liquid chromatograph

Abstract

A liquid chromatograph includes a liquid feeding unit capable of pre-pressurizing at a prescribed pressure regardless of the material of a pump. The liquid chromatograph includes a liquid feeding unit that feeds a mobile phase in a storage section to a column through a liquid feeding tube at a prescribed pressure, and the liquid feeding unit includes: a pump having a suction port connected to the storage section and a jet port connected to the liquid feeding tube directly or via another pump; a check valve provided at the jet port; and a pressure application control section that controls the pressure applied to the mobile phase in the pump before the mobile phase sucked from the suction port is jetted from the jet port, and controls the pressure in a manner that becomes a check valve opening pressure that opens the check valve provided at the jet port side, based on the compressibility of the mobile phase and the amount of compression of the inner wall of the pump accompanying the application of the pressure.

Description

Technical Field

[0001] This invention relates to a liquid chromatograph. Background Technology

[0002] Liquid chromatographs (LCs) are widely used as instruments for analyzing the components contained in liquid samples. In an LC, a liquid sample is introduced into a column along with the flow of a mobile phase delivered at a fixed flow rate. The various components contained in the liquid sample are separated over time and then measured using a detector. During this process, the delivery path is subjected to pressures (several MPa to tens of MPa) corresponding to the flow rate or the type and composition of the mobile phase. If only one pump is used to deliver the mobile phase, there will be a period during which delivery is not possible after the mobile phase is drawn in and before it is ejected. Therefore, in order to deliver the mobile phase continuously at a fixed flow rate, delivery units combining two pumps have been conventionally used.

[0003] In the liquid delivery unit, two pumps are connected in parallel or series. In the parallel connection, the two pumps are driven in opposite directions within the same cycle (one pumps while the other ejects), ensuring that at least one pump always ejects. In the series connection, during the period when the upstream pump ejects the mobile phase, the downstream pump draws in a portion of the mobile phase ejected by the upstream pump and passes the remainder through. During the period when the upstream pump draws in the mobile phase (without ejecting any mobile phase), the downstream pump ejects the corresponding amount of mobile phase that was just drawn in.

[0004] In the parallel connection type, check valves are installed at the suction port and discharge port of each of the two pumps. In the series connection type, check valves are installed at the suction port and discharge port of the upstream pump. The purpose is that, in the parallel connection type, the check valve at the suction port of one pump prevents backflow of the flowing phase to the suction port side when the pump discharges the flowing phase, and the check valve at the discharge port prevents the flowing phase from flowing into the discharge port side when the other pump discharges the flowing phase. The check valve of the upstream pump in the series connection type has the same function. Furthermore, in the downstream pump in the series connection type, since half of the flowing phase passes through during suction, no check valve is installed at the discharge port side. Also, since backflow of the flowing phase is prevented during discharge by the check valve at the discharge port of the upstream pump, no check valve is installed at the suction side.

[0005] In pumps equipped with check valves, the check valve is not opened until the pressure inside the pump reaches a predetermined value when the mobile phase is switched from the suction phase to the ejection phase. Therefore, in order to open the check valve at the same time as ejection begins, a pre-pressurization operation is performed to increase the pressure of the mobile phase inside the pump after the suction ends and before the ejection of the mobile phase begins (e.g., Patent Document 1).

[0006] The pressure of the mobile phase inside the pump during preloading (when the check valve is closed) is determined by the change in volume within the pump (corresponding to the displacement of the plunger) and the compressibility of the mobile phase. The compressibility of the mobile phase varies depending on its composition. Therefore, the change in volume (the displacement of the plunger) during preloading depends on the specific mobile phase used.

[0007] [Existing Technical Documents]

[0008] [Patent Literature]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2006-125367

[0010] [Patent Document 2] Japanese Patent Application Publication No. 07-077521 Summary of the Invention

[0011] [The problem the invention aims to solve]

[0012] Previously, the structural components of the liquid delivery unit were made of metals such as stainless steel. However, using metals can result in trace amounts of metal ions dissolving into the mobile phase, potentially affecting analytical results. Therefore, in recent years, a liquid chromatograph has been developed that includes a liquid delivery unit, where the portion of the structural components in contact with the mobile phase is made of a resin that is virtually non-leaching into the mobile phase. The pump in the liquid delivery unit is either an integrally resin-made pump or a pump where the portion in contact with the mobile phase is made of resin and the surrounding metal portion.

[0013] Regarding pumps using these resins, the flow path expands during pressurization. Therefore, even under the same pre-pressurization conditions as conventional metal pumps, the pressure is insufficient. Consequently, the check valve is opened only by moving the plunger, resulting in a delay in the timing of the ejection of the mobile phase.

[0014] Furthermore, regarding the delivery unit of the pump using this type of resin, the following problems arise when performing low-pressure gradient control. Generally, the following control is referred to as gradient control: the mobile phase is supplied to the column while continuously varying the composition of the mobile phase by continuously varying the mixing ratio of multiple solvents with different compositions. Low-pressure gradient control is defined as obtaining the mobile phase by mixing these multiple solvents using only one delivery unit on a downstream side of the pump. In low-pressure gradient control, for example, when supplying a mobile phase mixed with water and acetonitrile to the column, the mixing ratio of water and acetonitrile is continuously varied from 90:10 to 50:50 over 20 minutes. At this point, only compressed solvent (compressed residual liquid) remains in the pump when the pump finishes ejecting the solvent. Therefore, considering that no new solvent can be drawn during the period from the start of the pumping action until the pressure of the compressed residual liquid drops to a certain value (when depressurization is complete), the amount of plunger movement during the period from the completion of depressurization to the completion of pumping is divided according to the target value of the mixing ratio of each solvent. Thus, each solvent is drawn into the pump in such a way that the mixing ratio is the target value (see Patent Document 2). However, if a liquid delivery unit including a resin pump is used for low-pressure gradient control, a problem arises where the actual mixing ratio in the mobile phase ejected from the pump deviates from the target value.

[0015] The problem to be solved by the present invention is to provide a liquid chromatograph, including a liquid delivery unit, which can perform pre-pressurization at a specified pressure or low-pressure gradient control at a specified mixing ratio regardless of the material of the pump.

[0016] [Technical means to solve the problem]

[0017] The first embodiment of the present invention, made to solve the aforementioned problem, is a liquid chromatograph, including a delivery unit that delivers a mobile phase from a storage compartment to a column through a delivery tube at a predetermined pressure.

[0018] The liquid delivery unit includes:

[0019] A pump has: a pump chamber; a plunger that reciprocates within the pump chamber; a suction port disposed in the pump chamber and connected to the storage section; and a discharge port disposed in the pump chamber and connected directly or via another pump to the delivery pipe.

[0020] A check valve is connected to the nozzle outlet;

[0021] The input unit receives information related to the compressibility of the mobile phase and the change in the volume of the pump chamber accompanying changes in pressure within the pump chamber; and

[0022] The pressure application control unit, based on the information input by the input unit, controls the plunger such that the pressure applied to the flow phase in the pump chamber becomes the check valve opening pressure for opening the check valve before the flow phase drawn from the suction port is ejected from the nozzle.

[0023] A second aspect of the present invention is a liquid chromatograph, including a delivery unit that delivers a mobile phase to a column through a delivery tube at a specified pressure. The mobile phase is a mixture of multiple solvents with different compositions.

[0024] The liquid delivery unit includes:

[0025] The solvent supply unit includes: multiple solvent supply flow paths; and a switching mechanism that selectively switches one solvent supply flow path from the multiple solvent supply flow paths.

[0026] A pump has: a pump chamber; a plunger that reciprocates within the pump chamber; a suction port disposed in the pump chamber and connected to the solvent supply unit; and a spray outlet disposed in the pump chamber and connected directly or via another pump to the liquid delivery pipe.

[0027] The input unit receives information related to the compressibility of the mobile phase and the change in the volume of the pump chamber accompanying changes in pressure within the pump chamber; and

[0028] The flow path switching control unit controls the timing of switching the solvent supply flow path using the switching mechanism based on the information input by the input unit.

[0029] [The effects of the invention]

[0030] The pressure of the mobile phase within the pump chamber depends not only on the compressibility of the mobile phase but also on the volume of the pump chamber, which changes due to the compression of the pump chamber walls, plunger, sealing material in the gap between the plunger and the pump chamber walls, and the flow path from the pump chamber to the check valve caused by the applied pressure. The amount of change in pump chamber volume depends on the material of the pump chamber walls, etc.; if the material is metal, it is negligible; if the material is resin or other easily compressible materials, it is not negligible. Therefore, in the first-type liquid chromatograph, based on the compressibility of the mobile phase and the change in pump chamber volume due to the pressure change, the plunger is controlled such that the pressure applied to the mobile phase within the pump chamber becomes the check valve opening pressure before the mobile phase drawn from the suction port is ejected from the nozzle. Here, plunger control can be achieved by adjusting the plunger's position or movement speed per unit time, and the change in pump chamber volume can be determined in advance using pre-experiments. By controlling the plunger in this way, at the moment the mobile phase is ejected from the nozzle, the pressure of the mobile phase in the pump chamber becomes high enough to open the check valve, thus allowing the mobile phase to be ejected from the pump at the appropriate time. Furthermore, by having the operator input information related to the compressibility of the mobile phase and the change in the volume of the pump chamber caused by the compression of components such as the pump chamber walls due to changes in pressure within the pump chamber, the pressure application control unit controls the pressure applied to the mobile phase inside the pump based on this information. Therefore, even if the compressibility of the mobile phase or the change in the volume of the pump chamber changes due to a change in the mobile phase used or a replacement pump, the pressure can be appropriately controlled.

[0031] Furthermore, if the volume changes due to pressure variations within the pump chamber during low-pressure gradient control, the timing of solvent extraction after depressurization differs from the case where the volume remains unchanged. Therefore, if the solvent introduced into the pump chamber is switched without considering the change in the timing of depressurization, the actual mixing ratio will deviate from the target value. Thus, in the second-type liquid chromatograph, the timing of switching the solvent supply path using a switching mechanism is controlled based on the compressibility of the solvent within the pump chamber and the change in the pump chamber volume due to pressure variations. This allows the timing of switching the solvent supply path to correspond to the change in the timing of depressurization, enabling the mixing of multiple solvents at the target mixing ratio. Furthermore, similar to the first-type liquid chromatograph, even if the amount of change in solvent compressibility or pump chamber volume occurs due to a change in the solvent used or a pump replacement, the timing of switching the solvent supply path can be appropriately controlled. Attached Figure Description

[0032] Figure 1 This is a schematic structural diagram illustrating the first embodiment of the liquid chromatograph of the present invention.

[0033] Figure 2This is a diagram showing the structure of the liquid delivery unit of the liquid chromatograph according to the first embodiment.

[0034] Figure 3 This is a diagram illustrating the profile of the cam in the liquid delivery unit of the liquid chromatograph of the first embodiment, the pump operation when the cam rotates at a constant speed, and an example of the rotation speed of the cam.

[0035] Figure 4 This is a flowchart illustrating a method for determining the compression amount in the liquid delivery unit of the liquid chromatograph of the first embodiment, taking into account the compression amount of the pump's inner wall.

[0036] Figure 5 This is a schematic structural diagram illustrating a second embodiment of the liquid chromatograph of the present invention.

[0037] Figure 6 This is a diagram used to illustrate the time period for solvent aspiration and the timing for switching the aspirated solution.

[0038] Figure 7 This is a flowchart illustrating a method for determining the timing of switching the solution being pumped into the pump by considering the compression of the pump's inner wall in the liquid delivery unit of the liquid chromatograph in the second embodiment.

[0039] Figure 8 This is a diagram showing the structure of the liquid delivery unit in a modified liquid chromatograph.

[0040] [Explanation of Symbols]

[0041] 1, 4: Liquid Chromatography

[0042] 11: Storage slot

[0043] 12: Liquid delivery pipe

[0044] 121: First liquid delivery tube

[0045] 122: Second liquid delivery tube

[0046] 123: Third liquid delivery tube

[0047] 13: Sample injection section (syringe)

[0048] 14: Tubing

[0049] 15: Detector

[0050] 20, 30: Pump unit (liquid delivery unit in the first embodiment)

[0051] 21, 31: First pump

[0052] 211, 311: First suction port

[0053] 212, 312: First jet outlet

[0054] 213, 313: First material cylinder (first pump chamber)

[0055] 214, 314: First plunger

[0056] 22, 32: Second pump

[0057] 221, 321: Second suction port

[0058] 222, 322: Second jet outlet

[0059] 223, 323: Second feed cylinder (second pump chamber)

[0060] 224, 324: Second plunger

[0061] 231, 331: First check valve

[0062] 232, 332: Second check valve

[0063] 24: Camshaft

[0064] 251, 351: First cam

[0065] 252, 352: Second cam

[0066] 26: Stepper motor

[0067] 27: Control Department

[0068] 28: Input Section

[0069] 29: Display Section

[0070] 333: Third check valve

[0071] 334: Fourth check valve

[0072] 40: Liquid delivery unit

[0073] 411: First Storage Department

[0074] 412: Second Storage Department

[0075] 42: Solvent Supply Department

[0076] 4221: First supply path (one of multiple solvent supply paths)

[0077] 4222: Second supply path (one of multiple solvent supply paths)

[0078] 423: Switching valve

[0079] 424: Switching Control Unit

[0080] 46: Mixer

[0081] 51, 52, 53: Rotation angle when pre-pressurization is complete (rotation angle when the check valve opens) Detailed Implementation

[0082] (1) First implementation method

[0083] use Figures 1-4 The first embodiment of the liquid chromatograph of the present invention will be described below. Figure 1 This is a schematic structural diagram of the liquid chromatograph 1 according to this embodiment. The liquid chromatograph 1 includes: a storage tank (storage section) 11 for storing the mobile phase; a delivery tube 12, one end of which is connected to the storage tank 11; a pump unit 20 disposed in the delivery tube 12; a sample injection section (injector) 13 disposed further downstream of the pump unit 20 in the pipeline; a column 14 disposed further downstream of the sample injection section 13 in the pipeline; and a detector 15 disposed further downstream of the column 14 in the pipeline. The sample injection section 13 is a device for injecting a sample solution into the mobile phase. The column 14 separates various components contained in the sample solution injected into the mobile phase over time. The detector 15 is a device for sequentially detecting the various components separated by the column 14, and may be a mass spectrometer, a photodiode array (PDA) detector, an ultraviolet-visible spectrophotometer, etc. In the first embodiment, the pump unit 20 corresponds to the delivery unit. The structural elements other than pump unit 20 are the same as those used in conventional liquid chromatographs.

[0084] like Figure 2 As shown, the pump unit 20 includes a first pump 21 and a second pump 22. Within and before and after the pump unit 20, the delivery pipe 12 includes: a first delivery pipe 121 connecting the storage tank 11 to the suction port (first suction port) 211 of the first pump 21; a second delivery pipe 122 connecting the nozzle (first nozzle) 212 of the first pump 21 to the suction port (second suction port) 221 of the second pump 22; and a third delivery pipe 123 connecting the nozzle (second nozzle) 222 of the second pump 22 to the sample injection section 13. Thus, the first pump 21 and the second pump 22 are connected in series via the second delivery pipe 122.

[0085] A first check valve 231 is provided at the first suction port 211, and a second check valve 232 is provided at the first spray port 212. Both the first check valve 231 and the second check valve 232 have the function of preventing the flowing phase from flowing back towards the storage tank 11.

[0086] Furthermore, no check valves are provided at the second suction port 221 and the second discharge port 222 of the second pump 22. This is because the second suction port 221 can prevent backflow of the mobile phase by means of the second check valve 232 provided at the first discharge port 212 of the first pump 21, and the second discharge port 222 must also allow half of the mobile phase drawn from the second suction port 221 to pass through during suction, as described below.

[0087] like Figure 2 As shown, the first pump 21 includes: a first feed cylinder (first pump chamber) 213, communicating with the first suction port 211 and the first spray port 212; and a first plunger 214, which reciprocates within the first feed cylinder 213. In this embodiment, polyether ether ketone (PEEK) is used as the material for the wall of the first feed cylinder 213 and the first plunger 214. PEEK has the advantage of being almost non-soluble in the mobile phase. Furthermore, it is characterized by being compressed when pressure is applied to the mobile phase within the first feed cylinder 213 by pressing in the first plunger 214, thereby changing the volume within the first feed cylinder 213. Additionally, the wall of the first feed cylinder 213 and / or the first plunger 214 can be entirely made of PEEK, or only the surface near the mobile phase can be made of PEEK while the remaining portions are made of metal. Moreover, resins other than PEEK can also be used.

[0088] Furthermore, a sealing material (not shown) is provided in the gap between the wall of the first feed cylinder 213 and the first plunger 214 to prevent the mobile phase from leaking out of the gap.

[0089] The second pump 22 includes a second feed cylinder (second pump chamber) 223 and a second plunger 224. The second feed cylinder (second pump chamber) 223 and the second plunger 224 have the same structure, volume and materials as the first feed cylinder 213 and the first plunger 214 of the first pump 21.

[0090] like Figure 2 As shown, the pump unit 20 also includes: a camshaft 24; a first cam 251 and a second cam 252 fixed to the camshaft 24; a stepping motor 26 that rotates the camshaft 24; and a control unit 27 that controls the rotation speed of the stepping motor 26. Furthermore, the liquid chromatograph 1 is equipped with an input device such as a keyboard or mouse (input unit 28) and a display (display unit 29), allowing input of control conditions via the control unit 27 from the input unit 28, which are then displayed on the display unit 29.

[0091] The first cam 251 contacts the rear end of the first plunger 214 and rotates with the rotation of the camshaft 24, thereby causing the first plunger 214 to reciprocate. The second cam 252 contacts the rear end of the second plunger 224 and reciprocates the second plunger 224 with the same structure as the first cam 251. The shapes of the first cam 251 and the second cam 252 are set such that the speed of the second plunger 224 is half the speed of the first plunger 214. Moreover, in principle, the first plunger 214 and the second plunger 224 move in opposite directions to each other (therefore, when the first pump 21 draws in the flowing phase, the second pump 22 ejects the flowing phase, and when the first pump 21 ejects the flowing phase, the second pump 22 draws in the flowing phase). However, when switching the pump that ejects the flowing phase between the first pump 21 and the second pump 22, and during the pre-pressurization described below, both the first plunger 214 and the second plunger 224 move in the pressing direction.

[0092] The operation of pump unit 20 will be explained. First cam 251 and second cam 252 rotate in conjunction with the rotation of camshaft 24, thereby causing first plunger 214 and second plunger 224 to reciprocate. When first pump 21 ejects the mobile phase from first outlet 212 (first plunger 214 advances), second pump 22 draws in the mobile phase ejected from first outlet 212 from second suction port 221 (second plunger 224 retracts). Second pump 22 only draws in half of the mobile phase ejected by first pump 21, allowing the remaining half to pass through and flow out from second outlet 222. Conversely, when first pump 21 draws in the mobile phase from first suction port 211, second pump 22 ejects the half of the mobile phase just drawn from second outlet 222. Thus, regardless of the suction / ejection phase of each pump, the mobile phase is always delivered at a substantially constant pressure and flow rate.

[0093] When the first pump 21 ejects the mobile phase, the mobile phase within the first pump 21 is compressed not only at the first outlet 212 side but also at the first suction port 211 side. However, the first check valve 231 prevents the mobile phase from flowing back into the storage tank 11. Furthermore, when the first pump 21 draws in the mobile phase, the second check valve 232 prevents the mobile phase in the second delivery pipe 122 or the second pump 22 from flowing back into the first pump 21. When the second pump 22 ejects the mobile phase, the mobile phase within the second pump 22 is compressed not only at the second outlet 222 side but also at the second suction port 221 side. However, the second check valve 232 prevents the mobile phase from flowing back into the first pump 21.

[0094] The pre-pressurization process will now be explained. When the first pump 21 ejects the mobile phase, the second check valve 232 is not opened until the pressure within the first pump 21 reaches a predetermined value (the check valve opening pressure), thus preventing the mobile phase from being ejected. Therefore, in the pump unit 20 of this embodiment, as described below, a pre-pressurization operation is performed to raise the pressure of the mobile phase within the first pump 21 to above the check valve opening pressure after the suction of the mobile phase in the first pump 21 is completed and before ejection begins. Furthermore, since the second pump 22 does not have a check valve, pre-pressurization is unnecessary.

[0095] The volume of the space containing the mobile phase in the first pump 21 at the end of the suction is set as V, the change in volume of the first pump 21 from the end of the suction to the opening of the second check valve 232 (during the pre-compression period) is set as ΔV, the change in pressure of the mobile phase in the first pump 21 during the pre-compression period is set as ΔP (ΔP is determined by the construction of the second check valve 232), and the compressibility of the mobile phase is set as β.

[0096] In previous liquid delivery units, ΔV was used to satisfy...

[0097] ΔV=βVΔP…(1)

[0098] The relationship between the pressure and the flow rate is used to determine the distance the plunger travels during preloading. The compressibility β varies depending on the composition of the mobile phase, therefore ΔV is determined for each component of the mobile phase.

[0099] However, as in this embodiment, when using a pump (first pump 21) containing a material that is compressed by applying pressure, ΔV needs to take into account not only the volume change caused by the compression of the flowing phase shown in equation (1), but also the volume change of the pump caused by the compression of the pump components, such as the pump chamber wall, plunger, and sealing material. Therefore, in this embodiment, the change in pump volume caused by the deformation resulting from the application of pressure to the flowing phase in the first pump 21 is defined as αΔP, and ΔV satisfies

[0100] ΔV=(βV+α)ΔP…(2)

[0101] The relationship is defined by specifying the distance the plunger travels during the pre-compression period.

[0102] The value of α depends on the pump material, so there is no need to change it unless the first pump 21 is replaced with a pump containing a different material. Therefore, the value of α is usually set to a constant, and only the compressibility β is input based on the composition of the mobile phase, thereby determining ΔV. If the first pump 21 is replaced, α is changed to a value determined by the material of the new first pump 21.

[0103] Next, while referring to Figure 3 The operation of the first cam 251 and the second cam 252 is explained with the pre-compression period as the focus. Figure 3 The upper section of the diagram, labeled "Cam Profile," illustrates the relationship between the rotation angle θ of the camshaft 24 (and the first cam 251 and the second cam 252) and the moving speed dr / dθ of the plungers (first plunger 214 and second plunger 224). Here, the plunger moving speed dr / dθ is the speed at which the plunger moves when the camshaft 24 rotates by a unit angle (1°) (note that this is different from the speed obtained by dividing distance by time). This relationship between θ and dr / dθ is determined by the shape of the cam. When dr / dθ is positive, it means that the plunger moves in the pushing direction; when dr / dθ is negative, it means that the plunger moves in the pulling direction.

[0104] By setting the cam profile in this way, when the camshaft 24 rotates at a constant speed, such as Figure 3 As shown in the middle section, the first pump 21 ejects the mobile phase when the rotation angle θ is 96° to 264°, draws in the mobile phase when the rotation angle θ is 264° to 360° (0°), and pre-compresses the mobile phase when the rotation angle θ is 0° to 96°. Here, 96°, which is the angle for completing the pre-compression when the camshaft 24 rotates at a constant speed, corresponds to the "reference rotation angle" described below. During pre-compression, dr / dθ is set to be less than that during ejection. On the other hand, the second pump 22 ejects the mobile phase during the period from the rotation angle θ from 240° through 360° (0°) to 120°, and draws in the mobile phase when the rotation angle θ is 120° to 240°. Furthermore, when the rotation angle θ is within the range of 96° to 120°, the second pump 22 continues to eject the mobile phase while reducing the moving speed dr / dθ of the second plunger 224, as the first pump 21 maintains the moving speed dr / dθ of the first plunger 214 when pre-pressurized (less than dr / dθ when θ is 120° or higher), thereby suppressing the amount of mobile phase ejected. Moreover, when the rotation angle θ is between 240° and 264°, both the first pump 21 and the second pump eject the mobile phase, so the moving speed dr / dθ of the first plunger 214 and the second plunger 224 is adjusted in a way that the flow rate of the mobile phase supplied to the third liquid delivery pipe 123 is fixed.

[0105] The timing of the end of pre-pressure (switching from pre-pressure to ejection) of the first pump 21 when the camshaft 24 rotates at a constant speed, as shown here, is set according to the timing when the first pump 21 uses a specific pump to deliver a specific mobile phase. In fact, the timing of the end of pre-pressure varies depending on the pump material and the composition of the mobile phase according to equation (2). In this embodiment, the shapes of the first cam 251 and the second cam 252 ( Figure 3The upper cam profile is set to be the same regardless of the material of the first pump 21 and the composition of the mobile phase. The rotational speed of these camshafts 24 is set by the following method, thereby adjusting the timing of the pre-pressure end according to each component of the material of the first pump 21 and the mobile phase. The control unit 27 controls the stepper motor 26 by rotating the camshafts 24 according to the set rotational speed.

[0106] When the material of the first pump 21 is harder than the material of the specific pump, or when the compressibility of the mobile phase is less than that of the specific mobile phase, the value of ΔV in equation (2) becomes smaller, and therefore preloading is completed faster than the timing set when the camshaft 24 rotates at a constant speed. In this case, even at a rotation angle θ of less than 120° for preloading while rotating at a constant speed, the mobile phase is ejected from the first pump 21. Therefore, according to Figure 3 The rotational speed example shown in the lower paragraph is for pattern 1, from the rotational angle at which preloading is completed ( Figure 3 The angle marked with symbol 51; the "rotation angle when the check valve is open" below; Figure 3 In the example, the rotation speed is slower than in the case of constant speed rotation, from the angle of 48° to the angle of completion of pre-compression (96°) during constant speed rotation. The rotation speed is set such that the combined flow rate of the mobile phase ejected from the first pump 21 and passing through the second pump 22, and the combined flow rate of the mobile phase ejected from the second pump 22 by the operation of the second pump 22, is consistent with the original ejection volume of the second pump 22. Therefore, after pre-compression is completed, the combined flow phase of the mobile phase ejected from the first pump 21 and passing through the second pump 22, and the combined flow phase ejected from the second pump 22, is supplied to the third delivery pipe 123, and the flow rate of this flow phase becomes the same as before pre-compression is completed.

[0107] When the material of the first pump 21 is softer than that of the specific pump, or when the compressibility of the mobile phase is greater than that of the specific mobile phase, the value of ΔV in equation (2) becomes larger, and therefore the preloading is completed later than the timing set when the camshaft 24 rotates at a constant speed. In this case, at a rotation angle θ after 120° of preloading is completed during constant speed rotation, the rotation speed is increased to reach the rotation angle at which the preloading of the first pump 21 is completed earlier.

[0108] In the aforementioned case, such as Figure 3 The rotation angle of mode 2 shown in the lower section when the pre-pressurization of the first pump 21 is completed ( Figure 3During the period from 96° to 120° (the angle indicated by symbol 52), i.e., when both pumps 21 and 22 are ejecting the mobile phase, the rotational speed of the camshaft 24 is increased from 96° to the rotational angle at which pre-compression is completed, compared to the constant-speed rotation. Then, the rotational speed is decreased to 120°. This allows the rotational angle at which pre-compression is completed to be reached earlier, and also prevents excessive flow of mobile phase from being supplied after reaching the aforementioned rotational angle.

[0109] like Figure 3 The rotation angle of mode 3 shown in the lower section when the pre-pressurization of the first pump 21 is completed ( Figure 3 When the angle (53 in the middle) is 120° or higher, from 96° to the rotation angle when preloading is completed, the rotation speed of the camshaft 24 is made faster than when rotating at a constant speed, thereby reaching the rotation angle earlier. At this time, during the period from 96° to 120°, the rotation speed is gradually and slowly increased, thereby suppressing the supply of excessive flow of the mobile phase.

[0110] The timing of pre-compression completion described so far is preferably set automatically by the software through input unit 28 by the maintenance manager or user of the liquid chromatograph 1 (hereinafter referred to as "operator"), who inputs information related to the pump material and mobile phase. (Refer to...) Figure 4 The flowchart illustrates an example of the operation of this software. Furthermore, in this embodiment, pre-pressurization is performed in the first pump 21, which includes the first plunger 214, but in the following description of the software operation, these are generally referred to as "plunger" and "pump".

[0111] First, the operator performs the prescribed operation using the input unit 28, thereby initiating the operation of the software by the control unit 27. The software accepts the input of the values ​​of α and β in the following manner (step 1). First, an input screen is displayed on the display unit 29, which is used for the operator to input information related to the pump material and the flowing phase. Here, as such information, the operator can input the values ​​of α and β in equation (2), or the operator can input or select the name of the flowing phase or the name of the pump material from the options, and then the control unit 27 retrieves the values ​​of α and β that have been pre-stored in the storage unit (not shown) according to each flowing phase and each material of the pump.

[0112] Next, based on the acquired values ​​of α and β, the control unit 27 calculates the amount of volume change ΔV in the pump until pre-pressurization is completed using equation (2) (step 2). Furthermore, the volume V in equation (2) is a value determined by the pump's construction, therefore it can be used without requiring operator input.

[0113] Next, the value of n is set to 1 (step 3), and the distance the plunger moves when the stepper motor 26 rotates n pulses (n = 1 at the time point, so it is 1 pulse) from the position where the preload begins is calculated based on the cam profile (step 4). Furthermore, the change in volume ΔV within the pump when the plunger moves the specified distance is determined. n (Step 5). This is because if the calculated ΔV n If the volume is less than ΔV (no in step 6), the volume inside the pump has not changed before the pre-pressurization is completed. Then, increase the value of n by 1 (step 7) and repeat the actions of steps 4 to 6.

[0114] On the other hand, if the ΔV obtained in step 5 n If the value is equal to or greater than ΔV (yes in step 6), it means that pre-compression is completed when the stepper motor 26 is rotated n pulses. Therefore, the position after the stepper motor 26 has rotated n pulses from the pre-compression start position is set as the pre-compression completion position (step 8). Furthermore, the pre-compression completion position is set so that the flow rate of the mobile phase delivered to the third delivery pipe 123 is as close to constant as possible until the ejection state of the mobile phase from the pump becomes normal. Figure 3 In the example, the rotational speed of the camshaft 24 is set up up to the rotation angle θ being 144° or higher (step 9). Through the above software actions, the timing of the preload completion (and the subsequent rotational speed of the camshaft 24) is set.

[0115] Multiple conditions, such as the timing of pre-compression completion, can be pre-stored in the storage unit. When starting to use the liquid chromatograph 1, these conditions are displayed on the display unit 29 for the user to select. In this case, the value of α (or the corresponding pump type) only changes when the pump is changed. Therefore, at the beginning of normal use of the liquid chromatograph 1, the user can also select only the value of β or the corresponding mobile phase type (in this case, the value of α is of course also the value determined according to the pump used).

[0116] (2) Second implementation method

[0117] use Figures 5-7 The second embodiment of the liquid chromatograph of the present invention will be described below. Figure 5 This is a schematic structural diagram of the liquid chromatograph 4 according to the second embodiment. The liquid chromatograph 4 includes: a first storage unit 411 and a second storage unit 412, a solvent supply unit 42, a delivery tube 12, a pump unit 20, a stirrer 46, a sample injection unit (syringe) 13, a column 14, and a detector 15. The delivery tube 12, sample injection unit 13, column 14, and detector 15 have the same structure as those in the first embodiment, therefore detailed descriptions are omitted.

[0118] The first storage section 411 and the second storage section 412 are storage tanks for storing solvents with different compositions. Hereinafter, the solvent stored in the first storage section 411 will be referred to as the first solvent, and the solvent stored in the second storage section 412 will be referred to as the second solvent. In addition, in this embodiment, these two storage sections, the first storage section 411 and the second storage section 412, are provided. However, when using a mobile phase mixed with three or more solvents for analysis, three or more storage sections may be provided.

[0119] The solvent supply unit 42 includes a first supply flow path 4221 and a second supply flow path 4222 extending from the first storage unit 411 and the second storage unit 412, respectively; a switching valve (switching mechanism) 423; and a flow path switching control unit 424. The switching valve 423 is a valve that switches the supply flow path of the solvent introduced into the liquid delivery pipe 12 between the first supply flow path 4221 and the second supply flow path 4222. The flow path switching control unit 424 controls the switching valve 423 to switch the supply flow path at a predetermined time, as described below.

[0120] Pump unit 20 has the same structure as pump unit 20 in the first embodiment (refer to the description). Figure 2 The first pump 21 and the second pump 22, whose walls and plungers are made of resin (PEEK), are connected in series. Check valves (first check valve 231 and second check valve 232) are respectively connected to the first suction port 211 and the first spray port 212 of the first pump 21.

[0121] In the second embodiment, the liquid delivery unit 40 is composed of a component obtained by combining the solvent supply unit 42, the liquid delivery pipe 12, and the pump unit 20 (unlike the first embodiment where the liquid delivery unit is composed only of the pump unit 20).

[0122] The stirrer 46 mixes the first solvent and the second solvent that flow into the pump unit 20 with a time difference and then delivers the mixture. The liquid formed by mixing the first solvent and the second solvent using the stirrer 46 is supplied as the mobile phase to the sample injection section 13.

[0123] The operation of the liquid delivery unit 40 in the liquid chromatograph 4 according to the second embodiment will be described below. The basic operation of the pump unit 20 in the liquid delivery unit 40 is the same as that in the first embodiment. That is, the first cam 251 and the second cam 252 rotate along with the rotation of the camshaft 24, thereby causing the first plunger 214 and the second plunger 224 to reciprocate. When the first pump 21 sprays solvent from the first nozzle 212, the second pump 22 draws half of the sprayed solvent from the second suction port 221, allowing the remaining half of the solvent to pass through and flow out from the second nozzle 222. When the first pump 21 draws mobile phase from the first suction port 211, the second pump 22 sprays the half of the solvent that was just drawn out from the second nozzle 222.

[0124] The solvent supply unit 42 switches the solvent supplied to the first pump 21 between the first solvent and the second solvent at the specified times described below. To explain this, the operation of the liquid delivery unit 40 in a conventional liquid chromatograph will be described first.

[0125] In conventional liquid chromatographs, the delivery unit 40 delivers the solvent to the first pump 21 during the time period ( Figure 6 The time period (referred to as "suction") is switched according to the same ratio as the mixing ratio of the first solvent and the second solvent. For example, during the two-cycle suction of solvent by the first pump 21, if the first solvent and the second solvent are mixed at a mixing ratio of 20:80, 40% of the first solvent and 60% of the second solvent are suctioned during the first cycle, and 100% of the second solvent is suctioned during the second cycle (in addition, the cycle unit for setting the mixing ratio is not limited to two cycle units, but can also be one cycle unit or three or more cycle units). However, during each suction period, the period from the start of the suction action (retraction of the first plunger 214) until the pressure in the first pump 21 drops to the specified value and the pressure is released (called the "empty period") is actually not possible to suction solvent. Therefore, the ratio of the suction volume of the first solvent to the second solvent is set during the remaining period excluding the empty period, thereby enabling the suction of the first solvent and the second solvent at the target mixing ratio. For example, in the example of the mixing ratio, if the gap period is 20% of the total suction cycle, the remaining 80% of the suction period in the first cycle can be divided into 40% for the first solvent and 60% for the second solvent. Thus, the timing for switching the suction solvent is when (100% - 20%) × 40% = 32% has elapsed since the end of the gap period (from the start of the suction operation, it is (20% + 32%) = 52%) (see reference). Figure 6 The phrase "pump compression deformation (previous)" is not considered.

[0126] However, if the materials of the components of the first pump 21 include resin or other materials that deform under pressure, the first cylinder 213 deforms due to the pressure applied to the remaining solvent after the ejection is completed before the suction operation begins. As a result, the position of the first plunger 214 at the time of depressurization differs from the case where no deformation occurs due to pressure, and consequently, the timing of the actual start of solvent suction also differs. Therefore, it is necessary to change the timing of switching the suctioned solvent in the case where no deformation occurs due to pressure (see [reference]). Figure 6 (Considering pump compression deformation).

[0127] Let the volume of the first pump 21 at the start of the suction action be V. m Let ΔV be the difference between the volume and pressure at a certain time from the start of the suction action to the completion of the depressurization action and at the start of the suction action.m and ΔP m The compressibility of the solvent remaining in the first pump 21 at the start of the suction action is set as β. m Let α be the change in volume of the first pump 21 caused by the deformation resulting from the pressure change within the first pump 21. m ΔP m From the start of the suction operation until the pressure release is complete, no solvent enters or exits the first pump 21. Therefore, without considering the deformation caused by the accompanying pressure change, the pre-pressurization condition is met, similar to that during the ejection operation.

[0128] ΔV m =β m V m ΔP m …(3)

[0129] The relationship is as follows. Considering the deformation accompanying pressure changes, similar to the preloading condition, the following condition is satisfied:

[0130] ΔV m =(β) m V m +α m )ΔP m …(4)

[0131] The relationship. In this embodiment, based on the relationship described in (4), the ΔV that accompanies the movement of the first plunger 214 is calculated. m With ΔP m The relationship. Furthermore, the first plunger 214 is moved to a position where the pressure inside the first pump 21 drops to a value sufficient to draw solvent (i.e., when depressurization is complete), ΔP. m The corresponding ΔV m The time is determined as the pressure relief is complete.

[0132] α m The value of α depends on the pump material, so there is no need to change it unless the first pump 21 is replaced with a pump containing a different material. Therefore, α is usually... m The value is set to a constant, and the compression ratio β is input only based on the composition of the solvent remaining in the first pump 21 (the solvent drawn in during the previous pumping, and, in the case of multiple solvents drawn in the previous pumping, the solvent formed by mixing these solvents). m This allows us to determine ΔV when the pressure relief is complete. m With the first pump 21 replaced, α m The value can be changed to one determined by the material of the new first pump 21. If the ΔV value is determined upon completion of depressurization... mThen, using the same method as before, the ratio of the first solvent to the second solvent is set from the position of the first plunger 214 at this time during the movement of the remaining first plunger 214, thereby determining the timing for switching the first solvent and the second solvent.

[0133] Similar to the first embodiment, the second embodiment also includes a control unit 27 and an input unit 28 (not shown), and preferably, the software automatically sets the parameters by having the operator input information related to the pump's material and solvent from the input unit 28. (Referring to...) Figure 7 The flowchart illustrates an example of the operation of this type of software. The description of the second embodiment up to this point has been based on the operation of the first pump 21 including the first plunger 214, but in the following description, the terms "plunger" and "pump" will be used in a general sense.

[0134] When the software starts operating through a specified operation performed by the operator using the input unit 28, the control unit 27 receives α. m and β m Input the value of α (step 11). m and β m The value can be directly entered by the operator, or the operator can enter or select from the options the name of the mobile phase (multiple solvents and their mixing ratio) or the name of the pump material. The control unit 27 then retrieves the α values ​​pre-stored in the storage unit (not shown) according to each mobile phase and pump material. m and β m The value of .

[0135] Next, the control unit 27, based on the acquired α m and β m The value of ΔV when the pressure relief is completed is obtained using equation (4). m The value (step 12). Additionally, in equation (4), the pump volume V at the start of the suction action... m The value is determined by the pump's construction, so it can be used without requiring operator input.

[0136] Next, the value of n is set to 1 (step 13), and the distance the plunger moves when the stepper motor 26 rotates n pulses (n = 1 at the time point, so it is 1 pulse) from the position where the suction action begins is calculated based on the cam profile (step 14). Furthermore, the change in volume ΔV within the pump when the plunger moves the specified distance is determined. mn (Step 15). This is because if the calculated ΔV mn Less than ΔV m (No in step 16) If the pressure relief is not yet complete, increase the value of n by 1 (step 17) and then execute the actions of steps 14 to 16 again.

[0137] On the other hand, if the ΔV obtained in step 15 mn With ΔV m Equal to or greater than ΔV m If (yes) is true in step 16, it means that the pressure relief is completed when the stepper motor 26 is rotated by n pulses. Therefore, the position after the stepper motor 26 has rotated by n pulses from the starting position of the suction action is set as the pressure relief completion position (step 18).

[0138] Next, the change in volume inside the pump from the time the depressurization is completed to the time the pumping action ends is divided according to the mixing ratio of the first solvent and the second solvent to be mixed, thereby determining the pumping volume V1 of the first solvent from the time the depressurization is completed to the time the solvent is switched (step 19).

[0139] Next, the value of k is set to 1 (step 20), and the distance the plunger moves when the stepper motor 26 rotates k pulses (k = 1 at that point, so it's 1 pulse) from the position where the pressure relief is complete is calculated based on the cam profile (step 21). Furthermore, the change in pump volume ΔV when the plunger moves the distance from the pressure relief completion position is determined. mk (Step 22). If the change ΔV mk If the suction volume V1 of the first solvent is less than the suction volume (not in step 23), then the value of k is increased by 1 (step 24), and steps 21 to 23 are executed again. On the other hand, if the ΔV calculated in step 21... mk If the value is equal to or greater than V1 (yes in step 23), it means that the solvent switching occurs when the stepper motor 26 rotates by k pulses from the point when the pressure relief is complete. Therefore, the solvent switching timing is set when the stepper motor 26 reaches the position after rotating by k pulses from the point when the pressure relief is complete (step 25). This concludes the series of operations.

[0140] This invention is not limited to the described embodiments, and various modifications can be made within the scope of the spirit of this invention.

[0141] For example, the embodiments described use a pump unit 20 formed by connecting the first pump 21 and the second pump 22 in series, but as described... Figure 8As shown, pump unit 30, which is formed by connecting the first pump 31 and the second pump 32 in parallel, can be used instead of pump unit 20. In this parallel connection, a first check valve 331 and a second check valve 332 are respectively provided corresponding to the first suction port 311 and the first discharge port 312 of the first pump 31, and a third check valve 333 and a fourth check valve 334 are respectively provided corresponding to the second suction port 321 and the second discharge port 322 of the second pump 32. Furthermore, the first pump 31 and the second pump 32, like the first pump 21 and the second pump 22 in the above embodiment, include a first feed cylinder 313 and a second feed cylinder 323, and a first plunger 314 and a second plunger 324. Both the first pump 31 and the second pump 32 are made entirely of resin, but pumps where the parts in contact with the flowing phase are made of resin and the rest are made of metal can also be used. In the modified example, a fourth check valve 334 is provided not only in the first pump 31 but also in the second pump 32, thus pre-pressurizing is performed before the mobile phase is ejected. The timing of pre-pressurization of the second pump 32 is the same as in the first embodiment, and can be determined based on equation (2) considering the change in capacity αΔP of each pump with pressure changes and the compressibility β of the mobile phase. The same applies to the first pump 31. The shapes of the first cam 351 and the second cam 352 can be appropriately determined according to the operation of the pumps in the case of parallel connection. In the case of low-pressure gradient control, the change in capacity αΔP of each pump with pressure changes is considered in the same way as in the second embodiment. m ΔP m and the compressibility β of the solvent in the pump m Once you are certain that the pressure relief is complete, you can proceed.

[0142] [Postscript]

[0143] Those skilled in the art will understand that the exemplary embodiments described are specific examples of the forms described below.

[0144] (First item)

[0145] The first liquid chromatograph includes a delivery unit that delivers the mobile phase from the storage compartment to the column through a delivery tube at a specified pressure.

[0146] The liquid delivery unit includes:

[0147] A pump has: a pump chamber; a plunger that reciprocates within the pump chamber; a suction port disposed in the pump chamber and connected to the storage section; and a discharge port disposed in the pump chamber and connected directly or via another pump to the delivery pipe.

[0148] A check valve is connected to the nozzle outlet;

[0149] The input unit receives information related to the compressibility of the mobile phase and the change in the volume of the pump chamber accompanying changes in pressure within the pump chamber; and

[0150] The pressure application control unit, based on the information input by the input unit, controls the plunger such that the pressure applied to the flow phase in the pump chamber becomes the check valve opening pressure for opening the check valve before the flow phase drawn from the suction port is ejected from the nozzle.

[0151] The pressure of the mobile phase within the pump chamber depends not only on the compressibility of the mobile phase but also on the volume of the pump chamber, which changes due to the compression of the pump chamber walls caused by the applied pressure. The amount of change in the pump chamber volume depends on the material of the pump chamber walls; if the material is metal, it is negligible, but if the material is easily compressible and deformable, such as resin, it is not negligible. Therefore, in the first-type liquid chromatograph, based on the compressibility of the mobile phase and the change in the pump chamber volume due to the pressure change, the plunger is controlled such that the pressure applied to the mobile phase within the pump chamber becomes the check valve opening pressure before the mobile phase drawn from the suction port is ejected from the nozzle. Here, plunger control can be achieved by adjusting the plunger's position or movement speed per unit time, and the change in the pump chamber volume can be determined in advance using pre-experiments. By controlling the plunger in this way, at the point when the mobile phase is ejected from the nozzle, the pressure of the mobile phase within the pump chamber becomes sufficient to open the check valve, thus allowing the mobile phase to be ejected from the pump at the appropriate time.

[0152] Furthermore, by having the operator input information related to the compressibility of the mobile phase and the change in the volume of the pump chamber caused by the compression of components such as the pump chamber walls due to changes in pressure within the pump chamber, the pressure application control unit controls the pressure, i.e. the pressure applied to the mobile phase within the pump, based on this information. Therefore, even if the compressibility of the mobile phase or the change in the volume of the pump chamber changes due to a change in the mobile phase used or a replacement pump, the pressure can be appropriately controlled.

[0153] The liquid chromatograph described in the first item can be used with either a parallel or series connection of the delivery unit. In the parallel connection type, both pumps are equivalent to the "pumps" in the first (and second and third) items. In this case, check valves are connected to the suction port and spray port of each of the two pumps, and the pressure of each pump is controlled by a pressure application control unit. In the series connection type, the upstream pump is equivalent to the "pump" in the first (and second and third) item. In this case, check valves are connected to the suction port and spray port of the upstream pump, and the pressure of this pump is controlled by a pressure application control unit, but no check valves are connected to the suction port and spray port of the downstream pump.

[0154] (Second item)

[0155] The liquid chromatograph in the second item is based on the liquid chromatograph in the first item, wherein...

[0156] The information related to the amount of change is information related to the amount of deformation of the material used in the pump chamber.

[0157] According to the liquid chromatograph in the second item, even if the amount of deformation varies due to the difference in the materials used in the pump chamber, the pressure can be appropriately controlled.

[0158] (Third item)

[0159] The third item refers to the liquid chromatograph based on the first or second item, wherein...

[0160] The pump also includes:

[0161] The cam converts the rotary motion into the reciprocating motion of the plunger; and

[0162] A rotating mechanism that causes the cam to rotate;

[0163] The pressure application control unit controls the plunger via the rotating mechanism in the following manner: when the rotation angle of the cam when the pressure reaches the check valve opening pressure (i.e., the rotation angle when the check valve opens) is less than a predetermined reference rotation angle, the rotation speed of the cam from the rotation angle when the check valve opens to the reference rotation angle is reduced; when the rotation angle when the check valve opens is greater than the reference rotation angle, the rotation speed of the cam from the reference rotation angle to the rotation angle when the check valve opens is increased.

[0164] In the third liquid chromatograph, when the rotation angle is less than the reference rotation angle when the check valve opens, pre-compression is completed rapidly, and the mobile phase is ejected simultaneously from the pre-compressed pump and other pumps. Therefore, by reducing the rotation speed of the cam, excessive flow of mobile phase is prevented. On the other hand, when the rotation angle is greater than the reference rotation angle when the check valve opens, pre-compression is completed slowly at the original rotation speed. Therefore, the rotation speed of the cam is increased to reach the rotation angle when the check valve opens earlier. By controlling the rotation speed of the cam in this way, even if the rotation angle when the check valve opens varies depending on the compressibility of the mobile phase and the compression of the pump's inner wall, the mobile phase can be supplied with appropriate pre-compression timing and ejection volume.

[0165] (Item 4)

[0166] The fourth type of liquid chromatograph includes a delivery unit that delivers the mobile phase to the column through a delivery tube at a specified pressure. The mobile phase is a mixture of multiple solvents with different compositions.

[0167] The liquid delivery unit includes:

[0168] The solvent supply unit includes: multiple solvent supply flow paths; and a switching mechanism that selectively switches one solvent supply flow path from the multiple solvent supply flow paths.

[0169] A pump has: a pump chamber; a plunger that reciprocates within the pump chamber; a suction port disposed in the pump chamber and connected to the solvent supply unit; and a spray outlet disposed in the pump chamber and connected directly or via another pump to the liquid delivery pipe.

[0170] The input unit receives information related to the compressibility of the solvent within the pump chamber and the change in the volume of the pump chamber accompanying changes in pressure within the pump chamber; and

[0171] The flow path switching control unit controls the timing of switching the solvent supply flow path using the switching mechanism based on the information input by the input unit.

[0172] If the volume changes due to pressure variations within the pump chamber during low-pressure gradient control, the timing of solvent extraction after depressurization differs from the case where the volume remains constant. Therefore, if the solvent introduced into the pump chamber is switched without considering the change in the timing of depressurization, the actual mixing ratio deviates from the target value. Thus, in the fourth liquid chromatograph, the timing of switching the solvent supply path using a switching mechanism is controlled based on the compressibility of the solvent within the pump chamber and the change in the pump chamber volume due to pressure variations. This allows the timing of switching the solvent supply path to correspond to the change in the timing of depressurization, enabling the mixing of multiple solvents at the target mixing ratio.

[0173] Furthermore, the liquid chromatograph in the fourth item is similar to the liquid chromatograph in the first item in that it can appropriately control the timing of switching the solvent supply path even if the solvent compression ratio or pump volume changes due to a change in the solvent used or a change in the pump.

Claims

1. A liquid chromatograph characterized by, The system includes a liquid delivery unit that delivers the mobile phase from the storage compartment to the column at a specified pressure via a delivery pipe. The liquid delivery unit includes: A pump has: a pump chamber; a plunger that reciprocates within the pump chamber; a suction port disposed in the pump chamber and connected to the storage section; and a discharge port disposed in the pump chamber and connected directly or via another pump to the delivery pipe. A check valve is connected to the nozzle outlet; The input unit receives information related to the compressibility of the mobile phase and the change in the volume of the pump chamber accompanying changes in pressure within the pump chamber; and The pressure application control unit, based on the information input by the input unit, controls the plunger such that the pressure applied to the flow phase in the pump chamber becomes the check valve opening pressure for opening the check valve before the flow phase drawn from the suction port is ejected from the nozzle.

2. The liquid chromatograph according to claim 1, wherein... The information related to the amount of change is information related to the amount of deformation of the material used in the pump chamber.

3. The liquid chromatograph according to claim 1 or 2, wherein... The pump also includes: The cam converts the rotary motion into the reciprocating motion of the plunger; as well as A rotating mechanism that causes the cam to rotate; The pressure application control unit controls the plunger via the rotating mechanism in the following manner: when the rotation angle of the cam when the pressure reaches the check valve opening pressure (i.e., the rotation angle when the check valve opens) is less than a predetermined reference rotation angle, the rotation speed of the cam from the rotation angle when the check valve opens to the reference rotation angle is reduced; when the rotation angle when the check valve opens is greater than the reference rotation angle, the rotation speed of the cam from the reference rotation angle to the rotation angle when the check valve opens is increased.

4. A liquid chromatograph characterized by, The system includes a liquid delivery unit that delivers the mobile phase to the column through a delivery tube at a specified pressure. The mobile phase is a mixture of multiple solvents with different compositions. The liquid delivery unit includes: The solvent supply unit includes: multiple solvent supply flow paths; and a switching mechanism that selectively switches one solvent supply flow path from the multiple solvent supply flow paths. A pump has: a pump chamber; a plunger that reciprocates within the pump chamber; a suction port disposed in the pump chamber and connected to the solvent supply unit; and a spray outlet disposed in the pump chamber and connected directly or via another pump to the liquid delivery pipe. The input unit receives information related to the compressibility of the solvent within the pump chamber and the change in the volume of the pump chamber accompanying changes in pressure within the pump chamber; and The control unit, based on the information input by the input unit, determines the timing for switching the solvent supply path using the switching mechanism according to the timing of the pump's depressurization completion, thereby mixing the various solvents at a predetermined mixing ratio.

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