodiment, step 3 (injecting the sample) and step 4 (switching the flow path selector valve 220 to the injecting position) of the flowchart are performed substantially simultaneously. That is, in this embodiment, after the sample is aspirated in step 2 above, the tip of the sampling needle 273 is inserted into the injection port 262, and the flow path selector valve 220 is switched to the injecting position. As a result, as shown in FIG. 8 , the flow path including the sample loop 261, the sampling needle 273, and the injection port 262 is inserted into the mobile phase flow path 204 leading from the mobile phase pump 202 to the column 203. As a result, the sample held in the sample loop 261 and the sample in the sampling needle 273 are swept away by the mobile phase and injected into the injection port 262, and then carried by the flow of the mobile phase into the column 203. The subsequent steps are substantially the same as those in the flowchart, and therefore will not be described here.

[0045] In the liquid chromatograph according to this embodiment, if a liquid delivery failure of the mobile phase pump 202 is detected during sample analysis, the destination of the mobile phase delivered by the mobile phase pump 202 can be easily changed from the column 203 to the drain (specifically, the second drain flow path 264) by switching the flow path selector valve 220 to the purging position (see FIG. 9 ). Therefore, unlike a conventional liquid chromatograph equipped with a total volume injection autosampler, there is no need to move the sampling needle 273 from the injection port 262 to a drain container or the like when purging the pump flow path. This reduces the time from when a liquid delivery failure is detected until purging of the pump flow path is started and the time from when purging of the pump flow path is completed until analysis is resumed.

[0046] While the present invention has been described above using specific examples of embodiments, the present invention is not limited to the above-described embodiments and may be modified as appropriate within the spirit and scope of the present invention. For example, in the flow path switching valves 120 and 220 according to the present invention, the shapes of the flow path grooves 151 to 153 and 251 to 253 provided in the rotor-side opposing surfaces 125 and 225 are not limited to those described above.

[0047] Another configuration example of a flow path switching valve according to the present invention is shown in Figures 10 to 12. Note that in Figures 10 to 12, components that are the same as or correspond to those shown in Figures 1 to 9 are designated by reference numerals with the same last two digits, and descriptions thereof will be omitted where appropriate. In the flow path switching valve 320 of this configuration example, the third flow path groove 353 has a generally T-shaped configuration, including an arc-shaped portion (hereinafter referred to as arc portion 355) that corresponds to 60° of the circumference of the circle described above, and a linear inward extension portion 354 that protrudes from the center of arc portion 355 toward the inside of the circle. Note that arc portion 355 corresponds to the first groove in this invention, and inward extension portion 354 corresponds to the second groove in this invention. Furthermore, both ends of the arc portion 355 correspond to the first and second portions of the present invention, the intersection of the arc portion 355 and the inward extending portion 354 corresponds to the third portion of the present invention, and the tip end of the inward extending portion 354 corresponds to the fourth portion of the present invention. The shapes of the first flow path groove 351 and the second flow path groove 352 are similar to those of the first and second embodiments. In this configuration example, at the loading position ( FIG. 10 ), the arc portion 355 of the third flow path groove 353 connects the third passage 333 and the fourth passage 334, at the injecting position ( FIG. 11 ), the arc portion 355 of the third flow path groove 353 connects the fourth passage 334 and the fifth passage 335, and at the purging position ( FIG. 12 ), the inward extending portion 354 of the third flow path groove 353 connects the first passage 331 and the seventh passage 337.

[0048] In the above embodiment, the seventh passages 137, 237, 337 are configured to open inside the single circle in the stator-side opposing surface 124. However, the seventh passages 137, 237, 337 may be configured to open outside the single circle in the stator-side opposing surface 124. In this case, the third flow channel 153, 253, 353 is provided with an outward extending portion that connects the first passages 131, 231, 331 and the seventh passages 137, 237, 337 at the purging position, instead of the inward extending portion 154, 254, 354 described above.

[0049] Aspects It will be apparent to those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0050] (Item 1) A flow path switching valve according to one aspect of the present invention comprises: a rotor; and a stator disposed opposite to the rotor in the axial direction of a rotation axis of the rotor, wherein the rotor slides and rotates relative to the stator; the stator has, on a sliding surface that faces the rotor, a first passage, a second passage, a third passage, a fourth passage, a fifth passage, and a sixth passage that open in this order and are spaced apart from one another on the circumference of a single circle centered on the rotation axis of the rotor; and a seventh passage that opens on the sliding surface at a position spaced apart from the circumference of the circle; the rotor takes a first rotation position, a second rotation position, and a third rotation position; and a first flow path groove that connects the first passage and the second passage at the first rotation position and connects the second passage and the third passage at the second rotation position; and a second flow path groove that connects the fifth passage and the sixth passage at the first rotation position and connects the first passage and the sixth passage at the second rotation position. a third flow channel that connects the third passage and the fourth passage at the first rotation position, connects the fourth passage and the fifth passage at the second rotation position, and connects the first passage and the seventh passage at the third rotation position.

[0051] (Claim 2) The flow path switching valve according to paragraph 2 is the flow path switching valve according to paragraph 1, wherein the third flow path groove has: a first portion that faces the opening on the sliding surface of the third passage at the first rotation position, faces the opening on the sliding surface of the fourth passage at the second rotation position, and faces none of the openings on the sliding surface of the first passage to the seventh passage at the third rotation position; a second portion that faces the opening on the sliding surface of the fourth passage at the first rotation position, faces the opening on the sliding surface of the fifth passage at the second rotation position, and faces none of the openings on the sliding surface of the first passage to the seventh passage at the third rotation position; and a third portion that faces none of the openings on the sliding surface of the first passage at the first rotation position and the second rotation position, and faces the opening on the sliding surface of the first passage at the third rotation position. a fourth portion that does not face any of the openings in the sliding surfaces of the first to seventh passages at the first rotation position and the second rotation position, and faces the opening in the sliding surface of the seventh passage at the third rotation position.

[0052] (Clause 3) The flow path switching valve according to clause 3 is the flow path switching valve according to clause 2, wherein the third flow path groove has a single groove extending from the first portion through the fourth portion and the third portion to the second portion.

[0053] (4) The flow path switching valve according to 4 is the flow path switching valve according to 2, wherein the third flow path groove has a first groove extending from the first portion via the third portion to the second portion, and a second groove extending from the third portion to the fourth portion.

[0054] (Item 5) A liquid chromatograph according to item 5 is a liquid chromatograph comprising: a mobile phase pump that delivers a mobile phase; a column; and an autosampler that injects a sample into a mobile phase flow path from the mobile phase pump to the column, wherein the autosampler has a flow path switching valve, a sampling needle, an injection port into which the tip of the sampling needle is inserted, a sample loop that holds the sample injected into the injection port by the sampling needle, and first and second drains from which liquid is discharged, and the flow path switching valve is the flow path switching valve according to any one of items 1 to 4, wherein the first passage is connected to the mobile phase pump, the second passage is connected to the column, the third passage is connected to one end of the sample loop, the fourth passage is connected to the injection port, the fifth passage is connected to the first drain, the sixth passage is connected to the other end of the sample loop, and the seventh passage is connected to the second drain.

[0055] (Item 6) A liquid chromatograph according to item 6 is a liquid chromatograph comprising: a mobile phase pump that delivers a mobile phase; a column; and an autosampler that injects a sample into a mobile phase flow path from the mobile phase pump to the column, wherein the autosampler comprises a flow path switching valve, a sample loop that holds a sample, a sampling needle connected to one end of the sample loop, an injection port into which the tip of the sampling needle is inserted, a metering pump that draws in and discharges the sample via the sampling needle, and first and second drains from which liquid is discharged, and wherein the flow path switching valve is the flow path switching valve according to any one of items 1 to 4, wherein the first passage is connected to the mobile phase pump, the second passage is connected to the column, the third passage is connected to the injection port, the fourth passage is connected to the first drain, the fifth passage is connected to the metering pump, the sixth passage is connected to the other end of the sample loop, and the seventh passage is connected to the second drain.

[0056] (Item 7) The liquid chromatograph according to item 7 is the liquid chromatograph according to item 5 or 6, further comprising: a pressure sensor for measuring the pressure in the mobile phase flow path; a judgment unit for judging whether or not a liquid delivery problem has occurred in the mobile phase pump based on the pressure measured by the pressure sensor when the rotor is at the first rotation position or the second rotation position and the mobile phase pump is delivering the mobile phase at a predetermined first flow rate; and a control unit for controlling the flow path switching valve and the mobile phase pump so as to move the rotor to the third rotation position and change the liquid delivery flow rate of the mobile phase pump to a second flow rate greater than the first flow rate when the judgment unit judges that a liquid delivery problem has occurred in the mobile phase pump.

[0057] DESCRIPTION OF SYMBOLS 102: Mobile phase pump 103: Column 104: Mobile phase flow path 105: Pressure sensor 110: Autosampler 120: Flow path switching valve 122: Stator 123: Rotor 125: Rotor side opposing surface 131: First passage 132: Second passage 133: Third passage 134: Fourth passage 135: Fifth passage 136: Sixth passage 137: Seventh passage 150: Flow path groove 151: First flow path groove 152: Second flow path groove 153: Third flow path groove 154: Inward extension portion 161: Sample loop 162: Injection port 163: First drain 164: Second drain 170: Sample collection portion 171: Sample container 173: Sampling needle 175: Metering pump 180: Control portion 181: Analysis schedule storage portion 182: Flow path switching valve control unit 183: Mobile phase pump control unit 184: Needle drive control unit 185: Metering pump control unit 186: Liquid transfer failure determination unit

Claims

1. A flow path switching valve having a rotor and a stator disposed opposite to the rotor in the axial direction of a rotation axis of the rotor, the rotor sliding and rotating relative to the stator, wherein the stator has, on a sliding surface that faces the rotor, a first passage, a second passage, a third passage, a fourth passage, a fifth passage, and a sixth passage that open in this order at a distance from one another on the circumference of a single circle centered on the rotation axis of the rotor, and a seventh passage that opens on the sliding surface at a position spaced from the circumference of the circle, the rotor takes a first rotation position, a second rotation position, and a third rotation position, and wherein the rotor has a first flow path groove that connects the first passage and the second passage at the first rotation position and connects the second passage and the third passage at the second rotation position, and a second flow path groove that connects the fifth passage and the sixth passage at the first rotation position and connects the first passage and the sixth passage at the second rotation position, a third flow channel that connects the third passage and the fourth passage at the first rotation position, connects the fourth passage and the fifth passage at the second rotation position, and connects the first passage and the seventh passage at the third rotation position.

2. The third flow path groove has: a first portion that faces the opening on the sliding surface of the third passage at the first rotation position, faces the opening on the sliding surface of the fourth passage at the second rotation position, and faces none of the openings on the sliding surface of the first passage to the seventh passage at the third rotation position; a second portion that faces the opening on the sliding surface of the fourth passage at the first rotation position, faces the opening on the sliding surface of the fifth passage at the second rotation position, and faces none of the openings on the sliding surface of the first passage to the seventh passage at the third rotation position; and a third portion that faces none of the openings on the sliding surface of the first passage to the seventh passage at the first rotation position and the second rotation position, and faces the opening on the sliding surface of the first passage at the third rotation position. a fourth portion that does not face any of the openings in the sliding surface of the first passage to the seventh passage at the first rotation position and the second rotation position, and faces the opening in the sliding surface of the seventh passage at the third rotation position.

3. A flow path switching valve according to claim 2, wherein the third flow path groove has a single groove extending from the first portion through the fourth portion and the third portion to the second portion.

4. A flow path switching valve as described in claim 2, wherein the third flow path groove has a first groove extending from the first portion through the third portion to the second portion, and a second groove extending from the third portion to the fourth portion.

5. A liquid chromatograph comprising a mobile phase pump that delivers a mobile phase, a column, and an autosampler that injects a sample into a mobile phase flow path from the mobile phase pump to the column, wherein the autosampler has a flow path switching valve, a sampling needle, an injection port into which the tip of the sampling needle is inserted, a sample loop that holds the sample injected into the injection port by the sampling needle, and first and second drains from which liquid is discharged, and wherein the flow path switching valve is the flow path switching valve described in claim 1, wherein the first passage is connected to the mobile phase pump, the second passage is connected to the column, the third passage is connected to one end of the sample loop, the fourth passage is connected to the injection port, the fifth passage is connected to the first drain, the sixth passage is connected to the other end of the sample loop, and the seventh passage is connected to the second drain.

6. A liquid chromatograph comprising a mobile phase pump for delivering a mobile phase, a column, and an autosampler for injecting a sample into a mobile phase flow path from the mobile phase pump to the column, wherein the autosampler has a flow path switching valve, a sample loop for holding a sample, a sampling needle connected to one end of the sample loop, an injection port into which the tip of the sampling needle is inserted, a metering pump for drawing in and discharging the sample via the sampling needle, and first and second drains from which liquid is discharged, wherein the flow path switching valve is the flow path switching valve according to claim 1, wherein the first passage is connected to the mobile phase pump, the second passage is connected to the column, the third passage is connected to the injection port, the fourth passage is connected to the first drain, the fifth passage is connected to the metering pump, the sixth passage is connected to the other end of the sample loop, and the seventh passage is connected to the second drain.

7. A liquid chromatograph as described in claim 5 or 6, further comprising: a pressure sensor for measuring the pressure in the mobile phase flow path; a judgment unit for judging whether or not a liquid delivery problem has occurred in the mobile phase pump based on the pressure measured by the pressure sensor when the rotor is at the first rotation position or the second rotation position and the mobile phase pump is delivering the mobile phase at a predetermined first flow rate; and a control unit for controlling the flow path switching valve and the mobile phase pump so as to set the rotor to the third rotation position and change the liquid delivery flow rate of the mobile phase pump to a second flow rate greater than the first flow rate when the judgment unit judges that a liquid delivery problem has occurred in the mobile phase pump.

Images